See also Issue 7 of the Newsletter. The 350 series had some inherent drift problems. The problem at least partially relates to thermal and voltage regulation in the rig. Dramatic temperature changes may cause drift until the rig thoroughly warms up. Since it is not worth the effort to stabilize the voltage regulation, it is much easier to stabilize the temperature. Swan always packed a lot of power (heat) into a small package and relied on air convection for cooling. Regulating the temperature should result in a much more stable, longer lasting, better performing rig.
Your local computer clone store (one of those "we'll make 'em up for you") has 3" 12 VDC muffin fans for about $5.00 that can be used to provide forced cooling. If you pop rivet them to the side of the case adjacent to the final deck in your Swan rig (the existing holes line up pretty well) you will see good results. Power them from within the rig or obtain an inexpensive power cube.
Much of the instability may go away because the extreme temperature fluctuations have been leveled out. Also you will extend the life of the rather expensive final amplifier tubes quite a bit. If you have a lot of other equipment nestled around your Swan, give the old rig a bit more breathing room. Short of major work on it, this may be the best answer. Expect the old girl to drift for about 20-30 minutes, though not nearly so much.
Did you know that Swan built over 82,000 rigs? At one time they were producing as many as 400 per month. Quite a success story from a company that started out on the strands of a shoe string! The Swan company was the classic American success story. Herb has said that he hand built most of the first rigs (the single banders) and even hand lettered the dials, etc. They were always designed to become multi band rigs and were made larger than they had to be because the mentality was one of bigness in those days.
After Herb sold the Swan company to Cubic in 1968, he stayed on for about five years until he formed the Atlas company, which produced some outstanding solid state rigs. After the Japanese entered the market, most of the American companies took a beating and Herb decided to suspend the production of Atlas equipment. The Atlas company is still in existence though and due to start producing high frequency ham rigs soon! Herb feels the time is right because the Japanese equipment is unnecessarily complicated, service is poor and prices are too high. He also feels he can produce a better performing and more reliable piece of equipment.
See the Swan Newsletter, Issue 9 for original text and additional information on pin layout.
Contributors. This section included information from Herb Johnson, Frank (W7QDC), Dave (N9HCW), Dean (WA9AZK) and others.
If your “S” meter is too generous, try using a RCA, Sylvania, or GE 12BA6 in the 2nd IF.
Do not use WD-40 or a cleaner containing oil or any greasy substance on the rotary switches. The insulating material tends to get soaked with oil which can be conductive and causing shorts through the insulation. A good commercial contact cleaner/lubricant is best. Rotary switches are about the most difficult things to repair, if it can even be done at all.
Do not use higher than suggested fuse ratings on power supplies. The transformers are hard to find and expensive (Peter Dahl) to replace. This usually causes the power supply to end up in the scrap heap. A 10 amp fuse is suggested for the 117X - you should use a 6 or even a 5 amp slow blow.
A good way to get rid of the 60 Hz hum often heard when connecting headphones to the power supply jack is to move the headphone jack to the radio. Be sure to use a jack that switches the audio to the speaker when the headphones are not plugged in. "Open" secondary audio transformers don't last very long.
Contributors. This section included information from John Bruchey, Dean (WA9AZK) and others.
Ground Braid. In the Swan 350 and the 500, the audio line is also used for the AC heater current producing 0.1 volts of AC at the headphones, causing a hum. One easy answer is to connect a low resistance braid between the transceiver and its power supply.
Ground Wire. A more sophisticated cure is to add a wire between the unused pin 11 of the Jones plug from the power supply to the transceiver. A good place to pick up ground is at the headphone jack. Connect the new wire to the rig using the unused pin 11. Either of the two method listed below avoids having a conductor carrying both the AC filament and the audio.
· In the Swan 350 the ground can be lifted from the output transformer and connected to pin 11 of the Jones plug.
· In the Swan 500 the ground can be lifted from terminal 3 of relay K2 and connected with a piece of wire to pin 11 of the Jones plug.
Perhaps one of the most important things that we can do to make our rigs last longer and give the best performance is to keep them properly tuned and aligned. In general, the Swan manuals do a pretty good job of explaining the alignment procedure, but there are two areas they could improve upon. After discussing these with John Bruchey, he agrees. Since Swan produced a myriad of transceivers, these "rules" will apply to the more popular 350, 500, and 700 series (and maybe others). They make alignment easier and more exact and are similar to those outlined in the 270B and SW-240 manuals that work fine.
Probably the area that misses the mark the most in the alignment procedure in the manuals is the section dealing with peaking the VFO circuit. The manual suggests the placement of a volt meter (reverse polarity) between pin 1 of the 12BE6 (receiver mixer) and ground. The procedure goes on to explain that on a negative scale, the voltage is peaked at certain frequencies, etc. If you have ever done this, you will notice that some of the circuits will not clearly peak or that the maximum reading (minimum in this case) requires you to totally remove the slugs (probably the 40 meter slug) from its form. Here is the answer, based on discussion with John Bruchey.
Instead of connecting a volt meter as described, simply clamp a lead from a field strength meter to the 30 pf capacitor which comes off pin 1 of the 12BE6 mixer, (usually C-702) and adjust the slugs for maximum reading on the same frequencies as shown in the manual. This will greatly simplify the procedure and appears to be the most accurate way to align the circuit. It is not necessary to put the rig into the transmit mode for this procedure. You should see a clear peak when the slug is well within its coil form.
The other area of improvement is in the alignment of the driver and mixer circuits. Instead of removing the screen voltage by disconnecting a wire and measuring voltage across a 1 K resistor, etc., use the following method:
· Do not disconnect the screen voltage.
· Do not use a volt meter.
· Instead, with the P.A. TUNE knob placed in the appropriate position and the rig tuned to the proper frequency and band shown in the chart, (a) turn the microphone gain down, (b) use the PTT to activate the transmitter circuit, (c) inject a little carrier with the carrier balance control, and (d) peak the driver as in normal tune-up. Immediately resonate the finals by dipping the current with the TUNE control. Then peak each related coil in the mixer and driver circuits, being careful not to exceed 100 mA cathode current and only transmitting for about 15 seconds. If you exceed 100 MA, adjust the carrier balance to minimize the current.
This method is suggested in other Swan manuals. Presumably the reason Swan suggested you disconnect the screen voltage to the finals and tune these circuits as indicated was to help eliminate damage to the finals. If you take a little care and avoid driving the finals too hard or too long, I believe you will find this to be a superior and faster method. Dean, WA9AZK.
There have been times when a rig is so "twisted" out of alignment on the 10 meter circuits that it seems "I'll never bring the old gal back to proper working order." This has usually occurred when the well-intentioned owner turns the slugs within the coil forms several revolutions. Generally, most circuits only need to be touched just a little. Usually a ¼ to ½ turn is more than is needed. This is especially true on 10 meters.
Since there are several places where the 10 meter slugs in both the Mixer and RF Driver circuits will allow them to resonate like a Stratavarious violin, the trick is to find the proper spot of resonance. To do this, use another receiver tuned to the transmitter’s frequency and monitor the “S” meter, peaking each of the coils for maximum “S” meter reading. So, if you ever have a problem getting your Swan to perform on 10 meters as it should (or for that matter any frequency), try this method. Dean, WA9AZK.
Contributors. This section included information from K6KA, Jack (KJ6KI), Clarence (W7LII), John Bruchey, Dean (WA9AZK) and others.
Other than the obvious screw drivers, needle nose pliers, etc., there are a number of useful items to have on hand, including:
· ¼" nut driver (cheap ones will round the hex head). Swans have many of this size sheet metal screw. The power driven variety may not be a good choice since over tightening can occur.
· Non-conductive type screw driver. One with a small metallic insert works well on trimmer caps.
· A bulb or other suction type de-soldering device. The wick type material is fine, but the suction device is best for the larger solder joints associated with Swans.
· Coil adjusting tools. Make sure it is exactly the right one. The wrong size may damage the small ferrite slugs, which are difficult to extract and replace. With two or three of the proper size, during alignment of sections with 2 or 3 slugs requiring sequential adjustment, they can be left in place.
· Butane pipe lighter. The lighter is shaped like a fountain pen and has an adjustable flame. While pricey, it’s ideal for heating the tubing.
· "Dial a value" resistor, capacitor, inductor charts.
· Parts cabinets.
· Section of short nap carpet or towel. Use on your work surface to protect equipment while servicing.
· Multi outlet power strip.
· Soldering irons (A couple of wattages).
· 409 cleaner. Works well on sprucing up the front cover plates as does automotive wax. Go easy on the wax, though. Many brands have a fairly aggressive abrasive. It has been reported to discolor aluminum.
· Brake/parts cleaner. With an old radio stripped down to the bare chassis, a spray brake/parts cleaner may be used on it. Be sure if you do this that all plastic and painted parts are removed. Don't forget to lube everything after this aggressive treatment.
