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P.O. Box 3526, 98009 Tel: (425) 746-6310 Fax: (425) 746-6384
© 1997 SGC Inc.
the power output is approximately 50% of these figures, even though all types are
frequently listed for transceivers. Also, the power levels are a logarithmic function, not a
linear function. For example, a transmitter with a 50-watt output is not half as "strong" as a
transmitter with a 100-watt output. A 10-watt transmitter is half as "strong" as a 100-watt
unit (10 X 10 = 100).
Frequency stability is of utmost importance with an SSB transceiver. All transceivers have a certain amount of
drift when they warm up (especially) and are operating. Older units, such as the much older
tube transceivers, could often drift as much as 1 kHz in an hour while warming up and
operating. Because SSB has a narrow signal and when you slightly tune off of the center of
the signal it sounds duck-like, SSB transceivers can only drift a tiny amount. A crystal oven is a constant-
temperature component that holds the frequency of a radio on a particular channel, without drifting.
The frequency steps for radios have only come about since the advent of digital, synthesized tuning. Before,
you would tune the radio continuously through the radio bands. With digital tuning, you must tune the radio in
steps. Because of the varying frequencies of radio stations (especially with quite a bit of the older, analog equipment
still in use) and because of the effects of interference (damaging part, but not all, of a signal), it is best for the digital
receiver to be able to tune in increments as small as possible. However, for convenience, it can be handy to tune
across the bands in other steps, such as 5-kHz steps for tuning across the shortwave broadcast bands (most
shortwave broadcasters are separated by 5 kHz).
The sensitivity of a radio receiver is the amount of signal that is necessary for the
receiver to distinguish it as a signal and not as noise. The difference between a receiver with
excellent sensitivity and one with poor sensitivity is that you will not be able to hear some
weak stations on the receiver with poor sensitivity. As a result, sensitivity is important when
monitoring the HF spectrum or when communicating over very long distances.
Sensitivity is the amount
of signal needed for the
receiver to distinguish it
from the
background noise.
FREQUENCY STEP
SENSITIVITY
Power Output is the
number of RF watts
that the transmitting
portion of the
transceiver will send
into the antenna.
Frequency Stability is
critical with an SSB
transceiver.
FREQUENCY STABILITY AND CRYSTAL OVEN
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