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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