Hello John,

"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."



When you look at older (pre-PLL) VHF communication gear of the more
professional kind they didn't use 5th or higher overtones but employed
frequency multiplier stages. For good reason, one being the offset you
had mentioned. I'd never run a crystal on its umpteenth harmonic and
always designed in multiplier stages like the radio folks did. With
today's cheap logic chips that doesn't even cost much in extra parts.

and that you replied with:


"That is total and absolute bullpuckey."



Look on the bright side. Some of us, including me, didn't know the
expression "bullpuckey". I got a kick out of it.

Regards, Joerg

http://www.analogconsultants.com

Harold Johnson wrote:

I'm currently
using a SAW at 660 MHz for the clock in a 9951 DDS.

Interesting factoid: I was looking to experiment with 100MHz
oscillators largely as a clock source for my own AD9951 experimentation
(using the AD9951's built-in PLL multiplier at 4x). I was hoping to
experiment a bit with 20 MHz crystals I already had in hand before
ordering some "real overtone" crystals cut just for me. I've been
looking at AD app note AN-419 and it's Butler oscillator, in
particular, although the clock input of the AD9951 probably has
different requirements than the AD9850 targetted in AN-419.

Does the AD9951 really work at 660MHz? I thought it was only good to
400MHz...

So far my experimenting has used the on-chip oscillator at 25MHz and
the PLL at 16x to get to 400MHz.

Actually, it's better
than my 200 MHz 7th overtone tripled to 660

We bandied about "non-harmonic" relations here but how you get from 200
to 660, I don't know.

Tim.

"W3JDR" bravely wrote to "All" (01 Mar 05 10:34:17)
--- on the heady topic of " Using non-overtone crystal in overtone mode?"

It did oscillate. I was some really oddball frequency inbetween but as
I recall it was neither the mean nor any other obvious relation. I
suppose it was where their response curves complimented but I'm not
sure. Did it only for curiosity's sake to see if it they could be used
for filtering but tried making them oscillate for fun. I know, simple
pleasures... ;-)

A*s*i*m*o*v


W3 Reply-To: "W3JDR"
W3 Xref: aeinews rec.radio.amateur.homebrew:8665

W3 Depending on whether the circuit is designed for overtone oscillation
W3 or harmonic generation, how perfect the overtone crystals are, and how
W3 the circuit is tuned, I'd expect either:
W3 1) No oscillation
W3 2) Very close to 100.1 MHz
W3 3) Very close to 100.3 MHz

W3 What did you experience?

W3 Joe
W3 W3JDR


W3 "Asimov" wrote in
W3 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?


.... All things are possible. Except skiing through a revolving door.

Interesting factoid: I was looking to experiment with 100MHz
oscillators largely as a clock source for my own AD9951 experimentation
(using the AD9951's built-in PLL multiplier at 4x). I was hoping to
experiment a bit with 20 MHz crystals I already had in hand before
ordering some "real overtone" crystals cut just for me. I've been
looking at AD app note AN-419 and it's Butler oscillator, in
particular, although the clock input of the AD9951 probably has
different requirements than the AD9850 targetted in AN-419.

The built-in multiplier is quite noisy and makes the 9951 run terribly hot.

Does the AD9951 really work at 660MHz? I thought it was only good to
400MHz...

Yes, if you DON'T use the on board multiplier. I've had it to 750 MHz just
to check it since I had heard of some DL's overclocking it to that
frequency. Properly heat sunk to the eval board, and without the multiplier,
it's cool as a cucumber. AD rates it only to 400 MHz but a sample of 6 units
all operate well at 660 MHz.

So far my experimenting has used the on-chip oscillator at 25MHz and
the PLL at 16x to get to 400MHz.

Actually, it's better
than my 200 MHz 7th overtone tripled to 660

We bandied about "non-harmonic" relations here but how you get from 200
to 660, I don't know.

Well, this one is a 220 MHz 7th overtone from ICL specially surface treated
for low noise and operating in a Stephensen bipolar/FET Butler. But as I
mentioned to Doug, afraid my MMIC tripler makes a bad job of the 660 output
despite a 3 pole final filter. The SAW is not near the Q of the crystal, but
the SNR is much better.

Regards

W4ZCB

In message , Joerg
writes

When you look at older (pre-PLL) VHF communication gear of the more
professional kind they didn't use 5th or higher overtones but employed
frequency multiplier stages. For good reason, one being the offset you
had mentioned. I'd never run a crystal on its umpteenth harmonic and
always designed in multiplier stages like the radio folks did. With
today's cheap logic chips that doesn't even cost much in extra parts.
Often cheaper to multiply up than buy an expensive 5th overtone that was
difficult to pull onto frequency and fussy to set up.
The exception would be current and size saving for some portables.
--
dd

Hello Douglas,

Often cheaper to multiply up than buy an expensive 5th overtone that
was difficult to pull onto frequency and fussy to set up.


