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Arthur Pozner Apr 9, 9:31 am show options
Newsgroups: rec.radio.shortwave
From: (Arthur Pozner) - Find messages by this
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Date: Sat, 9 Apr 2005 12:31:37 -0400
Local: Sat,Apr 9 2005 9:31 am
Subject: Question for Pete KE9OA
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455KHz resonators are commonly used in remote controls. Have not tried
building a lattice or a ladder filter with them yet. But, what if
it just might be succesful-- that's why experimenting is fun.
Collins mechanical filters do have very good rejection just as Pete has
stated, in fact, at 455KHz it might as well have better
selectivity/rejection/low distortion/phase linearity than any other
filter type. I believe R-2000 is a triple conversion receiver, has
anybody ever try changing out the first (roofing) filter.Just for the
sake of experimenting.
------------------------------------------------
Sadly the R2000 uses a variable first IF. Or at least that is what
I tink after a long study of the service manual.
My large diagram is at work, I was in a hurry when I left Friday.

But looking at the service manual that I have at home:
Thefirst ceramic fitler is centered at 9.875, but is rated at +/-
130KHz for the 3db points, and +/- 2MHz! for -30dB points.
The manual says the first If 45.85~45.90MHz then that is
converted to 9.850~9.90 MHz.

I doubt if there is enough market numbers for anyone to make
and market a 9.865MHz +/-15KHz filter. Ihave looked, but have
found one. Building a latice filter is in my dream book.

I tried Pete's suggestions and a set of three stacked 555Is in
series may do the trick. I put the widest one first, followed the
narrower, ending with the narrowist. They are all within spec,
but after measuring 11, I went with the narrowist, that had the
proper center freq. 1 had the center freq at 453.8.

I am listining as we speak and the results are well worth the effort.
It pays to have frineds with well stocked junk rooms. I was given
12 older maxon MCB25 CBs. One was still in the plastic, so I
decided to add that one to the RF stable. That is just what I need,
another radio!

I tried to use the 455 3 pinresonators and found they make great
CW fitlers. The bnadwidth is too naroow, and by stacking them you
get pretty decent skirts.

Terry