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HomeHF SystemsAustralasiaHF ConditionsHF Communications Warning Tuesday, Jan 24 2017 19:34 UT

HF Communications Warning


(last updated 24 Jan 2017 19:30 UT)

SUBJ: SWS HF RADIO COMMUNICATIONS WARNING 17/09 ISSUED AT 0310UT/24 JANUARY 2017 BY THE AUSTRALIAN SPACE FORECAST CENTRE. DEGRADED HF PROPAGATION CONDITIONS EXPECTED FOR 24 JANUARY 2017 IF COMMS DIFFICULTIES EXPERIENCED TRY A LOWER FREQUENCY BAND _____________________________________________________________ HF COMMUNICATIONS FORECAST (AUSTRALIAN/NEW ZEALAND REGION) FREQUENCY BANDS T-index MUFs 2 4 6 8 12 16 22 26 _____________________________________________________________ 24 Jan: 5 normal/-15% 2 4 6 8 12 12 16 22 Note: An IPS MUF depression HF Warning and IPS shortwave fadeout HF Warning are both current. Shortwave fadeouts degrade lower shortwave radio frequencies first (through increased ionospheric absorption) and the usual strategy during shortwave fadeouts is to try a higher frequency. In contrast, during periods of ionospheric MUF depression, the upper frequencies are degraded first and the usual strategy is to use a lower frequency. In general use a lower frequency if you are having trouble with your normal workable frequency. If a shortwave fadeout occurs during a period when ionospheric MUFs are depressed the available HF bandwidth will be "squeezed", with increased absorption raising the lowest usable frequency and the ionospheric depression lowering the highest usable frequency. Under such conditions it is suggested that the HF communicator operates on the highest usable frequency, even though this may well be in fact lower than what is normally supported for that particular circuit.

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