[App_rpt-users] RTCM PTT circuit

[Robert A. Poff WB3AWJ]

I would think that it should switch 100ma with no problem. 
Make sure you put a diode across the relay coil (band toward + volts) to suppress back emf when the relay releases. 

As to the Hamtronics exciter.... 

I had to use one (TA451) on a local club UHF repeater that I redid as an Allstar node. That repeater always had sounded horrible before. 
And to no surprise, with the Allstar node it sounded absolutely RANCID. I needed to bypass all the mic processing and the really nasty clipper, 
and inject the transmitter audio downstream just after the splatter filter, and essentially directly into the phase modulator. Through an isolation 
resistor (somewhere around 4.7K if I remember correctly). 

Now it sounds as smooth as my Mastr II / Allstar repeaters do. 

----- Original Message -----

From: "Bryan Fields" <Bryan at bryanfields.net> 
To: "app rpt-users" <app_rpt-users at ohnosec.org> 
Sent: Friday, March 7, 2014 5:44:12 PM 
Subject: [App_rpt-users] RTCM PTT circuit 

I'm interfacing the RTCM with a hamtronics exciter and will be using a small 
relay to key it. 

Can it sink 100 ma to ground for the relay or do I need a driver transistor? 

-- 
Bryan Fields 

727-409-1194 - Voice 
727-214-2508 - Fax 
http://bryanfields.net 

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