[ARC5] Backwave

[Mike Morrow]

> If one has not disconnected the antenna relay, then surely that is
> quite noisy and unacceptable. But the selector relay makes very little
> noise in my experience.

But...*both* relays [K-53 (MO HV and PA cathode) and K-54 (Antenna terminal)] in these transmitters are SELECTOR relays and are NEVER keyed in the original design.  Both remain energized, even when receiving, as long as the transmitter select switch on the transmitter control box is positioned for that transmitter.  Thus, there are NO keying noise issues from the transmitter.

On key-down, K-52 (HV keying) in the modulator, and K-55 (Antenna switching) in the antenna relay unit energize.  Also, in the typical three-receiver rack, all three relays (K-1, K-2, K-3) energize to switch the AF busses from receiver AF to modulator sidetone AF.

Thus, in the typical two-transmitter and three-receiver command set, five relays respond to key or PTT operation.  None of them are in the transmitters.

This is all old often-covered stuff of little interest to most hams.

Mike / KK5F