FB Stefan
We still have a big lack of sunshine so the Grabber is going on now
with battery on float charger which I will remove in the morning.
Good luck. hope the WX holds out.
Eddie
On 25/11/2011 18:04, Stefan Schäfer wrote:
Eddie, VLF,
The coil and PA and all the parts are here now and maybe i will do
first tests tomorrow in the afternoon on 8970 Hz.
The goals would be to resonate on the frequency and apply 50 kV
rms or
more. Oh i just calculated: My coil has about 550 mH and the
antenna
473 pF. So i need about 100 pF from somewhere else, remembering my
homemade plate capacitor with the cola bottles as the spacing
insolator
;-) The coil has about 320 Ohm DC resistance and if i actually
want to
apply 50 kV, i would need 1.2 kW for that. No problem for the PA i
think. The ERP will be below 1 mW anyway :-(
But the background noise is extremely low in the last time and if
i can
a stable signal over several hours i expect to be visible in many
spectrograms.
73, Stefan/DK7FC
Am 15.11.2011 22:35, schrieb qrss:
Stefan
I look forward to your tests, please try and give me a warning
even for
the spontaneous tests so I can leave my Grabber, http://g3zjo.bplaced.net ,
on
overnight if needed. Also, due to lack of sunshine on the solar
panel
here, I have been running a dirty earth supply to charge the
battery,
during tests I can remove this for cleaner signals.
73 Eddie G3ZJO
On 15/11/2011 20:09, Stefan Schäfer wrote:
VLF,
Am 15.11.2011 17:03, schrieb DENNIS EASTERLING:
[...] I also have a mini-whip, but
this
has been extended for
VLF purposes. [...]
...which is good since soon there will be some activity again
on 8970
Hz. If you like you can join in to the group of successful
listeners on
the 33 km band.
Yesterday i carried my TX coil to the fixed antenna here. Also
the PA
and variometer part of course. I do inted to use the fixed
antenna.
I did some calculations about the radiation resistance and
losses and
power at maximum voltage (50 kV rms on the wire) and found
that the ERP
will be about 10 dB higher than expected, i.e. i could radiate
something in the range of many 100 uW up to 1 mW or
theoretically up to
2 mW. We will see and measure.
Paul Nicholsen reported about a very senistive receiver in USA
that
allows long time integration, i.e. not producing a spectrogram
but
integrating a given TX time into a single bin, like Paul
usually does.
Here on the fixed antenna i could do night transmissions. 500W
TX power
key down for 24h is no problem (as long as there is no rain).
So i am optimistic and looking forward to some new work on the
dreamers
band!
Also i would be interested if there is (still) some interest
in VLF in
this group. For Paul, a endless straight "carrier" would be
the
optimium while a radio amateur may like to have some true ID
and maybe
a message to be read and displayed. What about the grabber
runners and
new prepared VLF receiving stations?
Probably i will start next week but may do some spontaneous
tests
before...
73, Stefan/DK7FC
PS: I would like to see other VLF transmitting stations as
well. What
about G3XIZ, DF6NM, OE3GHB, OE5ODL, OK2BVG, DJ8WX? We all
could leave
some common traces again in the excellent dark spectrogram
backgrounds!
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