Re: External Amp

W0PWE
 

I bought one of these out of curiosity more than anything but if it worked I was going to use it as a 40M only amp while operating mobile with my scratch built Bitx40. To my surprise it worked pretty well. Output on 40 was about 50 watts with 1 watt drive and 70 watts with 5 watts drive. I built a 3dB attenuator for the input and a 40M LPF using T50-6 cores. I also built a signal operated PTT driver based on the WA2EBY design. My heat sink was salvaged from the motor control board that died in our Bosch washing machine. It is about 50mm x 100mm and the fins are about 50mm tall. After a long winded transmission the heatsink was just a little warm and the MOSFETs were likewise.

Then one day I was speaking a little too loud into the mic and the MOSFETs shorted. New MOSFETs should be in the mailbox when I get home today so I will try again. I think if I work on keeping the drive level down it will serve it's intended application just fine. I have certainly had more than $18 worth of fun with it so far. 73.
Jerry - W0PWE

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