|
PS: Forgot to mention that you may also need
to consider directivity: The broadcast station used for the
measurement should preferably be close to one of the main lobes (ie NE
or SW). If there is significant deviation, you could either correct
the measurement using the cosine of the azimuth difference, or simply
orient the reference loop the same way as your ground antenna.
73, Markus
Sent: Saturday, September 20, 2014 9:25 AM
Subject: Re: LF: DX with 472 kHz, earth electrode antenna, 25 Watts
output :-)
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
|