And these special cuts can indeed be fussy. They can also be a
procurement nightmare.

The exception would be current and size saving for some portables.


Even then it could be done. Besides the discrete solution there are
blazingly fast logic inverters such as the ALVC series. These are
usually under 20 cents and come in the super tiny TSSOP format. Now I
just wish they had unbuffered versions to do the oscillator part with.
If a 74HCU04 is needed for other jobs on the board it could run the
oscillator but for any reasonable speed these require more than 4V.

Regards, Joerg

http://www.analogconsultants.com

In article , 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.

This reminds me of a colleague who can easily tell everyone
qualitatively that a situation deviates from theoretical ideals and as a
result (using my words and not his) "$#!+ (poop) will splatter!" But he
at least often in my experience have trouble saying this quantatively!

For one project, I decide to try something, and tell my boss what I am
trying. This colleague of mine says (using words of mine and not his),
"slop will spatter"! (As in light for adding optics to a light source for
a specific application. This application has multiple LEDs shining onto
an optical device with multiple elements.)
Boss tells me that what I delivered to him and he found working should
not have worked according to this colleague of mine, due to stray beams
forming. So what do I do - I send photos to the boss of the beam pattern
including the stray beams predicted by my colleague. I even named these
stray beams after my colleague. But they were minor due to most light
produced by the light source being on paths that resulted in adding to the
desired beam combination as opposed to the undesired stray beams.
Furthermore, my boss's industrial designer designed a baffling system
that blocked the small amount of light from the multi-element light source
that was on paths towards the stray beams as opposed to the desired rays
that were "on course" to be utilized by the multi-elemt optical assembly
as planned.

So beware that the situation may not be much worse than ideal when
someone can tell you how you are deviating from ideal!

In article , John Fields wrote:
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.

Now suppose someone makes a crystal oscillate in some overtone mode that
the crystal manufacturer recommends against and is predicted to be
"inharmonic" but turns out to be only a few hundred or even sometimes a
few 10's of KHz from a multiple of a frequency that results from being
used as directed?

As I said in different words in a different post - correctly predicting
that $#!+ (AKA "slop") will spatter does not necessarily that much will
spatter nor that any will spatter far, and maybe in many cases it is
doubtful that both much will spatter and that much will spatter far.

- Don Klipstein )

Was it crystal-locked, or free-running....did it change frequency when you
tuned the circuit? If it wasn't crystal locked, then the experiment wasn't
too meaningful

Joe
W3JDR

"Asimov" wrote in message
...
"W3JDR" bravely wrote to "All" (01 Mar 05 10:34:17)
--- on the heady topic of " Using non-overtone crystal in overtone
mode?"

It did oscillate. I was some really oddball frequency inbetween but as
I recall it was neither the mean nor any other obvious relation. I
suppose it was where their response curves complimented but I'm not
sure. Did it only for curiosity's sake to see if it they could be used
for filtering but tried making them oscillate for fun. I know, simple
pleasures... ;-)

A*s*i*m*o*v


W3 Reply-To: "W3JDR"
W3 Xref: aeinews rec.radio.amateur.homebrew:8665

W3 Depending on whether the circuit is designed for overtone oscillation
W3 or harmonic generation, how perfect the overtone crystals are, and
how
W3 the circuit is tuned, I'd expect either:
W3 1) No oscillation
W3 2) Very close to 100.1 MHz
W3 3) Very close to 100.3 MHz

W3 What did you experience?

W3 Joe
W3 W3JDR


W3 "Asimov" wrote in
W3 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?


... All things are possible. Except skiing through a revolving door.

On Wed, 2 Mar 2005 01:41:06 +0000 (UTC), (Don
Klipstein) wrote:

In article , John Fields wrote:
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.

Now suppose someone makes a crystal oscillate in some overtone mode that
the crystal manufacturer recommends against and is predicted to be
"inharmonic" but turns out to be only a few hundred or even sometimes a
few 10's of KHz from a multiple of a frequency that results from being
used as directed?

---
If it's not an integer multiple of the fundamental then it won't be a
harmonic.
---

As I said in different words in a different post - correctly predicting
that $#!+ (AKA "slop") will spatter does not necessarily that much will
spatter nor that any will spatter far, and maybe in many cases it is
doubtful that both much will spatter and that much will spatter far.

---
If the prediction came true, then it came true.

--
John Fields