[Ips-hf-warning] IPS HF COMMS WARNING

rwc rwc at ips.gov.au
Sat Sep 10 11:11:40 EST 2011


SUBJ: IPS HF RADIO COMMUNICATIONS WARNING 11/39
ISSUED AT 10/0105Z SEPTEMBER 2011
BY THE AUSTRALIAN SPACE FORECAST CENTRE.

DEGRADED HF PROPAGATION CONDITIONS EXPECTED
FOR 10 SEPTEMBER 2011
IF COMMS DIFFICULTIES EXPERIENCED TRY A LOWER FREQUENCY BAND

Depressions of 15-30% have been observed at times over parts
of the Australian region so far today as the result of recent
increases in geomagnetic activity. Further depressions of
15-30% are expected at times for the remainder of the day.
_____________________________________________________________

HF COMMUNICATIONS FORECAST (AUSTRALIAN/NEW ZEALAND REGION)
                                   FREQUENCY BANDS  
       T-index  MUFs          2  4  6  8 12 16 22 26
_____________________________________________________________
10 Sep   30    -20%/normal    2  4  6  8  8 12 16 16 

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.

IPS Radio and Space Services        email: asfc at ips.gov.au
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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