Using non-overtone crystal in overtone mode?
 

Are "overtone" crystals cut differently than "fundamental" crystals?
Or are they just specified differently?

In particular, say I took a garden-variety 20MHz fundamental
microprocessor crystal and instead used it at its fifth overtone,
trying to hit 100 MHz. The LC network is there to make sure that it's
on its fifth overtone. Will this "misuse" mean that the oscillator
will be harder to start up, less stable, more noisy, ???, than a
crystal oscillator made out of a real overtone crystal? I don't mind
if I "miss" 100 MHz by a several tens or hundreds of ppm, as long as
it's stable there.

If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)

Tim.

Tim Shoppa wrote:

Are "overtone" crystals cut differently than "fundamental" crystals?
Or are they just specified differently?

In particular, say I took a garden-variety 20MHz fundamental
microprocessor crystal and instead used it at its fifth overtone,
trying to hit 100 MHz. The LC network is there to make sure that it's
on its fifth overtone. Will this "misuse" mean that the oscillator
will be harder to start up, less stable, more noisy, ???, than a
crystal oscillator made out of a real overtone crystal? I don't mind
if I "miss" 100 MHz by a several tens or hundreds of ppm, as long as
it's stable there.

If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)

Tim.

Overtone crystal cuts are not fundamentally different from fundamental
crystal cuts, so to a 1st-order approximation they'll work. Crystals do
have spurious responses that can cause mode jumping, and these responses
don't necessarily map the same way the overtones do, so using a 20MHz
crystal at 100MHz may or may not work, depending on the luck of the
draw. Other than that I don't know of any differences.

IIRC Digi-Key has 100MHz crystals, but I may be remembering 100MHz
oscillators. YMMV. IDNKWTFIAS. Caviat Emptor (so _that's_ what CE
means! Here I thought it was a quality mark). Etc.

--

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

Tim, would a 100MHz oscillator module do for you? See DigiKey
CTX318LVCT-ND, for example.

Cheers,
Tom

On 28 Feb 2005 11:23:50 -0800, "Tim Shoppa"
wrote:

Are "overtone" crystals cut differently than "fundamental" crystals?
Or are they just specified differently?

In particular, say I took a garden-variety 20MHz fundamental
microprocessor crystal and instead used it at its fifth overtone,
trying to hit 100 MHz. The LC network is there to make sure that it's
on its fifth overtone. Will this "misuse" mean that the oscillator
will be harder to start up, less stable, more noisy, ???, than a
crystal oscillator made out of a real overtone crystal? I don't mind
if I "miss" 100 MHz by a several tens or hundreds of ppm, as long as
it's stable there.

---
You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental. It's more like the slab of
crystal is vibrating like the drumhead of a steel drum with small
areas of the slab vibrating at higher frequencies, instead of the
entire slab virbarting at just one frequency.

Check out "Chladni patterns" if you're interested.

Here's some pattrens for violin tops and circular plates:

http://www.phys.unsw.edu.au/~jw/chladni.html
---

If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)

---
Anybody who makes crystals ought to be able to help you out; here's a
start:

http://www.icmfg.com/

--
John Fields

John Fields wrote:
On 28 Feb 2005 11:23:50 -0800, "Tim Shoppa"
wrote:


Are "overtone" crystals cut differently than "fundamental" crystals?
Or are they just specified differently?

In particular, say I took a garden-variety 20MHz fundamental
microprocessor crystal and instead used it at its fifth overtone,
trying to hit 100 MHz. The LC network is there to make sure that it's
on its fifth overtone. Will this "misuse" mean that the oscillator
will be harder to start up, less stable, more noisy, ???, than a
crystal oscillator made out of a real overtone crystal? I don't mind
if I "miss" 100 MHz by a several tens or hundreds of ppm, as long as
it's stable there.


---
You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental. It's more like the slab of
crystal is vibrating like the drumhead of a steel drum with small
areas of the slab vibrating at higher frequencies, instead of the
entire slab virbarting at just one frequency.

Check out "Chladni patterns" if you're interested.

