First QRP TX
300W HF amp
My first homebrew QRP TX was a simple solidstate CW transmitter using SL100,
SK100 and BD139 giving about 5Watts on 40 Mtr band. This circuit was popular in South India and
was known as ' VWN' circuit.
- A RFC similar to the one used in the VFO circuit is used in SK100
collector to ground end.
- BD139 Tank coil is 4.4 uH and is wound with 24 swg enameled copper wire on
a piece of polythene pipe of 1.7 cms OD & lenght 3 cms. Tap at 13th ,
15th and 16th turns. 13th tap can be used for 50 Ohms coax/ inverted
'V' Ant or 15th tap can be used for 75Ohm coax/ Dipole Ant.
- Mount BD139 on a
- Keep input current (BD139) at less
The VFO was a Colpitts oscillator using two BFW10's.
RFC in place of 1K2 Resistor if Oscillator doesn’t start
can be constructed by winding 150 turns 36 swg enameled wire on a 100K, ˝ W