On Mon, 28 Mar 2005 21:19:44 GMT, "Dale Parfitt"
wrote:


"Bill N2CQR MOHBR" wrote in message
. com...
I really enjoyed the message thread sparked by the pictures of
Dale's very FB HB RX. We need more of that kind of discussion...

Here is what I've been working on in London:

Hi Bill,
I have trouble keeping up with where in the world you are, but visit your
site regularly to see what you are up to.
I would encourage others to brew their own xtal filters. uP xtals are cheap
enough today that you can buy a pile and match up what you need. W7ZOI's
articles on crystal filters takes the mystery out.
Probably the most difficult part is characterizing individual crystals so
you can plug in the numbers. I use an HP network analyzer, but Wes also
shows a test jig for doing this. Alternatively, N2PK's VNA will do an
excellent job. In the end, you can make better filters than you can buy- and
for a heck of a lot less $$.
N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz
filter; the other with a homebrew 250 Hz filter- it took no imagination to
discern which one was cleaner.
Now, I'll go have a look at Bill W0IYH's site.

Dale W4OP

Dale & Bill,
Jim, K8IQY has the Precision VXO and Crystal test rig that uses the
PVXO as a driver for the candidate IF filter crystal under test. I'm
currently building both of those.

73,
Ted KX4OM