Accessories & Special Features
Antenna tuners are known by several names; impedance matching unit,
tuning unit, matchbox, transmatch, etc. They do not actually tune the
antenna, but convert whatever impedance is presented by the antenna
system at the input to the feed line into a 50-ohm load so that your transmitter
will deliver maximum power output. Some radios have an
automatic antenna tuner or ATU built-in, but if yours doesn't and your antenna's
SWR is much higher than 2:1 on a frequency you wish to use,
then you'll need an external antenna tuner, either automatic or
manually-adjusted. A model rated at 300 watts will accommodate the
output of a 100-watt transceiver with room to spare. Manual antenna
tuners often include an SWR meter or directional wattmeter, but these
can also be purchased as individual items and are very handy shack
accessories.
An SWR meter can be used as an antenna system test instrument or
to monitor the state of an antenna. Directional wattmeters measure
the power flowing back and forth in your feed line and may also be
calibrated to show SWR. Both power and SWR meters are designed to be
used at either HF or VHF and will provide uncalibrated readings at
other frequencies.
Antenna switches allow you to select different antennas quickly. The
"common" port of the switch connects to the output of the radio or
antenna tuner with a short jumper of coax and the antenna system coaxial
cables then connects to the selectable ports of the switch. Some radios
have an antenna switch built-in. As long as weÆre on the subject, it's
useful for an HF transceiver to have a receive antenna (RX ANT) input
for a special receiving antennas or external filters.
All manufacturers offer separate speakers for their radios that sound
somewhat better than the radio's small built-in speakers. For the
highest quality "copy" of signals, though, use a pair of headphones.
A set intended for music will do or you can buy headphones designed specifically
for radio communication. A boom-set is headphones combined
with a boom microphone. The boom mike frees you from having to hold a
hand mike or speak into a desk microphone. The voice-operated transmit
(VOX) option of most radios frees your hands from having to press a Push-to-Talk
(PTT) switch.
--- SBBSecho 3.01-Win32
* Origin: The Thunderbolt BBS - wx1der.dyndns.org (57:57/10)
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