[TenTec] Argo V Transmit Audio

[Paul Christensen, Esq.]

With so many similar complaints on the Argo V, I had to take a look at the
schematic to investigate...

Actually, Ten Tec did a nice job in the mic pre-amp design.  I suspect the
nominal output of the hand mic is over-driving U17A.  There are two possible
fixes for this...both easy:

1) R271 is a PC-mounted potentiometer located "ahead" of U17 and can be
adjusted to offer a lower input level into U17.  The front panel MIC control
is actually located "after" U17 and thus *no amount *of adjusting the front
panel mic control will assist in reducing distortion if U17 is already being
overloaded by hot audio from the mic.  If you only use one mic...(i.e., the
hand mic), you can adjust R271 to bring the audio within an optimal range
for U17.  I would suggest first setting the front panel mic control to
11 or 12-o'clock...and THEN adjust R271 for just a flicker of ALC action on
the
front panel LED with normal voice.

2) If you use more than one mic with the Argo V, it may be better to install
a simple two-resistor voltage divider in the hand mic consisting of a series
10K and shunt 10K resistors (lessen the shunt resistance to reduce output
from the mic even further) in the mic audio line.  The mic input Z of Argo
is ~ 10K-ohms based on what I see on the schematic.  The voltage divider can
be installed in the mic head or at the mic plug (preferable) with small
1/8-watt metal film resistors.

-Paul, W9AC


 ----- Original Message -----
> From: "KXBill" <w7kxb at cox.net>
> To: <tentec at contesting.com>
> Sent: Saturday, March 22, 2003 16:09 PM
> Subject: Re: [TenTec] Argo V Transmit Audio
>
>
> > Hello Tom:
> >      I have had the same problem with the factory supplied hand mic.
The
> > mic is QPS.  TT should either replace their present hand mic with
> something
> > that works, or make it or an upgraded hand mic an option and drop the
516
> > price accordingly.
> > Cheers
> > Bill Harris
> >
> > _______________________________________________
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> > TenTec at contesting.com
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>