AMANDX PRESENTS


RECEIVER SPECS



Once you start looking for a new receiver whether it be your first or an up-grade from your present receiver all of those numbers on the spec sheets can become a little over whelming. This article will attempt to take some of the mystery out of these numbers and give you an idea what to look for when you are out looking from a new receiver. As radios go up in price you will see more features on them but the true specs of the things that count may not improve rapidly with a rapid rise in price. A higher price tag may not mean a higher grade of receiver so look at the specs very carefully.

COVERAGE- This will include all of the frequencies that the receiver can pick up. On some analog receivers there may be several bands that are covered but that does not mean you will be able to hear everything. Digital receivers also may have gaps in coverage. To insure you can hear almost everything the receiver should have specs that read:

150 KHZ to 30 MHZ inclusive. This is total coverage of all Longwave, Mediumwave and Shortwave frequencies save for the lowest of the code, teletype, and navigation stations.

530 KHZ to 30 MHZ inclusive. This covers all of the Mediumwave and Shortwave frequencies.

FREQUENCY READOUT- This will tell you how the frequency is displayed on the dial or digital readout. The more accurate the readout the easier it is to tune in the stations. Most digital receivers now have readout to 1 KHZ or Kcs. That means that the frequency display will show: 15.252 when you are on that frequency. If there is 5 KHZ readout the receiver will display either: 15.250 or 15.255 on the readout and you may have to fine tune to hear the 15.252 station. If there is no fine tuning you will have to be content with a with a weaker off frequency signal. When using SSB tuning for utility or Ham band stations this can be very frustrating. More advanced receivers have read out to 100 or even 10 Hz. This means a readout of 15.252.4 or 15.252.42. Analog receivers may have much poorer readout although there are some that do have 1 KHZ readout available.

MODES OF RECEPTION- This will tell you what type of methods of reception the radio can receive. There are several types of transmission methods used: AM- This is Amplitude Modulation and is used by Mediumwave stations and most international shortwave broadcasters.

SSB- This is Single Side Band and is used by Ham band operators and many utility stations. Some receivers may have a way to select USB (Upper Side Band) and LSB (Lower Side Band). Other receivers had a BFO (Beat Frequency Oscillator) that you can tune to select the correct Sideband.

CW- This is for Continuous Wave or Morse Code used by various stations across the entire radio spectrum.

FM- This is for Frequency Modulation which is used by a few stations above 28 MHZ and does not necessarily mean that the FM broadcast band is covered. The FM broadcast band which goes from 88 to 108 MHZ uses FM as a mode of transmission.

SENSITIVITY- This will tell you how much of a signal your receiver will have to receive so you can hear something. This is measured in microvolts. The lower the number of microvolts needed to produce a signal the weaker the station can be for you to be able to hear it. A good receiver will have a sensitivity of at least 1 microvolt from 2 to 30 MHZ. Many have lower sensitivity below 2 MHZ so as to avoid overload in the AM broadcast or Mediumwave band. A very good receiver will have about 0.5 microvolt sensitivity on SSB and around 4 microvolts on AM.

SELECTIVITY- This will tell you how wide the filters are on the receiver. The width of the filters are measured KHZ and the wider the filter the wider the radio will receive. If a filter is measured at 6 KHZ that means it will hear 6 KHZ on both sides of the frequency you are tuned to. For example if you are on 15.200 and you have a 10 KHZ filter you may get interference from stations as low as 15.190 and as high as 15.210. This can make for poor reception due to splat from near by stations. Filters to look for, when listening to weak stations and digging out those rarer stations or just plain better reception on the crowded bands would be rated at: AM filters at either 6 KHZ or for finer listening 4 KHZ.

SSB filters should be around 2.5 KHZ to 2.3 KHZ or as low as 1.8 KHZ for, for the most crowded of conditions or listening to teletype transmissions or CW.

FM filters for, for FM Wide operation should be around 150 KHZ while FM Narrow should be in the 15 KHZ range.

CW filters will range from .500 KHZ to .250 KHZ for, for sharp listening in crowded situations.

There are other specs such as Dynamic range, Image rejection etc., but if you see a receiver with good specs as per above these will most likely be of a high quality. As stated above take a close look at the specs of the receiver and make sure you are getting a unit that will do what you want it to. There is no use buying a lot of "bells and whistles" if you do not need them. On the other hand many a listener has been turned off by buying a receiver with bad specs and then wondering what the hobby is all about and why signals are so poor most of the time.

Here is a joke receiver for you to look at






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