My SupeRX/TX 40 -- now on 7030 kHz
Click on schematics for a better view
Details on the receiver: https://archive.org/details/73-magazine-1991-04
Details on the transmiiter: https://archive.org/details/73-magazine-1991-12/page/10/mode/2up
Article on MXM Industries of Smithville,Texas:
Click on images for a better view
Click on images for a better view
Posts
Thanks for the details, William. For $1, a ready to go rig, easy to pack for travel. It looks smaller than your straight key!
ReplyDeleteI'm a sucker for cute little minimal rigs like this one from 30 years ago! Notice the reviews saying there's 'no drift even after switch-on', with a free running VFO at 7.5MHz and another free running 455kHz BFO I find that surprising. Maybe expectations were different back then. Also note the ceramic filter hanging off the first NE602, no impedance matching, not even a DC blocking C .. a super simple superhet, if it works, don't knock it. Paul VK3HN.
ReplyDeleteThanks Paul. Yea it does show some hand capacitance effects on receive (which is annoying) but the crystal controlled transmitter is rock solid.
ReplyDeleteAs for the filter, I'm thinking that the impedances of the two chips might have been right at 1500 ohms -- from my Q-31 adventures (inspired by your AM rig) I think this might be the right impedance for this ceramic filter. So maybe no matching network was needed? I am not sure of the width of the filter in mine, but it sounds too tight for SSB and a bit too broad for CW. 73 Bill N2CQR