100 MHz Crystal
 

"PDRUNEN" wrote in message
...
Hi Group,

I have a crystal marked 100MHz, it the smaller package found in the CBs.

What I want to do is connect this up to a ECL or Fast TTL and get a 0 to 5
Volt
square wave output that can drive 50 ohms with 2.5 volts or more.

Anyone have a good circuit or suggestions?

Tnx de KJ4uo

It will oscillate at the fundamental, not the marked 100 MHz overtone
frequency. At 100 MHz, I'd guess that's a 7th or 5th overtone cut.
Most likely 7th, 20 MHz is about the limit for fundamental crystals.

Pete

" Uncle Peter" wrote in message
news:o0bZc.124585$Lj.108231@fed1read03...

"PDRUNEN" wrote in message
...
Hi Group,

I have a crystal marked 100MHz, it the smaller package found in the CBs.

What I want to do is connect this up to a ECL or Fast TTL and get a 0 to
5
Volt
square wave output that can drive 50 ohms with 2.5 volts or more.

Anyone have a good circuit or suggestions?

Tnx de KJ4uo

It will oscillate at the fundamental, not the marked 100 MHz overtone
frequency. At 100 MHz, I'd guess that's a 7th or 5th overtone cut.
Most likely 7th, 20 MHz is about the limit for fundamental crystals.

That used to be the case, but 40 MHz fundamental crystals have been
available for some time. I've got some.

Leon

On Tue, 31 Aug 2004 23:05:53 -0400, " Uncle Peter"
wrote:

It will oscillate at the fundamental, not the marked 100 MHz overtone
frequency. At 100 MHz, I'd guess that's a 7th or 5th overtone cut.
Most likely 7th, 20 MHz is about the limit for fundamental crystals.

So how does one tell if the xtal is fundamental or overtone? Not for
xtals marked 100Mhz, obviously, but for much lower frequencies which
could be either..
--

"What is now proved was once only imagin'd." - William Blake, 1793.

"Leon Heller" a écrit dans le message de
...
" Uncle Peter" wrote in message
news:o0bZc.124585$Lj.108231@fed1read03...

It will oscillate at the fundamental, not the marked 100 MHz overtone
frequency. At 100 MHz, I'd guess that's a 7th or 5th overtone cut.
Most likely 7th, 20 MHz is about the limit for fundamental crystals.

That used to be the case, but 40 MHz fundamental crystals have been
available for some time. I've got some.


I guess this is not for the garden variety crystals, but I've seen (can't
remember where) that IC etching technology has been applied to crystals
manufacturing which resulted in crystals of over 200MHz fundamental
frequency.


--
Thanks,
Fred.

Paul Burridge wrote in message . ..
On Tue, 31 Aug 2004 23:05:53 -0400, " Uncle Peter"
wrote:

It will oscillate at the fundamental, not the marked 100 MHz overtone
frequency. At 100 MHz, I'd guess that's a 7th or 5th overtone cut.
Most likely 7th, 20 MHz is about the limit for fundamental crystals.

So how does one tell if the xtal is fundamental or overtone? Not for
xtals marked 100Mhz, obviously, but for much lower frequencies which
could be either..

Easy. Look for resonances near 33.3MHz, 20MHz and 14.3MHz. Or...put
it in an oscillator circuit which favors fundamental mode and see
where it oscillates.

Cheers,
Tom

"Paul Burridge" wrote in message
...
On Tue, 31 Aug 2004 23:05:53 -0400, " Uncle Peter"
wrote:

It will oscillate at the fundamental, not the marked 100 MHz overtone
frequency. At 100 MHz, I'd guess that's a 7th or 5th overtone cut.
Most likely 7th, 20 MHz is about the limit for fundamental crystals.

So how does one tell if the xtal is fundamental or overtone? Not for
xtals marked 100Mhz, obviously, but for much lower frequencies which
could be either..

I have used fundamental cut crystals on their overtones and overtone
crystals on their fundamental. NOTE, the frequencies will NOT be exact
harmonics/multiples. Somewhere I have information giving the typical
differences.


The crystal Colpitts is one sure bet. Stay away from circuits with
inductors and tuned circuits for a fundamental oscillator. Some IC
oscillators can give misleading results. They can pound the rock too hard.


here's some circuits thanks to GOOGLE:

This type is my favorite. Used in just about all Motorola channel elements
of Motrac through Micor and probably beyond.
http://homepage.tinet.ie/~ei9gq/tx_circ.html
Though seems to me, the lower cap should be 100 rather than 220pf, but they
are REALLY non critical. One page I found had them both at 1000pf.

