Recent measurements of carrier from VO1NA on 8270.0075Hz
Night: 19th/20th 13.9 dB phase 3.0 deg 0.065 fT H-field only
Day: 20th 10.5 dB phase 101.4 deg 0.034 fT H-field only
Night: 20th/21st 12.1 dB phase 8.0 deg 0.058 fT H-field only
10.8 dB phase 0.0 deg E-field only
14.4 dB E-field and H-field combined
Day: 21st 12.3 dB phase 104.8 deg 0.038 fT H-field only
10.1 dB phase 100.3 deg E-field only
15.2 dB E-field and H-field combined
Day: 22nd 9.9 dB phase 156.5 deg 0.034 fT H-field only
Apart from today, the day and night phases look repeatable
enough for stacking but more measurements would be nice.
Here's Joe's daytime 21st signal with combined E and H,
http://abelian.org/vlf/tmp/171022a.gif
This ought to be visible further into Europe.
Some progress now with the new E-field rx. For some time
I've had a puzzle where the new rx performs on average
0.13 dB worse than the old at the Alpha F1 frequency, when
it should really be half a dB or so better. I traced the
extra noise to somewhere in front of the front-end.
Now after moving the rx about 20 metres to a new location
and putting in a new grounding system, the noise floor is
about right.
Signals from Joe and Stefan have been very useful: some
comparison S/N dB readings on recent carrier signals:
DK7FC 5170.005 Hz
-----------------
Old RX New RX
2017-10-21_11:00,+3.5h 13.27 17.07
2017-10-22_13:00,+3.5h 6.66 15.96
VO1NA 8270.0075
---------------
Old RX New RX
2017-10-21_11:00,+7h 5.98 8.82
Alpha F1 11904.7619
-------------------
Old RX New RX
2017-10-21_11:00,+60m 41.48 42.09
2017-10-21_12:00,+60m 37.84 38.40
2017-10-21_13:00,+60m 37.88 38.70
2017-10-21_14:00,+60m 32.13 32.68
2017-10-21_15:00,+60m 41.09 41.54
2017-10-22_10:00,+60m 41.15 42.04
2017-10-22_11:00,+60m 40.38 41.85
2017-10-22_12:00,+60m 41.75 42.82
2017-10-22_13:00,+60m 36.80 37.14
The improvement is roughly as expected now. More improvement
at lower frequencies because the old rx is pretty bad down
there - good enough for whistlers and things but not up to par
for weak amateur radio signals.
I suspect that the extra noise was coming from the grounding
system, either thermal noise or some sort of electrochemical
noise. There's a nice shiny set of 6 ground rods at the new site-
https://www.screwfix.com/p/earth-rod-3-8-4ft/28044
These are very strong and drive in easily in the soft ground here.
I'm having a lot of trouble with mechanical interference as the
antenna flexes slightly in the wind. Also some interference
coming in along the DC supply, and one of the DC-DC isolating
converters very occasionally doesn't start up when power
is applied.
I'll get whatever measurements I can over the next day or two
then the rx and antenna is back in for yet another re-build.
--
Paul Nicholson
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