[time-nuts] retry: PRS10 has spurious frequencies
SAIDJACK at aol.com
SAIDJACK at aol.com
Sun Apr 22 18:17:30 EDT 2007
(Sorry, retry the attachement was too big for the list:)
In a message dated 4/22/2007 11:30:22 Pacific Daylight Time,
henk at deriesp.demon.nl writes:
>Hello,
>The output spectrum of my just bought PRS10 has spurious frequencies
>from 580MHz in steps of 10MHz up to 680MHz. The 580MHz and 680MHz
>signals just above the noise. The 630MHz amplitude 60dB down the
>10MHz. Does anyone know if this a normal output?
>Henk
Hi Henk,
I have a expensive 10MHz ultra-low-noise Wenzel oscillator that we bought
some months ago that has similar very nasty noise on it's output.
See the attached HP8563E plot, you can see the worst spur at 280MHz at
-56dBm, which is about -50dBc/Hz!
The Wenzel has a measured phase noise floor of -169dBc/Hz at 10Khz.
In comparison, see our Jackson-Labs Fury GPSDO output measured exactly the
same way - one can only see the second and third harmonic everything else is
killed by the seventh-order low pass filter.
I asked Wenzel about this noise, and they said "we see it too, it's caused
by the HP8563E spectrum analyzer itself, we are not worried about it".
Well, Wenzel went silent when I sent them the attached plots of an MTI-230
OCXO raw output, and our Fury GPSDO output both measured on the same 8563E
setup. Never heard from them since.
I think the measurements show that it's pretty important to put a low pass
filter on the output of OCXO's.
I wonder what is generating such high frequency, high energy spurs in these
OCXO's.
bye,
Said
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