Here's some pattrens for violin tops and circular plates:

http://www.phys.unsw.edu.au/~jw/chladni.html
---


If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)


---
Anybody who makes crystals ought to be able to help you out; here's a
start:

http://www.icmfg.com/


In an AT cut crystal the overtone modes are close, but not exactly on,
the odd harmonics of the fundamental. Furthermore, all of the
literature that I've read on AT cut crystals reports that they vibrate
in the bulk of the crystal, in shear mode -- see figure 7 he
http://literature.agilent.com/litweb/pdf/5965-7662E.pdf.

Perhaps you're thinking of SAW devices?

--

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

I don't know why off-the-shelf crystals are needed when Jan Crystal (Ft.
Myers FL) will make the crystal to your specifications in a few days for the
same amount of money. They can do fifth ot at 100 MHz. quite easily.

Jim



If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)

Tim.

On Mon, 28 Feb 2005 13:27:04 -0800, Tim Wescott
wrote:


Furthermore, all of the
literature that I've read on AT cut crystals reports that they vibrate
in the bulk of the crystal, in shear mode -- see figure 7 he
http://literature.agilent.com/litweb/pdf/5965-7662E.pdf.

Perhaps you're thinking of SAW devices?

---
No, I was thinking they vibrated in thickness compression. Thanks for
the correction.

--
John Fields

"Tim Wescott" wrote
in message ...
....
In an AT cut crystal the overtone modes are close, but not exactly on, the odd harmonics of the fundamental. Furthermore, all of
the literature that I've read on AT cut crystals reports that they vibrate in the bulk of the crystal, in shear mode -- see figure
7 he http://literature.agilent.com/litweb/pdf/5965-7662E.pdf.

One effect to watch out for with use of unspecified
overtone modes is that the behavior of the resonator
is not ideal; the presence or size of nearby spurs and
the Q depend on how uniform the thickness is that
determines frequency and the placement and size of
contact metal. The wavelength is typically much less
than the dimension along the non-shearing axis, so
having a single mode of resonance near the nominal
frequency or its overtones is not guaranteed, except
by careful construction and verification. So, clearly,
a guarantee about the behavior near the fundamental
resonance cannot be extended to the overtone modes.

If I was trying to build a stable and pure oscillator
operating at a crystal overtone, I would buy the
crystal specified for the overtone I would be using.

--
--Larry Brasfield
email:
Above views may belong only to me.

Larry Brasfield wrote:

"Tim Wescott" wrote
in message ...
...

In an AT cut crystal the overtone modes are close, but not exactly on, the odd harmonics of the fundamental. Furthermore, all of
the literature that I've read on AT cut crystals reports that they vibrate in the bulk of the crystal, in shear mode -- see figure
7 he http://literature.agilent.com/litweb/pdf/5965-7662E.pdf.


One effect to watch out for with use of unspecified
overtone modes is that the behavior of the resonator
is not ideal; the presence or size of nearby spurs and
the Q depend on how uniform the thickness is that
determines frequency and the placement and size of
contact metal. The wavelength is typically much less
than the dimension along the non-shearing axis, so
having a single mode of resonance near the nominal
frequency or its overtones is not guaranteed, except
by careful construction and verification. So, clearly,
a guarantee about the behavior near the fundamental
resonance cannot be extended to the overtone modes.

If I was trying to build a stable and pure oscillator
operating at a crystal overtone, I would buy the
crystal specified for the overtone I would be using.

I pointed that out in a previous post. But hey -- wouldn't it be fun to
have an oscillator that yodels?

--

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

On Mon, 28 Feb 2005 13:29:15 -0800, "RST Engineering \(jw\)"
wrote:

I don't know why off-the-shelf crystals are needed when Jan Crystal (Ft.
Myers FL) will make the crystal to your specifications in a few days for the
same amount of money. They can do fifth ot at 100 MHz. quite easily.

