In message , FranK Turner-Smith G3VKI
writes
"Fred Roberts" wrote in message
...
On 28/11/2015 22:11, gareth wrote:
Spike recently commented upon his success with DX by implementing at
the base of his vertical antenna a fan of 300 ground wires pointing
in the direction that he wished to work.

I've not seen my suggestion before, but why could one not just have a
1/4 wave vertical, with the other 1/4 wave making up the dipole being
rotatable for the desired direction of working?

This was covered in, IIRC, Pat Hawkers Technical Topics many years
ago. The Americans had done some research on this very topic during
the Vietnam war, if one bends a vertical dipole so that the two
elements are at right angles to each other it is possible it would
seem to get some directivity in the direction of the horizontal element.


As I'm sure we both know, if a horizontal half wave dipole is turned so
the element runs east to west, the maximum radiation will be north and
south, with nulls to the east and west.
If the dipole is now turned vertically, the nulls would be upwards and
downwards and the horizontal radiation would be omni-directional.
I've not tried this, but my gut feeling is that if the elements were at
right angles you would get a combination of the two radiation patterns,
hence some degree of directivity in the form of a null in the direction
the horizontal element was pointing.

Isn't it the other way around?

Think what happens if you start with the radiation diagram of a straight
vertical dipole, and then consider what happens when you progressively
raise the lower leg. The once-straight halfwave dipole starts to form a
V, and in the direction of the legs of the V, the radiation will start
to become somewhat more concentrated. Away from the legs of the V, the
radiation starts to become more spread out. However, I don't think you
can go too far with this reasoning before you start to lose the slight
amount of benefit you obtained.
--
Ian