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Old June 17th 04, 12:41 AM
J M Noeding
 
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Default Need a low noise VXO for narrow sweep

Hi

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.

Any suggestions.

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/c.htm
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm
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Old June 17th 04, 06:20 AM
Tim Wescott
 
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John Miles wrote:

In article ,
says...

Hi

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.

Any suggestions.



Use a DDS hooked up to your PC's parallel port?

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------


A DDS isn't going to have good enough phase noise. The OP is correct in
using a pullable crystal oscillator.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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Old June 17th 04, 06:20 AM
Tim Wescott
 
Posts: n/a
Default

John Miles wrote:

In article ,
says...

Hi

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.

Any suggestions.



Use a DDS hooked up to your PC's parallel port?

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------


A DDS isn't going to have good enough phase noise. The OP is correct in
using a pullable crystal oscillator.

--

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


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Old June 17th 04, 06:23 AM
Tim Wescott
 
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Default

J M Noeding wrote:

Hi

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.

Any suggestions.

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/c.htm
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm


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.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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Old June 17th 04, 06:23 AM
Tim Wescott
 
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Default

J M Noeding wrote:

Hi

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.

Any suggestions.

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/c.htm
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm


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.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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Old June 17th 04, 12:35 PM
Richard Hosking
 
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Default

Why do you need such such good phase noise?
An average oscillator will be good enough to measure to -70 dBc or so.
You could use a DDS with a crystal clock - this will have good close in
phase noise (neasrly as good as the clock), though coherent spurs might
be a problem.

Richard


J M Noeding wrote:
Hi

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.

Any suggestions.

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/c.htm
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm


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Old June 17th 04, 12:35 PM
Richard Hosking
 
Posts: n/a
Default

Why do you need such such good phase noise?
An average oscillator will be good enough to measure to -70 dBc or so.
You could use a DDS with a crystal clock - this will have good close in
phase noise (neasrly as good as the clock), though coherent spurs might
be a problem.

Richard


J M Noeding wrote:
Hi

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.

Any suggestions.

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/c.htm
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm


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Old June 17th 04, 01:52 PM
J M Noeding
 
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Default

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
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