RE: [Repeater-Builder] Mitrek COS ?

Fri, 19 May 2006 09:15:11 -0700

Hi Richard and Neil...
In my instance, it floats between 3 and 3.5 volts....  which is just enough to confuse my controller as to which state the squelch is actually in.
 
Both approaches would probably work just fine...  but haven't had a chance to deal with it yet. 
 
I can think of a number of instances when one might want to disable the input tone. I haven't had a need to so far, so the issue hasn't been resolved as of yet. 
 
During the summer is when most station owners want to do maintenance on AM-Directional systems, so my days have been pretty full of late. <grin!>
 
Thanks for the ideas though....  I will check into it once I get a chance....

 73
Mike Perryman
www.k5jmp.us

-----Original Message-----
From: [email protected] [mailto:[EMAIL PROTECTED]On Behalf Of [EMAIL PROTECTED]
Sent: Friday, May 19, 2006 11:22 AM
To: [email protected]
Subject: Re: [Repeater-Builder] Mitrek COS ?

 
> Mike Perryman wrote:
>  I was having trouble with my micor in that the COS signal would never go completely to zero volts... 
 
Mocom-70 was good for that too ..  my solution came from a fire-alarm controller:

Details are fuzzy, but ~ it used some dual-input flip-flop comparator chip (7476 ?) ... sample (waffle-voltage) on one input & a reference on the other.
When the relative voltages reversed, made for a nice clean on-off at the output, and a xstr follower allowed for switching some juice...

/. 
  
 

Hmmm ... I have run into this problem in the past ... I fixed it

by biasing the emitter of the first (external) transistor off

ground with a voltage divider .. or sometimes by placing a diode

in series with the emitter.

One time - I think it was a Standard land-mobile radio, the COS

feed (aka squelch detector) was several volts above ground. In

that instance, I installed a voltage divider between A+ and ground

- to positive bias the added transistor above ground so when the

squelch opened, the sense lead to the external transistor turned

it on.

Make sense?

Neil


 






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