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 <[email protected]> wrote: > Date: Tue, 21 Aug 2018 22:49:49 -0400 > From: "Paul Christensen" <[email protected]> > To: <[email protected]> > 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 > > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > _________________ Topband Reflector Archives - http://www.contesting.com/_topband
