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[Yaesu] FT-900 Modification for Variable "RF" Gain Control

To: <yaesu@contesting.com>
Subject: [Yaesu] FT-900 Modification for Variable "RF" Gain Control
From: wa3gin@erols.com (Dave Jordan)
Date: Wed, 16 Jun 1999 22:35:56 -0400
Hi Folks,

When I first got my FT-900 brand new in the box I had reservations about
owning a rig that didn't have an "RF" gain control.  It's been several
now and I'm still missing that "RF" gain control.  I have a FT-1000 and
I'm just
used to cranking it back...it does make a difference in reception.  SO,
then I asked Yaesu to give me location for the fixed resistor that
controlled the
RF gain.

Tonight I decided to open up the FT-900 and do the deed.  I found
a free pin on the "CAT" socket that could be used to install a connector
with a
pot that I would parallel with the fixed resistor. So, I could unplug
the pot and
have the normal fixed setting or plug-it in and have some variability
over the
"RF" gain.  As it turns out what Yaesu sent me as a mode was a technical
bulletin TB-9448-A, a fix  to increase noise blanking performance, by
increasing the resistance of R2335 (on the back side of the xthe RF-Unit
board number F3251000C. I can scan in the location chart if anyone is
interested. R2335 was originally 3.3Kohms but can be increased up to 10K
ohms.  I added another 3.3K ohms in series.  Haven't got the box back
together yet but will report out on the results soon.

The question to the list and Yaesu technical support is simple.  I need
location of the fixed resistor that is responsible for setting the "RF"
gain of
the FT-900.  I would appreciate a fax or email enclosure of the specific

loation ASAP...

By the way, if you like the idea of a "RF" gain control but don't want
an outside connector with pot you could easily disable the sidetone
variable resistor and use it for this purpose. Another thought would be
simply use the pot to identify the favorite setting and use a fixed
resistor in
the plug. I've found that when I do crank back on the FT-1000 the
setting is always the same and the only time I turn it up these days is
to give a signal

OK, that is it...thanks in advance for any assistance,

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