When peaking the mixer and driver circuits, re-peak them two or three times. That is to say, after peaking the mixer coil, then peak the driver coil, then again peak the mixer coil, then again peak the driver, etc. Sometimes there is some reactance that changes the optimum points of tune. See also the Swan Newsletter, Issue 3.
Ever turn your radio on and get a warbling sound? Sometimes this problem is so pronounced that it completely masks all other audio. Most likely it is because the electrolytic twist lock can capacitor has failed. An easy fix is to simply bridge the defective capacitor. Don't forget that electrolytics have polarity. On the twist lock type, the isolated terminal is positive and the can is negative. The can type twist locks are very durable and should last a long, long time. However, electrolytic capacitors require a periodic applied voltage to maintain the dielectric properties. If a transceiver is unused for a couple years, they can dry out or chemically change such that the dielectric property cannot be re-established. Turn transceivers on from time to time or suffer the consequences.
So You Want to Go Off Balance. Something that comes up from time to time has to do with the way Swan designed various circuits with regard to off-setting the carrier balance when the radio is placed into the TUNE position. The 350s and the 500s (not Cs or CXs) required the operator to "inject" some carrier by off-setting the carrier balance if any power is to be generated in the TUNE position. This is inconsistent with the majority of the other Swan radios and sometimes is confusing. It is also easy to forget to null out the carrier after this is done.
A.4.4.1. Modification. So, what can you do to make this more consistent with the other rigs? Simple. Install a wire from the REC/TUNE wafer switch (usually the only unused terminal) to pin 9 if you have a 7360 or pin 1 if you have a 6JH8 balanced modulator tube. This will "take one of the deflection plates to ground" and fully off-set the carrier balance when you throw the old baby into TUNE. This might help eliminate those reports of "I hear carrier on your signal."
A.4.4.2. CW Operation. If you operate CW, your rig will put out ONLY full power which may be a bit hard on the finals and create other problems, but if you operate only phone, this will probably be a good solution. The best approach to this was what was done on the 700CX with different switch positions for CW and TUNE. There are many schematics available to refer to for this design should you have questions.
If it seems like your Cygnet 270B isn’t putting out the DC power on CW that it ought, you might initially think that a new final or driver was is in order, along with an alignment. If an old 240 puts out about 120 DC watts and it has just one 6DQ5 in the final, and a 350C with two 6LQ6s puts out about 250 watts DC, one would think that a Cygnet with one 6LQ6 and an adequate power supply should do better than 80 watts, right? Not so, for if you examine the manual (page 8, section 6) it states: "Note that the 270B operates at reduced power in TUNE-CW mode. The P.A. cathode bias resistor, R406 is in the circuit during TUNE and CW operation. In voice mode the bias resistor is shorted out, and the 270B operates at full PEP input rating." The same is true of later designs, such as the 350D.
If you have ever adjusted your S-meter instead of your bias there is an easy fix. Place any ¼" shaft knob on the bias control pot. When you reach back to make an adjustment, the knob permits easy identification by feel.
Contributors. This section included information from Monte (N7OQV), Grover (AA2GP), Dean (WA9AZK) and others.
The Swan-Net has a list of articles that have been done on Swan equipment over the years. Copies of many of these are already in the library. If you have copies of those that we do not have, please send me a copy. If you would like a copy of one or two, send an SASE. If you want several, contact the Swan-Net to determine costs.
There are several changes that must be made to use either the 8950 or M2057 finals in place of the 6LQ6's. The largest change is replacing the 9-pin compactron sockets with 12-pin compactron sockets. There are several styles of 12-pin compactron sockets available. To directly fit in place of the old sockets, the new ones must have a metallic mounting ring with mounting tabs and 4 ground solder lugs. The mounting tab holes must be 1-5/16" apart and allow mounting the socket on the underside of the chassis. The socket must fit into a 1" hole. The mounting tabs must be opposite pins 5 and 12. If the exact socket is not available, it should be possible to modify one to work. If the mounting tabs are too far apart, remove the mounting rings from an old 9-pin sockets and machine down the circumference of the new socket to fit the old mounting rings. If you find sockets the right size but have mounting tabs opposite the wrong holes, or if you find sockets that mount from above rather than from underneath, you should be able to re-orient the mounting rings, (Dave, WA0PND)
The M2057 tubes may vary somewhat in height. If it will not fit into the RF cage, add an extra bend in the deck that the sockets mount into. That deck rises from front to back so that the front tube sits lower than the rear tube. Add a bend at the rear so that the rear tube sits at the same level as the front tube. Finally, to gain just a little more clearance at the top, file off some protrusions from the top of the plate cap connectors.
Mount the sockets so that pin 1 is toward the right side of the transceiver. Once you have all the mechanical details taken care of, the rest is simple. It is time to wire the new sockets.
· You'll need the following parts that were removed when you removed the old sockets:
5 ea. 0.01 μf capacitor
2 ea. 100 Ω ½ watt resistor (you may want to use new ones to take advantage of longer leads)
· You'll need the following new parts:
3 ea. 0.01 μf capacitor
2 ea. 0.002 μf capacitor
2 ea. 1 Ω 5 watt or 10 watt resistor (wire-wounds seem to work without any problem).
· Depending on how the driver circuits align in your transceiver, you may also need the following:
1 ea. 91 pf mica capacitor
1 ea. 33 pf mica capacitor
· Don't solder connections until all you're done with the following list (unless you need to temporarily tack something to hold it):
1. Using one of the bus wires removed from the old sockets, run a bus wire through V5 pin 5, V5 pin 9, V4 pin 5, and V4 pin 9.
2. Connect V5 pin 3 to V5 pin 11.
3. Connect V4 pin 3 to V4 pin 11.
4. Connect V5 pin 2 to V5 pin 6.
5. Connect V4 pin 2 to V4 pin 6.
6. Connect V5 pin 6 to V4 pin 6.
7. Connect V5 pin 12 to ground.
8. Connect V4 pin 12 to ground.
9. Connect V5 pin 10 to ground.
10. Connect V5 pin 4 to ground.
11. Connect V4 pin 10 to ground.
12. Connect V4 pin 4 to ground.
12a Connect a 0.002 uf capacitor from V5 pin 3 to ground.
13. Connect a 0.002 uf capacitor from V4 pin 11 to ground.
14. Connect a 0.01 uf capacitor from V5 pin 11 to ground.
15. Connect a 0.01 uf capacitor from V4 pin 3 to ground.
16. Connect a 0.01 uf capacitor from V5 pin 6 to ground
17. Connect a 0.01 uf capacitor from V4 pin 6 to ground.
18. Connect the hot filament wire (brown on white) to V5 pin 1.
19. Connect V5 pin 1 to V4 pin 1 with short insulated (brown on white) wire.
20. Connect 0.01 uf capacitor from V5 pin 1 to ground.
21. Connect 0.01 uf capacitor from V4 pin 1 to ground.
22. Connect 0.01 uf capacitor from V5 pin 2 to ground.
23. Connect 0.01 uf capacitor from V4 pin 2 to ground.
24. Connect 1 Ω resistor from V5 pin 2 to ground.
25. Connect 1 Ω resistor from V4 pin 2 to ground.
26. Connect 100 Ω resistor from V5 pin 11 to terminal strip lug, orienting it so that it fits under and clears the bus wire running between the sockets.
27. Connect 100 Ω resistor from V4 pin 3 to terminal strip lug, orienting it so that it fits under and clears the bus wire running between the sockets.
28. Connect the 0.002 driver capacitor from terminal lug to V4 pin 9.
29. Connect the grid rf choke from terminal lug to V5 pin 5.
30. Connect the meter resistors (there were 3 in parallel in my transceiver) from terminal lug to wire that joins V5 pin 6 and V4 pin 6.
31. Solder all connections.
· Now do a complete alignment of the driver circuits per the manual. The grid capacitance may be a bit higher in the new finals since you may be unable to peak the 10 meter coil until changing C314 from 220 pf to 91 pf (note that the schematic shows this as being 91 pf but it was actually 220 pf). Likewise, to peak the 15 meter circuit you may have to change C319 from 68 pf to 33 pf. Also, be sure to adjust the neutralization correctly. If the neutralization isn’t correct on 10 meter, the 1 Ω cathode resistors may blow when it starts oscillating.
· Still run the final idle current around 50 ma. but since the M2057's will load up to about 700 ma., low voice peaks will run the meter up to an occasional 300 ma.
· Madison Electronics (800)-231-3057
· Antique Electronic Supply, 6221 S. Maple Ave Tempe, AZ 85283 (602)-820-5411
· Handmade Electronics, 1825 Roth Ave. Allentown, PA 18104
· Standard Radio, 360 Rabro Dr., Hauppauge, NY 11788 (516)-234-3330
· Kurluff Enterprises, 4331 Maxson Rd., El Monte, CA 91732 (818)-444-7079
· Richardson Electronics, Ltd. (800)-348-5580
If you own an HF-700S, you can dramatically improve your audio gain, by clipping out the connection from the side tone circuit to the grid of the audio amplifier tube. It will cut down the side tone, but it should dramatically improve audio amplification.
