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Message-ID: <3.0.1.16.19990421162322.2defab3c@mail.cc.kuleuven.ac.be>
Date: Wed, 21 Apr 1999 16:23:22
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: Signals Measured
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At 13:52 18/04/99 PDT, PA0SE wrote:
>To All
>
>This weekend I measured the strength of signals in the 2 km band.
>...
>Date  UTC  Station     Level in dBm
>17/4  0756 ON7YD       -80
>17/4  0757 G4GVC       -84
>17/4  0904 G3KAU       -78
>17/4  1054 G3YXM       -82
>18/4  0730 G3YXM       -81
>18/4  0740 G4GVC       -85
>18/4  0744 G3XTZ       -80
>18/4  1019 G4GVC       -84
>...

First of all I want to thanks Dick for doing this measurements in such a
well structured way.

I made the attempt to use this data to calculate my ERP and came to a very
strange result :
a. my signal level at PA0SE : -80dBm
b. path-loss for 131km (JO22GD - JO20IX) over medium ground : 60dB
Result : my ERP = -80dBm + 60dB = -20dBm = 0.01mW
However based on the antenna-dimensions and antenna-current I thought I had
an ERP of 60mW (+18dBm) at the moment Dick measured my signal, so somewhere
38dB is missing !

Puzzled by this result I did the same calculations for G3YXM and G3KAU who
have both about 1 Watt ERP as far as I know :

G3YXM :
a. his signal at PA0SE : -81.5dBm
b. path-loss for 438km (JO22GD - IO92BK) over good ground/sea : 73dB
Result : his ERP = -81.5dBm + 73dB = -8.5dBm = 0.14mW
Based on an ERP of 1 Watt (30dBm) the difference is 38.5dB

G3KAU :
a. his signal at PA0SE : -78dBm
b. path-loss for 347km (JO22GD - IO91VD) over good ground/sea : 69dB
Result : his ERP = -78dBm + 69dB = -9dBm = 0.13mW
Based on an ERP of 1 Watt (30dBm) the difference is 39dB

It is remarkable that in all 3 cases the difference is almost the same
(between 38 and 39dB). I determined the path-losses based on a graph that
HB9ASB distributed via this list last year. For the 100% over-land paths I
took medium ground, for the mainly sea paths (toward UK) I took good
ground/sea (these differ only very little upto 500km).

I wonder what is the cause of this 38/39dB difference ? 
The measurement made by Dick seem to be done in the right way and with good
equipement. And the results (converted to S-points) look also reasonable to
me.

As a last 'exercise' I did the same calculations for G4GVC, G3XTZ and DF2PY
whose ERP I don't know :

G4GVC :
a. his signal at PA0SE : -84.5dBm
b. path-loss for 395km (JO22GD - IO92JP) over good ground/sea : 72dB
Result : his ERP = -84.5dBm + 72dB = -12.5dBm = 0.06mW
Adding the average difference of 38.5dB : his real ERP = 26dBm = +/-400mW

G3XTZ :
a. his signal at PA0SE : -80dBm
b. path-loss for 353km (JO22GD - IO91SK) over good ground/sea : 69dB
Result : his ERP = -80dBm + 69dB = -11dBm = 0.08mW
Adding the average difference of 38.5dB : his real ERP = 27.5dBm = +/-560mW

DF2PY :
a. his signal at PA0SE : -87dBm
b. path-loss for 344km (JO22GD - JN49AX) over medium ground : 71dB
Result : his ERP = -87dBm + 71dB = -16dBm = 0.03mW
Adding the average difference of 38.5dB : his real ERP = 22.5dBm = +/-180mW

I wonder if G4GVC, G3XTZ and DF2PY have tried to determine their ERP, and
(if so) to what result they came ?

73, Rik


Rik Strobbe  ON7YD
rik.strobbe@fys.kuleuven.ac.be
Villadreef 14  B-3128 Baal  BELGIUM   (JO20IX)