J M Noeding wrote:

On Wed, 16 Jun 2004 22:23:01 -0700, Tim Wescott
wrote:


need a low-noise xtal oscillator using 14.7 or 15.7MHz rubber xtals in
series mode circuit to sweep xtal filters with good as possible noise
distance. The available xtals are believed to pull +/-10kHz or more.


This is a fairly standard circuit -- why not just look in an ARRL manual
or one of the many QRP transmitter designs for an oscillator? You can
check for phase noise by mixing it with a good (fixed) crystal
oscillator, or you can just trust it.


many of those amateur constructions are not very good, just put
together, and if they generate a sort of signal the constructors are
happy without worrying what they sound like. Some of the constructor
have of course well reputation, but ARRL handbook usually don't tell
who have designed it.

and in this case I want a definite low noise construction.

Remember when I built my first of many VHF/UHF beacons made after an
amateur concept I listened to the carrier with R-4C and converter, the
sound was awful, so I decided to built a new 12MHz xtal oscillator
using some practice described by Ulrich Rohde, DJ2LR. The improvement
on 144MHz was increadible, and I later learned that the sound was very
good compared with all sorts of rubbish somebody else used, even on
2320MHz

Jan-Martin, LA8AK
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

Well, that's why I suggested verifying it's phase noise with a good
fixed crystal oscillator. I certainly wouldn't proceed without doing
this check -- the nice thing is that unless the oscillators lock
together too tightly you get an upper bound to your phase noise, so you
know when you're doing well enough.

"Solid State Design for the Radio Amateur" has some good (older)
circuits. It's been superseded by "Experimental Radio Design" which
should also have some good ones.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com