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Hot switching with 1A2R

Rick N0VT
Rick N0VT Member ✭✭

I'm hoping someone else is using a 4O3A "1-amplifier-2-radio" switch (a.k.a. 1A2R) successfully and can help me out.

I am using a 1A2R with my 6600 and ACOM solid state amp. I have had to replace the relays in the 1A2R twice in 5 months and the folks at 4O3A believe that it's due to hot-switching.

Their tech support suggests connecting each unit in this manner:

1. From radio TX1 from radio to 1A2R PTT input.

2. From 1A2R PTT output to ACOM key in 

3. From ACOM key out to radio PTT.

Step #3 has me confused. Where would I plug in my footswitch?

It seems that the correct way to solve this would be to simply set the RCA TX delays to "0" and the TX Delay to "20" or larger to give all the relays time to close before RF goes out. Am I off base about this? I hope someone has already figured this out because both 4O3A tech support and I are tired of me going through relays so quickly.


Rick N0VT



  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    @Rick N0VT

    You might want to email 403A support directly as they don't monitor this group and they market that software.



  • Rick N0VT
    Rick N0VT Member ✭✭

    Already did.

    >Their tech support suggests connecting each unit in this manner:

    >1. From radio TX1 from radio to 1A2R PTT input.

    >2. From 1A2R PTT output to ACOM key in 

    >3. From ACOM key out to radio PTT.

  • N7WRH
    N7WRH Member ✭✭

    Rick, did you ever get this solved?


  • K9YK
    K9YK Member ✭✭

    I’ve got a 1A2R. No issues to report. I’ve got a beam for 20m and a doublet I use on 40, 80, and 160. The beam is on ANT1 a the doublet is on ANT2. I’ve got the radio set up so that transmissions on 20-6 key via TX1 and 160-40m key via the accessory jack (TX2 and TX3 are used with Xverters). I have the RF delay set at 100ms so no hot switching,

    A couple things that could be better …

    It would be nice if there was an option in SmartSDR to have the keying outputs follow the antenna selection in addition to the choices for keying by band. This would work much better for the 1A2R.

    The 1A2R has 18 relays in it and they make quite the clunk every time you key up. The 1A2R could have been better constructed if it had current limiting resistors on each of its relays so that it could be left engaged continuously rather than the shorter duty cycle of TX keying. This would eliminate the constant loud clunks every time you key the radio. Flex would also need to provide an option for the USB bit cable to set pin values based on antenna selection.

  • Rick N0VT
    Rick N0VT Member ✭✭

    In the "Timings" panel of the TX tab under Radio Setup, I set all the values to zero except TX Delay, which I have set to "40". No problems since then.

  • N7WRH
    N7WRH Member ✭✭

    Thanks - I think I now have things working too with the 6600M TX delay on 40. More testing to validate but seems perfect so far.

    SteppIR Vert and Midi Loop sharing KPA500 using RCA TX1 for one ant and RCA TX2 for the other. Also, SteppIR using RCA TX Req to SDA-2000 to avoid xmit during antenna tuning when the copper is spooling.

    I LIKE IT!


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