[NLRS] Link -- New phase-modulation WWVB signal

Wed Mar 13 12:01:36 EDT 2013

Still have several, have used one most recently when checking RF power 
with a broad band scope and a dummy load. Peak to peak divided by 2.8 
then squared and divided by 50. There I'm satisified with two digit 
precision when I know that the vagaries of a propagation path are going 
to make 10% changes in power undetectable at the other end. So I have 
been using a cheap printed wooden rule for that rather than my teflon 
guided Dietzgen log log duplex vector slide rule that weighs ten times 
as much.

73, Jerry, K0CQ

On 3/13/2013 9:52 AM, S. Earl Jarosh wrote:
> I miss the old days of slide rulers when hundredths resolution was good
> enough for the most part.......
>
>
> S. Earl Jarosh, N0HZ
> Twin City FM Club President
> Cell:  612.868.1313
> Off:   763.545.3275
> Home:  763.546.7897
> Fax:   763.546.7897
> earl at jarosh.org
> www.tcfmc.org
>
>   Twin City FM Club
>
>
>
> -----Original Message-----
> From: nlrs-bounces at mailman.qth.net [mailto:nlrs-bounces at mailman.qth.net] On
> Behalf Of Dr. Gerald N. Johnson
> Sent: Tuesday, March 12, 2013 9:57 PM
> To: Donn, WA2VOI
> Cc: nlrs at mailman.qth.net
> Subject: Re: [NLRS] Link -- New phase-modulation WWVB signal
>
>
>
>
>
> On 3/12/2013 7:46 PM, Donn, WA2VOI wrote:
>> According to the NIST web pages, they're a little better than that,
>> though they do acknowledge the difficuties of 60KHz work. :-)
>>
>> "The antennas are spaced 857 m apart. Each antenna is a top loaded
>> monopole consisting of four 122-m towers arranged in a diamond shape.
>> A system of cables, often called a capacitance hat or top hat, is
>> suspended between the four towers. This top hat is electrically
>> isolated from the towers, and is electrically connected to a downlead
>> suspended from the center of the top hat. The downlead serves as the
>> radiating element.
>>
>> As the length of a vertical radiator becomes shorter compared to
>> wavelength, the efficiency of the antenna goes down. In other words,
>> it requires more and more transmitter power to increase the effective
>> radiated power. The north antenna system at WWVB has an efficiency of
>> about 50.6%, and the south antenna has an efficiency of about 57.5%.
>> However, the combined efficiency of the two antennas is about 65%. As
>> a result, each transmitter only has to produce a forward power of
>> about 54 kW for WWVB to produce its effective radiated power of 70 kW."
>
> I'm sure I have that data here somewhere. But it will take another year to
> find it once I start looking for it.
>
> I have used WWVB and used to use WWVL to check my in house standard. I did
> it short time and I could see either random walk in my standard, variations
> in propagation time, or I figured movement of the vertical wire radiator in
> the wind. It might have been random variations in my test set up also.
>
> What I did was with a TRF receiver tuned to 60 kHz, I put that on the scope
> vertical (Tek 475) and I triggered the scope sweep with 100 kHz from the
> standard (Manson Labs, double oven, 5 MHz 5th overtone crystal in a sealed
> glass tube about the size of a 6146). The sine wave 60 kHz signal with 100
> kHz trigger gives the appearance of three power line phases. I selected a
> crossing of two sine waves and followed it across the scope, only when they
> were at high power part of each second. That way I maximized my S/N. When I
> got the standard tweaked so the crossing stayed within 100 ns for 15 minutes
> I figured I had it as good as I could do because the crossing was then
> wandering randomly in that 100 ns. That's 1.1x10-10, as good as an
> oscillator rated for 10-9 per day aging gets for such a short term
> measurement.
>
> It might have been better to have used the local standard's output for the
> horizontal sweep to take scope triggering out of the measurement, but then
> it would have been much harder to figure the error having to look for drift
> of a major fraction of that 100 kHz cycle lasting 10 microseconds (10,000
> nanoseconds). That standard has a 1 MHz output too which might have given
> some help but the scope sweep made it much easier to measure the amount of
> drift.
>
> I now have an HP 10811 oscillator without battery back up and I warm it up
> before using it with my microwave counter, but I have not checked it with
> WWVB or GPS. I am content with pretty good, say a part per 10 million which
> it should do unless savaged and I've not had to argue frequency that close
> in my life so I'm in a don't really care all that much. I'm not going to set
> up to run the station from that high quality frequency standard when I have
> a tuning dial on the IF.
>
> At 60, kHz QRM from NTSC TV sweep is a big problem and sometimes harmonics
> from arcs on the AC power line appeared to contribute considerable QRM.
>
> More conventional VLF frequency standard techniques use a phase locked loop
> with about a 10 hour time constant, maybe longer so the twice an hour phase
> shifts used on WWVB for identification don't kick the local standard out of
> lock. So I presume phase shift keying as proposed won't mess up those
> either. Though that way it can take a week to get a standard on frequency so
> they can plot the received phase and detect the ID shifts and detect when
> aurora is on the way. The VLF propagation shifts considerably several hours
> before aurora arrives. At the Iowa frequency standard maintained by W0PFP at
> ISU (dismantled when he retired early) it too three 6' tall racks of
> equipment to perform that function.
>
> I wonder how well the clock handles the known QRM sources when its based on
> the binary coding and the amplitude shift keying.
>
> 73, Jerry, K0CQ
>>
>> Basic clock is<1x10-12. Compensating for path delay allows UTC to
>> <100usec. Not too bad, actually, for consumer use (i.e., $20 clocks).
>>
>> 73 Donn
>> WA2VOI/0
>>
>>
>
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