[NLRS] Fwd: Fw: [MNDX] WWV Reference

[Ford Peterson]

> Consensus has been for decades that if you check WWV on HF the same time
> every quiet propagation day for a month you might get a result of a part
> in 10^7, 1 Hz per 10 MHz. And that may be better than your counter
> crystal. My house standards are a couple orders of magnitude more stable
> so I use WWVB on 60 KHz to check them and then I think I see propagation
> variations in a short time that I use for checking.
> 
> These days the handiest way to precision frequency is using GPS. The 1
> pps outputs can be 4 or 5 orders of magnitude more precise than WWV as
> received at 10 MHz. There is a commercial box or two, HP-2801A seems to
> be popular though touchy. There was a circuit in the most recent Eastern
> VHF Conference Proceedings using the 10 KHz output from a Rockwell-
> Collins GPS board and not a whole lot of circuitry to stabilize at 10
> MHz crystal oscillator and Luis Cuipedo (sp?) has boards for doing that
> with the 1 Hz output of most any GPS.
> 
> -- 
> 73, Jerry, K0CQ
> Dr. Gerald N. Johnson, electrical engineer
> All content copyright, Dr. Gerald N. Johnson

Jerry,

Thanks for the input.  The HP2810A you are referring to used to sell surplus for about $250 in QST.  Now they are up over $500 and occupy a good chunk of bench top space.  The GPS systems you are making reference to are quite the ticket, and well beyond the tolerance of the equipment being calibrated--to say nothing about expensive.  This little 10MHz Xtal filter and amp costs about $20 (less with a good junque box), can be made in a single weekend with ease, is just a wee bit bigger than a pack of smokes, and is powered from a generic 12v wall wart @100ma.  Best of all, it is completely impervious to temperature changes.  It's as accurate as WWV with a few phase inversions thrown in.

I talked with one of the lab techs at the TIS at the ARRL about this issue.  We talked about the phase inversions and what errors were thought to be introduced.  The consensus of opinion was that accuracy to a few hertz should not be a problem, even at 10MHz.  Obviously, if you have equipment that needs better accuracy, then spending the money and time to make that happen is well worth the investment.  On the other hand, I just need to calibrate my frequency counter, which at 0.1s updates is only accurate to 10 Hz.  When I set the counter to 1 Hz timebase, it flips within a few hertz of 10,000,000 once per second.  But heck, that beats the 200Hz error I had when I first powered it up to check it out.

Hip shot accuracy--no problems.  Precision instrument--not a chance.

Ford-N0FP
ford at cmgate.com