The same diode ring mixer and post mixer amp are used for transmitting and receiving. A pair
of miniature realys are used for TX/RX switching. I use a pair of National SPDT relays. These
relays are almost completely silent when changing over. Avoid using noisy relays, especially for
VOX operation. I use four standard silicon switching diodes 1N4148, 1N914 etc. I spent some
time with a fistful of diodes and a multimeter to select four that were closely matched for
forward resistance. Use 8 turns trifilar wound on a medium to high permeability toroid core,
for the transformers in the mixer. The mixer I.F. port is terminated by a 3dB attenuator.
The post mixer amp is a 2SC784. I intended to use a 2N3866 but I had none left in the
junk box. Use 8 turns bifilar wound for the output transformer. Have a look at the
80M Transceiver for more tips on making diode DBM's.
As you can see in the picture, the mixer is built dead bug style, on a piece of circuit board.
I was planning to etch a proper PCB but the circuit works so well, I decided to use the rough
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