Hello Roger,
If i can set up the system without any problem then i will send a long
carrier first and then i wait for some reports. Depending on what
people can receive i will then go on to DFCW-600 or DFCW6000 or will
run a constant carrier for some hours.
During that time i will build a circuit that permanently switches the
PA OFF if a current limit is exceeded (say 5A) OR if it falls
below another limit (say 3A). That should be a safety factor for
preparing a 24 hour transmission, key down on the voltage limit!
Don't hestiate to arrange your grabber Roger but do not expect to
much...
73, Stefan
Am 25.11.2011 20:36, schrieb Roger Lapthorn:
Stefan
Will you be sending a continuous carrier? My shack is occupied
by my grandson this weekend but I will see if I can set up some kit to
look for you.
73s
Roger G3XBM
-- Via my iPod Touch 4g --
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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