Lifting the Veil
While there will always be something new to be discovered about our physical universe, HF radio enthusiasts have come to understand (at least in part) the impact that solar activity has on radio propagation. While we regularly suffer through generally poor conditions at the bottom of each cycle, we can now take solace in the knowledge that the process is cyclical — and given some time, things will very likely improve.
Now consider for a moment that you’re a radio amateur experiencing the conditions of being at the bottom of a cycle — but it just happens to be the first “bottom” since HF was pioneered. Just a few years earlier your shortwave signals were easily received across the Atlantic and around the world but now HF communication wasn’t comporting to what had been previously observed.
It’s a good thing for us that this was observed at that particular moment in the slipstream of time.
Five hundred years earlier and yet another ‘religion’ would likely have been created in order to appease the solar gods. Seventy years later and some silly, multi-millionaire televangelist would likely have blamed the drop-off in HF propagation on one sin or another and we might never have arrived at the truth.
Kenneth B. Warner, then Secretary of the ARRL wrote about this in the February 1931 edition of QST magazine. Read his words and take note that he seemed to understand that the problem was related to solar activity even if he was unable to write with authority on the subject since it was mostly theoretical at that point:
The whole high-frequency world realizes now that, in addition to daily and seasonal changes in the performance of a certain frequency, account must be taken of a long-time change in atmospheric conditions seemingly dependent upon solar activity and therefore believed to be a cycle of approximately eleven years duration. Elaborate transmission measurement made last year are of little value in predicting performance next year. The whole story of course isn’t yet known, for high-frequency transmission is not yet eleven years old.
The bottoming out of long-distance radio signals wasn’t just a concern for the amateur since the advent of radio ushered in the era of broadcast and commercial radio as well. Old Sol also played tricks with these commercial interests:
In the meantime more than one expensive station has been planned and built only to find that the change in atmospheric conditions between the original tests and the completion of the station was enough to upset all calculations, making rebuilding necessary.
With much research and study science has been able to lift the veil on many of the mysteries surrounding the impact of the Sun and its activities with regards to the electromagnetic spectrum that we’ve come to enjoy here on Earth and those early radio amateurs who helped pioneer HF communication should get much of the credit. Their tools were somewhat crude but effective:
Draw yourself a sine curve, one cycle of which represents the sun-spot cycle of 11.1 years. Mark one “positive” loop Summer 1923, the date of the last sun-spot minimum. The next “positive” loop is then Summer 1934, when the next minimum occurs. The intervening “negative” loop is then seen to be the End of 1928, at which time it is known that there was a maximum of solar activity. It is apparent that we are entering the region of most rapid change, crossing the “node” this coming autumn. That is to say, while there will be irregularities, to be sure, it is reasonable to predict that we approach in 1934 a duplication of the conditions in 1923, that for the next several years the DX value of 7mc and 14mc will steadily decline and that by about next winter we should be able to resume trans-ocean two-way communication in the 3500-4000 band!
We’ve since learned that the cycles themselves can widely vary with regards to their intensity and duration, but overall, I’d say KB Warner and the radio hams of 1931 had a pretty good handle on prognostication — wouldn’t you?
73 de Jeff