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

[Doug Crompton]

Krys,

If you are using an unmodified ($2-3) USB FOB you need to put a cap on the
mic in (pink) connection because DC can be superimposed on the mic
connection for powering an external mic which is intended to be plugged in
there. On the green side you do not need a cap.

If you were using a DMK URI you would need nothing between the interface
and the radio in most cases.

Here is a schematic of the DMK URI -

http://dmkeng.com/images/URIx%20Schematic.pdf



*73 Doug*

*WA3DSP*

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

On Tue, Feb 28, 2017 at 1:22 PM, "Krys Beal via arm-allstar" <
arm-allstar at hamvoip.org> wrote:

> Is there any concern about isolation on the Tx side? I noticed there's no
> cap shown in the reference drawing. Thanks for bearing with me on this one,
> team. I'm sure I'll have more questions as the components arrive
>
> Krys
> K3EAL
>
>
> On Mon, Feb 27, 2017 at 3:36 PM David McGough <kb4fxc at inttek.net> wrote:
>
>
> BTW, if you're going to get new potentiometers, ideally try to find the
> "audio taper" (logarithmic resistance) variety....They'll be easier to
> set.
>
> 73, David KB4FXC
>
>
> On Mon, 27 Feb 2017, "Krys Beal via arm-allstar" wrote:
>
> > Thanks Doug. I'll pick up a couple of 50K pots. Is the 10uF capacitor
> that
> > is also listed a fixed value?
> >
> > On Mon, Feb 27, 2017 at 10:44 AM "Doug Crompton via arm-allstar" <
> > arm-allstar at hamvoip.org> wrote:
> >
> > > 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
> > > >
> > > >
> > > _______________________________________________
> > >
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> > > arm-allstar at hamvoip.org
> > > http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar
> > >
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> > >
> > _______________________________________________
> >
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> >
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> >
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