Monday, May 11, 2009

Frequently annoying questions

One reason why I sometimes wish I had never bothered releasing certain programs I have written is that it irritates me that people cannot be bothered to read the documentation and then write complaining about an "error" that has been explained in the online FAQ.

The program that causes most of the annoyance is VOAProp, since it is the most widely used of the programs on my site and has the most users. The most frequently annoying question is "why does the program display a SSN of 10 (or whatever) when there are no sunspots." The answer is that, in accordance with documentation for VOACAP, which VOAProp is merely a front-end to, the program uses a smoothed sunspot number, which is a rolling average over six months either side of the month in question. This value has nothing to do with the number of spots on the Sun's disc at this moment. This may not make sense to some people, but that is what VOACAP's developers say should be used, so that is what VOAProp uses.

The predicted values do get updated every month by NOAA, so the value used by VOAProp may not always be exactly the value in the latest data. I long ago lost interest in VOAProp and no longer develop or support it. And I can't be bothered to update the data file every time NOAA updates its predictions. Whether the value used is 10, or 5, or 15, makes little difference to the propagation map generated, so it just isn't worth the effort of updating it on a monthly basis.

One thing VOAProp demonstrates is that HF propagation cannot be predicted except in the broadest terms. As I have written before (probably somewhere in the VOAProp documentation), propagation models such as VOACAP were developed by short wave broadcasters who were interested in which bands would give solid, reliable propagation to a particular area most of the time. They were not developed with amateur radio DXers in mind, who are more interested in what might be workable on the fringes of propagation. So they will tell you where your signal is likely to be strong, but they are not very good at predicting where weak contacts might be possible.

The main purpose of VOAProp, and the one it was actually written for, is to demonstrate to inexperienced hams how propagation changes from day to day, month to month and between periods of high and low solar activity, so that they can learn which bands and what times of day offer the best chance of working certain areas. But the ionosphere will always have some surprises in store, which for me is what makes HF operation interesting.
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