Served Agency Facility Antennas

Served agency facilities usually have antennas mounted on the roof of a building or on a dedicated antenna tower. Antennas should be professionally mounted and cabled by people with the necessary safety equipment and training. Served agency facility antennas are subject to all of the general antenna system concerns.

Antenna Type

The SCCo BBS sites, several city EOCs, various hospitals, and other fixed sites use the Comet CX-333* tri-band collinear ground plane antenna. It is advertised has having 6.5/7.8/9.0 dBi gain at 146/223/446 MHz, respectively. It is about 10 feet tall, which makes it too large and heavy for most field setups. It is shipped as two sections which are joined in the middle during assembly. Although not mentioned in the assembly instructions, properly taping the joint in the middle will prevent water intrusion in the event that the O-ring fails. This is particularly important where the antenna may need to endure freezing temperatures and/or lots of flexing due to high winds, such as at mountain-top locations.

The SCCo EOC and some cities use the Suburban* tri-band vertical dipole from Austin Antenna. It is typically used at a fixed site but, with a substantial mast, could be used at a field site. As a center-fed, half-wave dipole on all three bands (2.14 dBi gain), this antenna does not have the gain of the Comet CX-333. But the radiating portion of the Suburban is only about 4 feet tall, so it will fit on crowded towers where taller antennas will not work.

Feedline

For runs of 100 feet or longer, ½″ Heliax (e.g., Andrew LDF4-50A*) will provide the lowest loss and highest shielding. For shorter runs, LMR-400 (e.g., Times Microwave*) is good enough.

For jumpers, superflexible Heliax (e.g., FSJ4-50B*) is best if the jumper doesn’t need to be moved. Otherwise, LMR-400-UF is best.

Prefer the use of N connectors throughout the system. Convert to the higher-loss “UHF” connectors only at the radio and/or antenna if needed.

Weatherproofing Connections

Weatherproof all permanent outdoor connections, regardless of connector type. N‑series connectors are considered weatherproof, but no competent installer would install them outdoors without additional weatherproofing. For permanent outdoor installations, comprehensive weatherproofing is needed to protect from water and condensation. The weatherproofing itself must be resistent to UV deteriorization.

Self-fusing splicing tape is used underneath to block water and fill in the gaps so the outer layer can go on smoothly. An example is 3M Temflex 2155* Rubber Splicing Tape. High quality electrical tape is used on the outside, to futher protect from water and to resist UV deteriorization. Examples are Scotch Super 33+ or Super 88*. Professional installers typically use three layers of electrical tape, with the last layer wrapped going upward (if the cable is vertical), so that the overlaps look like shingles on a house.

* Manufacturer, product, and vendor names and images on this page are given as examples and are not endorsed by SCCo ARES/RACES.