Shrink tubing. In addition to using it for insulating wire connections, it is excellent for "shoring up" coil forms that may be coming apart - the wax coated cardboard coil forms that sometimes start to unravel. Take the larger shrink tube, expand it a bit with needle nose pliers, slide it over the form that is coming apart and heat.
Coil Forms. While we are on the subject of coil forms, a useful product is plumber's teflon tape. Wrap it around the ferrite slugs that may be too loose (or too tight) and it will smooth things out for the next alignment job.
Cooling, Cleaning, Lubrication, Grounding. A few simple preventive maintenance type items will greatly improve operating efficiency, including: proper cooling of your radio, keeping your radio clean and lubricated, and properly grounding the radio. Poor grounding is the source of many operational problems. Just remember that ½ of your antenna system (electrically) is your ground.
Check Ground Effectiveness. So how can you check the effectiveness of your ground? A suggested check, based on a skilled computer controlled machine tools technician’s recommendations, is to measure the resistance between your equipment and ground. For a ground system consisting of a 1" ribbon cable hooked to a 1" copper cold water pipe that goes directly to the city hook-up, about 0.1 Ω resistance was measured. The technician indicated that anything less than one Ω was a good ground for his equipment.
Do you want the carrier balance knob to be positioned straight up when the carrier is nulled? One approach might be to change resistors on each side of the deflection plate circuit to bring the balance control back to the "noon" position, however this has proved unsuccessful. A simple answer suggested by John Bruchey was simply; "change balanced modulator tubes." It seems they are all a bit unique and deflect differently. With one or two tube changes you should find one that is just right. So, with a little tube swapping, all your rigs can have carrier balance knobs that point straight up when carrier is nulled.
Never, has any subject brought more requests than that of neutralizing finals. Even with decades experience performing the task of neutralizing final(s) on Swan radios, one will not "know it all" by any means. However, based on such lengthy experience the following observations are relevant.
Matched Tubes. First, lets talk about matched pairs of finals and that wonderful little gizmo known as a resonator. The question "must I use only matched finals" is certainly a frequent and important one. Some have never used a so called matched pair of finals, but always use tubes from the same manufacturing lot and have had good results.
Resonator. What is a resonator, what does it do, and how do you know if a tube has one on it? Answer: After asking a number of people, their purpose is still not known. Vendors who sell tubes don't even know what they are and whether their tubes have them or not. However, stay away from finals that have them! They can be found on 6LQ6 and 8950 types. The tubes that have them can be identified as follows: Looking from the top of the tube you will see a wire that connects between the plate cap connector and the actual plate. If there is a piece of metal about the size of a dime welded to the that wire, you have a tube with a resonator. If you have problems with the radio not wanting to neutralize, this is most likely your problem. A HF700s that was difficult to align had this little resonator on one of his finals – replacement of the tube resolved the problem.
Resonator and Grid Lead Radiator Issue. [Editor Note: These comments are made in addition to information originally posted on the Newsletter, based on recent Reflector discussion.] Back in the 70s and 80s, the term resonator was used by some when referring to the grid lead radiator. Since it was seldom described to anyone what the grid lead radiator actually looked like, the "getter" was occasionally mistaken for the GLR. There was also some misleading information as to what the GLR did. When all attempts to neutralize a radio on the higher bands failed, differences in the getter ring location (top or side of the tube) were noticed and it was assumed that the ring was affecting the neutralization capability – most likely these tubes did not contain the GLR. All PA tubes have a getter ring someplace in the tube while only half of PA tubes built during the late 70s and early 80s contained the GLR (See Compendium discussion). To complicate matters further, its quite possible, because of the complex interaction of components (especially at higher frequencies) to substitute a tube that contains the circular getter in the top for one that has it placed elsewhere and have the transceiver neutralize successfully, even though neither tube contained the GLR!
Noting the "matched" pair finals and the resonator issues, there is one simple thing you should always remember about final neutralization whether yours is a 1 tube radio or has multiple tubes in its P.A. A radio is properly neutralized when maximum output power (watt meter reading) occurs at precisely the minimum dip when tuning the P.A. PLATE and the radio is fully loaded. This condition will occur on a properly neutralized radio when it is tuned for maximum output power, and does not necessarily occur at lower power levels. This means that if your radio puts out the most power somewhere either side of the dip mentioned, your are not properly neutralized. If you remember this, you can "monitor" how well your radio is neutralized and this will certainly contribute to longer tube life and less potential for RF interference. If you don't understand anything else about neutralization but this, you have all the knowledge required to neutralize your radio.
Brief Neutralization Theory. Basically, the inner electrodes of tubes have differing capacitances and may sometimes feed back. Neutralization involves coupling some capacitance of the output energy of the tube to its input. By doing this, a cancellation of out of phase (undesirable) energy can be accomplished. (See the A.R.R.L. handbook for more detail)
Swan Neutralization Procedure. Swan has developed a somewhat elaborate method of P.A. neutralization as detailed in their manuals. This method is usually good enough to get any given rig into the ball park, but often (especially on 10M) the method alluded to previously works better. Use the Swan manual method and then load the rig up for maximum power output and fine tune the neutralization capacitors for maximum output at P.A. PLATE dip. Note - since the radio's cabinet and our bodies can adversely affect any given amount of capacitance, it is important (especially on 10M) that the bottom cover of the radio is on and that a well insulated screw driver is used to minimize additional capacitance from our bodies or surrounding objects.
Tune-Up Problems and Neutralization. Often tune-up problems occur when a rig is not properly neutralized. If your rig seems to be acting strangely, be suspicious that your radio is improperly neutralized. Things like funny screechy noises, pops, or sparks along with erratic meter indications are often symptoms of improper neutralization. Poor tube life and/or one tube glowing red hot when the other doesn't are also symptoms of this problem. Sometimes these problems will occur on one band and not another.
Evidently problems with this procedure were often encountered by Swan customers, because they issued a detailed supplemental sheet produced by Swan to help their users with this procedure. It is included with this Newsletter. (Not included in this summary).
Contributors. This section included information from Dave (WA0PND), John Bruchey, Dean (WA9AZK) and others.
Here are two relatively simple and inexpensive things that will significantly improve that environment and save you money and time.
· First, put a fan on your final amplifier enclosure area. Just pop rivet a 4" muffin fan to the outer cabinet right on the side of the radio.
· Second, remove the sheet metal skirt and the cover plate around the final deck enclosure and spray paint them with a flat black paint. Not only does the black color help to transfer heat away from the tubes into the sheet metal, more importantly, It reduces the possibility of focusing light energy back to a sensitive element within the final tubes. Always disconnect your power supply and ground out the plate connectors before working in this area of your radio.
There are a number of ways to keep band splatter, RFI and other annoying problems to a minimum. The roots of a good, clean signal come from practicing the following basic principles:
· Use proper tune-up procedures, which means for a Swan, tuning for maximum power output.
· Use an appropriate microphone gain, which means audio peaks should not exceed 50% of maximum P.A. current (dip at tube resonance) at maximum power output. This is usually about 175-200 M.A. on rigs with 2 tubes in the final, and 100-125 M.A. on single tube units. See your operating manual, and remember radios with weak final tubes might require a reduction in audio peaks (applying the 50% guide line above).
· Use a matched pair of properly neutralized final(s). See also the Swan Newsletter Issue 5.
· Use a good, low resistance direct ground. That means eliminate all sorts of "octopus" ground wires which can often create more problems than no ground at all. The best ground arrangement is to have only 1 ground lead (as short as possible) going to one rig at a time. An added benefit to good grounding is elimination of RF into and on your microphone, cleaning up your audio and minimizing "microphone bite!"
· Use a good, clean, tight, properly tuned antenna installation. No loose connections, please.
· This doesn't mean that the vast number of consumer products most of us and our neighbors have in our homes will not experience R.F. detection or overload, but using the above is a good first line defense against problems being generated at your station. In over 30 years of hamming there are no better practices to keep it clean!
A detailed service tip on maintaining those fancy smooth, backlash free tuning assemblies found on most tube Swan radios is given below. The sketch and information may help with a tuning knob that is hard to turn. After many years, the old grease will dry out, making it hard to turn. The procedure described will make it work very smoothly, just like new again. (John, WA7JPV)
· To lubricate the dial clutch assembly:
· Remove high and low speed knobs.
· Loosen (2) set screws through access hole. Remove nuts and star washers. Outer clutch assembly will now slide off of inner shaft.
· A bath of the clutch assembly in a solvent like rubbing alcohol with a good scrubbing with a tooth brush is advisable.
