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[Yaesu] RX Overloading

To: <yaesu@contesting.com>
Subject: [Yaesu] RX Overloading
From: w8fn@attglobal.net (Randy Farmer)
Date: Wed Feb 5 21:12:53 2003
>Sometimes when signals are loud on the band they all sound like heck on my 
>Turning off the noise blanker fixes the problem....
>Anyone else experienced this problem - and - did you find a cure?

Sorry -- there ain't no cure. What a noise blanker does is look in a 
wideband filter ahead of the narrow IF filters in the radio and punch out 
holes in the received signal when it sees large signals, on the theory that 
the large signals are impulse noise. Run-of-the mill noise blankers aren't 
smart enough to test the big signals to see if they really are pulsed, so 
anything large enough to make the NB threshold will cause the blanking. 
Unfortunately, the S9 +++ signals you see regularly, especially in 
contests, easily make threshold. As a result, you get strong off-frequency 
signals turning the desired signal on and off with their signal peaks. This 
is by definition cross-modulation. If you don't want it your only choice is 
to turn the noise blanker off in strong-signal environments.

73 & hope to see you in the next contest.

Randy, W8FN

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