[hpsdr] Excalibur checkout

[Graham / KE9H]

AA8K wrote:
 > My Excalibur oscillator was 10.5 Hz off at 10 MHz
 > against WWV and my Trimble Thunderbolt, after a 10
 > hour warm up.  I waited another day and zeroed it.
 > I'll check it again after a month or two.  I like
 > the beat LEDs.  I'll be using the Thunderbolt anyway.
 >
 > Mike - AA8K


Geoff wrote:
 > Powered up without smoke :-). 5Hz off against WWV on
 > 15MHz using the TCXO. I'm very happy, it's well
 > within spec. Time to get my LPRO101 integrated.
 >
 > 73 de Geoff vk2tfg.


All:

My personal experience, having built three of the
Excalibur modules, is that three out of three TCXO were
within 1 Hz., out of the box.

With Mike, AA8K's report I now have two reports of
errors out of the box on the order of ten Hz, but
within adjustment range such that they can be adjusted
to zero error.  I don't know if this is a problem, or
just a factory set error, with multiple hundreds of
kits shipped.

--

I had reports from several users that the "Phase
Display" built into PowerSDR could be used to
set/check the frequency of the TCXO in the absence of
a local 10 MHz standard or GPSDO.

Playing with the "Phase" display (not Phase 2), you
can see the phase error relative to the station you
are listening to.  You get a rotating "RADAR screen"
plot where distance from the center of the circle is
amplitude, and angle is phase.

So, tune to WWV, or your local frequency standard
station. Once a second rotation means one Hz error.
Two seconds to rotate once, means one half Hz error.
Ten seconds to rotate once means one-tenth Hz error.

Narrow the AM bandwidth to less than 100 Hz to wipe
the modulation off the carrier, so you are only
looking at the carrier, to stabilize the dot some.

Multiple dots at once, on opposite sides of the circle
means you are multiple Hz off frequency. Adjust until
you see only a single dot/plot spinning around.

Once again, don't bother trying to get the error below
one-half to one-quarter Hz, since the oscillator walks
around about one Hz over the course of a day.

There is also a granularity in the DDS/CORDIC built
into Mercury, in that its resolution is not infinite,
and it actually steps frequency in step sizes of about
0.03 Hz.

So realize that when you tune to a particular
frequency with Mercury, it means that the receiver is
on that frequency plus/minus 0.03 Hz.  So even when
locked to a GPSDO with an error in the milli-Hertz,
you can only use the phase display to measure your
friend's carrier frequency to about 0.1 Hz.

;-)

--- Graham / KE9H

==



 1263142319.0