· Put grease into inner end of outer clutch assembly and push onto shaft. This will force grease into the clutch assembly.
· (NOTE): To reassemble, care must be taken to align all parts or the assembly will bind, making it difficult to turn.
· Reinstall the clutch leaving the bolts loose enough so the spacer ring can be moved. Install the low speed knob only. Snug up the clutch set screws, then back them off just enough so the clutch will rotate on the inner shaft without turning the dial.
· If the dial moves, readjust the spacer ring slightly. With proper alignment, the tuning knob will rotate freely without moving the dial.
· At this point carefully tighten the (2) bolts that hold the spacer ring and clutch. Then tighten the (2) set screws on the clutch assembly.
· Remove the low speed knob and install the high speed knob. Reinstall the low speed knob.
A number of small little helpful tools or test switches are helpful when you service radios.
A.6.4.1. Foot Switch. Try making a switch so you can engage it with your foot, leaving your hands and eyes free to work where they should. Since we are always having to push the push-to-talk switch to set idle current or off-set carrier for neutralization, such a aid will be a real convenience. It can be any type of momentary switch with the appropriate wire and jack mounted to a small project box, or even a piece of wood. Remember, the center ring of the plug is the PTT connection!
A.6.4.2. Relay Cover Removal. Ever try to "lift" the plastic cover off the K-2 relay for cleaning? Take one of those small (give away) screwdrivers, heated up the tip with a blow torch and quickly put it in my vise and bent it just shy of 90 degrees leaving about a 3/16" leg. It is ideal for inserting under the relay lip to release the tabs that secure the cover to the base.
All amateur transmitter/ transceiver manufacturers of the vacuum tube era suggested, strongly recommended or flat-out dictated that only matched final power amplifier tubes be employed in their equipment. And, there are good and sound reasons for this; all geared to ensuring optimum performance and maximum tube life.
Same Generic Type. Obviously, all tubes in a set must be the same type (all 6LQ6's, all 6HF5's, etc.) Second, but not always an absolute necessity, tubes should be of the same brand - all RCA, all GE, etc. Third, and again not always a concrete requirement, the physical appearance of each tube in a set should be alike. The reason for this is because many tube manufacturers did not build every tube they sold. They routinely supplemented their own production with tubes from other makers. Since the country of origin is required on each tube sold in the USA, it is not uncommon to find, for example, two Westinghouse 12DQ6's, one made in the USA by General Electric and one made in Hungary by 'Slobovik Valve Co.' or the like. The two tubes don't look the same dimensionally, yet both have the Westinghouse label.
Similar Electronic Behavior. Next, each tube in a set must behave very similar to each other tube in that set. Sets may contain more than two tubes. Drake transceivers need (3) 12JB6's or 6JB6's, SBE SB1-LA and SB2-LA linear amplifiers employ (6) 6JE6/6LQ6's and the Galaxy 2000 sports (10) 6HF5's. In each case the tubes are wired in parallel and must share the load equally. Meaning, all plates are connected together with a common high B+ supply voltage, all screen grids are connected together to a common medium B+ voltage, all control grids are connected together with a common adjustable C- bias voltage and driver input circuit; and lastly, all cathodes are connected together to ground or a metering circuit.
With all appropriate voltages applied to any of the equipment mentioned above, current will conduct from the cathode to plate in each tube at a rate determined by the bias voltage setting. Using one of the most successful amateur transceivers as an example, the SWAN-350 bias control can be set to a position which will limit current to 50 ma. The cathode current meter is reading combined current which means the 6HF5's are conducting 25 mA each. Two 6HF5's are employed in order to double the power of a single 6HF5 - no other reason. The combined cathode current with no signal or drive is referred to as 'resting,' 'platform' or 'idle' current. Sort of a positioning of the launch point where the tubes can start their distortion-free amplifier duties.
What if the 6HF5's are not matched? And, this will almost always be the case if two tubes are pulled from stock at random. Plug in these two fellows and set the idle current to 50 mA for a real surprise. With any of several methods, measuring individual tube currents will show one tube conducting as much as the whole 50 mA while the other is conducting as little as zero. To make this a little clearer, we'll put numbers with both tubes - one conducting 40 mA and the other 10ma. The cathode meter reads 50ma, and the operator has no idea of the mismatch. Since the gain (amplification ratio) of each tube is roughly the same, by modulating in SSB enough to kick the cathode meter to about 20 0ma (remember about damped meters - this 200 mA is only about 1/3 of what's happening in the tubes during SSB) one tube is peaking 115ma and the other 85 mA or less since they don't always track evenly up the power curve with the same 30ma lag that existed at idle.
Get the picture? With unmatched tubes, one could be flat-topping while the other loafs. Things could be even worse. In reality, when analyzing (100) 6HF5's in the lab to identify matched pairs, the range of cathode currents observed under full voltage test conditions may start as low as 5 mA to perhaps 120 mA per tube. Can you imagine these two extremes in your rig? After biasing this combo to 50 ma, one tube would be so far into cutoff that any signal reaching the linear portion of that tube's power curve would sound like rattling castanets. The other tube, carrying that 50ma idle current soon becomes overheated and with the operator using the cathode current meter as a guide, is probably driving the pants off this tube trying to get peaks up to 200 ma.
During the matching procedure, all voltages are fixed; even the bias supply. Then, the resulting cathode currents are recorded and graphed for each of the (100) 6HF5's. By examining the graph we can spot the tubes that behave similar to each other. For instance, looking at the middle of a typical test graph we might observe that (1) 6HF5 conducted 71 ma, (4) 6HF5's conducted 70 ma, (1) 69 ma, (2) 68 ma, (1) 67 ma, (3) 66 ma, (6) 65 ma, (1) 64ma, and so on. Note the (6) 65 mA - that represents (3) matched pairs or (2) matched triplets or (1) matched set of six. Therefore, (2) 17 mA or (2) 45 mA or (2) 68 mA reading tubes would be perfectly satisfactory for use in the SWAN 350. These three different cathode currents, even though exactly the same test voltages were applied, results from very small differences in the placement of components inside each tube. So, as long as two or more tubes conduct similar currents, they are considered to be matched. In the case of our SWAN - 350, the adjustable bias voltage control permits us to accommodate the small assembly inconsistencies by actually dialing in the proper idle current, but that's not a substitution for proper tube selection."
Contributors. This section included information from John (WA7JPV), Stu (K4BOV), Dean (WA9AZK) and others.
When properly maintained and aligned to factory specifications, Swan audio quality is very difficult to transcend by any manufacturers amateur equipment past or present. And, it would be a shame to see these handsome rigs spend any more time in those dark hideaways just because that pesky drift appeared too tough to tame.
By mid 1965, anyone comparing ham gear based on price and performance, easily saw the Swan 350 as an exceptional buy. And not surprisingly, the Swan 350 soon became the hottest selling transceiver of that period. Even to this day the model name "Swan 350" is still the most recognizable of all Swan products. However, within a year or two of regular use, a lack of frequency stability began to appear and gradually worsened to a point of frustration and embarrassment to the user.
Although increased attention was directed toward VFO integrity in later Swan equipment, the same problem tended to develop. Most attempts at the user level to thwart this nuisance instability involved changing anything and everything in the VFO frequency determining network. Unfortunately, this effort rarely achieved complete success.
So, why was it that Swan amateur equipment built a reputation of having poor frequency control while others of the same era did not? Plain and simple - the Swan VFO needed to produce four (early Swans) or five (late Swans) selectable, widely spaced frequency ranges in order to cover the five different ham bands with a single conversion system. Other leading equipment of the day employed a separate crystal converter for each band which allowed for use of a single range VFO, typically covering a 500 KHz spread of 5.0 to 5.5 MHz.
A single range VFO requires no switching while the multi-range Swan VFO must be switched from band to band and is therefore ganged to the main band switch via a flexible mechanical link. Under perfect conditions, one section of the VFO rotary wafer switch (located inside the VFO compartment) selects the correct VFO range corresponding to the desired ham band. The other remaining section of the wafer switch grounds out the "not-in-use" VFO ranges so as to prevent any unwanted signals. Because the switch is actually connected to components of the tuned L/C circuits, it becomes a part of the overall frequency determining network. Remember, these types of oscillators are very sensitive to outside forces. Just moving your hand close to an open VFO compartment will shift the frequency.
Through use and time, various actions result in weakening the positive contact areas of the VFO switch. Dirt, wear and corrosion on these surfaces introduce resistance and capacitance changes. And, it doesn't take much to cause the observable frequency (what you hear coming in and what the other members of your QSO hear coming out) to jump, warble or drift. Just slightly moving the VFO switch by applying pressure either left or right on the front panel main band switch knob will cause frequency movement. Stu, K4BOV.