Jim



If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)

Tim.


a CB xtal will probably operate on 100MHz, althouth I've only seen
applications for 45 and 81MHz

-jm

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

In message .com, Tim
Shoppa writes
Are "overtone" crystals cut differently than "fundamental" crystals?
Or are they just specified differently?

In particular, say I took a garden-variety 20MHz fundamental
microprocessor crystal and instead used it at its fifth overtone,
trying to hit 100 MHz. The LC network is there to make sure that it's
on its fifth overtone. Will this "misuse" mean that the oscillator
will be harder to start up, less stable, more noisy, ???, than a
crystal oscillator made out of a real overtone crystal? I don't mind
if I "miss" 100 MHz by a several tens or hundreds of ppm, as long as
it's stable there.

If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)

Tim.

Overtone crystals are mechanical resonators and the overtone shear mode
which has additional shear planes within the volume wont occupy exactly
the same volume as the fundamental so the frequency will not be exactly
3X or 5X the fundamental but approx 2000ppm high or low?
The fundamental crystal will not be so accurately polished or
dimensioned as the overtone so it will not go well if at all also it may
have higher levels of spurious.
--
dd

"Tim Shoppa" wrote in message roups.com...
Are "overtone" crystals cut differently than "fundamental" crystals?
Or are they just specified differently?

In particular, say I took a garden-variety 20MHz fundamental
microprocessor crystal and instead used it at its fifth overtone,
trying to hit 100 MHz. The LC network is there to make sure that it's
on its fifth overtone. Will this "misuse" mean that the oscillator
will be harder to start up, less stable, more noisy, ???, than a
crystal oscillator made out of a real overtone crystal? I don't mind
if I "miss" 100 MHz by a several tens or hundreds of ppm, as long as
it's stable there.

If anyone knows of a place that ships off-the-shelf 100 MHz fifth or
seventh overtone crystals, I can avoid this whole exercise.... :-)

Tim.


Tim,

to get optimum performance one would grind the 100MHz 5.OT finer or
even polish it, and the thickness of the electrodes might be different
to get optimum Q.
But you should be ok by using a 20MHz fundamental in its 5th.

There are also manufacturers that make 100 in fundamental (up to about
200MHz), and many should have 100 in 5th as standard part...

Frank

On Mon, 28 Feb 2005 12:07:49 -0800, Tim Wescott wrote:


IIRC Digi-Key has 100MHz crystals, but I may be remembering 100MHz
oscillators. YMMV. IDNKWTFIAS. Caviat Emptor (so _that's_ what CE
means! Here I thought it was a quality mark). Etc.

Dialog news reader's tip popped up to say that CE is "creative
editing". It doesn't KWTF IDNKWTFIAS is, but I got everything but
the IAS part.

--
Best Regards,
Mike

On Mon, 28 Feb 2005 13:29:15 -0800, RST Engineering (jw) wrote:

I don't know why off-the-shelf crystals are needed when Jan Crystal (Ft.
Myers FL) will make the crystal to your specifications in a few days for the
same amount of money. They can do fifth ot at 100 MHz. quite easily.

Jim

Jan's what I was about to suggest. I thought the rock I needed would
have been off the shelf, but they made it and sent the test results.
--
Best Regards,
Mike

Active8 wrote:

On Mon, 28 Feb 2005 12:07:49 -0800, Tim Wescott wrote:


IIRC Digi-Key has 100MHz crystals, but I may be remembering 100MHz
oscillators. YMMV. IDNKWTFIAS. Caviat Emptor (so _that's_ what CE
means! Here I thought it was a quality mark). Etc.


Dialog news reader's tip popped up to say that CE is "creative
editing". It doesn't KWTF IDNKWTFIAS is, but I got everything but
the IAS part.

IDNKWTFIAS: I Don't Know What I Am Saying.

--

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

Hello Tim,

As Douglas said the frequency may be a bit off unless you get a crystal
made for 5th. An alternative for the 20MHz garden variety would be to
make a 20MHz oscillator, run it into a fast gate and fish out the 5th
the old fashioned way, with an LC circuit. Then run that through a gate
again if needed.

