[Top] [All Lists]

FT-900 mods (noise blanker) needed!

To: <yaesu@contesting.com>
Subject: FT-900 mods (noise blanker) needed!
From: dgmaley@inav.net (Dave Maley)
Date: Sat, 3 Aug 1996 09:23:30 +0000
> From:          josef.roell@banyan.siemens.at
To: <yaesu@contesting.com>
> Date:          Thu, 1 Aug 96 6:44:27 MSZ
> To:            <dgmaley@inav.net>
> Subject:       FT-900 mods (noise blanker) needed!

> Hi Dave !
> I mean that if you power on the rig while pressing the four buttons 
> simultanously and shorten the 2 testpins, it will display 02 and off (if no 
> general TX is possible). Maybe there are another settings on the place 01 or 
> 03 do modify other unknown factory defaults, maybe to increase the maximum 
> shift up to 7.6 Mhz to use it with a transverter on the 70 cm relais band - 
> who knows ? But I have no information on how to improve performance of the 
> noise blanker. Please, can you mail me the service bulletin if you have it in 
> a digital form or can you fax it, if it's not much paper ? The number is +43 
> 316 1707 788. 
> Thanks in advance.
> 73 de OE6RJD
> josef roell           
OK; this mod is simple enough that if you have access to the factory
service manual, you can do it. Yaesu states in bulletin # TB-9448-A,
dated 18 October 1994 that FT-900's with "Insufficient Noise 
Blanking" can have improved Noise Blanking by changing R2335.
It's present value is 3.3K ohm, and to test-select a value between 6.8K 
ohm and 10K ohm.  As you approach 10K, some receive audio distortion 
will be noticed. 
I believe I ended up using 9.1K ohm in mine with some distortion on 
 signals with a high peak to average ratio.
  I believe this was a fitting trade
This is a chip component on the bottom of the receiver board, so it 
does require removing this board and popping off the chip.  There is 
room for a 1/8W. leaded component.
It really made the blanker work though. It now takes the tops off
lightning crashes on 75Mtrs.
So get out the bright light and glasses and have fun!
Dave  WA0ZZG.

<Prev in Thread] Current Thread [Next in Thread>
  • FT-900 mods (noise blanker) needed!, Dave Maley <=