VU2VWN's 7 on 7 Qrp

Submited By Nadisha 4S7NR

This is a VFO control, easy to build 7 watts QRP on 7 Mhz from Vasantha VU2VWN. If you are in close VU, you may hear hundreds of hams using this QRP on 7MHz - AM. They just modulate the whole Driver/Amp section using a Audio transfomer. It is very populer (specially) in South India.

VFO works with two MPF102 FEts. It should be enclosed. Many VU hams put this VFO on a Card-Bord box and wrap it with Aluminium foil. And they oparate the VFO using 6V battery and 5.1v Zener diode. I change it with 7805 three pin voltage regulator and still works okay (I mean with out any hum).

BD139 should be mounted on a large heat sink. Once everything is finish, Supply 12v to the Amp (not 24v) connect a 24v 5W bulb as the load. C4 should be tuned to the minimum brightness of the LED. Total DC current to the RF amp should be 200-300 and it should never exeed 400mA (at 12V). On its full power 28V power amp will take about 300-400mA (max 500). Use 75 ohm coax, to feed the dipole.

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