".J.S..." wrote in message
. ..

"John Passaneau" skrev i en meddelelse
...
Hi:
There is a large amount of interaction between the dipoles as they are
tightly coupled to each other.
The shorter or higher frequency are affected more by changes to the lower
frequency i.e. longer dipoles than the lower frequency dipoles are by
changes to the higher frequency or shorter dipoles.

Strange..
I can understand that hanging a long wire next to a short will affect more
than the other way round.

But if they are both up there, I would have thought trimming the long wire
would not change its affect on the short wire much.

So to keep hair pulling to a minimum start with the lowest frequency
dipole,
tune that for the lowest SWR or for resonance and then do the next lower
one.

Ok, thats the order of trimming, but do you install one wire at a time or
all of them at once ?




/JS

Yes put up all the wires at the same time. There will be an effect on the
lower frequency antennas by the higher frequency ones and putting up all the
wire will get you closer on the first try than putting them up one at time
and tuning them will. I've used this type of antenna for years and they work
quite well. The interaction between the dipoles can be minimized by putting
the dipoles at right angles to each other. That is say, run the 80m dipole
north/south and the 40m dipole east/west. That minimizes the coupling and
the dipoles act almost like single band antennas. In my system I have a
160/80/40/30 meter dipole antenna. It has the 80/40 wires running parallel,
spaced about 12" apart and at right angles to that is a loaded (shortened)
dipole for 160m and the loading coils in the 160m antenna act like traps and
make a 30m dipole. It's all feed with one coax.
The 80m dipole acts just about the same as if it was the only dipole up
there, but the 40m dipole is strongly affected by the 80m wire. The most
noticeable effect is the SWR bandwidth is a bit smaller than I would expect
from a single 40m dipole and the tuning is a bit more sensitive.By that I
mean it takes a smaller change in length of the 40m wire to move the
resonate point some KHz's than it would with a single band dipole. All that
means is you have to be careful with how much you cut off and take it in
baby steps, not big chunks. I first up the 80/40 antennas and a year later
I decided to get on 160 so I added the 160 wires. When I added the 160/30m
wires at right angles to the 80/40m ones there was almost no noticeable
effect on the 80/40m dipoles. You can download the EZNEC demo antenna
modeling program and see how the antennas interact your self. One thing you
will notice is that when your operating on 40m the 80m is also working a
little bit too. Anyway I have DXCC on 80 and 40 and working on it on 160 and
30m which are the last bands I need DXCC on.

Good luck


--
John Passaneau
State College Pa.