Clean and/or Replace VFO Switch. Well, it's not always easy. If cleaning the VFO switch does not reduce the problem, a new, unused or otherwise unworn switch of exact contact layout should be substituted. After disconnecting the old switch you can prove to yourself that the switch was at fault by hardwiring one band at the points previously made by the switch contacts. This simulates a single range VFO. Under this set-up any drift should be minimal and, if evident, merely warm-up related. By selecting 80 meters for the hardwiring test on the earlier 5.1745 MHz IF transceivers, the 20 meter band is automatically operational as both bands utilize the same VFO range. Additionally, when connecting 40 meters in this manner, the later 5.5 MHz IF equipment can be easily aligned to operate on 17 meters as both bands use the same VFO range. (The green scale on late Swan VFOs is already calibrated for 17 meters)
Warm-Up Drift. Should correction of warm-up drift be considered essential, positive and negative compensating capacitors are available to "tighten" things up.
External VFO. In the event changing a worn VFO switch is not an easy task for the user, an external VFO is the next best move. Most Swan external VFOs did not develop any serious drift problem. And, any external VFO manufactured between the time of the Swan 240 and the Swan 700CX can be made to operate any Swan of that period, even the 600T and 600R twins. Some being directly interchangeable and others requiring one or more minor wiring changes. Some pruning of the tuned circuit coils and calibration is also required when using the late 5.5 MHz IF designed VFO with early 5.1745 MHz IF transceivers and visa versa. When using an external VFO with any drifting Swan, the control circuitry of the model 22(B) VFO adapter and similar circuitry built into later VFOs should be reverse wired for optimum results. That is, you want the external VFO to be "A" and the internal "B". This means the highly stable external VFO is transceiving in position one and is the transmit only VFO in position two. So when operating split frequency, the internal VFO is receiving and therefore any drifting on that VFO is only noticeable to the user who can re-adjust the VFO to his own liking as needed without affecting the transmit frequency.
Crystal Control. Crystal control is another option. All Swan crystal controlled external oscillators can be made to operate any of the equipment discussed. These units hold up to 10 crystals and employ a vernier control to flex the crystal frequency over several KHz for tuning refinements. Since production of Swan crystal oscillators was much, much lower than the variable oscillators, they are somewhat hard to come by. However, all Swan VFO boards are convertible to crystal control and can be outfitted with the same type vernier as a means of tuning the crystal over a 4 or 5 KHz range. Plus, remember that in early Swans, the 80 and 20 meter bands employ the same VFO range. So one crystal would get you on both bands. For example, the crystal required for operating around 3920 KHz. And we say "around" because the exact frequency is factored in only when we know the precise setting of the carrier oscillator and whether normal or opposite sideband is desired. But, we can get close enough for the vernier to put us right on.
Calculate as follows: 3.920 MHz + 5.173 MHz carrier oscillator frequency = 9.093 MHz crystal frequency. Looking at that same crystal we also see the 20 meter frequency: 9.093 MHz + 5.173 MHz = 14.266 MHz operating frequency.
Crystal Manufacturer. The original manufacturer of Swan crystal filters is:
K & L Quartztek, 20 South 48th Avenue, Phoenix, AZ 85043, (602) 272 7944
Be Very Careful in working with tube radio voltages, especially with the 900+ High Voltage use in the power amplifier section. Disconnect power supply from the radio when making the changes specified below. Unplugging the AC plug is insufficient, as at least 30 seconds or more will be required for the power supply HV bleeder resistor to drain the 900 V stored in the power supply filter capacitors and connected to the P.A. tube!
· Disconnect the power supply from the radio, remove the main top cover of the radio, and remove flat cover HV cage, connect radio up to a 50 Ω dummy load.
· Put (or leave) final tubes to be matched in radio.
· Connect radio up to power supply. "BE VERY CAREFUL."
· Tune radio up as usual into dummy load. (any frequency is OK)
· Push PTT and set resting current to say, 100 to150 mA (not to critical). Don't touch setting again until all testing is done.
· Disconnect power supply. "THIS IS IMPORTANT."
· Disconnect "one" of the two plate connectors hooked to the top of the final tubes. (note which one it is)
· Connect Radio to power supply again. "BE CAREFUL"
· Turn radio on and let warm up. (2 or 3 minutes)
· Push PTT and note new resting current. It should be less than previous setting. Write it down.
· Disconnect power supply again. "BE CAREFUL"
· Hook up plate cap to final tube where it was previously removed, and remove the (other) plate cap that was connected.
· Connect radio to power supply ("BE CAREFUL"), turn on radio and let it warm up again.
· Push PTT and note resting current. Write it down.
· Do this for all final tubes. Matched tubes should have resting currents within about 10 mA or less of each other for best results. If they don't, keep trying other tubes until a match is obtained, or get a matched pair elsewhere.
One tool frequently used is the promotion type screwdrivers, often given away as advertisements. Place shrink wrap tubing over the metal shaft so when you neutralize finals you don't short out the screwdriver against the bottom cover on the rig. Another "tool" used frequently is a good quality, small flashlight. While this is not technically a tool, it is sure necessary for the serious Swan repairer!
Power to “S” Unit Relationship. Recall the relationship between power and signal strength - doubling of power represents about ½ “S” unit (3 dB to be exact).
Need for Linear Amp? Understanding this and if you still insist upon using a linear amplifier on the back side of your already powerful Swan, it is a good idea to have ALC (has many names, but Automatic Level Control will do) hooked up. The powerful Swan would otherwise overdrive most linear amplifiers.
ALC Mod. To add an ALC circuit, simply install a 100 KΩ ½ watt resistor in series with pin #1 of the 6EW6 (12BA6 later units) 1st IF Amplifier. Then install a 0.01 μF capacitor between the output side of the resistor and ground. An RCA jack is then mounted on the rear with the center conductor connected by wire to the junction of the resistor and capacitor. Hope it helps keep the splatter down! (Drawing is displayed on original page - If needed, send SASE to WA9AZK.
Title, Source and Date on publication of 94 separate Swan related articles on modifications, reviews, service bulletins are available. Many of these articles are held in our archives by Norm/W7RXG. If you desire this list, (all on one page) send SASE to K4BOV.)
Contributors. This section included information from Monte (N7OQV), Stu (K4BOV), Dean (WA9AZK) and others.
Many Swan single sideband transceivers became 36 years old this year. Remarkably, this 1st generation of Swan radios and the 3 and 5 band units that followed continue to maintain a significant presence in both American and foreign amateur communities. Few electronic devices for any purpose have achieved such tenure. With the pool of capable tube era service technicians dwindling to near nonexistence, it becomes apparent that Swan owners must themselves be prepared for the task of troubleshooting and isolating ailing radio circuitry. In order to carry out these future tasks, our motto "Know Thy Swan" is absolutely the order of the day.
A.8.1.1. Troubleshooting. First off, the pioneers of Swan radio prepared operation and maintenance manuals that included only a voltage chart for circuit values reference. During that period which saw the single-bander and then the 240, 400, 350, 500 and 500C models, the engineering and technical writer staffs reasoned that isolating defective components would be best accomplished through observation of circuit voltages. TIMES HAVE CHANGED! Today, amateur radio enthusiasts do not routinely work with or experiment with the lethal high voltages associated with vacuum tube radio equipment. Therefore, for the sake of safety the most basic non-hazardous approach to troubleshooting is resistance measuring.
A.8.1.2. Resistance Chart. This line of thinking requires that a resistance chart be produced showing the measured values found while the radio was in good working condition. So, when something does go wrong beyond tube failure, there will be a means of comparing working radio and non-working radio circuit resistance figures. A resistance chart layout can look similar to the voltage chart shown in any Swan manual. In addition to listing all tubes for the given model to be examined, include lines for K1 and K2 relays, VOX socket, Jones plug, and accessory socket. The resistance readings at these non-tube locations can be important in many situations. For example, each model of radio had 2 or more series and the owner may not possess the schematic which relates to the series on hand. The model 350 (64-67) evolved through 4 series where the K1 relay in each series controlled different functions and/or switched different valued components. Also, K2 was a 2 pole relay in early and 3 pole in late 350 series transceivers. Remember, it is essential to keeping on hand a complete record of circuit parameters that exist when your radio is operating properly. Also, after tube checking and visual inspections for breaks, burns, etc, the most basic non-hazardous approach to troubleshooting is resistance measuring. Further, a resistance chart must be prepared by the owner because such aids where not included in most Swan manuals
Redundant Measurements. Since there are 100 or more measurement points, it's not hard to make a mistake somewhere in the process. So, if one has the time (this is good training, too!) make the measurements again and record them, comparing one to the other.
Safety. Remember, all measurements are made with the power supply disconnected from the radio (and maybe stored in a separate room - You never know!). Do whatever it takes through testing or calibration to make sure your Ω meter is accurate as possible.
See the Swan Newsletter, Issue 2 for this information.
