EMRFD Message Archive 368
Message Date From Subject 368 2007-01-26 20:10:44 Jim Miller 100Mhz Crystal Sources?
on where to source a 5th OT 100Mhz crystal?
Not looking for excellent specs just something to get started with.
Once I'm happy with the oscillator perhaps I'll get something more fancy.
73
jim ab3cv369 2007-01-27 03:08:11 Luiz Amaral Re: 100Mhz Crystal Sources?
third (second) harmonic at the colector of the oscillator transistor?
Luiz - PY1LL
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370 2007-01-27 03:20:21 Loren Moline WA7S... Re: 100Mhz Crystal Sources?
source with harmonics for 432 and up.
Loren
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371 2007-01-27 07:36:09 Graham Haddock Re: 100Mhz Crystal Sources?
For less than the price of a crystal, you can buy a whole 100 MHz oscillator
in a can. These were the clock oscillators for the DDS-30 units, and
work fine.
372 2007-01-27 07:44:55 Jim Miller Re: 100Mhz Crystal Sources?
oscillators as well.
i'm also going to play with temp stabilization and gps disciplining.
i'll post failures and successes.
73
jim ab3cv373 2007-01-27 08:20:27 Joe Rocci Re: 100Mhz Crystal Sources?
If you want accuracy, stability and low noise, you're better off building
your own. Many of those low-cost oscillator blocks are pretty bad - in fact,
some of them are just RC oscillators that are internally phase locked to a
low frequency crystal. Yes, it puts out what seems like a stable 100 MHz,
but the phase noise is horrible.
The biggest problem you'll encounter with 5th and 7th overtone crystals is
"mode jumping". There can be many spurious crystal resonances close to the
desired resonance, and it's sometimes a real balancing act to get everything
just right so that the oscillator starts up reliably and oscillates in the
right mode.
Good luck
Joe
W3JDR
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374 2007-01-27 10:05:36 larry allen Re: 100Mhz Crystal Sources?
You have probably been told this before but I will say it for myself....
Crystals can't oscilate beyond approximately 10 mhz....
It would be too fast for them to mechanically vibrate...
Anything above 10 mhz is done through multiplication....
Larry ve3fxq
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375 2007-01-27 10:53:06 Lasse Re: 100Mhz Crystal Sources?
are special versions that do go way higher ~200 MHz!
These super high frequency crystals (inverted mesa) do have the
"normal" thickness at the rims but are etched down to very thin in
the middle. This allowes it to be attached to the electrodes and
maintain certain rigidity and still operate at very high fundamental
frequencies.
This document (http://www.vectron.com/products/xtal/vxd1.pdf) from
Vectron Inc do offer fundamental crystals up to 50 MHz!
And this document do explain the inverted mesa crystal
http://www.raltron.com/corp/pdfspecs/news_inverted.pdf You might be
able to design a crystal oscillator with no multiplicator stages to
operate at 1 GHz! I.e fifth or seventh overtone.
There is no multiplication occuring with-in the crystal, it is just
that the amplifier which the crystal is attached do have a gain
larger than 1 on this very frequency and selects which overtone the
oscillator will operate on (fulfills the Barkhausen criterion).
As much as I need a spellchecker, I hate it when it turns Megahertz
MHz into millihertz mHz :)
There was an article by John Stephenson, KD6OZH, which was published
in NOV/DEC 1999, QEX. about a low-noise high stability crystal
oscillator around 100 MHz.... This oscilator has proven to be very
easy to design and gives very nice performance, and I have had it
phase locked with ease!
Remember that an overtone crystal is stiffer than a fundamental i.e.
if you want to turn it into a vcxo with "large" adjustment range you
might want to use fundamental or 3:d overtone. Going higher will give
you problems!
Lasse SM5GLC
At 19:05 2007-01-27, you wrote:
>Greetings....
>You have probably been told this before but I will say it for myself....
>Crystals can't oscilate beyond approximately 10 mhz....
>It would be too fast for them to mechanically vibrate...
>Anything above 10 mhz is done through multiplication....
>Larry ve3fxq
>
>
>----- Original Message -----
>376 2007-01-27 11:27:03 Luiz Amaral Re: 100Mhz Crystal Sources?
MHz for the AT cut. Above that, the quartz foil becomes very thin to be
worked on. So, on higher frequencies, they are prepared to oscillate on odd
overtones. These ARE NOT harmonics (these are exact integer multiples of the
fundamental), but other natural vibrating frequencies (really close to odd
harmonics). It is similar the case of a vibrating string: the several modes
are not exact integer multiples of the minimum one. They depend on the
thickness and elasticity of the string (as xtals do).
For overtone oscillations to occur, the electrodes377 2007-01-27 11:57:58 larry allen Re: 100Mhz Crystal Sources?
My understanding came from and guy came to our ham club in the 70's.. I
guess technology has come a long way since then....
However when I reread the question another question came to my mind...
What is the purpose behind your oscilator?....
Just asking...
Larry ve3fxq
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379 2007-01-27 12:55:17 Jim Miller Re: 100Mhz Crystal Sources?
oscillators and good RF SMD construction. I've got everything I need to do
toner transfer PCBs.
The eventual practical use will be to drive a AD9958 after getting some 5th
harmonic suitably generated, amplified and filtered.
Along the way I want to play with thermal stabilization and disciplining it
with a GPS receiver, ala Shera.
Chris Bartram (GD4DGU) has some good info on his website that I'm using as a
basis.
73
jim ab3cv380 2007-01-27 13:16:14 larry allen Re: 100Mhz Crystal Sources?
and thanks for the project detail....
Larry ve3fxq
----- Original Message -----
381 2007-01-27 13:36:34 Jim Miller Re: 100Mhz Crystal Sources?
http://www.christopherbartramrfdesign.com/blaenffos/indexGW4DGU.html
73
jim ab3cv