Hi Robert,
See my comments in your original message below.
>From: ROBERT <rwebb@danka.plc.uk>
To: <antennaware@contesting.com>
>Date: Fri, 16 Apr 1999 10:11:33 +0100
>
>Hi all,
>
>I have an 80m end fed wire which goes 30ft up the side of the
>mast and the the remainder is horizontal toward the house, this
>is fed against 4 1/2 wave buried radials, bent around the
>garden.
>
>1st question is how close can the wire be to the tower before
>its performance is affected?
If you are tuning the system with a tuner, I wouldn't worry too
much about the tower to wire interaction. If the tower isn't
near resonance on 80 meters, the coupling should not be very
significant. If the tower system isn't terribly lossy, effect on
efficiency shouldn't be too bad. But do connect the tower base
into the radial system.
>
>2nd question is I have been feeding it with 50ohm coax and using
>an mfj tuner, now I am feeding it with 450 ohm ribbon cable
>conected to the balunced line terminals on the tuner. What
>worries me is that im forcing equal currents into my radials as
>i am into the antenna itself. Is this ok or am I doing something
>wrong. Maybe the heat will help the flowers grow, and i could
>sell the idea to my xyl.
>
> Tnx Robert ( G0URR )
If the feedpoint is at the junction of the vertical wire and the
radial plane and the feedline is decoupled from the radiating
system, no matter what kind of transmission line you use to feed
it, the currents will be equal on either side of the feedpoint.
How long is the feedline from the tuner to the feedpoint? The
ladder line is less lossy than coax alright. But only if it is
properly routed clear of nearby objects. For a short run, the
inclusion of the balun losses may eliminate the advantage. The
feedpoint impedance (if I understand your system correctly)
should be fairly low. Probably below 50 ohms. Unless the line
is long or the coax is _VERY_ lousy for some reason, I don't see
the motivation to go to all the routing bother of the ladder
line.
73, Eric N7CL
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