[hpsdr] Excalibur checkout

[Graham / KE9H]

Jeff:

Yes, you must verify that the local AM station is on frequency.  I think 
they
only need to be within 10 Hz to meet their license requirement,
although most are much better.

Your clip shows about one Hz difference at 660 kHz.  Well within the 
station's
legal requirement, and really not good enough to use to set your oscillator.

You must realize that the error scales with frequency. 1 Hz error at 1 MHz
is 10 Hz at 10 MHz. The higher the frequency station you use to set 
frequency
(assuming it is on frequency), the more accurate (percentage error wise) 
your
setting will be.  WWV at 5, 10, 15, or 20 MHz are ideal, if you have a 
reasonably
strong signal.

The goal is to set within one Hz at 10 MHz, however that scales for your
available reference frequency.

--- Graham

==

jkelly wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Graham,
>
> Can I use standard broadcast stations to achieve the same test?
> I guess I would have to confirm that they are on freq first.
> I just did a quick test with a local sports station:
>
> http://mysite.verizon.net/jkelly/hpsdr/phase/hpsdr.swf.html
>
> Does this look right to you?
>
> Jeff
> KT2K
>
> ----- Original Message ----- From: "Graham / KE9H" <KE9H at austin.rr.com>
> To: <aa8k73 at gmail.com>
> Cc: "HPSDR (open)" <hpsdr at openhpsdr.org>
> Sent: Sunday, January 10, 2010 11:51 AM
> Subject: Re: [hpsdr] Excalibur checkout
>
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> 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
>>
>> ==
>>
>
>


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