[arm-allstar] How do you determine proper Rx resistor values

[Doug Crompton]

Krys,

  Resistor values have nothing to do with the Nano but rather the audio
in/out of the USB audio FOB which would be used in conjunction with the
Nano for control. The audio is adjusted with the RX/TX gains in
simpleusb-tune-menu and both have a range of 1 to 999 with a median value
of 500. The default values are set to 500 when you initially setup. In
addition there is a parameter in simpleusb-tune-menu called rxboost which
can boost the level by 20db when on. It is on by default.

It is also important to note that RX is what the node radio receives when
you transmit to it from another radio and TX is what you hear on that radio
when your node is transmitting. So you have to look at it in the
perspective of the node radio not the radio/handheld, etc. you use to talk
to your node.

Because there are so many different radios and sound FOBs used with Allstar
it often becomes necessary to add additional attenuation in the form of a
resistor or resistive divider in series with the audio leads. Unfortunately
there is no list of values for a particular combination. I would start out
with 10K on both the TX and RX sides. If the simpleusb-tune-menu audio
settings are no pegged or very close to one extreme or the other then you
are probably OK. At least one commercial FOB has pots and that might be a
way to go. Use a couple of 10K or higher pots on the TX and RX lines and
with the SW values set at mid point adjust the pots. Then you have plenty
of SW adjustment if you desire.

If you want to use fixed resistors I would start out with 10K. For the
Baofeng 888 we use 10K for both the RX and TX and it works out well keeping
the settings within +-200 of the midpoint. Put the resistors in a place
where they can easily be changed if necessary.

I hope that did not confuse you. If you have any more questions let me
know.


*73 Doug*

*WA3DSP*

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

On Mon, Feb 27, 2017 at 9:04 AM, "Krys Beal via arm-allstar" <
arm-allstar at hamvoip.org> wrote:

> I've recently purchased the preassembled HamVOIP Nano interface. While
> looking at the Rx portion of the interface schematic there is a note
> indicating that resistor values indicated are for the DMK URI, and should
> be adjusted for my specific application. My plan is to use a TH-9000D
> modified per the writeup on the HamVOIP website. How do I determine the
> proper resistors to use for this application.
>
> 73
> Krys Beal
> K3EAL
> _______________________________________________
>
> 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
>
>