Regards, Joerg

http://www.analogconsultants.com

On Mon, 28 Feb 2005 12:07:49 -0800, Tim Wescott wrote:

IIRC Digi-Key has 100MHz crystals, but I may be remembering 100MHz
oscillators. YMMV. IDNKWTFIAS. Caviat Emptor (so _that's_ what CE
----------
means! Here I thought it was a quality mark). Etc.

I Do Not Know WTF I Am Saying?

Thanks,
Rich

Rich Grise wrote:

On Mon, 28 Feb 2005 12:07:49 -0800, Tim Wescott wrote:

IIRC Digi-Key has 100MHz crystals, but I may be remembering 100MHz
oscillators. YMMV. IDNKWTFIAS. Caviat Emptor (so _that's_ what CE

----------

means! Here I thought it was a quality mark). Etc.


I Do Not Know WTF I Am Saying?

Now Rich, that's being awfully harsh on yourself.

--

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

"John Fields" bravely wrote to "All" (28 Feb 05 14:34:30)
--- on the heady topic of " Using non-overtone crystal in overtone mode?"

JF From: John Fields
JF sci.electronics.components:12029 rec.radio.amateur.homebrew:8635

JF Check out "Chladni patterns" if you're interested.

I've done some putzing with crystals. What frequency say would a
100.3MHz xtal in series with a 100.1Mhz xtal settle on? 100.2Hz?

A*s*i*m*o*v

.... It's kind of fun to do the impossible... -Walt Disney

That is total and absolute bullpuckey.

Jim


---
You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental.

Hello Jim,

That is total and absolute bullpuckey.



Huh? See the 2nd paragraph (mode):

http://www.euroquartz.co.uk/tech-xtal.htm

Regards, Joerg

http://www.analogconsultants.com

Rich Grise wrote:
On Mon, 28 Feb 2005 12:07:49 -0800, Tim Wescott wrote:

IIRC Digi-Key has 100MHz crystals, but I may be remembering 100MHz
oscillators. YMMV. IDNKWTFIAS. Caviat Emptor (so _that's_ what CE

----------

means! Here I thought it was a quality mark). Etc.


I Do Not Know WTF I Am Saying?

Thanks,
Rich


OK, silly I know, but I cant figure out YMMV...

OTOH, WTF, IAAR

Cheers
Terry

RST Engineering wrote:
That is total and absolute bullpuckey.

Jim



---
You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental.

sorry dude, 50 years of IEEE UFFC papers suggest *you* are wrong. I was
surprised when I learned this too.

Cheers
Terry

Terry Given wrote:

OK, silly I know, but I cant figure out YMMV...

Your Mileage May Vary


--
Beware of those who post from srvinet.com!

Michael A. Terrell
Central Florida

I read in sci.electronics.design that Terry Given
wrote (in ) about 'Using non-
overtone crystal in overtone mode?', on Tue, 1 Mar 2005:

OK, silly I know, but I cant figure out YMMV...

Year 2005. (;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I read in sci.electronics.design that douglas dwyer
wrote (in )
about 'Using non-overtone crystal in overtone mode?', on Mon, 28 Feb
2005:
Overtone crystals are mechanical resonators and the overtone shear mode
which has additional shear planes within the volume wont occupy exactly
the same volume as the fundamental so the frequency will not be exactly
3X or 5X the fundamental but approx 2000ppm high or low?

I remember being told by a crystal 'expert' that with some cuts the
difference can be much larger than that. Is that so?
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Depending on whether the circuit is designed for overtone oscillation or
harmonic generation, how perfect the overtone crystals are, and how the
circuit is tuned, I'd expect either:
1) No oscillation
2) Very close to 100.1 MHz
3) Very close to 100.3 MHz

What did you experience?

Joe
W3JDR


"Asimov" wrote in message
...
"John Fields" bravely wrote to "All" (28 Feb 05 14:34:30)
--- on the heady topic of " Using non-overtone crystal in overtone
mode?"

JF From: John Fields
JF sci.electronics.components:12029 rec.radio.amateur.homebrew:8635

JF Check out "Chladni patterns" if you're interested.

