[time-nuts] What equipment can I economically use to measure jitterand noise sidebands?
jmiles at pop.net
Sat Jul 14 14:34:06 EDT 2007
Too many dimensions to that question. :) What carrier frequencies and
offsets are you interested in; what noise levels are you interested in
measuring; and what's the budget?
An 8662A ($2000 minimum for a good one, usually) plus an 11729B/C
($500-$2000 depending on options?) plus a good baseband spectrum analyzer
($1000-$2000) is clean enough to measure many sources, and much better than
any spectrum analyzer by itself. That is the minimum amount of money you
will have to spend for serious HF-to-microwave measurement, I think.
The next step down is an HP 8568A or -B which sells for not much more than
its weight in scrap metal, and is a great analyzer for PN measurement as
long as you don't need to look below -110 dBc/Hz, at offsets below 100 Hz,
or at carriers beyond 1500 MHz. Most of the hardcore 'nuts' will not be
satisfied with this noise-measurement floor, but if you are just playing
with homebrew UHF PLLs, it will probably do nicely.
If your work is limited to DC-HF measurement then you certainly can't beat
the Wavecrest units people have been talking about. I haven't played with
one of those yet, but I'm starting to want one. Interfacing one of those to
an 11729/8662A sounds attractive, but the noise floor would still be limited
by the 8662A or similar tunable source, just as it is when you use a
conventional spectrum analyzer with an 11729/8662A. If you don't need
general-purpose tuning capabilities then a Wavecrest box with a fixed
downconverter will certainly outperform anything with an 8662A.
I don't know anything about measurements on modulated signals; most of the
time these measurements are made on CW carriers or perhaps on pulsed ones
(see HP's AN 386). Maybe the Wavecrest software helps with this? Since the
BER of a digitally-modulated signal depends on carrier phase noise and phase
hits among other things, I would guess that running your link's existing BER
diagnostics under controlled conditions would be the easiest way to observe
-- john, KE5FX
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Peter Vince
> Sent: Saturday, July 14, 2007 4:34 AM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] What equipment can I economically use to measure
> jitterand noise sidebands?
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+jmiles=pop.net+jmiles=pop.net at febo.com
> Might I ask what you guys are using to measure jitter and oscillator
> noise-sidebands? I think Mike was lucky to pick up the Wavecrest
> recently, but is that the only option? Is there anything else, maybe
> older and cheaper, if not quite so high-tech?
> I would like to be able to characterise both the usual frequency
> oscillators, but also other odd frequencies, and digitally modulated
> signals - any suggestions?
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