Stby vs. Opr on 75S1

Discussion in '"Boat Anchor" & Classic Equipment' started by KO4CQ, Jun 8, 2021.

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  1. KO4CQ

    KO4CQ Ham Member QRZ Page

    I've been operating a Collins S Line (75S1, 32S1) for over 30 years, mostly in transceive mode. It works perfectly in STBY mode, and the same in OPR mode. So I wonder, what's the difference? The manual is of no help here. Thanks!
  2. WA1GXC

    WA1GXC Ham Member QRZ Page

    See equipment manual, Section I "Installation"--Para. 1.2

    Collins S-Line follows convention of most modern-designed amateur gear for muting function. For normal operation,
    MUTE line connection is grounded by internal transmitter control relay to enable receive-mode. In transmit mode, MUTE line is
    lifted from ground; depending upon specifics with different manufacturers, several tube cathodes are lifted off-ground or high bias voltage
    impressed on several tubes to cut-off.

    Collins OPR mode is essentially, "OVERRIDE-ON" at all times. "STBY" is what others would normally label as "Normal", receiver-
    muting controlled by transmitter relay switching.

    Some 1950's transmitters were a pain and did not come equipped with internal T/R relay for receiver control.

    If you leave a S-Line receiver in OPR mode-select, you'd normally blow your ears out.

    Last edited: Jun 9, 2021
    N2EY likes this.

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