Hello Paul, Jim, VLF,
Very nice, thanks for the spectrum peak plot! It looks like the daytime
offers a better SNR on that 46 km band on our distance, at least when
QRN is low, and it was quite low during the last days.
Actually my idea was to run the carrier for 48 hours or so, maybe
Alex/RN3AUS can pick up something in 47 uHz?
But the safety function tripped again and i have not been in Heidelberg
during that time. Now i'm back, it all looks uncritical. Not sure if
that is a software problem or an actual short cut of some windings
which is then stopped by software after 1 second.
I continued with some optimisations of the 8 x 33 T106-52 cores put
inside the coil. The big rod is now cut into two big rods, about in the
center. It has an adjustable air gap now, to fine tune the resonance
frequency. At first this was done by two layers of Kapton foil, see
attachment.
Without an additional air gap the resonance it arround 6440 Hz. With
the foil there was no significant difference (< 5 Hz) and with a 3
mm plastic spacer the frequency rose to 6590 Hz. So maybe a 1mm spacer
is a good idea. Still to be done... Anyway i can tune to the 460 mA at
6470 Hz. Now the carrier is running again since 12:50 UTC.
With 25.8 dB in 69.4 uHz we can easily try 30 characters in less
than 3 hours!
Ah, a spontaneous test! Let's try that! I can continue with the carrier
later...
Hm but the noise looks stronger today, so i go to 4 seconds:
f = 6470.100000 Hz
Start time: 15.Apr.2017 13:20:00 UTC
Symbol period: 4 s
Characters: 30
CRC bits: 10
Coding 16K25A
Duration: 3h, 48m, 16s
Antenna current: 460 mA
3 seconds may be to risky but later we will see if it would have been
possible :-)
Nice games! And the technical background, it is all very satisfying.
And the recent 85 characters, it would eben be remarkable on LF!
Later there will follow a shorter message for Eddie...
73, Stefan
Am 15.04.2017 09:42, schrieb Paul Nicholson:
Markus wrote:
> My carrier was on air from 13:30 until 20:35 UT.
Averaged 0.06 fT, S/N 13.0 dB in 39.7 uHz, phase -88.6 degrees.
Not bad for 1028 km at 6470 Hz, and I suppose about 5 or 10uW ERP?
Here is 4 hours of Stefan's signal yesterday
http://abelian.org/vlf/tmp/170414a.png
--
Paul Nicholson
--
|
Resize of 20170415_140237.jpg
Description: JPEG image
|
