Paul_Morphy wrote:
"Ken Scharf" wrote in message
. ..


Looks like some fun ahead experimenting with
this and maybe a homebrew spectrum analyzer in the
works to scan around 8.3866mhz (in my test oscillator
I'm getting 8.389855mhz, better let the oscillator and
the frequency counter warm up for a while).


Maybe they're designed for a circuit with parallel C, not series type..

You're probably intending to make a sweep generator and view the bandpass on
a scope, right? This site has a suitable sweep generator
http://www.intio.or.jp/jf10zl/


Time to smash some surplus 9pin tube sockets up for
crystal socket pins ....


But you're going to solder the xtals directly to boards for the actual
filters, right? You could make a board pretty easily, all the xtals having
the same pin separation. Lotta drilling.

Inspired by you I bought a bunch of HC-49s on eBay. They will plug into a
DIP socket, which is what I'm using in my measurement jig. Buffered
oscillator running off 9 V, no pulling when I hook up the counter.
http://tinyurl.com/3dpdn

73,

"PM"


Yes I built a similar oscillator, a bit cruder though
I clipped my scope probe to the output and connected the
probe to the counter. I noticed that the frequency drifts somewhat
when the crystal is first plugged into the test oscillator. I
guess I need to let the frequency counter warm up for about a
half hour before taking any measurements, the oscillator may
also need a warmup period, and perhaps even the crystal.
If you handle the crystal while inserting it into the socket
the heat from your hands probably affects the crystal, though
I noticed that if I continue to hold the crystal with
two fingers things stablize more quickly (is my hand acting
as a crystal oven?) Total drift is under 250hz.