Saturday, May 19, 2012

ARNSW Home Brew 40m AM challenge attempted contact

It's great to see a few people working on the latest ARNSW Home Brew group "challenge" project - to build a 40m AM transmitter. I'm on the way, but my design only puts out 2W, but Stephen, VK2BLQ is running his IRF510 on 24V and getting 5W or more. His design features a beautifully stained breadboard base to give the machine "soul".

I was able to receive Stephen readability about 3 and we coordinated on 2m (on my old favourite channel "D", 147.475MHz) to get things set up. Unfortunately, he couldn't hear my transmission but just look at the wreck of a rig I was using (the one in the foreground).

One thing that has worked out pretty well is the piece of aluminium I bent into the simple "U" shaped chassis you see above.

Incidentally, the $220 IC-725 is going well. I replaced the right hand dial lamp with a 12V yellow LED. It's not as bright as the light on the left (that hasn't blown) so I might replace it too to balance things up.

The band noise on sideband sounded very different between upper and lower and I've now adjusted the BFO on the upper side to bring them in to line (that's the one that sounded out of kilter). This was purely done by ear but it seems to have done the trick.

Keen eyed viewers will note a new addition to the shack - a BHI NES10-2 MK3 Noise Eliminating Speaker. So far I'm very impressed and will post a review shortly with a demo.

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