Hi Rik,
Thank you for collecting and posting this information. The conclusion,
therefore, (and for those not having the time to study this) is that at
least a moderate loss of signal signal occurs when a typical set of radials
are drooped more than 20deg from the horizontal, right? I'm not sure I buy
the "shielding effect" that the drooping radials impose, but I suppose the
'canceling effect' due to the reversal in current is one way to look at how
a shield works.
Bill A
-----Original Message-----
From: Rik Strobbe [mailto:[email protected]]
Sent: Tuesday, October 22, 2002 7:58 AM
To: [email protected]
Subject: Re: LF: Re: Drooping top loading
John, G4CNN, did some extensive calculations on drooping toploads (umbrella
antennas). A summary of his work and a link to the webpage with all info can
be found at :
http://www.qsl.net/on7yd/136ant.htm#Umbrella
<http://www.qsl.net/on7yd/136ant.htm#Umbrella>
73, Rik ON7YD
At 12:16 22/10/2002 +0200, you wrote:
To All from PA0SE
In order to find the effect of drooping top load wires upon the radiation
resistance I modelled an umbrella antenna using K6STI's antenna simulation
program Antenna Optimizer.
The antenna modelled consists of a vertical wire of 10 m with at the top
four wires of 10 m each in the directions N, E, S and W. The wires include
an angle of alpha degrees with the horizontal. All wires have a diameter of
1.5 millimetres. The antenna is erected over perfect ground.
Alpha Rrad Capacitance
(degrees) (mohm) (pF)
0 26 256 (horizontal top wires)
20 18 254
40 12 250
60 8 237
80 8 175
73, Dick, PA0SE
JO22GD
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