Technalogix TAV-1000, Manual

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Technalogix Ltd
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VIII-4
Antenna and Tower Recommendations
Your preliminary engineering workgroup should establish your antenna and tower requirements, both for receiving
and transmitting antennas. Construction of sturdy, high quality antenna/tower systems will pay off in terms of
coverage of your service area, the overall quality and saleability of your radiated signal, and reduced
maintenance expenses. Technalogix provides complete turnkey antenna systems if needed. If your site is
serving as a translator, your receiving antenna should be in line of sight to the originating station all year round.
The foliage will change with season. Transmitting antennas can enhance or seriously impair the
transmitter/translator output.
The selection, routing, and length of coaxial cable are extremely important in the installation. If there is a 3 dB
line loss in the cable between your unit’s output and the transmitting antenna, a 1000-watt unit will only deliver
500 watts to the antenna. Buy the best cable you can obtain, route it via the shortest way to the antenna, and
keep it straight. Do not form it into sharp bends on its way. Do not use any more cable fittings for the installation
than absolutely necessary. All cautions here apply equally to all coaxial cables in the system - input and output.
Pay attention to radial ice accumulation when designing the transmission system. It is not uncommon for at
least an inch of ice to build up on the tower and antenna. This in turn significantly increases the weight, cross
section, and wind loading of the system.
Attaching the transmission line to the tower is crucial to maintain a safe and reliable operation. Nylon wire ties
and electrical tape will breakdown in the sunlight and ultimately fail, creating a potentially dangerous situation. It
is important to use proper clamps and hoisting grips and also ensure that the transmission line is grounded to
the tower in several locations. When high currents flow through the tower in the event of lightening strikes, some
of that current will flow through the outer conductors of the transmission lines. Due to the resistance difference
between the steel tower and copper transmission line, a significant voltage can be developed, often resulting in
arcing between the outer jacket and outer conductor, thus pitting the conductor.
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Preventative maintenance is crucial in ensuring that safety is maintained. Specifically, check that
transmission line grounds are tight and are not missing any hardware. Frequently inspect support
clamps or spring hangers. Consider investing in an ice break (ice bridge), if you haven’t already done
so, as shards of falling ice can damage the transmission line – and if it is going to happen, it will
happen at an important time. Check the tower light photocells and conduit.
The better-known tower manufacturers offer complete technical and safety documentation with their towers. Be
sure that you have this information as it regards wind loading, guying, etc. The best-designed antenna system
will function poorly if shortcuts and compromises are used during installation. Follow the manufacturer’s
instructions exactly, along with any engineering data prepared for the site. Be absolutely safe and certain about
this aspect as human lives may be at stake.