You're right! I couldn't believe it as I remembered
213 as being around 1 db for 100 feet at 1:1. But at
a lower frequency it is wuite effecient. At twenty
meters it would cost you 20 watts out of you 100.
Anyway, the discussion started from an assertion that
tuners are worthless and the losses are prohibitive,
ans "why for the life of me, I can not understand why
anyone would use balanced line in this day and age."
Here is a QST article that makes it clear. A forty
meter dipole is fed first with coax (213 if I remember
right). It is then fed with balanced line, and the
results grafted. It is only plastic covered 1"
spoaced feedline, too. You will see, that the highest
performance for coax at 1:1 at it's resonant freq., is
higher in loss than the 450 ohm (9:1) matching the
same antenna. What's more important, the 450 ohm line
out performs at almost every other freq, with the
swr's at over 20:1 (tuner losses included). I think
with that we can put this to rest. Now do the same
experiment with 600 ohm 5 inch spaced Open wire line,
and the system is obvious superior to a resonant fed
50 coax antenna, not just on design freq., but about
anywhere. Bottom line: you gain nothing and lose
bandwidth and power by going with coax. I'll keep my
open wire line in the shack, whenever losses are a
concern.! Thankyou.
http://www.vk1od.net/loll
--- Barry Gross <barry.n1eu@gmail.com> wrote:
> On 1/19/06, Gary Hoffman <ghoffman@spacetech.com>
> wrote:
> >
> > I think the point being missed here by one of the
> posters is that if the
> > feedline is really excellent....like the 1/2 inch
> Heliax, or perhaps 450
> > ohm
> > transmitting ladder line, or less radically,
> perhaps Times Microwave
> > LMR-400, the losses in the feedline are trivial,
> no matter the mis-match.
>
>
> The loss for 100ft of RG-213 on topband for a 5:1
> SWR is 0.4dB - I'll keep
> it in the shack, thank you very much.
>
> 73, Barry N1EU
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