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Fun, low cost, easy little project to activate On The Air sign on xmit

I have an "On the Air" sign run by low power USB (or batteries) that I typically turn on when operating my 6600M. I wanted to see if Flex has a way to trigger the sign only when transmitting and sure enough, the accessory port provides the needed connections. Use a cheap (~7$) relay w/optocoupler, a few accessory port connections via 15 pin break out serial port to trigger the relay on xmit, activate the port in xmit settings, power the relay via 12V and the low voltage sign gets 5V from the radio when transmitting. Works great!


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

    You can use USB bit levels available on the back of the radio to do exactly this.

  • Mike VE3CKO
    Mike VE3CKO Member ✭✭✭

    This also works. I have the plus side of the LED on-the-air sign going to +12v shack misc power supply. On my 6700 there are 3 TX outputs to key amps. I use TX3 to provide the ground to complete the circuit for the LED sign. In the TX Band Settings you have to of course select the bands you wish to have the sign to be on when transmitting.

    To be honest I haven't checked the spec on the the TX RCA outputs to see if they can handle the current of a few LEDs but it should draw any current just a ground path, that correct Mike ?

  • N7WRH
    N7WRH Member ✭✭

    My OTA sign only requires 4.5 volts so the accessory port works great (5v?) w/12v shack power for the optocoupler relay. I'm afraid if I bypass the relay and wire the sign to 12v it may not handle the additional v??

  • N7WRH
    N7WRH Member ✭✭

    Thanks Mike and Mike! Using the USB cable from Flex, it was super easy to simply tap the negative (black) and Pin 0 using BIT directly to the On Air sign which provides sufficient V+ for the sign to operate on xmit. Simplicity at its finest.


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

    Cool! You'll have to take a video and share it here.

    You can find a ton of these little signs on Amazon.


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