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

[Christopher Bowne]

The low BFO injection is apparently a design issue.  If you look at the receiver schematic, you will see there is no direct coupling of the BFO stage to either the detector or an IF stage!  I increased the injection in my SLRM back in my Novice days well over 50 years ago when it was my main receiver using a twisted pair of insulated wires as a “gimmick” cap between the cathode of the half of the 12SN7 BFO cathode (the plate is actually bypassed for RF) and the grid of the 2nd IF stage.  Did this above the chassis by inserting the stripped ends of the gimmick caps small diameter wire into the appropriate tube socket holes of the subject tubes, and then reinserting the tubes.  Worked pretty well.  More recently I have used either a Rockland frequency synthesizer or a URM-25 signal generator as an external BFO,   Injecting the signal into the IF chain, makes for a very robust and adjustable injection level. 

I also have an RCH which as built has a very robust BFO.

Chris AJ1G Stonington CT




Sent from my iPhone

> On Sep 8, 2019, at 22:43, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
> 
> I have always thought the Scott receivers were excellent.
> 
> One of the first such I ever had was an SLR-F....which was named the RCH by the Navy.
> 
> The SLR-F/RCH covers some MF and lower HF frequencies, up to 24 MHz.
> 
> I have two now, one of which is deaf, which I want to restore and use.
> 
> They are excellent receivers, stable, reliable, not particularly sensitive, but sensitive 
> enough.
> 
> And I really like the flywheel tuning.
> 
> The dial on your SLR-M looks almost identical to that in the SLR-F.
> 
> BTW, if you don't know, the SLR stand for Super Low Radiation.
> 
> Ken W7EKB
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