I can report reception of some VLF signals from Dex
W4DEX as WH2XBA/4 during the previous two nights.
Sending OP-2H with 100W at 29500 Hz from 2014-03-11 03:00
onwards produced a signal in Todmorden which averaged 0.135 fT
http://abelian.org/vlf/tmp/29500_140311a.gif
http://abelian.org/vlf/tmp/29500_140311b.gif
and S/N was 16.2dB in 125uHz.
The transmission began at 23:00 UT with 50W carrier until
02:00 when it switched to 100W of OP-2H.
The signal is only slightly weaker than WH2XBA/1 transmitting
at the same time on 29499 Hz. /1 was averaging 0.146 fT over
the same period.
I sent the signal data to Markus DF6NM who was able to get a
good deep search detection out of it:
2014-03-11 05:14:00 WH4XBA ... -55.0dBOp 100% 15.7dB
Measurements ended before the signal vanished because of the
appearance of military signals on a nearby frequency.
Interestingly, the phase of Dex's transmission was almost
constant throughout the night:
http://abelian.org/vlf/tmp/29500_140311c.gif
Phase bounces around +/- 25 degrees but there is no significant
trend of the phase between 00:00 and 05:30. What variation there
is can be attributed to noise in the 1.66mHz measurement band.
Then last night Dex made a transmission at 33950 Hz. The 50W
carrier appeared at 2014-03-12 03:00 UT and averaged 0.107 fT
between 03:00 and 07:00 and S/N was 20.6dB in 69.4uHz bandwidth.
Here too, the phase was fairly constant:
http://abelian.org/vlf/tmp/33950_140312a.gif
Path length WH2XBA/4 to Todmorden 53.703N 2.072W: 6194km.
--
Paul Nicholson
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