90
The SGC Building, 13737 S.E. 26th St. Bellevue, Washington 98005 USA
P.O. Box 3526, 98009 Tel: (425) 746-6310 Fax: (425) 746-6384
© 1997 SGC Inc.
As described very early in this user guide, the frequency is the number of radio waves
that pass by a given point in a second. The frequency is "where you are" on the radio. It
also determines how far your signal can travel and when it can travel the furthest. It is very
important to have an accurate digital frequency readout on a transceiver or your signal
could stray into areas where it is not authorized and cause potentially dangerous interference. The frequencies of
various transceivers and other equipment are determined with a frequency counter.
Gain and levels describes a number of different aspects of radio. Gain describes an
increase in a signal, whether current, voltage, or power. On a transceiver, the gain control
is what controls the volume. In an amplifier, the gain would be
the improved output signal (in dB) over what was input to the amplifier. With an antenna,
the gain is the improvement in signal strength (in dB) over a reference antenna (usually
an omni-directional antenna or a half-wave dipole).
The level of a signal usually refers to how loud it is. As a result, the levels of a received signal are usually
measured on an S-meter (see the next section) or on a linear LED meter.
Any time that a transmitter is used, it must be outputting into a load. A load is anything that the output power
can be pumped into. If the transmitter is operated without any sort of load connected, the final amplifier stage could
become severely damaged. The problem is that you should never test a transmitter on the air for the first time, if you
are unsure about how to operate it, and if you are unsure whether it is working properly. You could create harmful
interference to other stations.
To test transmitters without actually operating into an antenna, dummy loads were created. A dummy load is a
load that will dissipate the energy from the transmitter instead of emanating it into the ionosphere. Nearly all
commercial dummy loads are large oil-filled cans. These dummy loads change the transmitted energy into heat,
which is absorbed by the oil. Because different transmitters output different amounts of power, different sizes of
dummy loads must be used. Dummy loads for typical amateur powers (under 500 watts) are relatively inexpensive
and are readily available.
FREQUENCY
An accurate Digital
Frequency Readout
is an essential HF
transceiver feature.
GAINS AND LEVELS
dB Gain describes an
increase in signal level.
Level refers to how
loud the signal is.
DO-IT-YOURSELF LIGHT-BULB DUMMY LOAD
To Next Page