I've done some putzing with crystals. What frequency say would a
100.3MHz xtal in series with a 100.1Mhz xtal settle on? 100.2Hz?

A*s*i*m*o*v

... It's kind of fun to do the impossible... -Walt Disney

John Woodgate wrote:
OK, silly I know, but I cant figure out YMMV...
Year 2005. (;-)

Honestly John! That should be AMMV.

I read in sci.electronics.design that Paul Burke wrote
(in ) about 'Using non-overtone crystal
in overtone mode?', on Tue, 1 Mar 2005:
John Woodgate wrote:
OK, silly I know, but I cant figure out YMMV...
Year 2005. (;-)

Honestly John! That should be AMMV.

The promulgation of a 'horrible hybrid' is justified in pursuit of a
whimsical coincidence.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

On Mon, 28 Feb 2005 18:33:53 -0800, "RST Engineering"
wrote:

That is total and absolute bullpuckey.

Jim


---
You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental.

---
RST what???

--
John Fields

In message , Frank Moe
writes
There are also manufacturers that make 100 in fundamental (up to about
200MHz), and many should have 100 in 5th as standard part...
High frequency fundamentals are real and can be purchased to at least
250MHz note they are expensive, their Q which is ultimately material
related reduces with increased frequency (loss is per cycle) such that
it may be no higher than a SAW resonator . Still better than a SAW as
the temperature coefficient for the SAW only has the linear cancelled
whereas the AT cut has the parabolic term cancelled.
Finally the 5th overtone will only pull 1/25 times the fundamental.
Finally finally the SAW can be run at much higher power levels so noise
floor is much better.
Finally finally finally a SAW needs a mask which gives a high up front
cost and lead time.
The difference in frequency for overtone /X fund may be much more than
2000ppm where the plate is not very parallel and the plate back and
electrode diameter non optimum. Beware AT cut strip crystals ie a long
section of a circular diameter these may not like overtone operation.



not pull with external reactance change perhaps a byt
--
dd

In message , John Woodgate
writes
I remember being told by a crystal 'expert' that with some cuts the
difference can be much larger than that. Is that so?
Yes depends on electrode diameter plate diameter plate back (electrode
thickness) and parallelism. ie I would not be surprised at 10000ppm.
--
dd

Hi Doug, great to hear from you and the info in your posts. I'm currently
using a SAW at 660 MHz for the clock in a 9951 DDS. Actually, it's better
than my 200 MHz 7th overtone tripled to 660 with an MMIC although I do think
my MMIC tripler is most of the culprit.

Reason for the post, I think you've changed ISP's on me again, my mail to
you gets bounced. Would you pse address me a short note to the e-mail
address and give me the current one? That is, if it's not me you're trying
to get rid of!

Regards

W4ZCB

You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental.

There is a related phenomenon in the field of piano tuning. It has
long been known that overtones (called "partials" by piano people) of
piano notes are not exactly related to pitch of the fundamental
frequency by whole numbered ratios. Instead they are related by
factors like

1.000
2.003
3.007
4.018
5.039
6.092
7.211
etc.

The amount by which this series deviates from the ideal whole-numbered
ratios is called "inharmonicity" and it differs from one string to
another. The stiffer the string, the more inharmonicity. Long thin
strings, as are found on harpsichords, have almost no inharmonicity.
Short strings in the highest section of the piano have the most
inharmonicity. Since one of the goals of piano tuning is to make
partials of different notes come out the same, this phenomenon of
inharmonicity makes piano tuning inherently more difficult than
instruments that have no inharmonicity, like pipe organs.

What is perhaps more like quartz crystals is carillon bells. They are
tuned at the factory, and each partial is tuned independently and
separately by grinding away metal from different levels on the bell.
In view of these related phenomena, it is no wonder that overtones of
quartz crystals are independent of each other and from the
fundamental.


