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Re: VLF: 300 mA on 8270 Hz

To: [email protected]
Subject: Re: VLF: 300 mA on 8270 Hz
From: DK7FC <[email protected]>
Date: Sat, 30 Sep 2017 17:13:47 +0200
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Hi Paul,

Great work! Very interesting. I like to have these techniques too. I'm on the way!
Now the 100 char message is almost through, the 4th time. No results so far?

I like the idea of stacking messages very much! After the very good results from my recording in France (ZEVS and 4470 Hz in 424 uHz) i like to build the Raspi up at my parents QTH in 39.4 km distance. Still don't know how the QRM situation is there but there will be results. It could be interesting to do a new 970 Hz experiment and stack several days to decode a message over that new longest distance. Just some thoughts.
I wonder how many days can be stacked to improve the SNR.
2 > 3 dB
4 > 6 dB
8 > 9 dB (like WSPR-2 vs. WSPR-15)
16 > 12 dB
31 > 15 dB
and so on. But will it actually rise the SNR by 15 dB if i transmit a month? In smaller steps this could be checked. And BTW this is what we already started now with the 100 character series!
73, Stefan

Am 29.09.2017 13:41, schrieb Paul Nicholson:
I used Alpha signals to get a rough calibration of the E-field
rx and I retrospectively apply this to the recent recordings.

Below are the daily results already reported for the 16K21A
12 char message just using H-field:

 2017-09-22: +0.4 dB phase 126.0 list rank 8225;
 2017-09-23: +1.6 dB phase 131.0 list rank 0;
 2017-09-24: +0.3 dB phase 134.0 list rank 242;
 2017-09-25: +2.2 dB phase 127.2 list rank 0;
 2017-09-26: +1.2 dB phase 132.8 list rank 0;

Stacking gives Eb/N0 = +7.7 dB.

Now with E-field as well:

 2017-09-22: +3.7 dB phase 134.9 list rank 0;
 2017-09-23: +5.4 dB phase 139.8 list rank 0;
 2017-09-24: +1.1 dB phase 135.9 list rank 0;
 2017-09-25: +4.9 dB phase 133.9 list rank 0;
 2017-09-26: +2.8 dB phase 139.1 list rank 0;

and stacking the five days is 10.7 dB.

By adding in the E-field, the antenna pattern is changed
from a figure-8 to a cardiod.  We might expect to gain 3dB,
or more if a lot of the background noise is coming off the
back of the beam.

Some days, not so much improvement, depends where the noise
is coming from.

But generally, you can see that it is well worth the effort
of 3-axis reception.

Looks like I haven't got the E-field phase calibrated quite
right, calibrated at 11904 Hz, there will be some few degrees
phase shift at 8270 Hz.

This afternoon I will try the 100 char message with 2 repeats
so far...

Paul Nicholson

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