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Friday, December 5, 2008

Excellent HF propagation continues

The sunspot count continues to be zero, and has been at that level since November.

It is well known across the engineering profession that sunspot activity is only one of many geo-physical conditions which affect long-distance HF propagation. I am continually amazed at the self-styled rubbish which is being written in hobby newsgroups by people with little understanding of HF transmission, falsely believing, without qualification, that low sunspot activity is "causing" long-distance propagation to be non-existent.

These people fail to understand that low sunspot activity will cause a depression of Optimum Working Frequencies to as low as 10 MHz for long-distance transmission paths crossing darkness, or semi-darkness regions. Transmission on daytime paths continues to be excellent worlwide on frequencies between 15 MHz and 22 MHz

During periods of low sunspot activity, HF commmunication services shift operating frequencies downwards for maintaining effective simplex or duplex transmission over darkness zones or long distance circuits.

Here in Melbourne, propagation continues to be very good on all bands at appropriate times of the day and night, for long-distance transmission paths. Some strong daytime signals are already appearing from Asia and Africa on 7 and 9 MHz, following all-daylight paths, some of this supported by multi-mode propagation via reflection off the top of Sporadic-E clouds over north and central Australia, with no intermediate ground reflection.

These phenomena occur regularly here in Victoria during our summer months, with Absorption Limiting Frequencies dropping to very low levels between our local noon and mid-afternoon.

Here's a summary of propagation highlights of December 4 from Melbourne, with long-path denoted as "LP", Asian daytime paths as "AS", African daytime paths as "AF":

7125 MOLDOVA VOR Kishinev Russian 0445 LP
7150 RUSSIA VOR Krasndar English 0445 LP
7220 GERMANY RL Wertachtal Tatir-Bashkir 0455 LP
7295 MALAYSIA RTM Kajang English 0400 AS
7485 THAILAND R. Farda Udon Farsi *2000-2130*
9530 VIETNAM VOV Hanoi nat network Vietnamese 0430 AS
9700 TURKEY VOT Turkish *0500 LP
9730 MYANMAR R. Myanmar Yangon, Burmese 0400 AS
9745 S. AFRICA Channel Africa Meyerton English 0450 AF
9750 MALAYSIA V. of Islam Kajang English 0430 AS
9850 VIETNAM VOV Hanoi dialects network 0445 AS
9875 VIETNAM VOV Hanoi dialects network 0445 AS
11580 USA WYFR Okeechobee Portuguese 0415
11660 CHINA CNR2 0400 AS
11730 INDIA AIR Arabic *0430 AS
11805 CHILE CVC Santiago Spanish 0415
11895 ROMANIA RRI English 0430 LP
11925 IRAN VOIRI Hebrew *0430 LP
12045 CHINA CNR1 0400 AS
12060 IRAN VOIRI Turkish *0430 LP

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