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Doug,
For
two meter operation a DB-224 in the only way to go but please read my privious
post about fixing new antennas before installing them.
Paul
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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