[Antennas] feed line choice for McCoy dipole?

2003年2月06日 21:13:48 -0600

Durwydd,
Yes you can construct your own.. Of any impedance. There are many 
articles and ideas on
how to do that.. However, from what you said about the height of your
wires, you would be in for quite a chore.. hi Most fans of balanced
line nowdays use either a heavy duty 300 ohm twin lead or a 450 ohm 
ladder line commercially made.. Depending on how much power you intend 
to put into the antenna, you may want to opt for heavy duty ladder line.
I highly recommend line made of #14 or #16 STRANDED wires. You can
connect the wire to the center insulator several ways like some of the
fellas suggested but just make sure you don't have any weight on the
solder joint to the antenna wire. Commercially made #14 STRANDED ladder 
line can be purchased from AES in Milwaukee or a few places on line.
I feed over a kw into mine.
Strongly suggest the book, "Lew McCoy on Antennas" Also look up
"balanced antennas" on line. If you go that route, you will have it 
made on all hf bands.. Great performance..
Have fun ! 73, Les, W�OJH
Durwydd MacTara wrote:
> 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: 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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