Francesco L. wrote:
. . .
I asked since an Italian dxer (i4ewh) in its scheme considers this splitter
absolutely necessary. I spoke with him and he told me the swr was greatly
reduced by this solution.

The SWR has nothing to do with the antenna pattern. A good SWR can be
had with a feed system which produces a lousy pattern, and obtaining a
good pattern can result in a poor feedpoint SWR. But the feedpoint
impedance is easily fixed with a matching network. A poor pattern is
much harder to correct.

Anyway here is the link so you can have a look.
It's a four element phased array:
http://i4ewh.altervista.org/ShortWav.../Verticali.htm

It's entirely possible that this arrangement does produce some nulls and
peaks. But it almost certainly isn't producing the pattern that the
author thinks and, if the resistors are doing anything at all, they're
wasting power which could be radiated. The _Antenna Book_ explains why.

Once again, I must repeat that low band dxing has no help for beginners and
better and simpler schemes can be found on the simple "vertical antennas" by
arrl and arrl antenna book. If you have any other site or web address where
I can find more material, please tell me.

There's a great deal of information about phased arrays in books and on
the web. I haven't done a comprehensive survey, but would guess that a
solid majority is wrong. And if you're not pretty well aware of the
basic principles and problems of feeding phased arrays, you probably
won't be able to tell which is and which isn't. Look over the _Antenna
Book_ information, both in the 21st Edition and the material from the
20th which is on the CD. If you find it too hard to understand, drop me
an email.

A last question to both of you: I would like to use this system (centered
for the 20 meters band) also for 40 meters and 10 meters. Should an antenna
tuner suffice?
Francesco ik8vwa

No. All an antenna tuner does is transform the feedpoint impedance. It
does nothing to produce the element currents you need in order to get
the pattern you want. It is possible to make a reasonably good
multi-band receiving array as long as it's electrically small. (An HF
receiving antenna doesn't have to be efficient.) But to make a decent
transmitting phased array for multiple bands usually requires a separate
feed system for each band, and probably separate elements for each band
also. You can, of course, use any of a number of simple feed systems on
multiple bands which will give peaks in some directions and nulls in
others. But the patterns won't be anything like the textbook patterns
for properly fed arrays.

Roy Lewallen, W7EL