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The Propagation

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The importance of understanding basic VHF and UHF propagation cannot be overemphasized. Unlike DXing on the shortwave bands, you can't just turn on the receiver, tune around, and expect to get a faraway station. On VHF and UHF the normal situation is no DX --- until some abnormal propagation occurs. Also, unlike shortwave, there are several different kinds of propagation above 30 MHz.  To DX effectively, you should be able to evaluate what you pick up.  This requires being able to tell one type of propagation from another. Fortunately, the propagation modes differ sufficiently from one another that by combining a little experience with the descriptions to follow, you should seldom have any difficulty assigning one definite propagation mode to each DX catch.
Why is this so important? If all you care about is the quantity of DX --- receiving each station once --- it may not matter so much. But it does matter for quality. For example, over the course of several years you may be able to pick up a given station by two, or even three different propagation modes. One will undoubtedly be much rarer than the other(s). For instance, a channel 2 TV station 1000 miles away is relatively easy to see via sporadic E, while the same station is very seldom subject to tropo propagation over such a distance. On the other hand, a channel 7 TV station will seldom cover such a distance, but when it does it will do so more readily by tropo than by sporadic E. So let's look at these mechanisms to which we owe our hobby.
 
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