Am 01.06.2016 12:39, schrieb Chris Wilson:
What's my best way to generate a very very stable carrier at
VLF?
There are different philosopies as you know. But i find the really best
(and easiest) way is to use SpecLab and (1pps + NMEA) or (1pps + NTP).
That may sound complex to you, i don't know.
Let me tell you, as i started with the Raspberry Pi, i knew absolutely
NOTHING (!) about Raspi and Linux. I didn't start with a complex task
but with very simple stuff....
So i would suggest to start generating a tone on the headphone output of
your PC using SpecLab. Connect a audio PA, better build your own stuff
instead of ebay...
Buy a large ferrite core and wind a RF transformer with say 300V rms
output voltage. Build a dummy load with 1 kOhm and 100W. 1 kOhm is a
typical loss resistance for a small VLF antenna, both inv-L and earth mode.
Generate the wanted frequency, without ultra stable stability in a first
step.
Start with local tests in a range of less than 5 km. Later you can go to
slower modes / bandwidths, where you will need the stable signal.
For te first tests, SpecLab will be stable enough without pps and you
can easily generate any tone, QRSS, DFCW and so on.
Make sure you have the right attitude to VLF: There will not be a quick
success over 100s of km in a week.
I have a 10 MHz and 1PPS Trimble Thunderbolt GPS box operating 24
hours, 7 days a week, with 10MHz, 5MHz, 1Mhz, and from 100kHz to 1Hz
in decades, from a professionally made divider box. Can that be
incorporated? http://www.perdrix.co.uk/FrequencyDivider/index.html
The 1pps and a NTP time server program like Dimension 4 will do a good
job. This is what i'm using on my VLF TX PC.
73, Stefan
Best regards,
Chris 2E0ILY mailto:[email protected]
Sounds interesting. I've managed about 50km with 250W and a 700m
long wire. But that was in 3.8 mHz, which is fast mode for VLF. But
it was one of the standard modes these days :-)
Before TXing EbNaut i would suggest to experiment just with a
stable carrier and detect it in some distance. Generating an
absolutely stable carrier is the first step and essential for all EbNaut
experiments following.
The G4WGT VLF grabber may be helpful but i don't know the distances between
you...
Nice to see some starting activity.
I have to repair (and improve) the preamp for my VLF remote
grabber, thus the limited performance in the moment.
73, Stefan
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