Factors which affect HF/SSB communications
Frequency selection
Time of day
Weather Conditions
Man-made electrical interference
There are a number of different factors which will affect the success of your communications
via HF/SSB radio. These are outlined below:-
Frequency selection is perhaps the most important factor that will determine the success of
your HF/SSB communications.
Generally speaking the greater the distance over which you want to communicate, the
higher the frequency you should use.
Beacon call, a Selcall (selective call) function built into the Barrett 950 transceiver, makes
finding the correct frequency to use easy. Beacon call is based on the network transceivers
all having a selection of frequencies that will accommodate most ionospheric conditions.
When in standby the network transceivers scan these frequencies waiting for a call (Selcall
or beacon call) from another transceiver. The transceiver wishing to check for the best
frequency to operate on sends a Beacon Call to the station he wishes to contact. If his call
to the other station is successful he will hear a revertive call from the station he is calling,
indicating the channel he selected was suitable for the ionospheric conditions prevailing. If
he does not hear this revertive call or it is very weak, he tries on another channel until a
revertive call of a satisfactory signal strength is heard.
(Refer to Selcall (selective call) section of this manual for full details on Beacon call
operation.)
As a rule, the higher the sun, the higher the frequency that should be used. This means that
you will generally use a low frequency to communicate early morning, late afternoon and
evening, but you will use a higher frequency to cover the same distance during times when
the sun is high in the sky (e.g. midday). You will need to observe the above rule carefully if
your transceiver has a limited number of frequencies programmed into it, as you may only
be able to communicate effectively at certain times of the day.
Certain weather conditions will also affect HF/SSB communications. Stormy conditions will
increase the background noise as a result of ‘static’ caused by lightning. This background
noise could rise to a level that will blank out the signals you are trying to receive.
Interference of an electrical nature can be caused by overhanging power lines, high power
generators, air-conditioners, thermostats, refrigerators and vehicle engines, when in close
proximity to your antenna. The result of such interference may cause a continuous or
intermittent increase in the level of background noise.
BARRETT 950 HF TRANSCEIVER
PAGE 130