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Russ brought up the point that some techs really shy away from
the DB-224 because of the potential noise problem. I've been scared of the
fiberglass collinears because of the element solder joint crack issue and it's
resultant noise problems.
What's the commercial 'antenna of choice' for two-meter
repeater operation here at Repeater-Builder?
One more tid bit of information. Our noise began when
the tower was shortened from 440' to 360'. And a tower crew left a steel
winch line tied off for several weeks very near our DB-224. That hints
towards possible element damage or structural (i.e. loose / disturbed hardware)
problems.
--- And a huge thanks for all of the excellent
observations and advice to date!
Doug
----- Original Message -----
Sent: Saturday, January 08, 2005 5:34
PM
Subject: [Repeater-Builder] Re: Decibel
Products DB-224 Antenna & Noise
There is another possibility
that I have run into with my Decible
Products Antennas of the DB-224
type: If the elements of the
antenna are not welded to the metal
suport on one end, corrosion can
occur and movement can be
experienced. If the DB-224 antenna you
are using is not "welded" but
is simply a physical contact between
the non insulated end of the element,
it is not a good antenna for
repeater use for the very reasons that others
have pointed out -
loose connections in the field of the
antenna.
When you make the inspection of your antenna determine if your
antenna has the conductive end of each element welded to the
standoff
or just a physical connection. I wish I had a picture I
could attach to
show you what I am talking about. I hope my
explaination is
clear.
I have been cautioned many times by the local technicians that
work
on these all the time about the use of Decible Products DB0224 (and
other models for other bands) antennas in repeater use.
I do not
have a Decible Products DB type antenna on my repeaters. I
have three to
put up. They will all be modified before installation
to make sure that
the physical connection of the elements are welded
when they are not
supposed to be insulated from the supports.
This discussion has been
very good reading. Thank everyone for their
contributions to this
thread.
My fiberglass antenna (yes singular - one triband antenna for
all
three repeaters) was broken in Hurricane Frances this year. When it
broke, crackling was very pronounced when there was an input signal
and the system was repeating. It would go away on the squelch tail
and
when the repeater identification was transmitted.
when the wind
subsided a few moments the crackle decreased. When the
wind picked up, the
crackle picked up. Inspection of the antenna
from the ground with
field glasses found it to be bent over at 90
degrees and hung up under the
support of a nearby Microwave dish.
Replacement of the antenna between
hurricanes was required, but,
when replaced, no crackle since Hurricane
Frances during hurricanes
Ivan, Jeanne or Karl (4 between August 25 and
September 24 is too
many and I hope that is the last of that
schedule!)
Russ
N4KOX
145.11 MSR 2000 reapter
444.700 MSR 2000
repeater
53.21 Micor Repeater
--- In [email protected], Kevin Custer
<[EMAIL PROTECTED]...>
wrote:
> Please read this:
> <http://www.repeater-builder.com/antenna/cracking.html>
>
> Kevin
>
>
> > There is
only crackle when receiving a signal, never on the
repeater tail.
>
>
> > Might help to mention that I can listen directly to
the receiver
audio
> > at the repeater and hear the
following:
> >
> > Receiver weak signal - Xmtr turned
on - Crackle
> > Receiver weak signal - Xmtr turned off - No
crackle
> > Receiver no signal (squelched) - Xmtr turned on - No
crackle
> > Receiver no signal (squelched) - Xmtr turned off - No
crackle
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