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The existing mount exact size I do not know, but it
is at least 3 feet off the leg (and offset to make the antenna vertical,
since the tower (450 ft. self supporting) slopes slightly). I have had a
Sinclair co-linear (6 dB) up at this height a number of years ago and it
seemed to have a reasonable number of nulls. I have now a 3dB (ugh!) co-linear
that must be really suffering from its anemic gain (its only six to
seven ft. tall). I am wishing that the dB224 will at least fill in the
nulls somewhat over this lackluster antenna (a 3dB gain co-linear from
AntennaX).
Our 2 meter repeater antenna, a dB224, has its
dipoles set in the omni manner and it seems to work as expected. There are nulls
as one would expect.
Roger W5RD
222.58/224.18 MHz
On the air since 1982
----- Original Message -----
Sent: Saturday, February 11, 2006 11:54
AM
Subject: RE: [Repeater-Builder] dB224 4
bay 220 MHz Antenna on VERY LARGE TOWER face
Rodger,
I have a DB-228
that is mounted in the center of the Northwest face. The faces are 8 across
if memory serves me correctly. We are at 635 Center of
Radiation and only running
12.5 watts in to the cavities but we are getting 45 50 mile radius coverage
from the repeater. I have not noticed any REALLY bad nulls any were in the
coverage pattern. I say that but I have also not done a commercial style drive
on the repeater either. I really did not see it necessarily at the time but
may do one at a later date. When the antenna was mounted, we turned the top
four dipoles away from the tower and the bottom four dipoles to the tower. I
know that you asked about a DB-224 and not a 228 but maybe this information
will help a little bit. The antenna is only sitting 24 off of the face, and
you said that you would be mounting off of a leg. Do you know how far off of
the leg you are going to be able to get? If you are going to be less that 2
3 I would turn all of the dipoles in to the tower leg. If you can get
4 or more away from the tower I would point each one of the dipoles 90
degrees apart staring at the top and working you way down
clockwise.
-----Original
Message-----
From:
[email protected] [mailto:[EMAIL PROTECTED]
On Behalf Of Roger
White
Sent: Saturday,
February 11, 2006 7:40 AM
To:
[email protected]
Subject: [Repeater-Builder] dB224 4 bay
220 MHz Antenna on VERY LARGE TOWER face
Monday, I am having this antenna
put up on a triangular tower, whose face is greater than 20 ft. across where
the antenna is going on one leg. I know from years of operation on this
tower (or any tower that is this large), the antenna pattern will have
many nulls around the tower. Does anyone have any experience on mounting
an antenna on a large tower to minimize the nulls? The antenna will be
mounted on a leg (not in the center of the face which may be more preferably).
I have the choice of placing the dipoles equally around the antenna mast, all
facing the tower or all facing away from the tower. Any suggestions (or does
it really matter on a tower of this size)?
YAHOO! GROUPS LINKS
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- Re: [Repeater-Builder] dB224 4 bay 220 MHz Antenna on VERY LAR... Roger White
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