[TowerTalk] Dipole fed with balanced line?

[Steve Hunt]

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
>
>