[arm-allstar] modify cm108 fobs

[Doug Crompton]

Alan,

 Glad that eliminating the pot worked out for you. I am surprised that a
100K pot in the maximum through signal position had that much effect. That
would be like putting a 100K resistor to ground from that line which I
would not think would have a great effect. Are you sure it was a 100K pot
and turned all the way up?

The circuit you are using is not unlike the one we generally use. I prefer
a FET (2n7000) for the PTT keying device with a 10K resistor from the FOB
to the gate and a diode from source to drain. The COS is through a Schottky
diode and the audio lines we generally put resistors in series of 5-50K for
level reduction if necessary. All very simple.


*73 Doug*

*WA3DSP*

*http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*


On Thu, Aug 3, 2017 at 1:56 PM, "Alan Matthews via arm-allstar" <
arm-allstar at hamvoip.org> wrote:

> guys
>
> apologies for bombarding you all with my gibberings.
>
> the fob design that I have always used can be found at the following
> address....
>
> http://www.repeater-builder.com/projects/fob/startech-fob.html
>
> this always worked well with Startech fobs.
>
> I am using this circuit with the open board fobs from China, I have made
> NO mods to the board, I have NOT removed any components.
>
> Current status as of 18:30hrs UK time.
>
> Since my last email I have just bypassed the 100K potentiometer and
> attached the mike input direct to the fob, the input levels have increased
> immensely to the levels required, my settings in usb tune menu are now at
> 650 to give mid point range in the graph.
>
> I am now sorted, however I would love to hear from fellow builders ideas
> as to what I should actually be doing with modifying the fob.
>
> thanks for your guidance.
>
> regards
> _______________________________________________
>
> arm-allstar mailing list
> arm-allstar at hamvoip.org
> http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar
>
> Visit the BBB and RPi2/3 web page - http://hamvoip.org
>
>