Switch it around

A project log for Simple Digital Mode Transmitter

A low-power, all-digital transmitter.

robgRobG 05/25/2021 at 13:430 Comments

Replaced the TX/RX relay today. Was previously SPDT, now DPDT configured so that the RX port is shorted to ground during transmit for a bit more isolation. When I've got a 10W PA hanging off the other port, and only 10mW (1000x less) into the receiver will damage it, I want to be very sure that I've got all the isolation I can manage!

Relay is a Relpol RM822N-2112-85-S005. A quick look on my VNA shows >60dB from DC to 50MHz. That'll do...

Here's the circuit so far: