[Motorola] MOCOM questions again

Sun, 20 Oct 2002 01:14:21 -0700

Ken Cechura wrote:
> 
> wow...  the list has been pretty quiet lately...
> 
> anyway, i fixed my MOCOM base station....  turns out the fast-blow 20A fuse
> poped.  replaced it, and it came to life!!
> 
> now, I've asked before, but with system crashes, eudora crashing, and the
> loss of my MOCOM manual.... How do I connect a TNC to the mocom?  It
> receives and keys up the radio, but does not seem to be transmitting
> audio....  help?  do I need an impedance transformation in order to make
> the audio pass through?
> 
> any help from experienced people would be appreciated....  I think there
> was someone with a VE call that helped me last time....
> 
> thanks!!!
> Ken

Hello Ken; your query looks familiar. I remember answering something
like this a time ago. I installed some tncs onto mocom 70 machines for
our ham club and I found that the microphone jack expected a fair amount
of output from the mike. I think the Motorola mike is about the
equivalent of a carbon mike as it has a transistor inside and needs
voltage supplied from the mike jack. I found that the audio from the
mike went to a pre-emphasizer circuit so I had to take that into account
and fiddle with the tnc so it sent out audio that matched this
pre-emphasis. I also had to add a transistor to make up for the lower
level audio out of the tnc.
I Hope this is of some help.

> 
>       //////////////////////////////////////////////////////
>      //        Kenneth R. Cechura, KC9UMR                //
>     //             [email protected]                     //
>    //           President, W0EEE, 2002                 //
>   // University of Missouri-Rolla Amateur Radio Club  //
> //////////////////////////////////////////////////////
> 
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