Introduced in 1965, the Swan 117X universal power supply remained in production for more than a dozen years. Without any change in design it was produced longer and in greater numbers than any other Swan product. The "universal" meant it was capable of both AC and DC operation. In order to accomplish each mode using a single power supply, a rather interesting power transformer was required. In this case, the 117 VAC primary and high, medium and bias voltage secondary are of standard construction. The low voltage winding, however, is actually an 18 VAC secondary with 9 VAC and 12 VAC taps. With AC operation, the 12 VAC tap is selected through connections at the 15 pin Jones connector and feeds filament, lamp and relay current to the appropriate output terminals.
For the DC mode, an inverter (the Model 14X or later 14C) is attached to the rear of the power supply in place of the 15 pin Jones connector. With 12 VDC applied, the inverter flip-flops (like an AC generator) the battery voltage across the entire 18 VAC winding which is now operating as the PRIMARY. All output voltages exist just as with AC operation except the 117 VAC winding has become an un-terminated secondary. (If desired, light AC loads, such as a lamp, solder iron, electric razor, etc., can be powered here when a proper receptacle is mounted.)
The purpose of the foregoing was to point out the uniqueness of the 117X power transformer. And, the probability of not locating an exact replacement should the original fail. Well, with so few Swans going mobile these days, the "universal" transformer is no longer an essential item. Standard power supply transformers can now be salvaged from other manufacturers equipment to accommodate modern day needs. In some cases it may be desirable to employ the complete power supply and/or speaker cabinet of another manufacturer. The power supplies listed below are capable of running most Swan transceivers to at least the power levels indicated. All need a 12 pin Jones plug installed or existing plug rewired to conform with the Swan configuration. Some require one or more minor changes to ensure correct output voltages.
Make/Model SSB PEP Capability
Drake AC-3 325 watts
Drake AC-4 325 "
EICO 751 250 "
Galaxy PSA-300 700 "
Galaxy AC-35 400 "
Galaxy AC-48 250 "
Galaxy AC-384 600 "
Galaxy AC-400 700 "
Hallicrafters PS-150-120 350 "
Hallicrafters PS-500 650 "
Heath HP-23 250 "
National AC-200 250 "
National NCXA 300 "
National AC-500 700 " (HV:1100 VDC)
Tempo AC ONE 375 "
The Swan Electronics Corporation Model TCU Transmitter Control Unit is designed to operate in conjunction with the Swan SW-240 Single Sideband Transceiver to provide:
· Separate VFO for non- transceiver operation
· Extended coverage of the 80 meter CW band
· Reception of WWV or WWVH on 15 MHz
· Voice Operated Transmission (VOX)
· 100 KHz Crystal Calibrator
Minor modifications to the SW-240 are necessary. All hardware, modification parts, and mounting instructions are furnished with the TCU. The complete unit is housed in a cabinet which matches the SW- 240 Transceiver. Provisions have been included to mount the SW-117B AC power supply within the TCU cabinet to provide a complete, compact installation with all of the desired operating features.
1. WWV - 15 MHz
2. 80 M 3,500 to 3,650 KHz
3. 75 M 3,650 to 4,000 KHz
4. 40 M 7,000 to 7,300 KHz
5. 20 M 14.000 to 14,350 KHz
Front Panel Controls: VOX Gain, Anti-Trip, Main Tuning, VFO Selector, VFO Range, Calibrate ON-OFF.
Audio Output: Audio output through built-in 3" by 5"speaker, or by phone jack on front panel.
Power Requirements: All power requirements are supplied through 12 conductor cable from the
Dimensions: Width 13¼" Depth 11" Height 5 5/8"
Weight: 8½ pounds without SW-117B power supply.
Note: Rare complimentary 1963 Swan 240 External VFO specification sheet.
Contributors. This section included information from Stu (K4BOV), Dean (WA9AZK) and others.
Way back in Issue #1 of the "Swan News" a brief article stressed the importance of disconnecting any wires from pin #6 of the 6GK6 Driver tube socket. In the early days, Swan used this tube socket connection as a sort of terminal strip that made its way to ground. Well, it turns out that later versions of the 6GK6 tube tied that pin (internally) to the screen grid. Not so good! If your pin 6 is tied to ground, and you replace a driver tube with one of these newer style tubes (only about 25 years old), you will take out a 100 Ω resistor, an RF choke and the new tube! Therefore, each time you acquire a "new" rig, or work on an old one or a friend's rig, take the 30 seconds it takes to snip any connection to pin 6 and isolate it totally.
A.9.2.1. Voltage Chart. Now we will focus on the next step which involves voltage measurements. All Swan manuals did include a voltage chart, however, the accuracy of the values could not be fully relied upon due to many factors such as the variation in power supplies and capacities, and the many production changes to equipment that resulted in completely different circuit paths.
Voltage Chart, Measurement Points. It is known that voltage charts were not always updated to accommodate later runs of the same model radio. Additionally, the effect of accessory and modification loading was seldom addressed. With many of these radios being over 30 years old, there are few that have escaped the wrath of repairs, modifications, etc., and thus, a new voltage chart must be prepared. It can be patterned after the manual version, but additional check points should be added. For the purists, this would mean a space on the chart for the VOX and VFO socket and 12 pin Jones plug. It's a good idea to make up several copies of the blank voltage chart for any possible down the road tests. Always affix the model and serial number of the transceiver and power supply somewhere on the associated chart - even the date of test is good for record keeping.
Safety/Accuracy. With all clerical preparations complete, the next consideration is with safety and accuracy. Studying voltage levels in vacuum tube radio circuits can be dangerous. Therefore, extreme caution is mandatory during the voltage measuring process. For some, it will be necessary to review safety precautions connected with the handling of open electronic equipment and use of multi-meters. If one is the least bit apprehensive about a face-to-face encounter with the voltages awaiting, it would be wise to seek the assistance of someone experienced in electronics troubleshooting, as the information here would not be sufficient to provide adequate guidance on important safety measures.
Purpose. The intent here is to bring to light the need for having the circuit voltages or "vital signs" so to speak, of your properly working radio down on paper in the event you need to compare a "good" radio with a "broke" radio. Finally, a few pointers. The plate voltage to the Power Amplifier (finals) stage is applied at all times in Swan transceivers when the power is turned on regardless of whether in receive or transmit mode. Never remove the P.A. cage cover with power on. Think of it as a "rattlesnake in a cage." Of course, there are exceptions to any rule - most skilled and long time technicians are careful enough to work without the protective cover. But for now, we are measuring, not working - so, keep the lid on it!
Accuracy. Next, is accuracy. That's the whole idea, to refine the values provided in original Swan voltage charts to match those unique to the current radio readings. This means meter accuracy of less than 5% error.
Calibration Standards. Without precision calibration equipment, some Swan transceiver circuits can be employed as standards. For instance, the early Swans employed voltage regulator tubes to keep carrier oscillator tubes stable. The OA2 in Swan-350, 400, 500 and early 500Cs and 350Cs for example, can be used to set your meters at 150 VDC. The VFO zener diode that provides the regulated -10 VDC for early Swan VFOs and -12 VDC for later units can be relied upon for calibrating the lower range of voltmeters. Make sure which diode you are dealing with though, as many of these have been interchanged or replaced by other values. The Swan VFO does not care whether -10 VDC or -12 VDC is in place regardless of radio vintage. In fact, anything from -9 VDC to -15 VDC will work fine. It's the voltage regulation that counts.
Redundant Measurements. It's good practice to make all measurements a second time on another blank sheet, then comparing the two. Since there nearly 100 possible check points, it's not hard for even the best of us to make an error.
A.9.2.2. Technical Questions. Note: Stu will be happy to help you with your technical questions. You can FAX him at (607) 936 2463, e-mail: firstname.lastname@example.org (or our collective e-mail: email@example.com) or to K4BOV with SASE. Include serial numbers of equipment to be discussed.
See Swan Newsletter, Issue 4 for this information.
The topic of grounding comes up from time to time, and it is certainly one of the most important aspects of equipment installation. Think of ground as a place, a large receptacle, for electrons to flow and disburse. Also, in the event of RF energy, ground holds a lot of the same role.
A.9.4.1. Ground Problems. When we transmit, we subject ourselves, our surroundings, and our equipment to relatively strong electrical fields. Improperly protected from these fields, all sorts of strange things can occur. The most consistent one of these is audio distortion. This usually occurs because the strong RF field enters in any number of places in our communications system. It could be introduced into one of the stages of our transmitter, through our microphones, back through our coax, or even through the electrical system that provides power to our radios (115 VAC lines). So, how does grounding prevent these problems from occurring, and what is the role of grounding?
