[time-nuts] more is revealed about OCXO harmonics & level

[walter shawlee 2]

I decided to rip the add-on board apart, and go right to the oscilloquartz 8633 
output.
no surprise, >0dBm level, but alas, 20Mhz harmonics are only -35 dB down, and 
there's one at 30, etc..  hmm, what does this really mean?  well, when in doubt, 
go back and look at the data:

http://www.sungwhatech.com/product/pdf/aging/8663.pdf

rats, *the spec is only -25dBc for harmonics*.  phase noise looks good, as does 
stability, but
now I understand why I am seeing these spurs, it's in spec!  it does look like 
my level is out of spec though, I cannot get +4dBm even right from the module, 
perhaps that's why these units became surplus.  the date code on my OCXO 8663-XS 
is 2008.  I cannot identify what the X part of the dash number means, maybe 
lower output with my luck?

to make the board a bit safer to use, I made up a resistive splitter with 2 51R 
carbon resistors, and slipped ferrite beads on the leads to help control high 
frequency harmonic content.  I can now run the counter and SA at the same time, 
and get maybe -2dBm outputs, closer to 0dBm if I use only one.
if I add my outboard 10MHz bandpass filter, harmonics drop into the grass at 
-60dBm, but level goes to -5dBm.

clearly not as nice as the FE5680A Rb unit, but I will leave it in there just 
for comparison. I think I will filter one output, and leave one raw, since I 
have 2 jacks already at the front for outputs. but this was very instructive, I 
really did not expect to see so much harmonic content from a precision OCXO 
sinewave crystal oscillator.  a quick cross check on some of my other hp/FE 
ovenized standards in the lab does not show this kind of unwanted content.

what kind of results does everyone else get?

all the best,
walter

-- 
Walter Shawlee 2, President
Sphere Research Corporation
3394 Sunnyside Rd.,  West Kelowna,  BC
V1Z 2V4  CANADA  Phone: (250) 769-1834
walter2 at sphere.bc.ca
WS2: We're all in one boat, no matter how it looks to you.
Love is all you need. (John Lennon)
But, that doesn't mean other things don't come in handy. (WS2)