One more data point on the term "roofing filter."
I have a copy of the June 1981 RSGB Radio Communications magazine that
reviewed Drake's TR7.
It describes the design as follows:
"A low-noise, wide-dynamic range amplifier is used at 48.05 MHz to
precede the 10-KHz wide roofing filter."
Leaving aside the RSGB's odd use of hyphens, it describes the filter as
a "roofing filter" although Drake does not use the term in its technical
manual.
Is it the case that "roofing filter" is UK terminology that has made its
way to the US side of the pond only recently?
Jack
Geoffrey Mackenzie-Kennedy wrote:
Just cannot resist saying this Jack, the term "roofing filter" has
certainly been around for a long time - close to 50 years I believe,
possibly longer. I think that I first ran across the term being used
to identify the first IF filter in an Independent Sideband Receiver
which the company for whom I worked manufactured for HF Point-to-Point
applications in the very late 1950's, along with companion high power
ISB transmitters.
Perhaps some other term might be less confusing and prevent any misuse
of the term , but don't let us change from "roofing filter" now!!
73,
Geoff
GM4ESD
Jack Smith wrote:
The term "roofing filter" has been around a long time, at least 20
years.
Usually used in the context of up-converting receivers, where the
first IF is 40.455 MHz, or 45.000 MHz or even higher. The term means
the first selective filter in the receiver. If the first IF is > 30
MHz, the roofing filter is generally wider than one normally needs
for SSB or even AM, and the receiver's ultimate selectivity is
provided in a later IF stage.
As to why it is called a "roofing" filter, I imagine it derives from
the fact that it puts a "roof" over the receiver's selectivity.
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