Hi all - I need some help please - I have over the summer been building a
rotatable HORIZONTAL Waller Flag (HWF)for 160/80.
The dimensions are 26ft boom and the two loops are 16ft*7ft - I am intending to
increase the boom to 45 ft with 20ft*10ft as the output on 160 is low - 80m is
OK.
I have been carrying out experiments with the polar plot by using a medium wave
AM station located 65 miles away and all during daytime -
The polar plot program I am using is available free and written by Bob G4HFQ
G4HFQ Radio Programming Software .
I have two main problems - at first, I could not get any directivity at all -
the problem was not, as far as I know, to do with phasing - or more importantly
getting all the transformers wired correctly.
Bearing in mind this is horizontally polarised I did not think that an aluminum
stub mast would have any effect - all I have read and I have read everything I
can find on the internet - explains that a fiberglass stub mast is a must for
vertically polarised - that said I replaced my aluminum stub mast with a short
fiberglass pole..
This solved the problem with good directivity and the polar plot was close to
that shown in Eznec - (I did model the HWF in Eznec and changing the sub mast
from aluminum to no stub mast resulted in a slight change to the front to back
but only a small amount).
I then did some experiments by leaving the fiberglass stub mast holding the HWF
and put up beside it an aluminum pole first connected to the mast/tower and the
boom of the HWF and second to the boom and not the tower - the best results
were having no connection to the tower -
Has anyone got an answer on this part of my question - as I would like to use
an aluminum stub mast which will give me an extra 10ft in height.
My next and final problem - when I have the tower retracted approx 25ft and the
fiberglass stub mast I have good acceptable directivity - If I then raise the
tower by 20 feet then the polar plot is and directivity disappears - lower the
tower back down and the polar plot returns to normal.
I did have a masthead preamp installed I removed this - no difference - I then
put ferrites around the rotator cable and a common mode choke at the bottom of
the tower thinking that the coax lead which was originally coiled on the floor
with the mast down was now acting as a vertical antenna - none of these made
any difference. my direct email is dave@g3rcq.com
Thanks from Dave g3rcq
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