At 06:05 PM 5/29/06, Ken Brown wrote:
>Every filter in my receiver from the
>frontend bandpass filters to the first IF and second IF filters limit
>bandwidth before the final audio filtering. So there is virtually no
>filter, by that definition, that is not a roofing filter. I suspect
>that without a clear definition, the term is being used slightly
>differently by every one who uses it.
(snip)
For those of us in commercial telecommunications vocations, "roofing
filter" meant something that had an upper frequency cut-off...ie: a
"ROOF" over a lower band of used frequencies. (Also called a "Low
pass filter.") This roofing term was used for years in microwave
baseband applications.
Initially, I was confused with the "new" amateur radio use of the
term, since it NOW means a bandpass filter at or near the input
stages of a receiver. Hmmmm... is this now to mean the "roof" over
the radio? :-)
OK.. fine with me. I'll not be stubborn about it. It would be nice
to know when an electronics entity changes the meaning of a term....
After all, we did have some advance notice about the "cycles" to
"Hertz" changeover some years ago... :-)
Happy Memorial Day...
Perry w8au
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