A.9.4.2. Lightning. Grounding plays more than one role. First, by having a good low resistance ground for all your equipment (including your antenna), you provide a better, less resistant path for excess electrical energy to be dispelled to ground (e.g. a direct or nearby lightning strike). It has been said, "A well grounded antenna system is more likely to be struck by lightning, so why improve the chances of a strike by grounding?" Probably true, but look at the alternative! Think of it this way: If you drive without insurance, you will be more careful and, therefore, you will be less likely to have an accident. Not a good choice.
A.9.4.3. RF Ground. The other thing grounding does is "bleed" off RF. If your rig and associated equipment is properly grounded, you will send the powerful RF, that so much likes to get into everything, on a trip to hell. So if you have distortion in your audio, or get "bit" by that old D104, then look to a better ground for your solution.
A.9.4.4. Ground Configuration. What is a better ground?
Ground Rod. Here there are many opinions, but one thing can't be debated, the bigger (such as in wire gauge, pipe size, etc.) the better. When I say "big", I mean less resistance. So, don't be afraid to use a great big piece of major gauge wire for your ground, and the further away from the ground, the more important this becomes.
Multiple Ground Rods. It is probably true that multiple grounds are a good idea, too. Think of it this way. If your rig is throwing off a lot of RF and your ground is sending that RF to a cold water plumbing system within your house, chances are everything that is electronic is hooked to that same ground. what if the piping system is a wonderful conductor? And copper pipe is a wonderful conductor. What if the ground portion of that system isn't perfect, but the circuit is? Get the picture? Not only that, most telephone systems are also connected to the plumbing system. So, theoretically at least, a separate ground for your radio, your antenna, the phone and the electrical system in your house would be less likely to "cross-feed." Real life experiences have shown situations such as relocating a ground connection to eliminate an annoying hum in a phone system. Presumably the regular electrical system was feeding back into the phone system through the plumbing system. Once relocated, the problem disappeared. Also, how many of us have experienced microphone bite because we weren't properly grounded?
Our own Gary, VE4YH - see his Virtual Swan Museum at: www.pcs.mb.ca/~standard/
Visit AADE's Swan Radio Room at: www.aade.com/hampedia/swan/swan.htm
Front panels from late 1967 Swan 350s are not interchangeable with earlier panels and vice versa. The P.A. PLATE and Course Load controls are mounted higher on the early units. If a non-matching panel MUST be installed, new shaft holes will need to be drilled in the panel.
The Swan 400 was Swan's first 5 band amateur transceiver. At the time it went into production, the Swan 350 was already on the drawing board. The 400 sold well until 6 months later when the 350 was released. The rage at the time was for transceivers that employed built in VFOs, so the 350 quickly out paced the 400, as an external VFO was required for the latter. Even though the 400 had a slightly longer production period, only about 1200 units were built compared to 9000 of the popular 350. At the end of 1967 both models were discontinued to make room for the new 350C and 500C transceivers. But, the 400 was too good of a radio to retire completely. With a few minor changes in order to accommodate non technical operators and operation outside the ham bands, the 400 found service with military, industrial and commercial customers. Sales to those groups continued for over 6 years as the 400, initially dubbed the 400F, then the 400G, and, finally the 400H. The commercial 400s went completely unnoticed by the amateur ranks, and it is still equally unknown today that the original 400 design had continued production right through to the Swan HF700S - the last tube radio Swan produced. So, where'd the commercial 400s go?
Well, they are starting to turn up in flea markets, government auctions, military surplus, etc. These transceivers need only a Swan 117X or similar power supply – no speaker needed, as the 400 has a built in speaker. Specifications include continuous frequency coverage 2 through 24 MHz and limited tune-up requirements. In reality, this unit will cover 160 through 12 meters without any modification. Any Swan external VFO can be retuned to provide the necessary injection frequencies. Unfortunately, commercial use means commercial treatment. Therefore, it is difficult to come across any of these transceivers that have retained their original pleasing appearance. At any rate, should any of these radios become a part of your inventory, the service manuals are still available from Brock Publishing.
Swan User Sunday 14.250 5PM eastern WA9AZK UT Dean
W7RXG UT Norm
WA5BDR NM Jim
Swan Tech Wednesday 14.251 2300GMT K4BOV NY Stu
Swan Tech Sat 7.235 2-4PM eastern K4BOV NY Stu
K1QQ NJ Kent
Collins Tech Tuesday 3.955 8-9PM eastern W3ST P.A. Dave
Hallicrafters Saturday 7.280 1700GMT WB8DML OH Jim
Hallicrafters Sunday 14.293 1800GMT
Vintage SSB Sunday 14.293 1900GMT WB0SNF NE Andy
Heathkit Sunday 14.293 2030GMT WB6LRG CA Don
Periodic updates and further information can be found at:
Donations. Also, with the advent of computer operations and e-mail, we are not actively soliciting donations for the Swan News periodical. We will try doing it on the revenue from the publications and products available through our web pages. Feel free to forward the Swan News to those you believe would enjoy it's content.
Contributors. This section included information from Stu (K4BOV), Dean (WA9AZK) and others.
Electron tubes are still out there and available - for a price, that is. Look at what distributors want for 8950s! Not worth it - many 12 pin power pentodes will do just as good a job and maybe better. For example, the GE 6LB6 is the same tube as the GE 8950 except for filament voltage.
In order to cut costs during the final days of GE tube building, several TV horizontal output tubes were built with the same internal hardware. This means these tubes share the same rated plate dissipation. Take a look at the late 8950, 6LB6, 6KD6, 6JS6C, 6MC6, etc from GE - same plate! The 33 watt plate was selected as a common component for these tubes rather than continue the added cost of producing several different plates. Only minor socket wiring changes are necessary to make any of these tubes operate in Swan equipment.
6LF6. When going to more hefty tubes like the 6LF6, increased inter-electrode capacitance must be addressed in order to have satisfactory operation on higher frequencies such as 15 and 10 meters. This requires a small change in the RF Driver circuits to better match the output of the driver to the input of the 6LF6. Most 6LF6s are rated at 40 watts plate dissipation which will normally correlate to longer life, and, with adequate power supply capacity, more output power.
Height. Occasionally, you will find some of the 6LF6s too tall for your P.A. compartment. In this case, the socket platform can be lowered a ¼ inch or so to permit 6LF6 (and similar tall tubes) installation. RCA marketed a short 6LF6 with a unique styled 40 watt rated plate. This tube would appear to most people as a "dual plate" tube as it actually contained two 20 watt plates connected together side-by-side. Therefore the tube was no taller than a 6HF5 - it was a neat package.
For those wanting to use Swan radios to drive linear amplifiers, there are other options. First, consider that the Swan two tube P.A. radios (Swan 400 through HF700S) are capable of 250 to 400 watts PEP of SSB output. Most two tube 3-500Z linear amplifiers will do 1200 to 1300 watts PEP output on SSB. This range of power increase is about 4 to 7 dB. However, the driving power needed to see these linear amplifier levels is not 250 to 400 watts - it is about 125 watts.
Therefore, the RF output of the powerful Swan transceivers must be kept down, otherwise the grids of those 3-500Zs might start melting. A small change to the Swan 117X power supply will limit transceiver output to about 125 watts PEP for those wishing to regularly employ a linear amplifier. This change involves removing the high voltage rectifier circuit from the medium voltage rectifier and grounding the removed connection. That is, the wire from the negative side of the HV bridge rectifier, capacitor and 150 KΩ bleeder/divider resistor joint is disconnected from the positive output of the MV winding and reconnected to a convenient ground point.
This results in an output of roughly 600 VDC unloaded at the HV terminal and frees up the 275 VDC winding from having to supply current to the HV on transmit. There is no change to the transceiver at all, just reset the bias control for 50 to 60 mA and go!
Tube substitution is not just limited to plate "capped" tubes. If one has a handful of 6GE5s (used in Heathkit single bander "HW" series), 6GF5s, 6HB5s, etc, they will easily retrofit in Swan 12 pin P.A. tube radios.
With the "handful", it should be easy to find at least two tubes that are fairly well matched to each other. After rewiring the P.A. tube socket for the proper circuit configuration, the plate HV is merely fed down under the chassis (from the plate choke trough well insulated wire) to the plate pin lug. Cover the HV lug and that’s it. The RF Driver stages should be realigned after any P.A. tube substitution.
These smaller tubes will run about 125 PEP output with unmodified Swan power supplies and about 90 watts after reducing the plate voltage per the above instructions. Stu/K4BOV
Network website. Via this website, Swan enthusiasts can view a wide range of amateur radio and Swan related information. Additionally, we have made the site somewhat interactive by the inclusion of a Swan Radio QSO Room or chat room on two of the associated pages - both rooms are linked together, so, it doesn’t matter which page you enter from.
Reflector. Also, the Swan-Net E-Mail list or "reflector" was implemented at the first of the year. It is an extension of the Swan Nets and provides another method of keeping Swan owners in touch.
Silent Key. Other pages that are linked to and from the main Swan Radio Network page includes a Silent Key listing where we remember those that donated their friendship to us and have since been lost to the ages.
