The DDDR is simply a quarter-wave grounded vertical with its major part bent
over into a horizontal loop. The fact that it is looped back on itself is
intended to have some self-cancelling effect on the radiation from the
horizontal part. By design most radiation is from the short vertical part
so radiation resistance is low and it has gamma matching for feeding from
50 ohm coax.
Nothing magic about it but its usual proportions for HF are still impossible
for amateur 136 . (how would one keep the loop up ? )
Bryan g3gvb
----- Original Message -----
From: "hamilton mal" <[email protected]>
To: <[email protected]>
Sent: 06 January 2004 13:25
Subject: Re: LF: Horizontally polarised radiation
----- Original Message -----
From: Rik Strobbe
To: [email protected]
Sent: Tuesday, January 06, 2004 8:16 AM
Subject: Re: LF: Horizontally polarised radiation
Hello group,
It is an "idée fixe" that a horizontal wire must radiate a horizontal
polarized EM-wave.
A nice example of a mechanical horizontal construction that radiates a
vertical polarized signal is the DDRR antenna.
So a large horizontal topload close to ground will in most cases improve
the antenna efficiency (reduce the loss resistance ... footprint theory) but
the radiated signal will be nevertheless mainly vertical polarized.
73, Rik ON7YD
At 17:47 5/01/2004 +0100, you wrote:
Rik
I agree with your observations. Some are being misled by computer
modelling and antenna theory not applicable to the type of small LF antennas
used by radio amateurs.
73 de Mal/G3KEV
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