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Re: LF: VLF dj8wx on 8970.022Hz

from [Roger Lapthorn] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: VLF dj8wx on 8970.022Hz
From: Roger Lapthorn <[email protected]>
Date: Tue, 8 Mar 2011 19:51:32 +0000
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Uwe

Nothing visible on my grabber https://dl.dropbox.com/u/15047843/xbm_grab.jpg yet this evening but I have a high noise level in the evening hours from lights, TVs etc.Leave the TX running overnight please as I hope to see your signal after midnight and through tomorrow morning. In the 423uHz bandwidth and with the slow scroll speed it will be more difficult to see than when you were sending a continuous carrier a few days ago.

BTW, you may want to try the simple ERP estimate I made on G3XIZ's signal using an assumption for the effective height of the Marconi to derive a radiation resistance figure and using the measured antenna current. Chris tells me that my estimate was within 3dB of the figure calculated using the fempto-Tesla measurements by Paul Nicholson. It won't be accurate but may give you an "order of magnitude" estimate (uWs or mWs). As you were copied by several UK stations at around 600-700km a few days ago you must be at least 20-30dB (?) higher ERP that G3XIZ whose ERP has now been estimated as between1-2uW by 2 different methods. I would be surprised if your ERP was not at least 500uW.

73s
Roger G3XBM



On 8 March 2011 18:27, <[email protected]> wrote:

Hi all,

 

Im doing some measurements trying to find out how low (high?) the ERP of my system is.

 

the test lead of the oscilloscope in use has a resistor of 10Mohm. The oscilloscope advise text says that I have to multiply the result by 10.

OK. I added two other 10Mohm  in series multiplyed the result by 1000 and got 40000Vpp

using the twentieth of max TX power. 40kV? Is that possible?

the current from the coile foot into the radials was 0.145A (3 A with max power).

I cant measure the Tesla voltage when the  power is raised because the oscilloscope or other

instruments indicate results without connected to the object under test.

 

the station is on the air in mode QRSS3600 on 8970.022Hz since today 1640UTC.

 

current into the radials: one Ampere.

 

who will try to calculate the ERP?

the aerial in use can be seen at

 

http://dj8wx-dl.de/hompage500kHz/TX%20equipment.htm

 

fourth pic on the site. The shown 23m long wire has been lengthened to 43m.

 

best regards

Uwe/dj8wx

 





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G3XBM   GQRP 1678    ISWL G11088
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