Trader. Our Swan and Vintage Radio Trader is one of our more popular pages where hams can list wanted, trade or for sale items.
Virtual Museum. The Swan Virtual Museum is nearing completion and will soon showcase the entire Swan Radio line of equipment. The museum can be reached through several links we have placed on the various Swan Radio information pages.
Swan owners enjoy looking at their equipment and operating it. They truly appreciate what Herb Johnson brought to life. In the late 50s, Herb envisioned the eventual wholesale transition from AM to the new and more efficient SSB mode of transmission. He also knew this rush to SSB would not happen overnight or to the degree possible without a low cost affordable radio being offered the hams of that period. During 1960, he completed the design of his original "monobanders" and soon began assembling his first 10 units in a 2 car garage at his Benson, Arizona QTH.
Forty years later, we still marvel at what Herb accomplished with such meager resources. Many of these early radios are still in operation and routinely make their way into our Swan Net sessions each week. Swan Net operations are tailored to meet the "looking at", "operating" and "repair it" needs of Swan owners around the world.
The Swan User Net meets Sundays on 14250 KHz at 5PM Eastern and continues to be the parent operating schedule. Swan operators Norm/W7RXG in Salt Lake City, UT, Jim/WA5BDR in Roswell, NM and Jay/WB6MWL in Montclair, CA rotate net control duties on a weekly basis. This net reaches national and international coverage due to the time and day of operation - an excellent place to showcase ones Swan radio.
For assistance and guidance in equipment repair and alignment procedures, the Swan Technical Nets meet Wednesdays on 14251 KHz at 2300GMT and Saturdays on 7235 KHz at 2PM Eastern. Stu/K4BOV in Corning, NY and Kent/K1QQ in Sparrow Bush, NY handle net control for both technical nets while Jeff/WA8SAJ in Willoughby, OH takes a turn from time to time with the 40 meter session.
Notch filters added cost to early radios. Since use of this item and other accessory functions such as VOX, RIT, etc were not considered essential for communications, they were not incorporated. The plug-in VOX, for example, could be purchased separately. A real IF type notch filter was never offered. However, one can be incorporated in the early Swan 350 and 400 (and even the single banders and Swan 240 with some additional components) quite easily. Only a small change is required in the four pole crystal filter.
First, let us discuss the early four pole crystal filter. Prior to mid-1965, all Swan SSB transceivers employed four pole crystal filters. The filter is readily identified by the open 5 crystal complex (four crystals in the case of a Swan 240) mounted on top of the chassis in the middle of the left side. Four crystals are connected in such a way as to produce a band pass for a small range of AF signals at a frequency just slightly above the IF. The IF in this case is about 5.173 MHz. The IF carrier signal is generated in the Carrier Oscillator stage, then passed through the Balanced Modulator and on to the crystal filter.
The carrier signal is more finely tuned by the Carrier Oscillator trimmer capacitor so that the carrier frequency is right around the lower edge of the crystal filter band pass. That is, around 5.173 MHz. The range of the band pass or "open portal" runs from 5.173 to 5.176 MHz, a range of approximately 3 KHz. Speech audio from the microphone is impressed on the 5.173 MHz carrier, and, keeping with the laws of signal mixing, an audio frequency appears slightly below the IF and one slightly above the IF. The lower frequency is attenuated because it is outside that 3 KHz band pass while the higher AF easily passes through the filter - this is the upper sideband or "normal sideband" in the case of Swan equipment.
Now, here is where the notch comes in. There is a fifth crystal mounted within the crystal filter complex - it has nothing to do with altering the bandwidth of the filter, but does a lot for reducing and suppressing any residual carrier that can’t be handled by the Balanced Modulator. This is a "shunt" crystal - it shunts out it’s own frequency. Typically, this crystal is cut for 5173.1 KHz. The IF carrier hovers around that frequency, so, any carrier that is not nulled out or filtered out by the lower edge of the crystal filter, is shunted by the 5173.1 KHz crystal.
The object now is to make the frequency of this crystal adjustable across the full 3 KHz spread of the crystal filter band pass. Simply disconnect the wire from one side of the shunt crystal, place a 50 to 100 μμf variable capacitor in series with the crystal. Connect wires at each side of the variable capacitor and run to the "T" and "C" terminals of the auxiliary relay. So when the transceiver goes into transmit, the variable capacitor is switched/shorted out of the circuit.
There are any number of options for mounting the variable "notch" capacitor. It can be placed inside a small metal box external to the radio and connected directly by tether wires to the proper auxiliary relay terminals. Or, a carefully drilled hole in the front panel can be employed for a permanent, easy access location with tuning knob and all. Rotating the capacitor in a direction that reduces capacitance moves the notch frequency up and across the band pass of the filter. The notch is extremely deep and sharp - certainly not as linear nor with the stationary width retaining features of modern notch filters, but overall, will out perform most of them.
Since more and more new hams seem to be finding a fascination with AM operation, it appears this early transmission mode is not just an old timers game. We are hearing more discussions on the Swan Tech Nets about employing various manufacturers gear for AM schedules. However, many are unsure of how safe and effective Swan radios can be for AM use.
First, Swan has always been known for excellent audio quality. This has usually related to SSB. The Swan single banders of the early 60s sounded just as good back then as the new oriental equipment of today. Very little has changed in SSB transmitting content over the years mainly because SSB is SSB. So, if a near perfect reproduction of a persons voice was produced in the early days and since the human voice and ears have not changed since, certainly there is little or nothing further to be accomplished in making it sound any different.
It can be said though, that some manufactures equipment did produce better quality audio than others - maybe not a lot better, but discernible differences none the less. Swan has an edge on some of the SSB transceivers of the 60s and 70s by using Balanced Modulator AM generation as apposed to Screen Grid Modulation. Balanced Modulator AM is about as close to plate modulation as one can get. The Swan AM mode lacks only the double-sideband process. Meaning, the RF carrier does not contain the opposite sideband audio frequency due to the crystal filter suppressing the unwanted sideband it normally suppresses during SSB operation. This has absolutely nothing to do with the audio output quality of the transmitter - it remains excellent.
In fact, efficiency is increased by not wasting the power needed to amplify the unwanted or more specifically, unnecessary sideband. The only drawback that comes to mind about "single-sideband with carrier" type AM, is at the receiving station. That is, if one is copying AM delivered from a Swan transceiver, and, has the BFO turned on, the proper SSB position must be selected in order to hear the AF signal. With the BFO off, as most AM receivers are set, demodulation of the AM transmission is normal and oblivious to which sideband is present. Just as with SSB, if the Swan radio is properly aligned and at peak form, the AM quality will be of the highest order.
A.10.8.1.Optimum AM Performance. Two comments for ensuring optimum AM performance:
· Always run a fan on the P.A. tubes. Most two tube P.A. type Swans need an idle current of about 50 ma. So, with the carrier null adjusted for about 150 mA of carrier power, this increased duty cycle, coupled with longer transmissions associated with AM operating habits, will shorten tube life unless a fan is employed. It is not absolutely required that 150 mA carrier power be the AM operating level, 125 mA or even 100 mA is satisfactory as long as modulation peaks barely trip the meter 5 to 10 mA above the carrier level. 100 mA carrier power is equivalent to about 75 watts DC input and 150 mA would be roughly 125 watts DC input.
· Secondly, consider using a separate receiver. Otherwise, unless you have a means of turning off the carrier oscillator between transmissions, you will be constantly zero beating the AM carriers of the many participants of your "round table" QSO. Therefore, A good communications receiver can really enhance AM operation by offering variable selectivity, filtering, split frequency, BFO OFF, etc. An external receiver is easily paired with a Swan transceiver. Only two connections are required - the relay terminals on the rear of the Swan are used to mute the receiver and the V6 Output plug on the rear of 500CX and later model Swans is the antenna connection for the external receiver.
On Swan 500C and older units, the V6 output must be installed - just a RCA jack or coax connector, a 5 or 10 μμf capacitor and short piece of hook-up wire or coax.
The external receiver option has an additional incentive. The antenna connection described above is actually one that takes the signal off the output of V6, the receiver RF amplifier. In other words, the signal coming into the transceiver is first amplified by V6, then fed to the transceiver receive mixer stage AND to the V6 output. Therefore, the received signal is "pre-amplified" before it goes to the external receiver, essentially, adding an extra RF stage to the front end of the receiver.
http://www.geocities.com/latemod97 This page contains all, associated links, collective E-mail addresses for contacting Swan Net coordinators, etc. Feel free to contact us with suggestions, technical questions, submission of silent key information and equipment swaps/wants/for sales. All of us are proud Swan enthusiasts and want to do whatever possible to keep you enjoying and showing off your Swans.
Contributors. This section included information from Don (N1APY), Stu (K4BOV), and others.