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Re: LF: DX with 472 kHz, earth electrode antenna, 25 Watts output :-)

To: <[email protected]>
Subject: Re: LF: DX with 472 kHz, earth electrode antenna, 25 Watts output :-)
From: "Markus Vester" <[email protected]>
Date: Sat, 20 Sep 2014 09:25:35 +0200
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Hi Piotr,
 
congratulations on those results from your ground dipole!
 
In my opinion, it is somewhat difficult to estimate ERP directly from WSPR SNR figures, because the variations in skywave sttenuation and receiver noise floor are difficult to predict. I would probably go about it by using a receiver to measure the effective loop area Aeff of the ground dipole. This can be done with some broadcast station in the lower medium wave band, comparing receive level with that from a simple nonresonant loop with eg. 1 square meter. Only the voltage ratio (dB difference) is required so you don't need an absolutely calibrated receiver. Thus
 
 Aeff = voltage on ground antenna / voltage on reference loop * 1 m^2
 
If the frequency of the used broadcast station was significantly higher than your transmit frequency, you can make a correction for the increased skin depth:
 
 Aeff' = Aeff * sqrt (f_broadcast / f_amateur)
 
Then, during your transmissions you'll only need to measure the current to your ground antenna, and calculate ERP as
 
 ERP = 1.83 * 62342 ohms * Aeff'^2 / lambda^4 * current^2
 
Best 73,
Markus (DF6NM)
 

Sent: Saturday, September 20, 2014 8:32 AM
Subject: LF: DX with 472 kHz, earth electrode antenna, 25 Watts output :-)



Hi,

I reached OH8HTG WSPR,  1414,  km with my earth electrode antenna! TX is M1GEO project, DDS RN3AUS, electrodes are 20 meters apart. Antenna is directly connected to 50 ohm tx filter with serial 2,2 nF capacitor. SWR is about 1,1 to 1.4 according to weather. Direction of the antenna is NE, 50 deg.

So far my WSPR was received in DL, OK, OE corner by DH5RAE,  DJ0ABR and  DC1RJJ, about 650 km far. Also closer by SP2OVY and SQ5KLN.


Who can help me estimate EIRP power? I declare now in WSPR beacon 5 mW.



2014-09-20 02:14   SP5XSB   0.475636   -30   0   KO02ld   0.005   OH8HTG   KP34   1414   12 
 2014-09-20 02:12   DK7FC   0.475684   -9   0   JN49ik   1   SP5XSB   KO02ld   911   66 
 2014-09-20 02:06   SP5XSB   0.475636   -33   0   KO02ld   0.005   OH8HTG   KP34   1414   12 


Piotrek, sp5xsb


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