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[wxsig] MODEM2 Low TX audio - Fixed

Joe S. Borovetz wa5vms at tapr.org
Fri Feb 17 02:39:14 UTC 2006


At 04:40 AM 2/16/2006, you wrote:
>So, now the question is should we add something to the manual for radios
>that require higher drive to the mike input?

I do think the 100 pf output coupling cap is a mistake. It is a .1 on the 
PIC-E.

I interfaced to a Motorola Spectra and had already been there. If nothing 
else change the value of the cap.

Joe


>--
>73,
>John, W9DDD
>
>On Thu, 16 Feb 2006 Sct599 at aol.com wrote:
>
> >
> > Thanks Joe.  Works great now.
> > 73,
> > Scott
> >
> > In a message dated 2/15/2006 12:52:41 P.M. Mountain Standard Time,
> > wa5vms at tapr.org writes:
> >
> > Sct599 at aol.com wrote:
> > > Hello Group:
> > >
> > >  Adding a MODEM2 to my original T238.  I am connecting it to a ICOM
> > IC-2100
> > > which should work with the separate Mic audio (TX audio)  and  PTT lines
> > (not
> > > combined like an HT). The PTT and RX audio  are working properly.  My TX
> > audio is
> > > very low even with  adjusting V100.  The audio does change  with V100
> > >  adjustment but is still too low when even at max.  In 
> my   troubleshooting
> > of the audio
> > > path I have noticed two  things....
> > >
> > > 1. R101 is shown as a 10K on the schematic.  However, the instruction
> > manual
> > > and parts list calls for a  100K.  A 100K was provided and is what 
> I  have
> > > installed. I  jumpered past R101 and the audio did indeed increase 
> but not
> > to an
> > > acceptable level. What value should R101 be?
> > Change it to a 4.7 K  and the output coupling capacitor from 100 pf to a
> > .1 uf.
> >
> > This  should solve your problems.
> >
> > Joe
> > >
> > > 2. V100 is  supposed to be oriented on the board to match the
> > silkscreening.
> > > However, if you do so, the leads are not oriented   properly.  I 
> reversed
> > V100
> > > from the silkscreening to match the  lead  arrangement and the photo at
> > >  _http://beals5.com/wx/index.htm_ 
> (http://beals5.com/wx/index.htm)   under
> > "How to
> > > build a T238+"  Does the orientation of V100  make a  difference?
> > >
> > > Any other ideas?
> > >
> > > 73,
> > > Scott
> > >  _______________________________________________
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> > >
> >
> >
> >
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> >
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