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.
