"Bill N2CQR MOHBR" wrote in message
om...
Dale: I was faced with doing the complex analysis of the individual
crystal
parameters when I was building my first superhet (W1FB's "Barebones"
aka
"Barbados" RX). I just skipped all of the analysis and used the same
capacitor
values that Doug had used in his version. I'm sure my filter's
passband wasn't nearly as pretty as it could have been, but it
definitely produced the
desired "single signal effect." I was happy.

As I mentioned in the earlier post, I have an 80/40 meter tube type RX
(Mate
for the Mighty Midget"). It has a 455 kHz IF. This makes homebrew
filter making difficult! I tried, but crystals were hard to come by
in that freq
range. In the end, I threw in the towel and just used a 455 Khz IF
can
in lieu of the filter. Great for listening to AM! But now I want to
narrow
it down a bit, so I'm thinking about yanking out the IF can and
replacing
it with a commercial 455 kc filter from the junkbox. I need to figure
out
how to handle the impedance matching issues (input and output).

73 Bill M0HBR N2CQR CU2JL

Hi Bill,

I too built the Barbados RX- don't know what happened to it though.
Have you thought of using a Murata ceramic filter in your tube RX?
They make a 4KHz unit for under $3. Not CW selectivity, but I'll bet it will
be an improvment over what you have. Typcial Zin and Zout is around 1K.
Although I have never tried it, I wonder about the possibility of brewing
your own ceramic filter from some of Murata's 455KHz ceramic resonators.
Although not the Q of a quartz crystal, it may be worthwhile. I have some
here and think I'll put one on the network analyzer and see what
characteristics I get.

Dale W4OP