Re: LF: More EbNaut 137.777 - phase plot

[Markus Vester <markusvester@aol.com>]

Paul,

 

that's an interesting phase plot! Although it's probably hard to completely rule out a contribution from TX oscillator drift, the 3.5-cycle day-night change seems quite plausible.

 

Attached is a plot from a recent Loran-C operation from Wildwood, NJ. The top plot shows signal strength in two ways (red is the total received pulse energy, magenta the narrowband 100 kHz amplitude). The blue plot is continuous phase, also showing a similar 3.5-cycle phase advance during the morning hours. Given the larger distance (6595 km) and lower frequency (100 kHz), this is obviously a very nice match to your VO1NA result.

 

All the best,
Markus (DF6NM)

 

-----Ursprüngliche Mitteilung-----
Von: Paul Nicholson <vlf0403@abelian.org>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mo, 7 Dez 2015 12:27 am
Betreff: Re: LF: More EbNaut 137.777 - TA slot

It was a few hours before I got to the rx to retrieve the
battery so it continued on an almost dead battery and recorded
two more messages.

VO1NA 2015-12-05/06 16K21A 5S 5C QRO

start Eb/N0 Freq

13:30 13.0 -222 uHz
15:00 3.1 -256 uHz
16:30 3.9 -482 uHz
18:00 15.1 -558 uHz
19:30 17.3 -228 uHz
21:00 14.2 -330 uHz
22:30 18.7 -262 uHz
00:00 14.8 -253 uHz
01:30 17.0 -293 uHz
03:00 22.4 -41 uHz
04:30 20.8 -208 uHz
06:00 13.0 -216 uHz
07:30 17.0 -276 uHz
09:00 3.1 +20 uHz

Partial reception at 10:30 gave enough to measure +3 uHz.

I was able to measure the phase over the entire 21 hour
recording in 5 minute averages:

http://abelian.org/vlf/tmp/151206a.gif

This looks to me like propagation, not drift of the tx
oscillator. It's a pretty typical diurnal. I'm plotting
phase measured at a frequency offset of -255 uHz.

I think that Joe's oscillator is actually doing very well and
we are seeing mostly the effect of propagation. The phase ends
up nearly where it started and the total day/night change is
about -1250 degrees or about -3.5 cycles.
--
Paul Nicholson
-- 

Wildwood_151123-24.png
Description: PNG image