I have a unique site that I need some help figuring out exactly how to
handle a unique site installation.
Reading through both volumes of the R56 site standards books� I have yet to
find anything that talks about �abnormal� site installations.
Here�s the background.
One BIG bridge. Four concrete pillars. Roadway is approximately 200 feet
above the water. Pillar height above the road is 460 feet � about 660 feet
AMSL). Equipment access point is 100 feet below the top of the pillar
(about 560 feet above the water). This is where the equipment MUST be
installed. No option of placing it at the roadway due to some contractual
limitations. Access to the site is pretty severely limited due to the
traffic, coast guard, police, etc. This is truly one of the best sites
still available at no cost � very high � great vantage of the city � free,
and a minimal hardline run (<100ft) � did I mention free?
Besides the fact that the equipment has to be man-handled up to the access
point (been there, done that before � cargo net and a bunch of fat guys can
work wonders�) there is a problem with power and grounding.
The power in the access room is tapped from the bridge lighting system �
it�s entirely adequate for our requirements (about 16 amps absolute max)
but I am unsure of what the best way to protect the equipment from
transients would be. In the past, and in my experience, a simple
transtector (or similar MOV/SAD device) was entirely adequate for a site
installation (think typical, properly outfitted radio site). However,
there is NOTHING on the bridge AC system to my knowledge that provides even
a little protection to the power circuits on the bridge.
Let me tell you that the equipment being installed is a Motorola Quantar
repeater � not your run of the mill micor or MSF. Both of those (and
other) legacy gear have massive ferro-resonant power supplies that can
withstand a lot more abuse than the switching power supply in the
Quantar. Since this Quantar is mine (and not some billion-dollar
conglomerate) I would like to provide �well above average� power filtering
for it. I am debating some kind of APC UPS or something for the
repeater. I know I�ll hear volumes about that � but I definitely want
something that will prevent �sags� in the AC power as well as the ability
to clamp anything that gets past the old reliable Transtector. The idea
here is to plug an APC/UPS into the transtector�. Hopefully providing a
little better protection for the repeater. No, I am NOT hauling 4 deep
cycle marine batteries up 460 feet to the access point.
Ok, on to question #2�. Grounding. Or lack thereof. The only grounding
(besides the AC power system) is the lightning rods at the top of the
pillar. Besides the fact that there is no way to ground the Quantar
cabinet� The big question here is grounding the hardline. In all the
installs I have been a part of in the last few years, the hardline outer
shell was grounded at the TOP and BOTTOM of the tower � to the tower. I
have no luxury of this at this bridge. Discussing this with a local Moto
technician who installed a federal gov�t repeater on one of the other
pillars at this site revealed that the tower crew grounded the hardline TO
THE LIGHTNING RODS at the top of the pillar. Don�t think 10 foot rods
here� more like �rooftop� 1-2 foot rods� With the antennas mounted to the
railing (yes, it�s sturdy gavalized pipe sunk into the concrete). The
hardline on the other repeater is also grounded at the bottom of the pillar
near the government repeater (don�t know where though). I need some
opinions here. Should I even ground the hardline at all? My concern is
that the antenna (direct grounded) will need a proper ground path to shunt
any (!) strikes to �ground� � no ground = nowhere for the energy to go
(except blow apart the antenna)� trust me � I am NOT a big proponent of
tying the hardline to the lightning rods.
Anyway, if anyone out there has �been there � done that� � I�d love to hear
your thoughts and opinions.
If you made it this far - thanks for the read - i am also looking for what
motorola calls a "modular rack" or "T-rack" - basically an open 19" rack
that has a pedestal at the bottom. No way i am pulling a full size quantar
cabinet up to the top of the pillars... not to mention - it probably
wouldn't fit through the access door....if you have one of these and you're
in the southeast (florida, georgia, alabama, carolinas, etc) - please
contact me ASAP.
Doug
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