On Mar 23, 5:11*pm, "Tio Pedro" wrote:
"Edward Feustel" wrote in message news: * Pete,
The Ten Tec Transciever filters are at 9 MHz except in the "general
coverage up convert" receivers. in which case they are not narrow at
all.

Note that INRAD offers roofing filters 4-5 KHz wide at VHF frequencies
from 40 to 73 MHz ( see page 13 of their catalog ) with i/o impedances
of 50 ohms :http://www.inrad.net/inrad.php?mode=catalog

Ed, N5EI

Thanks Ed, *I haven't kept with this at all. *The INRAD 4 to 5 kHz BW
roofing filters sound very interesting though. *A lot better than the
18-kHz *BW 40.455-MHz monolythics I've played with in the past.

Pete

Hello, to you all who answered this thread lately,
I learned quite a lot, although I knew part of it.

What I can see is that there are roofing filters in the low VHF that
have a narrow bandwidth of about 5kHz. I also learned (was reminded)
that the dissipation power of a crystal could be less than the power
that it could pass. Thanks for the INRAD catatolg, I knew the firm,
I'll go back and have a look at the whole site; it is still my opinion
that it is cheaper to build than buy.

My goal is to have a roofing filter steep enough to be content with
the IQ processing in software and not in hardware, with a 2nd IF in
the dozens of kHz range.

A propos crystal filter, I experienced the SWAN 700CX 16-pole filter -
a dream!! I still have the transceiver in the basement, I would have
to reconstruct the electrolytics I suppose.

I do have the Rhode article on PDF, along with the basic program
adapted to MS-DOS QBASIC, just ask for it, I would send them, as I do
not know how to annex files to the thread.

73 from Jean-Daniel HB9AKQ