In message , Stefan Wolfe
writes

"Rick" wrote in message
.. .

I'm planning a dipole installation fed with ladder line and a
wide-range antenna tuner.

I'd like to be able to use it on 160 through 10. A half wave at 160
meters is a bit under 260 feet. Is there any particular reason I
should limit its length to 260 feet? I have enough room to make it
about 320 feet... any particular reason I shouldn' t do that?

Since you are using ladder line (assuming you use a suitable gauge for the
power transmitted), the dielectric and resistive losses losses are
insignificant even at relatively high SWR. I doubt it matters much whether
your feedline is 100 feet or 320 feet; most relected power will still get
transmitted out and not be absorbed as heat.



One answer as to what the optimum length of feeder should be is 'exactly
equal to the distance between the antenna feedpoint and the antenna
tuner'.

Being serious, be aware that one of Cecil's 'fortes' is the avoidance of
tuning unit losses by using a particular length of feeder, so that the
antenna plus feeder system naturally presents a good match for the
transmitter. On a given frequency, every length of antenna has an
optimum length of feeder, so you need to switch in the appropriate
length of feeder for each band. There is a lot of debate about how much
power you lose an antenna tuner. You may, or may not, want to consider
using this technique.

Your question was actually whether 320 feet would be better than 260
feet. When you go above a halfwave, the theoretical 'donut' polar
diagram starts to break up, but I doubt if you would see much difference
in the performance. Unless the antenna is pretty high above ground,
most of the radiation on 160m will be at a fairly high angle. A low
halfwave is fairly omnidirectional, regardless of the orientation of the
antenna.

Of course, on the higher frequency bands, the radiation will come
increasingly more off the ends of the antenna than broadside. On 10m,
it will probably be very directional, especially if the antenna runs in
a straight line.

Cheers,
Ian.
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