JJ wrote:

I am fimilar with Colpitts, Harley, Clapps, Bulter, Piece oscillators?

Which configuration with JFET or BJT would yield the highest performance
and least jitter?

JJ



Go get a commercial oscillator. They cost 3 to 10 US $...
Yeahhh, sure, square wave... Fixoit it and you know what you can exoect...
No more but no less!

cheers

Dan / M0DFI

On Fri, 17 Feb 2006 11:49:06 -0500, JJ wrote:


"Highest performance"? Is that output amplitude? Or minimum startup
time? Or startup reliability? Or lowest power requirement? Or what?

Jitter, that's a little easier to define but it's usually not the most
relevant parameter in radio. It is related to sideband and phase noise
and in fact cannot be completely decoupled from either.
tor :-)

Tim KA0BTD



Its not for a radio. I want to minimize the cycle to cycle variations in
timing and it should be simple enough to make with 1 or 2 transitors. So
not looking for NASA spec stuff, just reliable so it starts every time.

JJ
Epson makes a low jitter TTL osc. ~3pSec RMS jitter. ~$5 each. 100
MHz.

JJ wrote:
Risto Tiilikainen wrote in
:


Hi !

Any of those oscillators is OK if resonance circuit Q is kept high and
oscillation power in average low level.
High Q will guarantee easy and fast starting every time
Average low level keeps components cool and cycle to cycle variations
are reduced
Third important question is loading the oscillator.

73, Risto OH2BT

Good info thanks. What are other crystal series oscillators besides Butler
type?

JJ

One type not mentioned is the Franklyn, which IIRC is a cross coupled
multivibrator with one feedback path through the rock.

"Reg Edwards" wrote in news:dt8a26$hs7$1
@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com:

If it oscillates it doesn't matter about the type of oscillator
circuit.

There's no need to worry yourself.
----
Reg.

======================================
There is a drop in freq for Pierce and Colpitt after 1 min of startup. Can
be 100Hz.
Serious enough.

JJ

There is a drop in freq for Pierce and Colpitt after 1 min of startup. Can
be 100Hz.
Serious enough.
-------------------------------------

Not true.

100 Hz is a huge variation by crystal standards, especially in the lower
frequency ranges. If a crystal oscillator drifts substantially during
warmup, it usually implies two things:

1) The oscillator is driving the "so-called" parallel resonance of the
crystal, which is very dependent on circuit capacitance. I said "so-called"
because the parallel resonance isn't really a true resonance of the quartz,
it's a frequency where the crystal appears inductive enough to resonate the
combinationo fo the holder capacitance and the circuit capacitance.

2) The circuit is poorly designed.

BTW, some here have suggested just purchasing a 'can' oscillator. Be very
careful of these, and check the specs carefully. Many 'can' oscillators have
an internal programmable RC VCO that is PLL locked to a low frequency
crystal. The up-side is that the manufacturer will make any frequency you
want (some are even user-programmable). The down side is that RC VCO's have
horrible jitter ('phase noise') that isn't corrected by the PLL


Joe
W3JDR

ORIGINAL MESSAGE:

JJ wrote:

There is a drop in freq for Pierce and Colpitt after 1 min of
startup. Can be 100Hz.
Serious enough.

JJ

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sounds like you're driving the crystal too hard and it's heating up.
When something heats it expands and a larger crystal has a lower
frequency. If you want best stability, reduce the drive until the
circuit barely oscillates and make up the lower output with a stage of
amplification.

73, Bill W6WRT

On Fri, 17 Feb 2006 10:21:19 GMT, "W3JDR" wrote:

As a generalization, I think that any circuit that excites the crystal's
series resonant mode will probably outperform a circuit that excites the
parallel resonant mode, because the series resonance is higher Q and is less
affected by external influences.

Joe, a minor issue.

Frerking,"Crystal Oscillator Design and Temperature Compensation" (and
a lot of other folks) says the Q of the crystal is: Q = Xl / R,
where Xl is the motional inductance and R is the ESR. Thus the Q of
the -crystal- is not a function of the mode of operation. Short of
drastically changing R, the crystal Q is unaffected by external
circuitry.

If we speak of overall -circuit- Q then that is a different can of
worms.



Joe
W3JDR


"Tim Wescott" wrote in message
...
JJ wrote:
I am fimilar with Colpitts, Harley, Clapps, Bulter, Piece oscillators?

Which configuration with JFET or BJT would yield the highest performance
and least jitter?

JJ

AFAIK a well-designed Butler oscillator will have the lowest jitter, but I
doubt that you could do the "well designed" part without a lot of bench
work.

Any of the rest (considering a "Clapp" oscillator to mean a crystal
oscillator with rubbering) are good enough for communications work.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

JJ wrote:

Epson makes a low jitter TTL osc. ~3pSec RMS jitter. ~$5 each. 100
MHz.



Nice specs. Too bad the freqs. are not suitable for me.

JJ


Hi !

Why do you like to key the oscillator ?
Let it run all the time and key the later stage !

73 , Risto OH2BT

"Thus the Q of
the -crystal- is not a function of the mode of operation."
------------------------------

Wes,

If you're speaking of the Q of the crystal's inherent series resonance, then
you're right. However, most crystal oscillator circuits that we typically
see in common use operate in the parallel resonant mode, which isn't a
crystal resonance at all. It's the frequency at which the crystal's net
inductive reactance resonates the parallel combination of holder capacitance
and circuit capacitance. As such, it's quite affected by the circuit around
the crystal. When the crystal is operated in a parallel resonant mode as
described, the Q of the overall resonant circuit is much lower than the
crystal's resonant Q.

Joe
W3JDR

JJ wrote:
There is a drop in freq for Pierce and Colpitt after 1 min of startup. Can
be 100Hz.
Serious enough.

That sounds like crystal heating. All of these oscillators can drive
the crystal at various drive levels (depending on resistor and
capacitor values and/or tank circuit tapping) and different crystals
like different drive levels.

A tuning-fork type crystal (e.g. 32kHz watch crystal) is being
overdriven if the levels are as high as a microwatt.

Most HF-range crystals will take hundreds of microwatts to a few
milliwatts of drive.

Lots of the oscillator circuits in old handbooks are designed around
FT-243 crystals, which can take substantially higher drive levels
(sometimes the tube oscillator was putting out several watts) than
"modern" crystals. And even then those handbook circuits overdrove the
crystals to get more power out of the oscillator! By 1950's standards
100Hz of chirp/drift was not a big deal (was probably better than
average for most equipment.)

Tim.