[TowerTalk] Dipole fed with balanced line?

[Gene Fuller]

Hi Steve-
Yes, but.... There are so many variables The best answer all 
depends............. switching to open wire and a tuner then adds the 
question of tuner efficiency which is quite variable and some may tend to 
ignnore it if it's built into their radio or amplifier. And some may only 
want to operate in the PH or CW portion of the band, not both and some may 
only want "local" contacts where 30 feet fine and others may want their 
dipole 50,75, or 100 feet high for dx'ing. So, everyone needs to figure out 
what's right for themseleves. Our objective should be to enumerate,  and try 
to explain the importance of, the various choices.
Gene / W2LU

----- Original Message ----- 
From: "Steve Hunt" <steve at karinya.net>
Cc: "Towertalk" <towertalk at contesting.com>
Sent: Tuesday, January 17, 2012 1:43 PM
Subject: Re: [TowerTalk] Dipole fed with balanced line?


> Gene,
>
> EZNEC predicts the feedpoint impedance of an 80m half-wave at 30ft over
> average ground as 51 Ohms at resonance - that was close enough for me to
> call the RG213 "matched" ;)
>
> But you raise a very good point about bandwidth: in my model the
> half-wave dipole was resonant at 3.6MHz; by 3.8MHz the SWR on the coax
> had risen to 5.7:1, increasing feedline losses by 0.5dB. On the other
> hand the 100ft ladderline-fed system losses hardly change, so the "gap"
> between it and the half-wave is considerably narrowed. If you care to
> run the sums with 600 Ohm open-wire line feeding the 100ft dipole,
> rather than commercial ladderline, you can close the gap completely.
>
> 73,
> Steve G3TXQ
>
> On 17/01/2012 17:51, Gene Fuller wrote:
>> Hi Steve -
>> You 've made a good point , however:
>> an 80m dipole at 30 feet isn't going to be 1:1 on 50 ohm line and,
>> how does it look off resonance out towards the band edges ?
>> Gene / W2LU
>>
>>
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