poor-man's oven
I recall some years ago folks were talking about putting a PTC
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency
as a sort of poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1%
to 0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally
inexpensive thermistor, glued on on the other, hooked em both up to 3.3
or 5V.
Yeah, there's issues with room air blowing on it, and tolerances in both
the XO and thermistor, so your absolute frequency accuracy may not be so
hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but I
couldn't find it. There was some stuff from Oct 2007, but that was in
the context of a more complex circuit, and the thermistor was the
sensor. (discussions of TE devices too)
We did this years ago on a 430 MHz data radio with an utterly uncompensated crystal that would drift through the passband. After building our own for a while, we discovered that Yaesu had something even better available through their replacement parts shop -- a spring clip with PTC that snapped tightly over the crystal case. I never did any formal measurements, but it did improve stability quite a bit for radios that were sitting in uncontrolled environments.
John
On Jun 4, 2017, 8:18 AM, at 8:18 AM, jimlux jimlux@earthlink.net wrote:
I recall some years ago folks were talking about putting a PTC
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the
frequency
as a sort of poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1%
to 0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally
inexpensive thermistor, glued on on the other, hooked em both up to 3.3
or 5V.
Yeah, there's issues with room air blowing on it, and tolerances in
both
the XO and thermistor, so your absolute frequency accuracy may not be
so
hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but
I
couldn't find it. There was some stuff from Oct 2007, but that was in
the context of a more complex circuit, and the thermistor was the
sensor. (discussions of TE devices too)
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My SDR-1000 showed substantially less "WWV drift" after adding
the PTC thermistor to the TCXO. Sorry, no measurements because
that was before I had a GPSDO.
Mikr - AA8K
On 06/04/2017 08:13 AM, jimlux wrote:
I recall some years ago folks were talking about putting a PTC
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the
frequency as a sort of poor-man's OCXO.
Maybe you want to check out the work of Hans Summers he has done some
impressive low cost stuff:
http://www.hanssummers.com/ocxosynth.html
http://www.qrp-labs.com/ocxokit.html
Ralph
On Sun, Jun 4, 2017 at 07:19 jimlux jimlux@earthlink.net wrote:
I recall some years ago folks were talking about putting a PTC
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency
as a sort of poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1%
to 0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally
inexpensive thermistor, glued on on the other, hooked em both up to 3.3
or 5V.
Yeah, there's issues with room air blowing on it, and tolerances in both
the XO and thermistor, so your absolute frequency accuracy may not be so
hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but I
couldn't find it. There was some stuff from Oct 2007, but that was in
the context of a more complex circuit, and the thermistor was the
sensor. (discussions of TE devices too)
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
The gotcha is that you have multiple systems working against each other. The crystal in the TCXO has
one temperature characteristic. The compensation in the TCXO has a temperature characteristic. They
cancel each other out to a limited degree. The residual slope may (or may not) be as shallow as you
might think. Your PTC is at an arbitrary point on the residual curve. A somewhat more subtle issue is
the gradient between your PTC, the crystal, and the compensation as it cycles.
If the TCXO really isn’t a full TCXO, then some of this goes away. A +/- 2 ppm 0-50C “TCXO" may not have
any compensation in it at all. Some 0 to 70C parts are done as 2 ppm 0 to 50 and only compensated at the
hot end. They actually may be worse with the PTC than at room...
Yes this all assumes an AT cut in the TCXO. That’s a pretty good bet ….
Bob
On Jun 4, 2017, at 8:13 AM, jimlux jimlux@earthlink.net wrote:
I recall some years ago folks were talking about putting a PTC thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency as a sort of poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1% to 0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally inexpensive thermistor, glued on on the other, hooked em both up to 3.3 or 5V.
Yeah, there's issues with room air blowing on it, and tolerances in both the XO and thermistor, so your absolute frequency accuracy may not be so hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but I couldn't find it. There was some stuff from Oct 2007, but that was in the context of a more complex circuit, and the thermistor was the sensor. (discussions of TE devices too)
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bob, at the same time, look at all the guys here who absolutely insist that
the only way to use a double-oven OCXO is to put it in a tightly
temperature controlled environment. "Nuts", yes, but that's why we're here!
