[Elecraft] [K3] Roofing filters are misunderstood

[Jerome Sodus]

Hello Bill,
The term "roofing-filter" made sense back in the 1980's when I designed
roofing-filters at 70 MHz.
Bandwidths would be in tens of KHz.
The purpose then was to protect downstream circuitry by rejecting very
strong out-of-band signals that could cause overload; selectivity was not
the purpose. 
Selectivity was done further downstream.
So the term has become corrupted over the years.
73 Jerry KM3K


-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill
Turner
Sent: Monday, May 12, 2014 1:07 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] [K3] Roofing filters are misunderstood

ORIGINAL MESSAGE:          (may be snipped)

On 5/11/2014 7:25 PM, Fred Jensen wrote:
> I too think roofing filters are really not well understood. 

REPLY:

A large part of the misunderstanding is due to the name. Whoever chose 
the name "roofing" did a great disservice. A better name would simply be 
it's function:  1st I.F. filter.

That's what it is and that's what it does.

I have always thought that "roofing" was a marketing ploy to imbue it 
with some kind of magical powers.

73, Bill W6WRT

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