[Boatanchors] [ARC5] [Milsurplus] Scott SLRM - Low BFO Injection

[David Stinson]

On 9/11/2019 12:47 AM, Richard Knoppow wrote:

 >    I can't find the original post. How is it being determined that 
the injection is low?
First- my ears.  With the BFO on, one must turn the RF gain down at 
least 40% to get enough injection to copy CW.  At this setting, the 
audio level is earphone at best.  A look at the diagram shows that there 
is no actual injection of the BFO at all- it relies on half a 12SN7 and 
(very) stray capacitance.  Since this was not intended to be a 
"communications" receiver, I suppose the tiny BFO signal is intended as 
part of the "Special Low Radiation" design.

 >Many receivers have minimal BFO coupling both to avoid pulling of the 
BFO by the signal and to avoid activating the AVC when it can be used on CW.
No BFO pulling is evident.   If one sets the bandwidth/mode switch to 
"CW," the AVC is turned off.  CW/SSB audio level is now plentiful.

GL OM DE Dave AB5S



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