149BARRETT 4050 HF SDR TRANSCEIVER -APPENDICESFactors Which Affect HF/SSB CommunicationsThere are a number of different factors which will affect the success of commu-nications via HF/SSB radio. These are outlined below:Frequency SelectionFrequency selection is perhaps the most important factor that will determinethe success of your HF/SSB communications.Generally speaking the greater the distance over which you want to communi-cate, the higher the frequency you should use.Beacon Call, a Selcall (Selective Call) function built into the Barrett 4050 Trans-ceiver, makes finding the correct frequency to use easy. A Beacon Call is basedon the network of transceivers all having a selection of frequencies that willaccommodate most ionospheric conditions. When in standby, the networktransceivers scan these frequencies waiting for a call (Selcall or Beacon Call)from another transceiver. The transceiver wishing to check for the best fre-quency to operate on sends a Beacon Call to the station to be contacted. Ifthe call to the other station is successful, a revertive tone from the stationbeing called will be heard, indicating the channel selected was suitable for theionospheric conditions prevailing. If the revertive tone is not heard or is veryweak, another channel may be tried until a revertive tone of satisfactory signalstrength is heard.(Refer to Beacon Calls on page 30 for more details.)Time of DayAs a rule, the higher the sun, the higher the frequency that should be used. Thismeans that you will generally use a low frequency to communicate early morn-ing, late afternoon and evening, but you will use a higher frequency to coverthe same distance during times when the sun is high in the sky (for example,midday). You will need to observe the above rule carefully if your transceiver hasa limited number of frequencies programmed into it, as you may only be ableto communicate effectively at certain times of the day.
