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VK2TV > DIPOLE 08.07.05 03:52l 25 Lines 964 Bytes #999 (0) @ WW
BID : 1F0287VK2TV
Read: GUEST ON7IVO
Subj: Re: commerial dipole help
Path: ON0AR<ON0AR<ZL2BAU<VK4TRS<VK4DGQ<VK4WIE<VK2JSM<VK2PYU<VK2TV
Sent: 050629/0618Z @:VK2TV.#MNC.NSW.AUS.OC #:17861 [Kempsey, QF68JX] $:1F0287VK
From: VK2TV@VK2TV.#MNC.NSW.AUS.OC
To : DIPOLE@WW
Hi All,
VK2AUX wrote:-
> can anyone help with this question
> many folded dipoles used for two way radio's 'ie' taxi and base station
> have the 50 ohm feeder connected to the center of the folded dipole
> as the basic dipole feed point is around 200-300 ohms is the feeder tail
> coax an odd 1/4 wavelength with 75 ohm coax used as a matching section??.
> back to the main 50 ohm feeder? as cannot find any info on this type of
> construction. ps the coax dose connect direct to each side of the dipole
> feedpoint after being routed through the inside of the folded dipole tube.
> thanks.
The coaxial tail on the antenna is specially manufactured so that the last
quarter wavelength at the end that connects to the antenna has a reduced
diameter inner conductor, giving that section a higher impedance, to act as
a quarter wave matching section between the antenna and the 50 ohm tail.
Cheers ... Ray
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