Issue/Question about PTT out

[Joey G. (Bonehead)]

I'm having issues adapting amps to the PTT out of the N2ADR board and are asking if maybe someone has developed a way to get around it.  When in RX it reads about 140 ohms but zero on TX.  The issue is the amps I've tried to connect to it see the 140 as enough to go into TX so they stay in TX.  The only amp that doesn't is my RM Italy.  I've tried to build simple transistor circuts with no luck either.  Anyone out there have a schematic I can use to fix this?  It would be very much appriciated.  

Thanks!

73

Joe

K5BHD

[John Williams]

EXTTR is open collector. You need to pull up the line to some nominal voltage thru a resistor. My system uses 24V. Some use 12V. I think the spec is around 30V max. For my Neptune, I believe it has a pull up inside. Works fine. Don't know how the RM Italy amp implements PTT. 

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From: herme...@googlegroups.com <herme...@googlegroups.com> on behalf of Joey G. (Bonehead) <jcgre...@gmail.com>
Sent: Wednesday, November 26, 2025 8:58 PM
To: Hermes-Lite <herme...@googlegroups.com>
Subject: Issue/Question about PTT out

 

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[Joey G. (Bonehead)]

The RM Itali works fine with the PTT.  It's trying to get it to work with others.  I tried using a pullup resistor to fire a PNP transistor but it still fired the minute I connected the wire.  I ended up just connecting it to a 5v relay switching the negative with out a transistor and it seems to work.  TX only pulls 36mA so I believe it should be safe to drive directly.  I did put a diode across the relay coil as well.  Thanks for your input.

73 

Joe

K5BHD