On 5/17/2010 10:23 AM, Blake Bowers wrote:
If you have a copper ground rod in the radome then you make the antenna both
directional, and subject to a high VSWR.
Radome antennas like the one pictured do splinter - it is one of those
LMR facts of life. ANY antenna subject to a direct strike can be
damaged. The best antenna I have ever used for LMR is a DB224,
the design of which makes it totally unacceptable for WISP work.
(Unless you have a two way radio system in your installers
trucks LOL)
http://www.wiscointl.com/decibel/dipoles/db224.htm
This is the same style of antenna that dot many of the old AT&T
long lines towers across the country - I have never found one bad
at one of the AT&T sites.
For that matter, my MCI sites had radome antennas like the one
pictured, no copper ground rod going up through the antenna (I
can't even find one like that after some checking around) and I
never found one of those bad either.
That is a testament to proper grounding techniques, and a good
ground system at the base.
Lightning could really care less about your location on the tower.
Often times antennas on the side, half way down the tower will
be destroyed, and a similar antenna on the top is fine.
http://www.polyphaser.com/ when it was privately owned had a
fantastic book - "the grounds for lightning protection". The owner
had spent his life working in the field, and packed that knowledge
into the book. If you ever have a chance to get it - do so.
Another great source, but less info as to the WHY, is Motorola
R-56 standards. EVERYONE should have a copy - there is more
knowledge stuffed into that book than the encyclpedia, when it
comes to installing equipment at a tower site.
Bottom line - if lightning wants your antenna, it matters not where it
is located on the tower.
Don't take your organs to heaven,
heaven knows we need them down here!
Be an organ donor, sign your donor card today.
----- Original Message -----
From: "Kurt Fankhauser"<k...@wavelinc.com>
To:<lakel...@gbcx.net>; "'WISPA General List'"<wireless@wispa.org>
Sent: Monday, May 17, 2010 8:32 AM
Subject: Re: [WISPA] Hamvention
Which part is a myth?
Kurt Fankhauser
WAVELINC
P.O. Box 126
Bucyrus, OH 44820
419-562-6405
www.wavelinc.com
-----Original Message-----
From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On
Behalf Of lakel...@gbcx.net
Sent: Monday, May 17, 2010 8:20 AM
To: WISPA General List
Subject: Re: [WISPA] Hamvention
That is a myth.
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: "Kurt Fankhauser"<k...@wavelinc.com>
Date: Mon, 17 May 2010 01:36:07
To: 'WISPA General List'<wireless@wispa.org>
Subject: Re: [WISPA] Hamvention
You can't use a fiberglass omni at the top of a tower and expect it to
survive a strike unless it has a copper groundrod built inside of it
protruding from the top in which it was designed to take a strike. Learned
this from various HAM radio operators. Only 2.4ghz omni I know of that has
a
metal frame and can survive direct strikes are slotted waveguides such as
the various H-POL omni's you see. If I'm going to use a VPOL omni I make
sure I'm not the tallest guy on the tower.
Kurt Fankhauser
WAVELINC
P.O. Box 126
Bucyrus, OH 44820
419-562-6405
www.wavelinc.com
-----Original Message-----
From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On
Behalf Of RickG
Sent: Sunday, May 16, 2010 11:16 PM
To: wa4...@arrl.net; WISPA General List
Subject: Re: [WISPA] Hamvention
Ya, the pop (pun intended:) is growing so hopefully it gets sectors soon!
On Sun, May 16, 2010 at 8:03 PM, Leon D. Zetekoff
<wa4...@backwoodswireless.net> wrote:
On 05/16/2010 07:08 PM, RickG wrote:
I'm sorry Bob! I was slacking all night on a water tank after it took
a direct hit. Picture of omni attached. Even with LP in place, it
melted the cabling down to the enclosure and burned up everything in
it! I got it back up& running by dropping temporary cables down the
side of the tower. A dozen man hours later - it's all new. Maybe next
year!
We had a multi-band comet VHF/UHF for our club repeater on the top of a
10 story building in Coral Springs a number of years ago and it got
blown apart similarly. They work good but explode like that when hit.
Leon
I believe the Comet I mentioned was s VHF only - don't remember. It was
replaced with a folded dipole array like was pictured. Eventually, after
I moved to PA, it was replaced with a VHF staionmaster.
Even with good grounding, lighting will do it's damage. I don't believe
our antenna got a direct strike but very close. It must have hit the
building possibly even the antenna. What makes me think not is the
repeater stuff still worked fine once we put up a new antenna.
Good grounding is a must as is good protection.
Leon WA4ZLW
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