Fig 7 looks the same:
http://www.northcountryradio.com/PDFs/column007.pdf



Discover Circuits also has a lot of circuits.
http://www.discovercircuits.com/O/o-crystal.htm


--
Steve N, K,9;d, c. i My email has no u's.

P.S. the Educypedia has lots of circuit ideas, in general
http://users.telenet.be/educypedia/e...osciltypes.htm



If you do your own search, THIS is NOT a Colpitts crystal osc...
http://www.designnotes.com/CIRCUITS/colpitts.htm

On 1 Sep 2004 14:14:12 -0700, (Mike Monett) wrote:

Frequency multiplication tends to increase jitter as well as
frequency, however. To minimize jitter at the gigahertz level,
equipment builders have to start with super-low-jitter reference
oscillators. But the higher the reference frequency climbs, the
lower the final gigahertz signal's jitter.

Very interesting, Mike. By "jitter" do you mean phase noise?
--

"What is now proved was once only imagin'd." - William Blake, 1793.

"Paul Burridge" a écrit dans le message de
...
On 1 Sep 2004 14:14:12 -0700, (Mike Monett) wrote:

Frequency multiplication tends to increase jitter as well as
frequency, however. To minimize jitter at the gigahertz level,
equipment builders have to start with super-low-jitter reference
oscillators. But the higher the reference frequency climbs, the
lower the final gigahertz signal's jitter.

Very interesting, Mike. By "jitter" do you mean phase noise?

No. Jitter is jitter is jitter, but is related to phase noise that is phase
noise that is phase noise.


--
Thanks,
Fred.

Paul Burridge wrote in message . ..
On 1 Sep 2004 14:14:12 -0700, (Mike Monett) wrote:

Frequency multiplication tends to increase jitter as well as
frequency, however. To minimize jitter at the gigahertz level,
equipment builders have to start with super-low-jitter reference
oscillators. But the higher the reference frequency climbs, the
lower the final gigahertz signal's jitter.

Very interesting, Mike. By "jitter" do you mean phase noise?

Hi Paul,

Actually, I didn't write that. Those were excerpts from various
sites that discussed the pros and cons of inverted mesa crystals.

The main advantage of inverted mesa crystals is lower jitter (or
phase noise,) especially when you have to multiply to higher
frequencies such as the Ghz region. Inverted mesa crystals allow you
to start at a higher frequency, which reduces the multiplication
factor needed.

To answer your question, yes, phase noise and jitter are closely
related. Jitter is measured in the time domain and has units of
time, where phase noise is measured in the frequency domain and has
units of dBc. You can convert from phase noise to jitter by
integrating the phase noise curve.

There are many articles that discuss phase noise and jitter. Perhaps
the best are by Hajimiri and Lee:

Ali Hajimiri and Thomas H. Lee, "A General Theory of Phase Noise
in Electrical Oscillators", IEEE JOURNAL OF SOLID-STATE CIRCUITS,
VOL. 33, NO. 2, FEBRUARY 1998

http://www.chic.caltech.edu/Publicat...neral_full.PDF (441k pdf)

Thomas H. Lee, Ali Hajimiri, "Oscillator Phase Noise: A Tutorial",
IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 35, NO. 3, MARCH 2000,

http://www.chic.caltech.edu/Publicat...hase_tutor.pdf (212k pdf)

Dean Banerjee also discusses this in his book "PLL Performance,
Simulation and Design"

https://www.national.com/appinfo/wir...sBook_4_01.pdf

There is a worked example in "Measuring / Specifying Jitter in
crystal oscillators":

http://tinyurl.com/4jzfc

Wenzel has an Excel spreadsheet to calculate Allan Variance from
Phase Noise:

"This spreadsheet calculates the Allan Variance from supplied
phase noise intercepts. Total RMS jitter over the specified
bandwidth is also calculated."

http://www.wenzel.com/documents/spread.htm

Boris Drakhlis had two articles titled "Calculate Oscillator Jitter
By Using Phase-Noise Analysis," Microwaves & RF, Jan. 2001 pp. 82-90
and p. 157, but they seem to have disappeared from the web. I could
email them to you if you are interested, but they basically
duplicate the above info.

Ken Kundert also has some info on noise and jitter on his home page:

http://home.pacbell.net/kundert/

Most exciting to me is Rohde has found a way to significantly reduce
the phase noise in wideband vco's, which was previously dominated by
varactor noise. I keep searching for more information, but there
seems to be nothing in the USPTO or on the web. He sells modules but
I don't have the url handy.

Maybe some info will appear as time goes on and more people use them.

Best Regards,

Mike