-Robert Scott
Ypsilanti, Michigan

In article ,
Tim Wescott wrote:
[....]
Overtone crystal cuts are not fundamentally different from fundamental
crystal cuts, so to a 1st-order approximation they'll work. Crystals do
have spurious responses that can cause mode jumping, and these responses
don't necessarily map the same way the overtones do, so using a 20MHz
crystal at 100MHz may or may not work, depending on the luck of the
draw. Other than that I don't know of any differences.


There is a whole science of crystals all on its own. When they make a
crystal they make a thin disk of material. You would normally expect the
edge of the disk to simply be at right angles. Instead it looks like
this:



***********************
*
*
*
*
*************************

The exact angle and depth of that chamfer is how they control which
overtones are selected for and which are supressed. In fundamental
crystals, the maker usually grinds the chamfer so as to reduce the 3rd
harmonic responce.


--
--
forging knowledge

In article ,
Tim Wescott wrote:
[....]
I pointed that out in a previous post. But hey -- wouldn't it be fun to
have an oscillator that yodels?

No, it isn't fun. Trust me :

--
--
forging knowledge

In article ,
John Fields wrote:
[..]
You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental. It's more like the slab of
crystal is vibrating like the drumhead of a steel drum with small
areas of the slab vibrating at higher frequencies, instead of the
entire slab virbarting at just one frequency.

No, its more like a jello when you jiggle the dish side to side. The main
action of an AT cut is shear mode. In the harmonics, the motion looks
kind of like this:









If you think about the top two lines of text in my little drawing. I
think it is obvious that if the maker thinned it down by one line of text
just as you come to the edge, that portion of the crystal would not work
well at this harmonic. This is what they do in crystals intended for
fundamental operation. It knocks that activity down by several dB at the
overtone. This makes it very unlikely that a simple oscillator will take
off at an overtone.
--
--
forging knowledge

In article ,
Tim Wescott wrote:
[...]
In an AT cut crystal the overtone modes are close, but not exactly on,
the odd harmonics of the fundamental. Furthermore, all of the
literature that I've read on AT cut crystals reports that they vibrate
in the bulk of the crystal, in shear mode -- see figure 7 he
http://literature.agilent.com/litweb/pdf/5965-7662E.pdf.

Yes

In the ideal AT cut crystal "c mode" shear is the only activity. In the SC
cut, the "b" and "a" modes appear. The extra complexity of the mode
selection circuit is part of the reason that SC based OCXOs cost so much.

--
--
forging knowledge

Sorry, dude, 50 years of designing with crystals, right from when I ground
my first surplus WWII rock on a piece of glass with toothpaste as the
abrasive says that what the original poster asked is correct.

Will the harmonic be precise? No. Will it be "close", which is what the
original poster asked? You bet. Depending on the oscillator circuit, can
it be "pulled" on frequency? Perhaps.

But to say that the crystal doesn't resonate anywhere near the harmonic is,
as I said, bullpuckey.

Jim



"Terry Given" wrote in message
...
RST Engineering wrote:
That is total and absolute bullpuckey.

Jim

sorry dude, 50 years of IEEE UFFC papers suggest *you* are wrong. I was
surprised when I learned this too.

Cheers
Terry

On Tue, 1 Mar 2005 08:12:48 -0800, "RST Engineering \(jw\)"
wrote:

Sorry, dude, 50 years of designing with crystals, right from when I ground
my first surplus WWII rock on a piece of glass with toothpaste as the
abrasive says that what the original poster asked is correct.

Will the harmonic be precise? No. Will it be "close", which is what the
original poster asked? You bet. Depending on the oscillator circuit, can
it be "pulled" on frequency? Perhaps.

But to say that the crystal doesn't resonate anywhere near the harmonic is,
as I said, bullpuckey.

---
Sorry, dude, no matter how much time you've got in, if you go back
and read my post, you'll find that I wrote:

"You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental."


and that you replied with:


"That is total and absolute bullpuckey."


Notice that I didn't say "near", I said "at".

If you can find fault with anything I wrote in that post, I'd
appreciate specific criticism instead of that broad brush you painted
with.

--
John Fields