Propagation and HF Ladder

Propagation and the HF Ladder

The substantial numbers of HF Ladder slots earned on the high shortwave bands in both this calendar year (so far) and the last was to be expected, given that the previous two years have seen elevated sunspot counts. (See the graph below.) These numbers are consistent with the present stage of the Sun’s 11-year cycle: ‘Solar Maximum’, a time of high solar flare activity and – importantly for us – peak levels of the number of sunspots, around which skip-facilitating extreme ultraviolet radiation is produced. Unfortunately, the maximum of the current solar cycle (no. 24) has been feeble compared to peaks past, and widespread and consistent openings from Europe on 10m and 6m have been rare as a consequence. Most of the opportunities on these two bands have been presented by flighty sporadic-E propagation, which G0SYP and G3ZOD have done well to exploit.

Those lacking slots on the higher bands would be well-advised to make the most of the remainder of the sporadic-E season, which stretches from spring though summer and (if we’re lucky) into early autumn. They should also keep a close watch on the sunspot and solar flux counts, which influence the common (F-layer) skip, as these numbers can be very volatile. It’s a myth that the period at and around solar maximum means great propagation on the high bands day in, day out; sunspots have a tendency of accumulating unevenly across the Sun’s surface, so the levels of Earth-directed high-energy radiation that we need for skip will rise and fall – sometimes quite dramatically – over a 27-day solar-rotation period. Added to the brew can be high-speed solar particle streams and remnants of coronal mass ejections, both of which have been expectedly plentiful during the present solar maximum, and have often made life difficult on the high bands – even during times of high sunspot counts.

A lot of blah has been written recently about the so-so band conditions of late and the relative inadequacies of solar cycle 24. This is all true, but it misses the point; sunspot numbers over recent months have mostly been sufficiently high to facilitate even 28MHz propagation much of the time; the frequent bombardment of Earth’s magnetic field by fast particle streams from the Sun has generally been the guilty party when it comes to inactivity on the high bands and poor conditions, overall. When we get a break in the deluge, watch how the maximum useable frequencies climb up over subsequent days, even when the sunspot numbers are uninspiring. More rays and fewer bits are what we want from the Sun. Hopefully such happy coincidences are common in the run-up to 30 November.


Month Avg. Spot No. Trend
Jul-14 73 UP
Jun-14 71 down
May-14 75 down
Apr-14 85 down
Mar-14 92 down
Feb-14 103 UP
Jan-14 82 down
Dec-13 90 UP
Nov-13 78 down
Oct-13 86 UP
Sep-13 37 down
Aug-13 66 UP
Jul-13 57 UP
Jun-13 53 down
May-13 79 UP
Apr-13 72 UP
Mar-13 58 UP
Feb-13 38 down
Jan-13 63 UP
Dec-12 41 down
Nov-12 61 UP
Oct-12 53 down
Sep-12 62 down
Aug-12 63 down
Jul-12 67 UP
Jun-12 65 down
May-12 69 UP
Apr-12 55 UP
Mar-12 64 UP
Feb-12 33 down
Jan-12 58 down


2014 Average (Jan-Jul):   83

2013 Average (Jan-Dec): 65

2012 Average (Jan-Dec): 58






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