In article , J M Noeding
writes
On Mon, 08 Dec 2003 05:10:02 GMT, Uwe Langmesser
wrote:


Crystals will operate on a number of fo's.
I use three oscillators to test them and each gives a different fo.
Be careful and keep the drive level down as some oscillators can cause
damage.

I had to laugh when I read your post, it sort of reflects my experience, eg.
every experiment gives you new and unexpected answers.

And I thought it was only me...

Uwe

....and it is better when you can laugh about it.... sometimes it is
difficult to understand why your xtal won't operate on a 3rd or 5th
harmonic when it seems to work for everybody else - and you specified
proper overtone xtal for the manufacturer,
But it is a lot of bad constructions!

In the butler-type xo (popular in UK) you may operate a 27MHz xtal on
45 and even 81MHz (believe it was DCoDA who first described it)

But I believe the original question was something else? Xtals testers
were so popular in the 60's when amateur run around to surplus stores
buying FT-243 xtals, and several such xtal testers are described in
CQ, Ham Radio, QST, 73 DL-QTC, QRV, CQ-DL, Electron and other, they
run on fundamental frequency using colpitts or pierce type oscillator
and measured grid current as measure for excitation

73
Jan-Martin, LA8AK
--
remove ,xnd to reply (Spam precaution!)
The butler type is a tuned amplifier were there is ideally zero phase
across the crystal and hence the crystal can be simulated by a resistor
of equal (in practise lower) resistance than the crystal loss.
Hence a butler tuned to 100MHz will oscillate a 50R resistor at that
frequency.
The 100MHZ crystal if 5th overtone will have a fundamental response at
approx. 20MHz and a 3rd overtone response at 60MHz .
The fundamental response (resistance) will be much lower than the 5th
resistance and in a zero phase amplifier with flat response the crystal
will preferentially oscillate at 20MHz.
Higher order overtones have the same C0 or stray capacitance as the
fundamental but this has a lower reactance at higher frequencies.
This is the reason and increase in resistance at higher overtones that
overtone oscillators get increasingly tricky.

--
ddwyer

On Tue, 16 Dec 2003 17:06:27 +0000, ddwyer
wrote:


The butler type is a tuned amplifier were there is ideally zero phase
across the crystal and hence the crystal can be simulated by a resistor
of equal (in practise lower) resistance than the crystal loss.
Hence a butler tuned to 100MHz will oscillate a 50R resistor at that
frequency.
The 100MHZ crystal if 5th overtone will have a fundamental response at
approx. 20MHz and a 3rd overtone response at 60MHz .
The fundamental response (resistance) will be much lower than the 5th
resistance and in a zero phase amplifier with flat response the crystal
will preferentially oscillate at 20MHz.
Higher order overtones have the same C0 or stray capacitance as the
fundamental but this has a lower reactance at higher frequencies.
This is the reason and increase in resistance at higher overtones that
overtone oscillators get increasingly tricky.


main arguments are right, but I don't believe the frequency scheme is
right. If 20MHz is the fundamental, it doesn't make sense to tune the
2nd circuit to 100MHz, you could tune the 1st. You could also operate
the first tuned circuit at 60MHz and have o/p at 120 or 180MHz, with
sub-harmonics of n.order 60MHz.

It was a tendency 20 years ago to apply overtone xo's running at
150-200MHz, but they very soon dissappeared because of too much
instability problems

73
jm

http://home.online.no/~la8ak/c13.htm
--
remove ,xnd to reply (Spam precaution!)

On Tue, 16 Dec 2003 17:06:27 +0000, ddwyer
wrote:


The butler type is a tuned amplifier were there is ideally zero phase
across the crystal and hence the crystal can be simulated by a resistor
of equal (in practise lower) resistance than the crystal loss.
Hence a butler tuned to 100MHz will oscillate a 50R resistor at that
frequency.
The 100MHZ crystal if 5th overtone will have a fundamental response at
approx. 20MHz and a 3rd overtone response at 60MHz .
The fundamental response (resistance) will be much lower than the 5th
resistance and in a zero phase amplifier with flat response the crystal
will preferentially oscillate at 20MHz.
Higher order overtones have the same C0 or stray capacitance as the
fundamental but this has a lower reactance at higher frequencies.
This is the reason and increase in resistance at higher overtones that
overtone oscillators get increasingly tricky.


main arguments are right, but I don't believe the frequency scheme is
right. If 20MHz is the fundamental, it doesn't make sense to tune the
2nd circuit to 100MHz, you could tune the 1st. You could also operate
the first tuned circuit at 60MHz and have o/p at 120 or 180MHz, with
sub-harmonics of n.order 60MHz.

