SWS GRAFEX HF FREQUENCY PREDICTIONS ADDRESS NO. 1234 =============================================================================== Circuit: Karratha Perth Date: 17 April, 2026 T-index: 70 Bearings: 184 5 Distance: 1251 km First Mode |--------F r e q u e n c y (MHz)---------| Second Mode 1F 18-22 1E 5 1 5 10 15 20 25 30 35 40 2F 36-41 2E 14 UT OWF EMUF ALF |...|....| ....|....| ....|....| ....|....| OWF EMUF ALF UT 00 13.6 11.3 5.9 ASXMMMM MFF%%%... 9.3 6.9 3.6 00 01 15.0 13.1 6.7 SSXXMM MMBF%%%%.. . 10.1 8.1 4.1 01 02 16.0 14.1 7.2 SSSXMM MMBBF%%%%. ... 10.5 8.7 4.4 02 03 16.3 14.8 7.4 ASSXXM MMMBFF%%%. ... 10.8 9.1 4.5 03 04 16.4 15.0 7.5 ASSXXM MMMBBF%%%. ... 10.8 9.3 4.6 04 05 16.3 14.9 7.5 ASSXXM MMMBFF%%%. ... 11.0 9.3 4.6 05 06 15.6 14.5 7.3 SSSXMM MMMBF%%%%. .. 10.7 9.0 4.4 06 07 15.4 13.7 7.0 SSXXMM MMMFF%%%%. .. 10.4 8.4 4.2 07 08 14.8 12.3 6.4 ASSXMMM MMFF%%%%.. . 10.0 7.6 3.9 08 09 14.4 9.9 5.3 SSXMMMM MMFF%%%%.. . 9.7 6.1 3.2 09 10 12.2 2.0 0.0 XMMMMMMMMM FF%%%%... 8.2 1.2 0.0 10 11 9.3 2.0 0.0 XMMMMMMMF% %%%... 6.4 1.2 0.0 11 12 8.0 2.0 0.0 XMMMMMM%%% %... 5.7 1.2 0.0 12 13 6.9 2.0 0.0 XMMMMM%%%. .. 5.1 1.2 0.0 13 14 6.6 2.0 0.0 XMMMMM%%%. . 5.0 1.2 0.0 14 15 6.6 2.0 0.0 XMMMMM%%.. . 4.9 1.2 0.0 15 16 6.6 2.0 0.0 XMMMMM%%.. . 4.8 1.2 0.0 16 17 6.4 2.0 0.0 XMMMMM%%.. 4.8 1.2 0.0 17 18 6.2 2.0 0.0 XMMMMM%%.. 4.7 1.2 0.0 18 19 6.0 2.0 0.0 XMMMM%%%.. 4.3 1.2 0.0 19 20 5.7 2.0 0.0 XMMMM%%.. 4.1 1.2 0.0 20 21 5.0 2.0 0.0 XMMMM%.. 3.6 1.2 0.0 21 22 5.6 2.0 0.0 XMMMM%%. 4.2 1.2 0.0 22 23 10.2 7.9 4.4 ASMMMMFF %%.. 6.9 4.6 2.7 23 UT OWF EMUF ALF |...|....| ....|....| ....|....| ....|....| OWF EMUF ALF UT =============================================================================== |. USABLE LESS THAN 50% OF DAYS |% USABLE 50% TO 90% OF DAYS | |B BOTH E and F MODES 90% OF DAYS |M MIXED FIRST AND SECOND F MODES | |F FIRST F MODE ONLY |E E-LAYER PROPAGATION |P 90% E and 50-90% F | |S SECOND MODES ONLY |A HIGH ABSORPTION |X COMPLEX MODES | (c) 17-Apr-2026 BoM Space Weather Services, Sydney Australia +61-2-9213-8000