I myself have been extremely disappointed with the aging characteristics of
low-end TCXO's. They seem to age even worse than plain old crystal
oscillators, My theory, is this is because the temperature compensation
components are themselves aging more than an AT cut crystal does by itself,
but I've never ripped into one (they're way too tiny to rip into anyway!).
Tim N3QE
On Sun, Jun 4, 2017 at 9:36 AM, Bob kb8tq kb8tq@n1k.org wrote:
Hi
The gotcha is that you have multiple systems working against each other.
The crystal in the TCXO has
one temperature characteristic. The compensation in the TCXO has a
temperature characteristic. They
cancel each other out to a limited degree. The residual slope may (or may
not) be as shallow as you
might think. Your PTC is at an arbitrary point on the residual curve. A
somewhat more subtle issue is
the gradient between your PTC, the crystal, and the compensation as it
cycles.
If the TCXO really isn’t a full TCXO, then some of this goes away. A +/- 2
ppm 0-50C “TCXO" may not have
any compensation in it at all. Some 0 to 70C parts are done as 2 ppm 0 to
50 and only compensated at the
hot end. They actually may be worse with the PTC than at room...
Yes this all assumes an AT cut in the TCXO. That’s a pretty good bet ….
Bob
On Jun 4, 2017, at 8:13 AM, jimlux jimlux@earthlink.net wrote:
I recall some years ago folks were talking about putting a PTC
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency as
a sort of poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1%
to 0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally
inexpensive thermistor, glued on on the other, hooked em both up to 3.3 or
5V.
Yeah, there's issues with room air blowing on it, and tolerances in both
the XO and thermistor, so your absolute frequency accuracy may not be so
hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but I
couldn't find it. There was some stuff from Oct 2007, but that was in the
context of a more complex circuit, and the thermistor was the sensor.
(discussions of TE devices too)
mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
Hi
There is no way to know how every outfit makes their products. My guess is that
the temperature compensation “stuff” is pretty stable. At least it has been on all
the product I’ve designed :) I’d bet that the crystals in the TCXO’s are the culprit.
In some of the factories I’ve visited, they package their own crystals. They bring in the
blanks pre-sorted and take it from there. The aging pretty much all comes from the
plating / packaging process. It would not surprise me to find that long term aging is
not a major focus on parts headed for sort lifespan consumer electronics ...
Bob
On Jun 4, 2017, at 9:45 AM, Tim Shoppa tshoppa@gmail.com wrote:
Bob, at the same time, look at all the guys here who absolutely insist that
the only way to use a double-oven OCXO is to put it in a tightly
temperature controlled environment. "Nuts", yes, but that's why we're here!
I myself have been extremely disappointed with the aging characteristics of
low-end TCXO's. They seem to age even worse than plain old crystal
oscillators, My theory, is this is because the temperature compensation
components are themselves aging more than an AT cut crystal does by itself,
but I've never ripped into one (they're way too tiny to rip into anyway!).
Tim N3QE
On Sun, Jun 4, 2017 at 9:36 AM, Bob kb8tq kb8tq@n1k.org wrote:
Hi
The gotcha is that you have multiple systems working against each other.
The crystal in the TCXO has
one temperature characteristic. The compensation in the TCXO has a
temperature characteristic. They
cancel each other out to a limited degree. The residual slope may (or may
not) be as shallow as you
might think. Your PTC is at an arbitrary point on the residual curve. A
somewhat more subtle issue is
the gradient between your PTC, the crystal, and the compensation as it
cycles.
If the TCXO really isn’t a full TCXO, then some of this goes away. A +/- 2
ppm 0-50C “TCXO" may not have
any compensation in it at all. Some 0 to 70C parts are done as 2 ppm 0 to
50 and only compensated at the
hot end. They actually may be worse with the PTC than at room...
Yes this all assumes an AT cut in the TCXO. That’s a pretty good bet ….
Bob
On Jun 4, 2017, at 8:13 AM, jimlux jimlux@earthlink.net wrote:
I recall some years ago folks were talking about putting a PTC
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency as
a sort of poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1%
to 0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally
inexpensive thermistor, glued on on the other, hooked em both up to 3.3 or
5V.
Yeah, there's issues with room air blowing on it, and tolerances in both
the XO and thermistor, so your absolute frequency accuracy may not be so
hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but I
couldn't find it. There was some stuff from Oct 2007, but that was in the
context of a more complex circuit, and the thermistor was the sensor.
