[Elecraft] [K3] Roofing filters are misunderstood

[Nr4c]

Think of your roof blocking the rain so the ceiling doesn't have to work so hard. 

It's not used for band-pass, it's to let the DSP work less. 

Sent from my iPhone
...nr4c. bill


> On May 12, 2014, at 3:01 PM, Bill Turner <dezrat at outlook.com> wrote:
> 
> ORIGINAL MESSAGE:          (may be snipped)
> 
>> On 5/12/2014 9:33 AM, Jerome Sodus 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
> 
> REPLY:
> 
> I still don't get it. What does the word "roof" have to do with bandpass? That's where the confusion comes from.
> 
> 73, Bill W6WRT
> dezrat at outlook.com
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