|
Pse qsp to Stefan to SHOUT from his hill top and
face DOWN wind for an extra 23 dB. If all 9 DREAMERS face his
direction records could be broken without the KITE,
Do not break WIND to avoid QRM during the listening
period.
G3KEV
----- Original Message -----
Sent: Sunday, February 28, 2010 12:48
PM
Subject: LF: Re: VLF TX experiments this
sunday
Dear LF,
Stefan DK7FC just called me on the phone. He
asked me to inform the group that because of much heavier winds than expected,
he will not be able to transmit from the kite antenna today. He also
mentioned that the output matching of his PA (a converted SMPS
circuit) will require some more work.
Kind regards,
Markus (DF6NM)
----- Original Message -----
Sent: Saturday, February 27, 2010 3:33
PM
Subject: LF: VLF TX experiments this
sunday becomes more probably
Dear LF group,
Tomorrow, the wind forecast is
excellent! See http://www.windfinder.com/forecast/frankfurt
It
is almost to much wind but i have the new kite braid with a strenght of
500kg... So the antenna will be in a high angle and stable for tests. That
is the first positive news.
Yesterday i got such a air coil. It
has not 85mH but even about 100mH but It's Q is bad at 8,9kHz, just about
38. Anyway, i will easily handle 20kV rms. This will be the maximum voltage
on my single wire. There are several possibilities to increase the maximum
antenna voltage, well known and applied in the high voltage power fields but
this may be very difficult at a kite antenna. So i will start with a first
test at only 20kV, if the PA will give a proper power ;-)
That
coil is very heavy, about 50kg, really no fun to carry that and there are
better ways to realisethat. But it is available i get the chance to resonate
that 100m vertical at 8,9kHz. I tried to resonate it in the living room of
my parents since it it to heavy to carry it in my room in the first floor
;-) It was successfully resonated with 6x22nF/6kV plus a lower voltage C in
series, about 33nF/2kV and a DDS VFO with a sinus output, loosely coupled by
another air coil (in this way i will be able to make a transformation of the
resonated loop!(varying the coupling)). The 8,9kHz are well audible so i am
excited how the antenna and coil will sound when some 100W
applied;-)
The last problem is the PA since it is not yet
available. I will try to built it today or tomorrow in the morning but i
have also to spend some time with my YL. I hope that can be
arranged...
On the hill i have no internet but i will at least
inform Markus/DF6NM to give those who are interested a information
here...
I have to go now, and will inform
you...
73,
Stefan/DK7FC
________________________________
Von: [email protected]
im Auftrag von Alexander S. Yurkov
Gesendet: Sa 27.02.2010 20:37
An:
[email protected]
Betreff:
RE: LF: Fwd: Special Permits for Amateur Radio Operation below
9kHz?
> when back in the mid 90's the initial request for
a longwave amateur
> segment (what later turned out to be 137kHz) was
discussed, one of the
> big telecom "bobo's" stated that they saw no
harm that amateurs would
> transmit there with max. 1 W EIRP as with
that power one wouldn't be
> able to get any further than the other
end of the town.
> It turned out a bit different, unless you see the
world as one big town ;-)
Rik, after some theoretical estimations
done i am absolutely shure
QRSS communications at few 100s km (may be
more) is posible on 9 kHz.
There is lot of problems on TX side but them
to be solvable. Main problem
is high voltage on the TX ANT. I expect 100
- 200 kV is reachable with
some 'tricks' wellknown for power ingeneers.
For example one should avoid
free end of a wire with such a voltage. On
should use 'protecting rings'
on the ends. With voltage abt 100 kV seems
to be posible use not too high
antenna. Seems 20-30 m high well top
loaded marconi designed specially for
high voltage is adequate. Remember
effective height of 60m kite antenna
used in DK8KW experiment was 30m (if
wire was absolutelly vertical, does
it was?). With not too high voltage
and not too large ANT capacity 4.5 km
was reached. Another key problem is
noise level on this freq. Now we see
huge discrepancy on the noise level
got from different sourses. What is
the real noise level is not obvious
now. Can it be much lower time to
time? Experements to be usefull.
Look at DK8KW web side where 4.5 km
experiment is described. Waterfall
background is too smooth. Where
spherics are? This is why i expect RX
sensetivity was not as
high as posible. One should remember 4.5 km is
begining of the wave zone
on 9 kHz. At distanses more then 4.5 km field
decreases not too fast with
distance. Another critical distance is abt
100 km where 'waveguide'
propagation starts. At such distances one shold
increase TX ANT voltage
only in 3 times to reach distance 10 times more.
Anyway Stefan's
experiment will be very intesesting. And i hope it will
be not the
last
experiment.
Regards,
Alexander/RA9MB
|
