[Heath] More on the SB-104A rx noise...

[ChrisIwata at aol.com]

Yes, the noise blanker on the SB104 causes lots of noise
 
This is due to the 1350 IC on the board. I no longer have the  schematic, 
but as I recall the IC runs at full gain (I think it's  around 60dB)  then 
the signal is attenuated so the board provides  unity gain when engaged. Doing 
this lowers the signal, but the noise floor  is still there at high 
intensity.
 
This also shows up as hearing ghosts. The 3rd order intercept (dynamic  
range) is degraded, so you'll hear intermod ghosts from strong signals that are 
 way off the tuned frequency.
 
Noise blankers are tricky: Virtually all have side effects that limit their 
 usefulness. 
 
I tried some from Drake rigs, making the blankers from  schematics. When 
used on the 104, they weren't much better.  
 
Chris, KL7DM  
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