SWS GRAFEX HF FREQUENCY PREDICTIONS ADDRESS NO. 1234 =============================================================================== Circuit: Karratha Perth Date: 13 April, 2026 T-index: 80 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 37-42 2E 14 UT OWF EMUF ALF |...|....| ....|....| ....|....| ....|....| OWF EMUF ALF UT 00 14.3 11.6 6.1 ASSXMMM MFFF%%%... 9.7 7.1 3.7 00 01 15.6 13.3 6.9 SSXXMM MMBFF%%%%. .. 10.5 8.2 4.2 01 02 16.6 14.4 7.3 ASSXMM MMMBFF%%%% ... 10.9 8.9 4.5 02 03 16.6 15.0 7.6 ASSXXM MMMBBF%%%% ... 11.1 9.3 4.6 03 04 16.7 15.3 7.7 ASSXXM MMMBBF%%%% ... 11.1 9.5 4.7 04 05 16.6 15.2 7.7 ASSXXM MMMBBF%%%% ... 11.3 9.4 4.7 05 06 15.9 14.7 7.5 ASSXXM MMMBF%%%%. .. 11.0 9.1 4.5 06 07 15.7 13.9 7.1 SSSXMM MMMFF%%%%. ... 10.7 8.6 4.3 07 08 15.1 12.5 6.5 ASSXMMM MMMFF%%%%. .. 10.3 7.7 4.0 08 09 14.8 10.2 5.5 SSXMMMM MMFF%%%%.. . 10.0 6.3 3.3 09 10 12.8 2.0 0.0 XMMMMMMMMM MF%%%%%... 8.6 1.3 0.0 10 11 9.9 2.0 0.0 XMMMMMMMM% %%%.... 6.9 1.3 0.0 11 12 8.6 2.0 0.0 XMMMMMMM%% %%... 6.1 1.3 0.0 12 13 7.4 2.0 0.0 XMMMMMM%%% ... 5.4 1.3 0.0 13 14 7.1 2.0 0.0 XMMMMMM%%. .. 5.3 1.3 0.0 14 15 7.1 2.0 0.0 XMMMMMF%%. . 5.2 1.3 0.0 15 16 6.9 2.0 0.0 XMMMMM%%%. . 5.1 1.3 0.0 16 17 6.8 2.0 0.0 XMMMMM%%.. . 5.0 1.3 0.0 17 18 6.6 2.0 0.0 XMMMMM%%.. . 5.0 1.3 0.0 18 19 6.3 2.0 0.0 XMMMMM%%.. 4.6 1.3 0.0 19 20 5.9 2.0 0.0 XMMMM%%.. 4.2 1.3 0.0 20 21 5.2 2.0 0.0 XMMMM%.. 3.8 1.3 0.0 21 22 6.0 2.0 0.0 XMMMM%%.. 4.5 1.3 0.0 22 23 10.8 8.2 4.6 ASMMMMFF %%%.. 7.3 4.9 2.9 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) 13-Apr-2026 BoM Space Weather Services, Sydney Australia +61-2-9213-8000