[ARC5] Selectivity ratings of ARC-5 receivers.

[Geoff]

However receiver sensitivity and gain ratings have always been in dBuV AFIK 
at the RF thru audio driver stages. It changes to dBW at the audio output 
but based on dBuV as the source.
National, Collins and others listed stage gains in dBuV in the manuals even 
for commercial gear.

Carl


----- Original Message ----- 
From: "Mike Feher" <n4fs at eozinc.com>
To: <kgordon2006 at frontier.com>; "'Dennis Monticelli'" 
<dennis.monticelli at gmail.com>; "'ARC-5 List'" <arc5 at mailman.qth.net>
Sent: Tuesday, October 29, 2013 12:15 AM
Subject: Re: [ARC5] Selectivity ratings of ARC-5 receivers.


> 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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