[Antennas] feed line choice for McCoy dipole?

Thu, 06 Feb 2003 18:24:57 +0000

What do I consider in making a feed line choice when constructing these? 
There are many to choose from commercially, plus I can consruct open line 
feeder of any impedance I wish? more and more choices... HI HI

"Stupidity" is a Terminal condition; However Ignorance is curable!
             Durwydd MacTara

>From: Les Severson <[email protected]>
>To: Durwydd MacTara <[email protected]>
>CC: [email protected],  [email protected]
>Subject: Re: [Antennas] 80m dipole center connectors?
>Date: Thu, 06 Feb 2003 10:48:37 -0600
>
>The feedpoint impedance of a dipole only comes into play if you are
>feeding with a unbalanced coax feedline and you have your antenna
>cut for one particular frequency.. And the 72ohm center impedance
>changes dramatically if you qsy from one end of the band to the other.
>Therefore, SWR becomes a real issue.
>A balanced feedline such as open wire or ladderline will work fine
>and your antenna need not be cut for resonance. Anything length a half wave 
>or longer will work fine.  An extended double zepp will even get you some 
>gain.  You are not concerned with SWR until you match the tx.
>You must match your tx output impedance however, with a tuner and some sort 
>of balun.  (or a link coupled tuner) to change the impedance down
>to approx 50 ohm unbalanced for your tx output.  Most tuners nowdays
>have this option with a build-in balun.  You can run an open wire feed for 
>a great distance without worrying about feedline loss or SWR.
>The name of the antenna then is a center fed zepp or McCoy dipole..
>
>If anyone else on the reflector can explain it better, please do so. hi
>Good luck & 73  Les,  W�OJH
>
>
>Durwydd MacTara wrote:
>>I was always taught that the "natural" impedance of a free space dipole 
>>was 75 ohms. What gives here? Isn't impedance matching btween feedline and 
>>antenna important?
>>
>>  "Stupidity" is a Terminal condition; However Ignorance is curable!
>>             Durwydd MacTara
>>
>>>From: Les Severson <[email protected]>
>>>To: "Paul B. Peters, VE7AVV" <[email protected]>,[email protected]
>>>Subject: Re: [Antennas] 80m dipole center connectors?
>>>Date: Wed, 05 Feb 2003 14:21:30 -0600
>>>
>>>Hi Paul,
>>>I would seriously consider #14 450 ohm ladder line.  Not only for the 
>>>weight issue but for minimizing the loss for such a long run.
>>>Balanced feed works great !
>>>Good luck & 73,  Les,  W�OJH
>>>
>>>---------------------------------------------------------
>>>
>>>
>>>Paul B. Peters, VE7AVV wrote:
>>>
>>>>I'm in the process of building 2 new 80m dipoles. At a height of 110' 
>>>>and
>>>>125' respectively, they are at right angles to each other. Given I'm 
>>>>feeding
>>>>these with RG213, I wonder what suggestions I might gather from the 
>>>>group
>>>>about the choice of center connector. I have some older (but brand new)
>>>>Budwig units and a couple of 1:1 baluns. In each case, my concern is the
>>>>weight of 110' of coax hanging on the connector. Your thoughts would be
>>>>appreciated.
>>>>
>>>>73 de Paul, VE7AVV
>>>>StoneyGround Station
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>>>>
>>>>
>>>>
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>>
>>
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