Instruction manual

AL-800 Instruction Manual
15
CAUTION:
Never allow the high voltage to exceed 2700 volts under any condition.
For 120 volt operation, the wiring between the fuse box and the amplifier ac outlet must be number
12 gauge (or larger) in order to supply the current required (16 A) without a significant drop in the
line voltage. The 120 volt outlet should be fused properly for the gauge of house-wiring used, but
never exceed 25 amperes.
Grounding
Connect a good RF and dc ground to the ground post on the rear panel of the amplifier. Use the
heaviest and shortest connection possible. The best materials to use for ground connections are (in
order of effectiveness) smooth wide copper flashing, copper tubing, or solid copper wire. Never use
braided or woven conductors unless the lead needs to be flexible. Braided or woven conductors
offer a high impedance to both lightning and RF.
Water pipes, metal heating ducts, metal fences and other large metallic masses offer convenient RF
grounds. If a water pipe ground is used, inspect all the pipe connections to be sure that no plastic or
rubber connections are insulating the pipes. Insulated pipe connections will interrupt the electrical
continuity to the water supply line. Install a jumper around any insulated pipe connections you find.
Use heavy copper wire or flashing with stainless hose or pipe clamps for the jumpers.
The following tips will help prevent lightning damage and RF grounding problems:
1.) Avoid using braided or woven conductors, they have very high resistance to both RF and
lightning currents. RF and lightning flows along the surface of conductors, almost no current
flows in the center of the conductor. The lowest RF resistance occurs with wide, smooth
conductors.
2.) Avoid routing a single small gauge grounding conductor along the various pieces of equipment
(or to connect multiple ground sources). Instead, use multiple ground leads that connect to a
single wide buss at the operating position. Keep all ground leads as short and wide as possible.
3.) Buried radials provide much better lightning and RF grounds than ground rods do, although
both are needed for safety.
4.) Avoid sharp bends in ground leads. When changing the direction of a ground lead use a
gradual radius turn.
5.) Avoid second story operation. A good ground is much easier to obtain on the first floor or in
the basement of a structure.
6.) Air-core choke baluns should be used on all coaxial feedlines. The feedlines should be coiled
into several 4" to 6" diameter turns before they enter the building. Either directly bury the
feedlines a few inches deep in the ground for a minimum distance of ten feet or ground the
shields to a separate outside ground on the antenna side of the choke.