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RE: VLF: 8970 Hz transmissions, soon again here

To: _RSGB_LF <[email protected]>
Subject: RE: VLF: 8970 Hz transmissions, soon again here
From: Lubos OK2BVG <[email protected]>
Date: Sat, 26 Nov 2011 06:31:50 +0100
Importance: Normal
In-reply-to: <[email protected]>
References: <[email protected]>,<[email protected]> <[email protected]uleuven.be> <[email protected]> <[email protected]> <[email protected]>,<[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Hello Stefan, VLF!
I am looking forward to see your signal on my VLF Apollo grabber! You are right, that a noise is low. This effect  has been  very good visible on the last day picture, for example.
Well ...  the weather is bad hear. It is not suitable for my VLF kite  experiments at all.  The sun has been moved away, I think, because I have´t seen it for three weeks :-(   
There are fog and rain here only. Brrr!
Despite the weather and probles with antenna tunning (all is wet continuously) my beacon OK0EMW is transmitting every night and I am often active on 500kHz for a QSO as well. It is really interesting band and I hope, it will be  available for all hams soon. 

GL and 73!

Lubos, OK2BVG

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Date: Fri, 25 Nov 2011 19:04:38 +0100
From: [email protected]
To: [email protected]
CC: [email protected]
Subject: Re: VLF: 8970 Hz transmissions, soon again here

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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