[Heath] SB-303 Noise Blanker Schematic

ChrisIwata at aol.com ChrisIwata at aol.com
Sun Mar 16 16:59:27 EDT 2014

I checked out the schematic for the noise blanker: It is not the same as  
that for the SB104
If duplicated, it will probably (like the SB104 blanker) introduce lots of  
noise. The signal is passed thru an amplifier IC that adds about 8db  of 
noise. At least that's what the datasheet for the CA3012 says.  The  IC was 
designed to be used in FM receivers where noise is not a concern.   The amp 
has 70dB gain when run at full and typically was used as a limiting  amp. The 
signal may overload the following stages, if so you'll have  intermodulation 
problems as well.  
The pot on the panel apparently set the threshold for when the blanker  
kicks in.  But it seems if set too high even the intended received signal  will 
not pass.  Don't know for sure since I don't have the rest of the  SB303 
Chris KL7DM
In a message dated 3/15/2014 7:00:53 P.M. Pacific Daylight Time,  
pbrickey at verizon.net writes:

I have had quite a few questions about this, so I  thought I would send out 
the schematic that is in my SB-303 manual.
It is  attached.

Heath  mailing  list
Heath at puck.nether.net

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