[AMRadio] Windom Antenna


Donald Chester k4kyv at hotmail.com
Mon Dec 27 15:28:36 EST 2004


>I'm sorry if I'm seeming a little dense, but I can't get unwrapped from the
>'single wire fed version' of this antenna.
>
>Open wire output from the link has *2* wires.  I can see attaching them to 
>some
>open wire line, and feeding this Wyndom antenna at 1.8125, and having the
>antenna resonant on 3.6250, 7.250, 14.5 (oops - can't operate there) and 
>29Mc,
>but I simply fail to understand how one wire is going to feed an antenna 
>thas
>has two posts to connect to.
>

If the wire is clipped to the halfwave flat-top at the proper point, and the 
flat-top is resonant at the operating frequency,  the SWR along the feed 
wire will be 1:1 and if I recall correctly, the feedpoint impedance will be  
close to 300 ohms.  Yes, the feed wire will radiate some, since there is no 
opposing wire to cancel the radiation, but the majority of the radiation 
will be from the flat-top.  The other rf  feed terminal is ground.

Another example of one wire feeding a halfwave antenna is the end-fed zepp.  
One major difference is that the "dead" feeder physically parallel to the 
one actually connected to the antenna cancels most (but not all) of the 
feedline radiation.

Single-wire Windom feed is ideal for use with a pi-network, but of course 
the transmitter will need to be connected to a good rf ground.

Don K4KYV





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