Dear Lowfers,
just I am designing a TR-switch for my new TX. Estimated Power about 60dbm/60 Ohm.
The current situation with my TX 70W/60 Ohm:
The RX-Path is swiched via two reed-Relays (homemade coaxial ones, for qsk operation) to the receiver input, the TX-Path is switched via a reed-relay to the PA both from the common input of low-pass-filter, whitch is allways in the aerial path. My RX is an EKD 300 (Funkwerk Köpenick, late DDR). In transmit operation this will cause an sidetone with an pretty high volume, but not too much annoying noisy.
My experiments with an 1 Watt driver circuit:
The signal Path: Oscillator - Driver 1 Watt - Attenuator switchable 0d B...50 dB - TR-relays - RX-Input
TR-relays is a series of one Vac-Relay and three Reed-Relays (2 spst, 1 spdt).
All build up with coax connectors. It seems to be that
I am still far away from a S9 signal durig transmitting, even with this 1 Watt-Driver.
How You have solved this task? What is done in commercial equipment with similar power?
Is it necesary to have anyway a mute circuit for the receiver? An input voltage of 1 Volt will not be dangerous for the RX-input and cause some distortionin the audio-signal, but for a sidetone this is not a problem.
Waiting for reply
55, Hans-Albrecht Haffa DK 8 ND
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