Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]
<prev [Date] next>
[Advanced]
 <prev [Thread] next>

Re: LF: ERP calculations / measurements

from [Brian Rogerson] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: ERP calculations / measurements
From: Brian Rogerson <[email protected]>
Date: Sat, 06 Dec 2008 10:19:49 +0000
In-reply-to: <[email protected]>
References: <[email protected]> <001e01c94a77$cc1fa780$a402a8c0@Inspiron> <004e01c94a9c$dddbe860$0900a8c0@AM> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Rik and LF

Your email below prompted me to carry out another afternoon of measurements from higher ground for the station FS/ERP survey.  The results seem spectacular though I am unsure of what they mean.  I hope to place the data on my web site later.

73, Brian CT1DRP



At 09:36 20/11/2008, you wrote:
Hello group,

it seems to be generally accepted that a small vertical antenna has a gain of 3 (4.77dBi / 2.62dBd), due to the radiation pattern in the vertical plane.
But in very few cases this gain seems to be measured when doing ERP measurements.
As far as I understand this gain of 3 is based on a perfect ground (endless conductivity) that acts as a (perfect) mirror and thus creates the "mirror image" needed for radiation.
But what about a short vertical antenna above a not-so-perfect ground?
I have done some simulations with MMANA-GAL (15m high vertical at 500kHz) and over a perfect ground I get the expected 4.77dBi and a take-off angle of 0 degrees.
If the conductivity is not endless the gain drops and the take-off angle rises:
1000mS/m (salt water) = 4.5dBi / 9 degrees
500mS/m (clay) = 4.4dBi / 10 degrees
50mS/m (marsh) = 3.9dBi / 14 degrees
15mS/m (loam) = 3.5dBi / 17 degrees
5mS/m (wet sand) = 2.9dBi / 21 degrees
0.05mS/m (dry sand) = -1.5dBi / 32 degrees

Could this explain (a part of) the missing dB's ?

73, Rik  ON7YD - OR7T


Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm




<frameset rows="*,39" border=0 width=0 frameborder=no framespacing=0>
 <frame src="./erpvelevangle_files/chart002.htm" name="frSheet">
 <frame src="./erpvelevangle_files/tabstrip.htm" name="frTabs" marginwidth=0 marginheight=0>
 <noframes>
  <body>
   <p>This page uses frames, but your browser doesn't support them.</p>
  </body>
 </noframes>
</frameset>






<frameset rows="*,39" border=0 width=0 frameborder=no framespacing=0>
 <frame src="./fsvoneoverdist_files/chart001.htm" name="frSheet">
 <frame src="./fsvoneoverdist_files/tabstrip.htm" name="frTabs" marginwidth=0 marginheight=0>
 <noframes>
  <body>
   <p>This page uses frames, but your browser doesn't support them.</p>
  </body>
 </noframes>
</frameset>
[More with this subject...]
<Prev in Thread] Current Thread [Next in Thread>
Previous by Date:  RE: LF: 500KHz, Lubos OK2BVG
Next by Date:  LF: SAQ, Lubos OK2BVG
Previous by Thread:  LF: XGJ, victor13
Next by Thread:  Re: LF: ERP calculations / measurements, Andy Talbot
Indexes:  [Date] [Thread] [Top] [All Lists]