Hello Paul, VLF,
Am 22.10.2017 22:20, schrieb Paul Nicholson:
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
Interesting! And very promising.
Here it is the same, my VLF loops and their preamp lack sensitivity
below 5 kHz. It is because i choose a power saving preamp design (3 mA
at 5 V). VLF < 5 kHz was rather a low priority when i started building
up the stuff on the tree, which is more than a year ago now.
If you can gain 2.8 dB on 8270 Hz and even 3.8 dB or more on 5.17 kHz,
then how will it be on 2.97 kHz?!!! If you can gain 6 dB there, we could
repeat or great result in maybe just 2 days? Hard to imagine but we will
see. If i can manage to reach 300 mA at 2.97 kHz, the signal will be
another 5 dB stronger!!
What about my recent EbNaut night time transmissions? You should be able
to decode them and get additional S/N readings for comparisons at night.
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.
What's the improvement on 970 Hz? :-)
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
There have been discussions about pure copper into soil, at least for
transmit systems. I think the performance will decrease when a first
oxide layer will have built up. Maybe this will change the performance
of your system after some months?
For my kite experiments is used two earth rod like these:
https://www.amazon.de/Bettermann-Kreuzerder-Staberder-Tiefenerder-4012195373636/dp/B0014DOEI6
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.
OK, another carrier is on the air on 5170.005 Hz since 8 UTC, unteil 16
UTC, when the 3rd EbNaut transmission starts...
73, Stefan
|
