"John Passaneau" skrev i en meddelelse
...
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 ?



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.

Thats exactly what I am trying make on top of a flat-roof building.
The building is 56x12 m so I cant quite get anything at a right angle but I
will try to get as much angle as possible. Also it is not long enough for
the 160m but the idea is to go diagonal and then across at the ends like a
'Z'.

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

Thx and thx for the info



/JS