(discussions of TE devices too)
mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
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and follow the instructions there.
Look at the temperature coefficient of your XO. Then figure a very simply
control loop and a thermistor will keep a block of aluminum within 0.1C of
a set point. Use a decent size block and insulation
We drilled a deep hole then epoxied the thermistor. I think this step is
important as you want to measure the center of the black, not the surface..
Then epoxied a TEC (aka Peltier device) to the Al Block. TECs are nice
because they can both cool and heat. On the other side other TEC was a
rather large heat sink (or heat source depending on the polarity) a uP and
a PID loop controlled the output current. Place an insulator over the
controlled end of the block. I think a stainless steel vacuum insulated
coffee mug works well.
I think cheap thermistors are OK as they will never, in use, see
temperature swings of more then 0.1C so who care if they are linear or not.
They are all linear enough over a short range. What you pay for is being
perfect over a 100C range, you don't need that.
We used the pelter because we preferred a cool "oven" to a hot one. The
theory has that we get less electronic noise so we ran the TEC in cooling
mode. But for your use a resistive heater would be cheaper. But in
either case you see a coffee mug with a round chunk of Al shoved in and
heat sink fins showing.
When I was doing some contraction work, I thought of it would be fun to
toss an XO in the big hole that was going to get a truckload of concrete
poured into it. The temperature down there would be very stable.
On Sun, Jun 4, 2017 at 5:13 AM, jimlux jimlux@earthlink.net wrote:
I recall some years ago folks were talking about putting a PTC thermistor
on the TCXO of a FlexRadio SDR1000 to stabilize the frequency as a sort of
poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1% to
0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally
inexpensive thermistor, glued on on the other, hooked em both up to 3.3 or
5V.
Yeah, there's issues with room air blowing on it, and tolerances in both
the XO and thermistor, so your absolute frequency accuracy may not be so
hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but I
couldn't find it. There was some stuff from Oct 2007, but that was in the
context of a more complex circuit, and the thermistor was the sensor.
(discussions of TE devices too)
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/m
ailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California
Moin Chris,
On Sun, 4 Jun 2017 13:49:29 -0700
Chris Albertson albertson.chris@gmail.com wrote:
We used the pelter because we preferred a cool "oven" to a hot one. The
theory has that we get less electronic noise so we ran the TEC in cooling
mode. But for your use a resistive heater would be cheaper. But in
either case you see a coffee mug with a round chunk of Al shoved in and
heat sink fins showing.
What is the reason why you'd expect less noise with a TEC?
Attila Kinali
--
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering. -- The Doctor
Really??
The circuitry employed is something of a joke surely?
Relying on the MOSFET characteristics to limit warm up current is unwise.
The temperature sensor also would appear to suffer from large variations in output from one part to another.
Bruce
On 05 June 2017 at 01:21 "R. Kuehn" <rekuehn@gmail.com> wrote:
Maybe you want to check out the work of Hans Summers he has done some
impressive low cost stuff:
http://www.hanssummers.com/ocxosynth.html
http://www.qrp-labs.com/ocxokit.html
Ralph
On Sun, Jun 4, 2017 at 07:19 jimlux <jimlux@earthlink.net> wrote:
I recall some years ago folks were talking about putting a PTC
thermistor on the TCXO of a FlexRadio SDR1000 to stabilize the frequency
as a sort of poor-man's OCXO.
It's also referenced at
http://www.setileague.org/askdr/xtaloven.htm
where he says "order of magnitude improvement" with no numbers (from 1%
to 0.1% or from 1 ppb to 0.1 ppb?)
I wonder how well that actually works.
Say you bought an inexpensive (perhaps non TC) XO and an equally
inexpensive thermistor, glued on on the other, hooked em both up to 3.3
or 5V.
Yeah, there's issues with room air blowing on it, and tolerances in both
the XO and thermistor, so your absolute frequency accuracy may not be so
hot. But what sort of medium to long term performance can one expect.
I did some searches, because I'm sure we've discussed this before, but I
couldn't find it. There was some stuff from Oct 2007, but that was in
the context of a more complex circuit, and the thermistor was the
sensor. (discussions of TE devices too)
_______________________________________________
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_______________________________________________
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