[Elecraft] Roofing Filters - An Empirical Test

[Dauer, Edward]

I would be interested in knowing if anyone has done an empirical test and
observed the difference directly.  Specifically, since the sub receiver is
identical to the main receiver in every way, if someone has a K3 with, for
example, a 400 Hz filter in the main but only a wider set in the sub, and
then set the DSP bandwidth on both receivers to 200 Hz or so, what
differences they actually noticed.  I have no doubt the theory and the
engineering are sound - just curious what the difference sounds like in
the field . . . 

Ted, KN1CBR




>On May 12, 2014, at 9:33 AM, Jerome Sodus <jsodus at comcast.net> wrote:
>
>>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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