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.

Ok


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.

That's very very kind of you

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.

I was and still I'm conscious of this but my question was different
and maybe not so well expressed, so excuse me and read this please:
my intention is to use the two antennas also to radiate in the 7 mhz
band (spacing in this case would be 1/8 and the radiation lobe almost
omnidirectional) and 28 mhz (spacing would be 1/2 wavelength and the
radiation pattern should be end-fire). This is because the system
would be designed for the 20 meters band with 1/4 wave spacing between
the two elements, but as you know, that spacing corresponds to 1/8 and
1/2 respectively in the 40 and 10 meters band. I know the sensitivity
should not be the best but using an antenna tuner I think the
radiation patterns should be as predicted before, what do you think?