VU2JMX@BANGALORE                               

 

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Mizuho SG-9

Hallicrafters S20R

First QRP TX

6883B Linear

GE524 and GR345

300W HF amp

ICOM VHF

9851 DDS 

DDS and 16F628

HamGuide

 

          

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 heatsink.
  • Keep input current (BD139) at less than 200mA.

 

The VFO  was a Colpitts oscillator using two BFW10's.

  • Use RFC in place of 1K2 Resistor if Oscillator doesn’t start
  • RFC can be constructed by winding 150 turns 36 swg enameled wire on a 100K, ˝ W Resistor.

 

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