Mark
Any more info on the jumpy HPs appreciated.
--
73
Hank WD5JFR
"qrk" wrote in message
...
On 19 May 2004 06:08:37 -0700, (Steve
Kavanagh) wrote:

Thanks for all your comments. Since speculation has started here is
what I know about the capacitors.

Those used in the 2.5 GHz source are surplus from a company that makes
high quality stuff. They were probably procured to a military or
space specification but I am not sure. The 10.5 GHz source was
manufactured by MA/COM about 20 years ago. All of them are the usual
deep maroon (is that the right word ?) to brown colour.

Keep in mind I am being pretty picky. I consider short term frequency
jumps of much over 100 Hz to be unsatisfactory - that is 10-40 parts
per billion depending on which source is considered. The largest
observed jumps are about ten times this. Of course, since these are
crystal oscillators, the corresponding capacitance jumps must be much
larger, since the crystal should dominate the oscillator stability. I
would not consider them "crappy", just not as good as one might be led
to expect. I have used capacitors from the same provenance as those
in the 2.5 GHz source in LC oscillators at a few MHz with no observed
problems. The smooth portion of the warm-up drift is reasonably
normal in both cases...only the jumpiness is unusual.

Steve

Crystals can also jump. Just look at HP oven oscillators used in the
GPS time/frequency references. Very jumpy. A collegue tried 5
oscillators in the GPS time/freq reference and all were jumpy to
various degrees. He was noting sub-ppb jumps.

Mark

In article , Henry
Kolesnik writes
Mark
Any more info on the jumpy HPs appreciated.
--
73
This thread seems to be cloned from last week ; anyway as I said then
silver mica are known to be subject to scintillation which may be due to
de-lamination , later mica used powdered mica which may or maynot be
better. Encapsulated low value caps are often degraded by the
encapsulation material so sm would be better use NPO ceramic, microwave
types should be lower loss.
Crystals jump in a changing temperature due to unwanted modes passing
through the main mode as they have different temperature coeggicient.
These are fairly gross effects of .01 to 10ppm jumps.

--
ddwyer

In article , Henry
Kolesnik writes
Mark
Any more info on the jumpy HPs appreciated.
--
73
This thread seems to be cloned from last week ; anyway as I said then
silver mica are known to be subject to scintillation which may be due to
de-lamination , later mica used powdered mica which may or maynot be
better. Encapsulated low value caps are often degraded by the
encapsulation material so sm would be better use NPO ceramic, microwave
types should be lower loss.
Crystals jump in a changing temperature due to unwanted modes passing
through the main mode as they have different temperature coeggicient.
These are fairly gross effects of .01 to 10ppm jumps.

--
ddwyer