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how to make TX REQ interlock work for SteppIRs

I followed the SmartSDR manual 39.6 for setting up TX REQ to +13.6 via 1k ohm to the series connected SDA100 and SDA2000 controllers. So when either SDA contact opens there is +13.6 on TX REQ which is set to ACTIVE HIGH in the MAESTRO.  CAT control of PTT to PGXL/6700 Signature/Maestro.

Doesn't work with any setting of ACC or TX REQ inhibit. Strange also that 1K to 13.6 yields 10.5 volts on the RCA TX REQ input when either SDA contact opens. That meets the +1.5v spec. in the manual.

Some other posts indicate problems with how TX REQ works. How do I POSITIVELY disable TX with either steppIR tuning, for any tuning at any time, now matter how it is commanded? CAT TX is required for contesting and remote op.


Best Answer

  • Alan
    Alan Member ✭✭✭✭
    Answer ✓

    Two comments.

    The SDA100 relay board, opens, when the antenna is moving. It was intended to open the PTT to a amplifier to prevent high power TX, when the antenna is moving. SteppIR says anything less then 100 watts will not damage the antenna, so the design is to prevent an amplifier from operating.

    I inserted a SPDT relay to be operated from the SDA100 relay board and a 13.8VDC to the coil. On the normally open set of contacts, I used those to pull the Flex TX REQ to ground. That worked for me.

    I have since transited to TX inhibit using FRStack. FRStack can control your SDA 100, with or without you using a direct transceiver control cable. Use a FTDI, null modem cable from the SDA 100, lower DB9 to your Windows computer running FRstack. Find the COM port of the cable in your device manager and set that up in FRStack. Set up the options in FRStack to Inhibit TX on antenna movement.

    Alan. WA9WUD


  • Alan
    Alan Member ✭✭✭✭

    As an aside, based on my experience.

    When using the SteppIR with an amplifier, a sure fire way of damaging the antenna is to not match the SteppiR frequency to the TX frequency, BEFORE hitting it with high power.

    Double the problem, if you then use your fancy high power antenna tuner, to "fix" the SWR. You end up with a very good SWR at the transceiver, life is good again, while the SWR at the antenna is very large, causing high voltages, causing arching, causing expensive SteppIR stuff to burn up. Don't ask how I know.

    I have, now, set up Node-Red to watch out for such frequency mismatch conditions, and prevent TX if it sees same.

    Alan. WA9WUD

  • kz1w
    kz1w Member ✭✭

    TX REQ per manual is selectable to inhibit TX high or low. I selected high with the 10.5 high and 0.005v at low with internal SDA relays 13.6v through 1K on the TX REQ pin and SDA relays in series to TX REQ gnd. Doesn't work. TX is not inhibited with SDAs tuning or not.

    Grant KZ1W

  • halmassey
    halmassey Member ✭✭

    My SteppIR came with a Y-RCA cable that allows the SteppIR to prevent the amp from coming on....

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