[ARC5] ARC-2: Smart People Needed

[Kenneth G. Gordon]

On 1 Apr 2014 at 23:52, David Stinson wrote:

> Simplified circuit of the RT-91/ARC-2 receiver IF:
> 
> http://home.netcom.com/~arc5/ARC-2/ARC2IFCir.jpg

What are the values of the capacitors which are in parallel with the IFs' 
variable inductors?

Have you tried increasing the "Q" by reducing the value of the 5 pfd coupling 
capacitors?

> Why would reducing the coupling  here make
> the IF broader??

I don't know for sure, but I very vaguely remember something about 
"top-coupling" vs "bottom coupling" in regard to coupled circuits. I know in 
one receiver in an ARRL handbook, the selectivity was increased by going to 
"bottom coupling" although I cannot now remember exactly what that is or 
how it is implemented.

I think that it may have been something like the 5 pfd inter-IF coupling 
capacitors were moved from the "top" of the coils where they are now, to the 
"bottom" between the two grounded ends.

But I don't really remember it either. Maybe someone else here knows what I 
am talking about: I sure don't remember.

Have you looked at your copy of Terman's?

Ken W7EKB