[ARC5] Selectivity ratings of ARC-5 receivers.

[Mike Feher]

They are strictly talking about arbitrary amplitude ratios of 2X or 1000X.
So, if you want to think of it in terms of power then it is 3 dB to 30 dB,
and in voltage it would be 6 dB to 60 dB . 73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of Kenneth G. Gordon
Sent: Monday, October 28, 2013 11:45 PM
To: Dennis Monticelli; ARC-5 List
Subject: Re: [ARC5] Selectivity ratings of ARC-5 receivers.

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
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