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TX inhibit by RCA TX Req

Boyan LZ2BE
Boyan LZ2BE Member ✭✭

I want to implement a TX Inhibit function on my 6600 to prevent equipment damage in case my Steppir antenna start tuning while radio is transmitting at high power.

I have Tuning relay in SDA100, which is configured to switch to GND when antenna is tuning.
There are RCA and ACC TX Request inputs, active Low, which inhibit TX ONLY BEFORE TX start.
If 6600 is already transmitting then grounding RCA TX Req pin doesn't inhibit TX.
This is a BIG problem, because it will burn sliding contacts in EHU and it will cost a lot of money.

I built two simple boxes with a relay and a 100W dummy load inside for my SO2R setup to avoid this problem, but I think it will be much more simple and better if Flex team change the way of operation of TX Req pin.

I red somewhere about logic for such behavior. The operator will be able to finish the QSO and not to be interrupted by other operator.
My logic is different - I would prefer to have 100 NIL QSOs in a contest instead of burnt EHU :)

73! Boyan LZ2BE


  • JohnSweeney
    JohnSweeney Member ✭✭
    edited June 2020
    The tuning relay in the SDA100 is a set of dry contacts.  If you route the Amp PTT line through these contacts, the amp will not be engaged when the SteppIR is tuning.  SteppIR has a published schematic of how to use the PTT Relay.

  • Boyan LZ2BE
    Boyan LZ2BE Member ✭✭
    edited June 2020

    it doesn't work for all amplifiers. Acom2000 keep bias and relays to TX position if PTT + RF input are applied. Breaking only PTT doesn't change anything and you still have full power out into tuning antenna.

    I had K3 before 6600. PTT to GND from SDA100 was applied to K3 TX Inhibit and all was OK.
    I would like to see the same fully functional TX Inhibit port in Flex 6600 - a port which will cut RF output of radio to zero once activated despite PTT state.

    73 Boyan

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