[time-nuts] Test WWV timecube against Cesium, Rubidium, MASER or other precision time (UT-1) metrology
scmcgrath at gmail.com
Thu Dec 7 18:17:36 EST 2017
The timecube radios were simple superheterodyne AM receivers. I suspect the group delay of the timecubes will be small and fairly consistent due to the low component count,
Yet because of the low quality components performance variability between units will be quite high.
A more interesting test would be with a heathkit 'Most Accurate Clock' GC-1000 which was effectively a HFDO since it used HF WWV signals to discipline its timebase.
On Dec 7, 2017, at 3:05 PM, paul swed <paulswedb at gmail.com> wrote:
Way back in the 90s I measured the color subcarrier frequency of
geostationary satellites. That aren't actually stationary.
I knew the quality of the subcarriers for a number of the networks since we
originated the signals. CBS was Cs others were Rb and still others various
Xtals. I had direct access to the references.
I used an HP5360 and homebrew interface collecting the data on a computer.
I was using a wide variety back then.
No matter. I actually could see over long periods the orbital day to day
and seasonal behaviors. By gosh physics and such in action. The reference
was the 5360s oven oscillator that was quite good. I know times have
changed. The reason to do it was simply because I could.
All of that said I will believe the doppler shifts are your biggest impact
so not sure orders of magnitude really help and may actually confuse. You
will have the effects of earth, the moon and the satellites orbit. Now
thats some serious math and thinking. Some place along the line other great
stuff will work to mess with you.
On Thu, Dec 7, 2017 at 8:48 AM, Patrick Barthelow <apolloeme at gmail.com>
> Hello Friends,
> I am picking up locally a couple of vintage analog Radio Shack SW time cube
> radios, 70s vintage, 3 switchable SW frequencies. Two types, the one
> pictured and a Radio Shack model also that has WWV and Weather channel VHF
> I am interested in an accurate bench test to compare the analog shortwave
> radios time reporting
> hopefully UT-1 against other available references. For accuracy, and
> repeatability. Could eventually add an SDR to the mix, too.
> The 5,10,15 mhz radios obviously are subject to the WWV Ft Collins site,
> propagation distance delays, somewhat calculable, and the vagaries of
> Ionospheric propagation, and, propagation delays between the antenna and
> the measured tap point to the seconds ticks of WWV. I have some friends,
> microwave professionals, who are also hams here in Auburn who may enjoy
> doing a bench test, with published results, etc. But wonder if anyone else
> would be interested in borrowing a RS Timecube radio (and/or use an SDR)
> and designing an accurate bench test against available modern standards?
> We are talking probably HUGE UT-1 errors compared to what this group plays
> with, and that is OK but I think still a worthwhile test, especially if the
> errors using available and cheap equipment are predictable, and repeatable.
> Another question: Re precision frequency measurements of spacecraft
> carriers at earth ground stations. I have found a number of MASER labs,
> willing to help measure a 70 cm UHF carrier of a satellite planned mission,
> circling the moon. Fun, and overkill yes . But I would like to know if
> the MASER extra 3 orders of magnitude precision frequency measurement (over
> Rubidium, Cesium) is useful, or utterly wasted in measuring a lunar
> orbiting spacecraft frequency over as long a period as a month, in a coming
> satellite mission? Or, are Rubidium and Cesium and GPS disciplined
> references plenty accurate for accurate spacecraft orbit determinations?
> Best, 73, Pat Barthelow AA6EG
> apol <apolloeme at gmail.com>loeme at gmail.com
> *"The most exciting phrase to hear in Science, the one that heraldsnew
> discoveries, is not "Eureka, I have found it!" but:*
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