Re: VLF: 300 mA on 5170 Hz

[Paul Nicholson <vlf0403@abelian.org>]

I wrote:

> Is it too late to switch to 16K23A with 4 second symbols?

Oh I forgot, the Windows version doesn't have 16K23A yet.
I must finish the testing...

Eb/N0 and phase for the four recent 1 char messages:

 Night  H-field            (new) E-field       Combined
 20/21  7.1 dB -165.7 deg  13.0 dB -168.1 deg  13.6 dB -167.7 deg
 22/23  6.5 dB  174.9 deg  11.3 dB -166.7 deg  11.8 dB -168.7 deg
 23/24  6.8 dB -174.2 deg  13.2 dB -155.6 deg  13.8 dB -157.6 deg
 24/25  7.7 dB  168.5 deg  10.8 dB -176.1 deg  12.7 dB  176.7 deg

The new E-field rx is exposing poor performance of the loop rx
at this frequency.  The loops should always be better than the
vertical E-field, due to directivity.

It is OK at 8270, eg VO1NA

                         H-field     E-field

 2017-10-20_23:00,+8h    12.13 dB   10.75 dB
 2017-10-21_10:00,+8h    12.30 dB     9.3 dB

I suspect the problem is due to mains harmonics reducing
effectiveness of sferic blanking.  The rx itself is quite low
noise at 5170.

Main harmonics are usually worse in the H-field because of
non-linear load currents.  Also they are not so constant.
Plus they have much stronger sidebands than in the E-field.

I'm not sure my loops are in the best location.  There's an
underground stream running beneath the antenna, just a metre
down.  It drains off the hills behind and I suspect it may
be concentrating 50Hz ground currents.  I hope to survey the
area for a lower hum location.  This is quite difficult with
H-field because the hum level is not constant, therefore more
complicated to collect readings from a portable loop.

--
Paul Nicholson
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