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interesting
in the old days the Umm condenser for the spark rig was coke bottles held
in a strong solution of salt water
with the same inside the bottles,,,, not sure how the quality was but they
worked
bit messy if you tipped it over
Bob K3DJC
On Fri, 25 Nov 2011 19:04:38 +0100 =?ISO-8859-1?Q?Stefan_Sch=E4fer?= < [email protected]>
writes:
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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