JAMMER-20
A
2 WATT QRP CW TRANSMITTER FOR 20M
BY VAGISETTY KISHORE (VU3INK)
1. This is an easy to assemble 2 watt QRP
CW transmitter for 20M. The crystal used is 14.318 mhz crystal which is
the band for SSB signals. It would be better if you could procure 14.060 mhz
crystal.
2. The circuit is straight forward. It has
an OSCILLATOR stage (colpitt’s osc.) followed by BUFFER stage followed by DRIVER AMPLIFIER stage and finally POWER AMPLIFIER stage.
3. To assemble this transmitter, we must
be in possession of a good MULTIMETER and an RF PROBE.
4. The RF voltage at the emitter of Q1 (BC549)
should be 0.3V, at the collector of Q2 (2N2219) should be 1V, at the collector
of Q3 (2SC1173) should be 2.4V, at the collector of Q4 (2SC1173) should be 36
to 50V (without DUMMY LOAD). With 50 OHM DUMMY LOAD, the RF voltage should
measure between 13.6 to 15.2 volts.
5. L1 – 15 turns on (T68 – 6) toroid.
6. Equivalents for transistors used in the
circuit:
(a) Q1
– BC549, BC548, 2N2222, 2N3904
(b) Q2
– 2N2219, 2N2218, 2N3866, SL100
(c) Q3
& Q4 – 2SC1173, BD139, 2SC1162
7. RFCs - 20 turns on TV BALUN core (or) 50 turns (30
SWG wire) on ½ watt resistor. You can use commercial inductors also as RFCs.
8. Appropriate HEATSINKS need to be used
on Q2 & Q4.
9. Key Point : Based on my tests on Key Point, I have found that 'keying of the whole transmitter' is the best option. Just add a key at the power supply point.
9. Key Point : Based on my tests on Key Point, I have found that 'keying of the whole transmitter' is the best option. Just add a key at the power supply point.
73 !!
DE
(V KISHORE)
(V KISHORE)
VU3INK
