Bill, Carl answered most of this already, but here's another point.
Most of the rigs built in the past 15 years had a roofing filter which was
in its first IF, somewhere between 45 and 70 MHz. These were typically only
2-pole filters and wide as a barn door (20 kHz with skirts that were not
very steep). NOBODY ever advertised this filter within their rigs. They
advertised the IF filters (the ones you are probably thinking of) in the 2nd
and 3rd IF. It would be expensive and difficult to build a good filter at
these high IF frequencies. The problem is, with all of these rigs, a lot of
undesirable stuff happened before the signal reached the good crystal IF
filters in the 2nd IF.
By building a band receiver rather than a general coverage receiver, Ten-Tec
was able to keep the first IF at a much lower frequency (9 MHz) and use a
good quality crystal filter as this "roofing filter". This keeps the
garbage out of the later stages of the receiver.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Able2fly@aol.com
Sent: Tuesday, August 03, 2004 10:46 AM
To: tentec@contesting.com
Subject: [TenTec] Why "roofing" ?
Can someone please explain how a "roofing" filter differs from the old
fashioned (band pass) IF filter? Or is it just another name for it?
Bill K3UJ
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