[App_rpt-users] RTCM PTT circuit

[Kevin Custer]

There are some options....

http://www.repeater-builder.com/hamtronics/ta-51pl_mod.html
This modification was originally written to allow PL to be transmitted 
at industry standard levels.  Using this modification, with a suitable 
varactor, will provide full voice deviation of 5 kHz.  This works well 
on a TA451 because of the multiplication factor of 36.  This 
modification converts the transmitter from PM to FM.  You'll need to 
pre-emphasize and limit in software.  This gives the best sounding audio 
from an older Hamtronics exciter. Use only on ham bands - modification 
is not commercial use accepted.

http://www.repeater-builder.com/hamtronics/ta-51altaudio.html
Similar to what Robert mentioned, and should be fine as long as you are 
limiting without pre-emphasis in software.  Use only on ham bands - 
modification is not commercial use accepted.

http://www.repeater-builder.com/hamtronics/pdf/COR-3.pdf
Look at the circuitry associated with Q1 and Q2.

Kevin




On 3/8/2014 11:37 AM, Robert A. Poff WB3AWJ wrote:
>
> 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.
>
> ------------------------------------------------------------------------
> *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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.keekles.org/pipermail/app_rpt-users/attachments/20140308/59728133/attachment.html>