[ARC5] Selectivity ratings of ARC-5 receivers.

[Kenneth G. Gordon]

On 28 Oct 2013 at 20:35, Dennis Monticelli wrote:

> They may only be talking dB voltage, not dB power.

Ah, yes. Of course. I ALWAYS forget that difference. Rats! They ARE talking 
about db voltage.

>  So 2X is 6dB and
> 1000X is 60dB (vs 3dB and 30dB respectively in the power domain).   A
> 6 to 60dB shape factor of 26/7.3 seems about right for that IF strip.

According to the maintenance manual, that is exactly what it is. 

BTW, I have a document here (and I have no idea where it came from), 
which discusses ARC's experimentation with narrowing up the selectivity of 
those receivers after WWII by simply moving the two coils in the IF cans a bit 
further apart.

They were able to easily achieve 3 KHz at 6 db down even with the 6 - 9.1 
Mc receivers, with no loss in IF gain.

I bought a bunch of nylon "washers" to experiment with that idea. Doesn't 
look too difficult.

Thanks, Dennis.

Ken W7EKB