It was a tendency 20 years ago to apply overtone xo's running at
150-200MHz, but they very soon dissappeared because of too much
instability problems

73
jm

http://home.online.no/~la8ak/c13.htm
--
remove ,xnd to reply (Spam precaution!)

In article , J M Noeding
writes
On Mon, 08 Dec 2003 05:10:02 GMT, Uwe Langmesser
wrote:


Crystals will operate on a number of fo's.
I use three oscillators to test them and each gives a different fo.
Be careful and keep the drive level down as some oscillators can cause
damage.

I had to laugh when I read your post, it sort of reflects my experience, eg.
every experiment gives you new and unexpected answers.

And I thought it was only me...

Uwe

....and it is better when you can laugh about it.... sometimes it is
difficult to understand why your xtal won't operate on a 3rd or 5th
harmonic when it seems to work for everybody else - and you specified
proper overtone xtal for the manufacturer,
But it is a lot of bad constructions!

In the butler-type xo (popular in UK) you may operate a 27MHz xtal on
45 and even 81MHz (believe it was DCoDA who first described it)

But I believe the original question was something else? Xtals testers
were so popular in the 60's when amateur run around to surplus stores
buying FT-243 xtals, and several such xtal testers are described in
CQ, Ham Radio, QST, 73 DL-QTC, QRV, CQ-DL, Electron and other, they
run on fundamental frequency using colpitts or pierce type oscillator
and measured grid current as measure for excitation

73
Jan-Martin, LA8AK
--
remove ,xnd to reply (Spam precaution!)
The butler type is a tuned amplifier were there is ideally zero phase
across the crystal and hence the crystal can be simulated by a resistor
of equal (in practise lower) resistance than the crystal loss.
Hence a butler tuned to 100MHz will oscillate a 50R resistor at that
frequency.
The 100MHZ crystal if 5th overtone will have a fundamental response at
approx. 20MHz and a 3rd overtone response at 60MHz .
The fundamental response (resistance) will be much lower than the 5th
resistance and in a zero phase amplifier with flat response the crystal
will preferentially oscillate at 20MHz.
Higher order overtones have the same C0 or stray capacitance as the
fundamental but this has a lower reactance at higher frequencies.
This is the reason and increase in resistance at higher overtones that
overtone oscillators get increasingly tricky.

--
ddwyer

On Mon, 08 Dec 2003 05:10:02 GMT, Uwe Langmesser
wrote:


Crystals will operate on a number of fo's.
I use three oscillators to test them and each gives a different fo.
Be careful and keep the drive level down as some oscillators can cause damage.

I had to laugh when I read your post, it sort of reflects my experience, eg.
every experiment gives you new and unexpected answers.

And I thought it was only me...

Uwe

.....and it is better when you can laugh about it.... sometimes it is
difficult to understand why your xtal won't operate on a 3rd or 5th
harmonic when it seems to work for everybody else - and you specified
proper overtone xtal for the manufacturer,
But it is a lot of bad constructions!

In the butler-type xo (popular in UK) you may operate a 27MHz xtal on
45 and even 81MHz (believe it was DCoDA who first described it)

But I believe the original question was something else? Xtals testers
were so popular in the 60's when amateur run around to surplus stores
buying FT-243 xtals, and several such xtal testers are described in
CQ, Ham Radio, QST, 73 DL-QTC, QRV, CQ-DL, Electron and other, they
run on fundamental frequency using colpitts or pierce type oscillator
and measured grid current as measure for excitation

73
Jan-Martin, LA8AK
--
remove ,xnd to reply (Spam precaution!)

in article , WA44NBI at
wrote on 12/7/03 9:33 PM:

Crystals will operate on a number of fo's.
I use three oscillators to test them and each gives a different fo.
Be careful and keep the drive level down as some oscillators can cause damage.
Bob
WA4NBI


I had to laugh when I read your post, it sort of reflects my experience, eg.
every experiment gives you new and unexpected answers.

And I thought it was only me...

Uwe

Crystals will operate on a number of fo's.
I use three oscillators to test them and each gives a different fo.
Be careful and keep the drive level down as some oscillators can cause damage.
Bob
WA4NBI