Am 14.12.2017 09:41, schrieb Paul Nicholson:
Added to the growing list of amateur achievements
at VLF
http://abelian.org/vlf/amateur-radio/
It has been a very successful season so far. I hope this
encourages more people to have a go at VLF, we need more
transmitters and receivers.
Indeed!
Recently i thought "VLF is the new LF".
From the view of a HF amateur, LF is complex because of the large
coils, the high voltages, the sepcial narrow band modes, the genaration
of stable frequencies, the few number of active stations... Oh and it is
sooo deep! Actually it can't work. Oh, and why do these crazy OMs use
such low frequencies at all? The 20m band is so much easier ("Youuure
5ee9e", "CQ DX"...)...
VLF is just another step in this direction. The coils are larger, the
voltages higher, the ERP lower, the frequency must be even more stable,
the modes are even more narrow...
AND, not to forget, like HF->LF, LF->VLF is a few orders of magnitude
more fascinating, exciting, exceptional!
I can see only positive tendencies, the lower it goes :-)
Perhaps the perception is that it is difficult? Surely not.
Don't believe all those stories you hear about how hard it is
to radiate, or how difficult it is to find a location to
receive from!
Let's see -
- Low cost. You don't need expensive SDRs or test equipment.
Your PC soundcard is signal generator, spectrum analyser,
and SDR, all in one. Transmitter is just an audio amplifier,
even a low quality one. The most expensive thing you'll buy
is a load of wire for a loading coil.
- GPS timing? £18 quid for a NEO-7 module and you know your
frequency to the micro Hertz. Buy two, you'll use them!
- Easy to build. Just audio frequency signals, nothing critical
about layout. VLF is great for the homebrew enthusiast.
Indeed!!
- You don't need a huge ERP. 10uW and you're on the air. Your
LF antenna will probably do better than you think at VLF.
Uuuh but 10 uW is not so easy. The critical thing is the voltage, not
the power. Capacity is needed, and radiation resistance of course.
- UK Notice of Variation? No problem, a simple application form,
and if enough apply, maybe the regulators will make that easier.
- Where else can you operate at the cutting edge with such
simple equipment?
In case you thing my location here is specially good, it certainly
isn't. The mains here at the top of the Calder Valley is very
rough, terrible sidebands. All the properties around here get
their power by overhead lines at 12kV and one of the two 33kV
lines feeding Todmorden is only a km away. The nearest 12kV
line is just 120m from the E-field antenna. 140mV RMS of 50Hz
on the E-field probe and a lot of harmonics. Reception here is
bad! You can probably do better in the suburbs.
How many times per century does amateur radio find a green field
to explore?
Currently, about once per week! :-)
Not just a new band but a whole new frequency range.
Don't miss out on this one!
Exactly!
And the lower we go, the more it makes sense to think in wavelength
rather tahn in frequency. Because otherwise a QSY from 2970 Hz to 2470
Hz means a difference of just 500 Hz, which is not much. But it is a
difference in wavelength of 20000 m!
73, Stefan
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Paul Nicholson
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