Hi Olin,

I agree that +/- 20Hz is not accurate enough for the measurement I'm
trying to do.

I did test it against WWV on 5MHz and it showed a discrepancy, but it
varied a bit due to fading and multi-path so I was looking for a local
source which I would receive by ground wave. WWVB would be an option
but it is too low in frequency for me to see a 1ppm discrepancy and
also it is too weak most of the time in my apartment.

In the end, I was able to use the analyzer's time domain function to
see the beat frequency between my Fluke signal generator and WWV on
5MHz and verify that they are definitely within 1/2 Hz of each other.
Since that's 100ppb, I can conclude that the 6ppm discrepancy between
the analyzer and the signal generator is due almost entirely to error
in the analyzer's reference.

Sean


On Mon, Sep 7, 2009 at 7:33 AM, Olin Lathrop<olin_piclist@embedinc.com> wro=
te:
> If you really need accurate, how about using one of the WWV transmissions?
> Their carriers are derived from NIST atomic clocks, and are therefore hig=
hly
> stable, accurate to many digits, and traceable. =A0The only problem is ph=
ase
> distortion due to multi-path problems if you're not close to a transmitte=
r.
>
> It used to be you could use the TV color carrier from any of the major
> networks as a reference. =A0I don't know where the color carrier comes fr=
om
> for any of the remaining NTSC signals. =A0The networks had accurate time
> references for producing the color carriers, and routinely compared them
> against the NIST standard. =A0They would regularly publish the offsets so=
 that
> measurements using their color carrier were traceable, although you had to
> wait until the offsets were published to do the actual tracing. =A0There =
were
> even some commercial frequency measuring products based on this.
>
> A more modern approach would be to make a frequency counter gated by the =
1Hz
> signal from a GPS. =A0GPS satellites have their own atomic clocks, so GPS=
 time
> is also highly accurate. =A0I don't know about short term accuracy though=
 as
> exported by common GPS receivers. =A0You'd probably want to observe the t=
arget
> frequency over some time period with the GPS-gated frequency counter.
>
>
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