Half the clocks in our house check WWW every night.
-----------------------------------Wes Attaway (N5WA)(318) 393-3289 -
Shreveport, LAComputer/Cellphone ForensicsAttawayForensics.com
------------------------------------
-------- Original message --------From: Don Kirk <wd8dsb@gmail.com> Date:
8/25/18 2:55 PM (GMT-06:00) To: jim.thom@telus.net Cc: topband
<topband@contesting.com> Subject: Re: Topband: OT - US Hams, WWV closure
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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