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

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

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 , 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 )

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

A solid slab of crystal naturally oscillates at frequencies at which one of
its three dimensions, length, breadth and thickness, is a mechanical
1/2-wavelength. It can easily be induced to oscillate at harmonics of the
fundamental.

It can also oscillate in one of several mechanical modes, eg., longitudinal,
breadth-wise or in torsion. And in shunt or series-resonant electrical
modes.

The circuit it is embedded in can encourage a preferred frequency. It is
easy to select harmonics. Self-preference is also given to the frequency
which has the highest Q, ie., the least mechanical loss. This is usually the
fundamental.

It does not oscillate EXACTLY at multiples simply because it has three
dimensions and Length, Breadth and Thickness slightly 'interfere' with each
other.

A poorly cut crystal, eg., lack of parallelism, at which there may be no
strong preference may jump erratically between two non-harmonically related
frequencies.

Frequency versus temperature curves depend on oscillation mode and on the
angle at which the slab is cut relative to the direction of the individual
crystals in the bulk material lattice as found by optical means. Cubic
curves are best because they contain a flat horizontal portion.