Date: Sat, 10 Jun 2017 16:24:23 -0400
From: Markus Vester <markusvester@aol.com>
To: rsgb_lf_group@blacksheep.org
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Subject: ELF: ZEVS phase and frequency accuracy?
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I've been wondering whether the 82 Hz carrier from the ZEVS transmitter is =
accurate and synchroneous to UTC. So I set up a colour spectrogram on the D=
L0AO grabber
 http://df6nm.bplaced.net/dl0ao/VLFgrabber/vlfgrabber_dl0ao_test.htm
(scroll down to near the bottom), which shows the phase with reference to a=
 1pps harmonic on the other channel. The colour sequence is red-yellow-gree=
n-blue for retarding ZEVS phase (unfortunately opposite to the way it's don=
e on LoranView).

During the last six hours, the colour has changed from red to green, indica=
ting a 120=C2=B0 delay. This Looks like the carrier is ~ 20 uHz below 82 Hz=
 (-0.25 ppm, quite a large difference on a relative scale). I am asking mys=
elf how it the transmit frequency is physically being steered, possibly "Al=
exanderson-style" by setting the velocity of a rotating machine? If the fre=
quency offset turns out to be real and stable, it could be a means for DX'e=
rs to differentiate the real ZEVS signal from possible local receiver artif=
acts. I wonder whether anyone else could verify the offset?

On the other hand, I wouldn't yet rule out a diurnal propagation effect, ev=
en though at a distance of less than a wavelength this should not produce s=
uch a large phase change. There could also be local effects on the receive =
site from variable humidity in the vegetation near the E-field probe.=20

So the big question is whether or not the phase trend will continue tonight=
 and tomorrow.

Best 73,
Markus (DF6NM)
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<div style=3D"font-size:10pt;font-family:arial,helvetica,sans-serif;color:b=
lack;">I've been wondering whether the 82 Hz carrier from the ZEVS transmit=
ter is&nbsp;accurate&nbsp;and synchroneous to UTC. So I set up a colour spe=
ctrogram&nbsp;on&nbsp;the DL0AO grabber<br>&nbsp;http://df6nm.bplaced.net/d=
l0ao/VLFgrabber/vlfgrabber_dl0ao_test.htm<br>(scroll down to near the botto=
m), which shows the phase with reference to a 1pps harmonic on&nbsp;the oth=
er channel. The colour sequence is red-yellow-green-blue for retarding ZEVS=
 phase (unfortunately opposite to&nbsp;the way it's done on LoranView).<br>=
<br>During the last six hours, the colour has changed from red to green, in=
dicating a 120=C2=B0 delay. This Looks like the carrier&nbsp;is ~ 20 uHz be=
low 82 Hz (-0.25 ppm, quite a large difference on a relative scale).&nbsp;I=
 am asking myself how it the transmit frequency is physically being steered=
, possibly "Alexanderson-style" by&nbsp;setting the velocity of a rotating =
machine?&nbsp;If&nbsp;the frequency offset turns out to be real and stable,=
 it could be a means for DX'ers to differentiate&nbsp;the real ZEVS signal =
from possible local receiver artifacts.&nbsp;I wonder whether anyone else c=
ould&nbsp;verify the offset?<br><br>On the other hand, I wouldn't yet&nbsp;=
rule out a diurnal&nbsp;propagation effect, even though at a distance of&nb=
sp;less than a wavelength this should not produce such a&nbsp;large&nbsp;ph=
ase change. There could also be local&nbsp;effects on the receive site from=
 variable humidity in the vegetation near the E-field probe.&nbsp;<br><br>S=
o the big question is whether&nbsp;or not the phase trend will continue ton=
ight and tomorrow.<br><br>Best 73,<br>Markus (DF6NM)<br></div>
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