(updated July 3, 2011) - changes to the oscillator section, resistor R4 added and resistor R2 value changed. Now Q1 does not get so warm.
A simple output network. No variable tuning capacitor is needed. Can tune-up output at T2 - 3 by increasing or
decreasing the amount of turns or wire.
- The Guerrilla - AM MF/HF transmitter, 10 watts, class-E, flyback topology.
( last update: May 13, 2010 )
- The modulator. Audio input is from the "headphones out" from
below: a build by Channel Z Radio and received over 2000 miles away on 6964 KHZ
a computer, or portable MP3, CD, or tape player.
component details and notes:
XTAL - crystal
Q1 - 2N3053 - a heat sink on this would be nice. Gets warm.
Q2 - IRF510 - heat sinked. Does not get hot.
R1 - 100,000 ohms
R2 - 47 ohms .5 watt rating.
R3 - 2200 ohms, but anything from 1k to 10k is OK here.
R4, R6 - 10 ohms
R5 - 470 ohms. ( adjusts gain of modulator )
R7 - 1000 ohms
R8, R9 - 1000 ohms
R10, R11 - 100 ohms
C3 - .01 µF disc
C4 - output shunt capacitor. for 3.9 MHz; 680 to 1000 picoFarads, 100 V., for 7.2 MHz; 470 picoFarads, 100 V.
C5 - 1200 picoFarad, silver mica, 100 V., But a compression trimmer capacitor
that covers up to around 2000 pF is best, for tuning up.
C6 - 47 µF, but anything from 10 to 470 µF is OK here, 3 volts or greater rating.
C7 - .01 to .1 µF disc ceramic
C8 - .1 µF disc ceramic
C9 - .1 µF disc ceramic or film, mounted close to the junction with T1 (also, add one near the junction with L1 )
C10 - 100 µF electrolytic, with at least a 15 Volts rating.
C11 - .047 to .1 µF
C12 - 1000 µF electrolytic, with a 12 volt or greater rating.
C13 - 2.2 µF, but anything from 1 to 4.7 µF is OK.
C14 - trimmer capacitor or small variable inductor, to change frequency a little. Or a fixed value capacitor 22 to 470 pF.
C15 - .1 µF disc ceramic
C16 - .1 µF disc ceramic
L1 - flyback inductor, 24 turns of AWG #20 or 22 on a T50-2 core.
L2 - for 3.9 MHz, 16 turns. for 7.2 MHz, 11 turns. AWG #20 on a T50-2 core.
L3 - for 3.9 MHz, 40 turns. for 7.2 MHz, 23 turns. AWG #30 on a T50-2 core.
L4 - for 3.9 MHz, 20 turns. for 7.2 MHz, 15 turns. AWG #20 on a T50-2 core.
U1 - TDA2003 - heat sinked. 10 Watt car radio audio amplifier IC.
T1 - The modulation transformer was made from a choke core, Radio Shack p/n 270-030A.
Remove the bobbin, and the wire on it. Using AWG 20 or 22 magnet wire,
wind 55 turns, stop and twist for the center-tap, then continue on with 75
more turns. The end of this winding is +Vmod, going to the transmitter.
- update: R.S. p/n 270-030A is not sold any more. Use the secondary side of a
transformer,
12 vct 1.2 amp, such as R.S. p/n 273-1352. With this set-up, you will not get full modulation in the positive direction,
due to the impedance ratio, and resistance of the wire in the transformer. But it will work, and be adequate.
(May 11, 2010) - Here is the latest modulation transformer. Taking apart a transformer, that has separate E and I sections, remove the bobbin.
Take three 12 ft. lengths of number 22 magnet wire (or better yet, 20 or 18, if it will fit) and braid them together. Then wind this on the bobbin
with from 40 to 45 turns, making it a trifiliar winding. Then wire up as shown.
This makes for a 1 to 3 voltage ratio, a 1 to 9 impedance ratio.
Full modulation in the positive direction is attainable.
. . . that's all folks, from radioanarchy. . . . . . . . .
