[Antennas] 80m dipole center connectors?

2003年2月06日 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: 2003年2月05日 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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