[Ips-hf-warning] SWS HF SWF COMMS WARNING issued 2359 UT on 19 Aug 2017 [SEC=UNCLASSIFIED]

[rwc]

SUBJ: SWS HF RADIO COMMUNICATIONS WARNING 17/34
ISSUED AT 2358UT/19 AUGUST 2017
BY THE AUSTRALIAN SPACE FORECAST CENTRE.

Chance of significant flare activity from AR2671(N12E09).

DEGRADED HF PROPAGATION CONDITIONS EXPECTED
FROM 20-21 AUGUST 2017
IF COMMS DIFFICULTIES EXPERIENCED TRY A HIGHER FREQUENCY BAND
_____________________________________________________________

SOLAR ACTIVITY FORECAST       HF COMMS FADEOUTS
20 Aug:  Low to moderate      Possible
21 Aug:  Low to moderate      Possible

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 bom.gov.au
Bureau of Meteorology
PO Box 1386                         WWW: http://www.sws.bom.gov.au
Haymarket NSW 1240  AUSTRALIA       FTP: ftp://ftp-out.sws.bom.gov.au
tel: +61 2 9213 8010                fax: +61 2 9213 8060 

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