hi Piotrek,
thanks for your infos.
only one question again:
I can try this in a field in the countryside .. this field is large
(about 100 meters square) but no builds, then no ground bands in
ground.
I can plant in the soil 2 to 4 rods (aligned along a side of the field)
.. no problems for distance: up to 100 meters is ok ..
according to you experience, can this setup to be ok ???
(for example: 2 or 3 rods near the TX (the "ground") and the
fourth rod placed 20 to 100 meters away (the "antenna")
...
thanks , 73 de Mauro IK1WVQ
At 10.59 20/09/2014, Piotr Herko wrote:
Hi,
Tnx Marcus for methodology for EIRP level estimation. I try
calculate!
Mauro,
 Earthing  connected to shack is from band around my home. Band in
about 1,5 meters deep in ground. It is connected to all my equipment.
This band is first for safety on home.Â
Electrode is about 20 meters far from nearest point of 'normal' earthing
point. Second electrode is simply 2 meters vertical  rod pounded in
soil. This electrode is directly connected to tx output with 2,2 nF
capacitor in serial. For connection I use isolated wire. Capacitance was
selected to get lowest SWR. I was using for it home made NWT-7, DK3WX
project, simple network analyser. It is simple observe on analyser where
is minimum SWR, then change capacitor to get low SWR. But it is no
problem  use SWR meter for it only. Output from tx is 50 ohm 5th order
filter. Â Isolated wire lay simply on ground. I dont see any significiant
changes between wire on ground and hanging on fence. SWR is 1.1 to 1.4
according to weather.
I dont  know exatly  what soil is in my garden!  I think it is sandy
clay.
Piotrek, sp5xsb
On Sat, Sep 20, 2014 at 10:00 AM, Markus Vester
<[email protected]>
wrote:
- 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.
- Â
- 73, Markus Â
- From: Markus Vester
- Sent: Saturday, September 20, 2014 9:25 AM
- To:
[email protected]
- Subject: Re: LF: DX with 472 kHz, earth electrode antenna, 25
Watts output :-)
- Hi Piotr,
- Â
- congratulations on those results from
your ground dipole!
- Â
- 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
- Â
- Â Aeff = voltage on ground antenna /
voltage on reference loop * 1 m^2
- Â
- 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:
- Â
- Â Aeff' = Aeff * sqrt (f_broadcast /
f_amateur)
- Â
- Then, during your transmissions you'll
only need to measure the current to your ground antenna, and calculate
ERP as
- Â
- Â ERP = 1.83 * 62342 ohms * Aeff'^2 /
lambda^4 * current^2
- Â
- Best 73,
- Markus (DF6NM)
- Â
- From: Piotr Herko
- Sent: Saturday, September 20, 2014 8:32 AM
- To:
[email protected]
- Subject: LF: DX with 472 kHz, earth electrode antenna, 25 Watts
output :-)
- Hi,
- I reached OH8HTG WSPR, Â 1414, Â 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 02:14Â Â SP5XSBÂ Â 0.475636Â Â
-30  0  KO02ld  0.005  OH8HTG Â
KP34Â Â 1414Â Â 12Â
- Â 2014-09-20 02:12Â Â DK7FCÂ Â 0.475684Â Â
-9  0  JN49ik  1  SP5XSB Â
KO02ld  911  66Â
- Â 2014-09-20 02:06Â Â SP5XSBÂ Â 0.475636Â Â
-33  0  KO02ld  0.005  OH8HTG Â
KP34Â Â 1414Â Â 12Â
- Piotrek, sp5xsb
|