[Ips-hf-warning] IPS HF COMMS WARNING issued 0134 UT on 24 Aug 2015

[rwc]

SUBJ: IPS HF RADIO COMMUNICATIONS WARNING 15/40
ISSUED AT 0134UT/24 AUGUST 2015
BY THE AUSTRALIAN SPACE FORECAST CENTRE.

These HF depressions for the next three days (24 to 26 August) 
are due to continuos low levels of ionising solar flux. Further 
depression could be expected on 25 and 26 August associated with 
possible after-effects of the CME which is expected to arrive 
on the 24 Aug.

DEGRADED HF PROPAGATION CONDITIONS EXPECTED
FROM 24-26 AUGUST 2015
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 Aug:   50          -13%      2  4  6  8 12 12 16 22
25 Aug:   40          -18%      2  4  6  8  8 12 16 22
26 Aug:   40          -18%      2  4  6  8  8 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.

Space Weather Services              email: asfc at ips.gov.au
Bureau of Meteorology
PO Box 1386                         WWW: http://www.ips.gov.au
Haymarket NSW 1240  AUSTRALIA       FTP: ftp://ftp.ips.gov.au 
tel: +61 2 9213 8010                fax: +61 2 9213 8060 

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