Interesting…
In my case I have a horizontal 80 meter loop up 30 ft, fed with about 42 ft of
450 ohm ladder line currently with a 4 to 1 balun just outside the shack window.
Swr is flat except on 80 and 60 meters (6:1 or better).
Wonder what would happen if I switched the ladder line for lmr400 coax and
installed the balun at the feed point?
Eznec indicates 60 meter swr would be off the chart.
On Jul 29, 2013, at 11:22 AM, Steve Hunt <steve@karinya.net> wrote:
> ARRL literature has consistently underestimated the losses of ladderline. For
> example, the matched losses quoted in the ARRL Antenna Book - at least up to
> the 21st edition - are about one half the figure you arrive at from a basic
> analysis of the copper losses.
>
> The QST article "The lure of ladderline" also grossly underestimates the
> ladderline losses. At 3.8MHz a 66ft dipole at a height of 30ft over average
> ground has a feedpoint impedance of around 11-j964 Ohms; that would produce a
> loss of 8.9dB in 50ft of Wireman 551 ladderline or 6.1dB in the superior 554,
> compared with 1.37dB quoted in the article. Even 600 Ohm open-wire line would
> have a loss of over 2dB with that load.
>
> Don't get me wrong, I like balanced transmission lines; but be very wary
> about any of the loss figures quoted by ARRL.
>
> If you do the basic maths on the copper losses, you'll arrive at a matched
> loss figure almost exactly twice the ARRL figure. Call me cynical but: did
> ARRL forget that there are two conductors and failed to multiply by two?
>
> Steve G3TXQ
>
>
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