(26-04-2013, 08:37 AM)Joe Wrote: It shows what a Dark Art it is in that what shouldn't work does and what should, doesn't.
- Joe
Yes, agreed: when dealing with 'R.F.' and especially aerials, it certainly often appears that way. The problem with this area of electronics - and especially aerials - is that there are so many 'variables' that are not apparent to us, and of those that are 'visible', they are often outside of our control. Consequently, for most people in most situations, the solution is either to trust a manufacturer / installer to provide a suitable product and (hopefully) to have it fitted correctly or, for those of us with some knowledge, to use 'tried and tested standard designs', such as a dipole, etc. and follow simple 'rules', such as as 'high as possible' and 'in the clear' as much as possible, and, if it's a directional aerial, to try to get it pointing in the 'right direction', which within itself, can be fun. Once those basics have been established, we're then into the relatively murky waters of impedance matching, SWR, cable losses, etc. And it is often difficult to assess the importance of these particular 'variables', since to do so requires not only a thorough understanding of the principles involved, but also access to the necessary (and often complex and expensive) test gear to determine and measure them. Consequently, on the one hand, the whole area of 'aerials' is wide open for the enthusiastic experimenter, but on the other, it is also open for questionable and spurious designs to be produced.
Just my views, based on my experience, of this fascinating topic.
Al.
