AMERITRON ATR-20 Gebruiksaanwijzing - Pagina 6

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ATR-20 Instruction Manual

If unsuccessful, but the tuner does adjust and operate when switched to a dummy load or a different

antenna, read the

Antenna System Hints

5.0

GROUNDING

To minimize RFI, single wire feedlines (such as used with Windom or longwire antennas) should be

kept away from other wiring. Radiation will be minimized if the single wire feeder runs parallel and

reasonably close to the wire that connects the tuner to the outdoor ground. The antenna feed wire should

be adequately insulated to prevent arcing or accidental contact.

Safety requires good dc and RF tuner grounding. It is particularly important to have a good RF ground

while using a single wire feeder. When using a single wire feeder, the tuner needs something to "push"

against in order to force current into single wire feedlines. If a good RF ground is not available, RF will

usually find it's way back into the power line (RFI), transmitter audio circuits (RF feedback), or the

operator (RF burns).

Water pipes and ground rods provide good dc and ac safety grounds, but they are often inadequate for

RF grounding because they are single conductors. Ground rods by themselves are almost useless for

dependable RF grounding.

RF grounds perform better when "spread out" over a large area, especially when they employ multiple

connections directly to the equipment ground point. Water pipes, heating ducts, and fences may work

well enough in many cases (especially if they are connected together with multiple wires), but the best

RF grounds are radial systems or multi-wire counterpoises. Radials and counterpoises provide large, low

resistance surfaces for RF energy.

RF and lightning travels on the surface of conductors. Braided or woven conductors have high surface

resistance for lightning and RF currents. Ground leads for RF and lightning should have wide smooth

surfaces. Avoid the use of woven or braided conductors in RF and lightning grounds unless the lead

needs to be flexible.

CAUTION:

For operator safety, a good outside earth ground or water

pipe ground should always be installed and connected to the

case of the ATR-20.

connects to the transmitter and other station accessories.

wing

connection(s).

6.0

ANTENNA SYSTEM HINTS

1. Many people believe a ladder line fed antenna requires a 4:1 balun. The input impedance of a ladder

line feedline can actually range from a few ohms to many thousands of ohms, depending on feedline

and antenna length. The best balun for such systems is always a 1:1 current type balun. A current or

choke-type balun guarantees minimum feedline radiation and maximum balun efficiency and power

handling.

2. As a general rule, all balanced antennas should employ a choke-type balun at the feedpoint when fed

with unbalanced (coaxial) feedlines. It is often a good idea to use a choke balun near any coax fed

antenna regardless of antenna type. Considerable common mode currents can flow on the outside of

section.

Make certain the safety ground also

nut

post

marked

GROUND

provided

Ameritron Antenna Tuner

for

ground