A Time Nut would measure phase change across the path of totality using GPS
locked SDR receivers :-)) As was done on the Eclipse that passed between the
UK and Iceland a couple of years ago. Keflavik NRK's ionospheric signal was
returned from inside the path of totality to most of the north of the UK,
giving a good measure of the change in height of the "apparent reflection
height" in the D-layer.

The quoted program looks a bit scattergun......lets record everthing and see
what's there.
Hopefully it will involve a lot of school kids and maybe interest them in
science and electronics. If it does that it will be more useful that we
could imagine.

Alan
G3NYK

----- Original Message -----
From: "John Ackermann N8UR" jra@febo.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Thursday, August 03, 2017 8:10 PM
Subject: [time-nuts] Fwd: [hpsdr] SDR experiment for the solar eclipse

That experiment is happening, too.  Folks will be monitoring WWV and CHU
in narrowband mode with the same tools they use in the frequency
measuring tests.  (You can't really do direct phase comparisons on HF
frequencies because between the noise and the ionospheric effects,
including doppler shift, it's really hard to lock to the RF cycle the
way you can at VLF.)

We were originally going to put a 5071A-locked beacon on three ham
bands, but decided WWV and CHU would be better sources, and logistics
were turning into a problem: I'm going to be doing my wideband recording
from a cottage in northern Michigan.  But I'm still a time-nut, so the
receiver will be GPSDO-controlled, and there will be a stratum 1 NTP
server in the cottage to provide timestamps. :-)

John

On 08/03/2017 03:57 PM, Alan Melia wrote:

Hi John appreciate the problems at HF, and Boulder is very close to the
track of the totality to use WWVB  Enjoy the event hope you record some
interesting effects.

Best Wishes
Alan
G3NYK

----- Original Message -----
From: "John Ackermann N8UR" jra@febo.com
To: time-nuts@febo.com
Sent: Thursday, August 03, 2017 9:20 PM
Subject: Re: [time-nuts] Fwd: [hpsdr] SDR experiment for the solar eclipse

On 8/3/17 12:10 PM, John Ackermann N8UR wrote:

Here's a time-nuts connection
some ionosphere scientists I've been working with suggest that you sync
your SDR and make it receive ionosonde transmissions.  These are
precisely timed to start at the top of the minute (hence the utility of
a decent clock). They also have well characterized transmit power and
pattern.

There are open source implementations of chirpsounder receivers for
GNURadio and for platforms like USRPs.
Juha Vierinen at Univ of Tromso, Norway has been very active in this.

https://hackaday.com/author/jvierine/

http://www.sgo.fi/~j/gnu_chirp_sounder/

Hi John,

My favorite write-up about atomic clocks and eclipses (a null result) is at:

http://www2.mpq.mpg.de/~haensch/oldStuff/eclipse/eclipse.html

There you will find a good summary, thorough methodology, and many plots for the 1999 eclipse. Plus they posted all the raw data (H-maser, cesium, rubidium), a time-nuts dream. There is no model for why an eclipse should affect time at the atomic (quantum) level so a null result is fine. If nothing else, it sets an upper bound on measurement precision or a lower bound on clock anomalies, if they exist.

Much more dramatic is what an eclipse might do to the ionosphere, as this may affect both GPS and HF radio. So I'm very please to see the ham community milking this rare opportunity for all it's worth.

/tvb

On 8/4/17 7:22 AM, Tom Van Baak wrote:

It is of great interest - the fact that we have an ionosphere (which
helps keep us alive) also is one of the bigger factors in accurate time
distribution from space since the medium is refractive - not only does
it change the speed at which a wave propagates through, but the
propagation path is not a straight line.

The ionization is almost entirely due to the sun. There is some small
effect from terrestrial upper atmosphere phenomena propagating upwards,
and then there's also human caused changes (HAARP and other heaters,
rocket launched clouds of easily ionizable material, and the occasional
high energy nuclear reaction in the upper atmosphere/space).

There's a lot that is unknown about the time constants of the ionization
and deionization, since the usual situation is that you gradually reduce
the solar input (sunset) and increase it some 12 hours later. And
there's not, often, the chance to have a "step function" in the solar
illumination vs horizontal distance.

The real challenge is that it's a short event - with conventional
ionosondes, the sweep is minutes long (which is fine given the usual
slow diurnal variation), which is significantly longer than the duration
of totality. That long slow sweep makes synchronization less critical -
if you start off by a few milliseconds, as long as your receiver
bandwidth is wide enough, you still capture the sweep.

It's not going to happen this time, but something where "all frequencies
get measured every few seconds" would be wonderful. There are some
ionosondes using a broadband PN waveform.  And there's some interesting
propagation experiments that have been done over the Cascade mountain
range using TV and Radio stations as a form of pseudo random transmit
signal.

But you could do a real interesting science experiment with several
dozen (or hundred) RTL-SDR receivers, a good oscillator for timing, and
a data logger spread over several thousand km. In conjunction with the
existing ionosondes, you could collect a lot of oblique measurements of
the ionosphere during the eclipse.

Then would come (years of) post processing -

there is no reason for an eclipse to affect time. However, working on the 1999 data made available by the German group, I had found a periodicity in the noise in one of the time series. In particular, a pattern (a peak) was repeated every 35 minutes, which was the periodicity recorded by a gravimeter in Trieste (Italy)
http://xoomer.virgilio.it/iovane/xtrieste.htm
I discarded those data because they didn't match in time the Trieste's disturbances.
I suspect that an eclipse-related cause might affect in some way the atomic clock circuitry (or even magnetic shielding) with a (weak)  possibility of causing artifacts.

Keep an open eye.

i8iov