[Yaesu] FT-900 Modification for Variable "RF" Gain Control
donald.s.tucker@exgate.tek.com
donald.s.tucker@exgate.tek.com
Thu, 17 Jun 1999 15:08:17 -0700
TB-9521 dated 20 April 1995 says if there is low AM TX modulation to change
R1258 on the Local Unit board from 10K to 4.7K. If you want a copy give me
your mail address.
Don W7WLL
-----Original Message-----
From: David G. Maley [mailto:dgmaley@soli.inav.net]
Sent: Thursday, June 17, 1999 2:33 PM
To: Tucker, Donald S
Cc: wa3gin@erols.com; yaesutech@worldnet.att.net; yaesu@contesting.com
Subject: RE: [Yaesu] FT-900 Modification for Variable "RF" Gain Control
btw....
What AM circuit change????
Dave
WA0ZZG
On Thu, 17 Jun 1999 donald.s.tucker@exgate.tek.com wrote:
>
> I did the resistor value change (3.3K to a 10K)to the blanking circuit in
my
> FT-900. The improvement was enormous, but still was not sure it was as
good
> as it could be (also did the Yaesu suggested AM circuit change-forget the
TB
> number but have a copy if anyone interested). In talking with Yaesu on the
> phone about the noise blanking mod, I learned that the best value to
achieve
> the most effective blanking was not necessarily 10K, but could be some
value
> less than, or even slightly more. Since I use my FT-900 exclusively in my
> car, noise blanking is a prime issue. Wonder if anyone ever replaced the
> fixed value with a variable value (a 10 or 12K pot) and literally set the
> value to achieve the highest blanking efficiency?? If so think the FT-900
> owners would be interested in your experience. Still a great rig, but
never
> had the SSB filter, which Yaesu no longer says is available. Understand
> Irad (?) has one. Is the improvement worth the effort???
>
> Don W7WLL
>
>
> -----Original Message-----
> From: Dave Jordan [mailto:wa3gin@erols.com]
> Sent: Wednesday, June 16, 1999 7:36 PM
> To: Yaesu Technical Support; yaesu@contesting.com
> Subject: [Yaesu] FT-900 Modification for Variable "RF" Gain Control
>
>
>
> 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
> years
> 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,
> back
> 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
> the
> 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
> beeper
> variable resistor and use it for this purpose. Another thought would be
> to
> 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
> report.
>
> OK, that is it...thanks in advance for any assistance,
> dave
> WA3GIN
>
>
>
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