Hi Jim,
You said "The accuracy of both devices far exceeds my needs", but let me
play the devils advocate. Unless you send those devices into an accredited
lab on a regular basis, you can't say they are accurate (unless you can
check them from home on a regular basis directly against a frequency
standard that's traceable directly back to NIST which would be WWV, WWVH,
WWVB, etc.).
I'm sure this sounds like a radical viewpoint, but just wanted to play the
devils advocate on this one.
P.S. NIST did publish a document about GPSDO traceability and here is the
URL to it which is good reading and it partially supports some of my
comments, but not totally.
https://ws680.nist.gov/publication/get_pdf.cfm?pub_id=842479
Don (wd8dsb)
On Sat, Aug 25, 2018 at 12:33 PM Jim Thomson <jim.thom@telus.net> wrote:
> Date: Tue, 21 Aug 2018 22:49:49 -0400
> From: "Paul Christensen" <w9ac@arrl.net>
> To: <topband@contesting.com>
> Subject: Re: Topband: OT - US Hams, WWV closure
>
> <Several options: (1) CHU is still operating on several HF frequencies
> that
> reasonably cover North America; (2) In the U.S., AM broadcast stations are
> required to maintain +/- 20 Hz carrier stability (73.1545). However,
> nearly
> all modern BC transmitters can easily meet 2 Hz, and some are now
> phase-locked to a precision standard.
>
> Most modern amateur gear covers the MW band. One could sample several AMBC
> stations, throw out the outliers, then calculate a geometric mean and
> attain
> a very accurate reference. Incidentally, some legacy ham-band-only gear
> never did cover WWV -- or if it did, it was received by a different band
> mixing scheme, then a pre-selector is peaked for resonance.
>
> In the shack, I use a GPSDO with a distribution amp that locks several
> transceivers and some test equipment. A surplus $100 USD rubidium standard
> is Velcro-strapped to my HP frequency counter. It comes up to temperature
> and locks within 5 minutes of powering. The accuracy of both devices far
> exceeds my needs.
>
> Paul, W9AC
>
> ## After very carefully aligning the .25 ppm TCXO in both my yaesu
> MK-Vs...
> using the 20 mhz wwv, I tuned across the entire AM 540-1710 khz
> band, and only found
> ONE station that was dead on freq, and that was CBC on 690 khz, in
> Vancouver BC.
> The rest were several hz too high..or several hz too low. Some were
> as much as 20 hz off freq.
>
> ## Even if you could find just one AM broadcaster that was dead on
> freq, the 540-1710 band is
> much too low to align a TCXO. If say you were off by 1 hz at 1000
> khz, you would be off 10 hz
> at 10 mhz..and 30 hz at 30 mhz, etc. And with no high freq WWV to
> compare to, you would have no
> clue as to which of the myriad of 540-1710 AM broadcast stations is
> actually anywhere close to being on freq.
>
> ## CHU broadcasts on just 3.33 mhz, 7.85 mhz..and 14.67 mhz. All 3
> are pretty weak here on the west coast.
> WWV is instead used here on the west coast, as CHU is typ too
> unreliable.
> The price tag on all this surplus GPSDO / rubidium gear will
> skyrocket if and when WWV is shut down.
> I can not see WWVB being shut down at all, too many consumer devices
> rely on it.
>
> Jim VE7RF
>
>
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