Almost a year ago, I made a POTA activation from DC in Freedom Plaza. I'm discussing antennas and buildings today with Bill Meara of the soldersmoke blob and published this map to carry along the conversation. I alternately convince my myself that buildings do not matter, and then a few weeks later, that they do.
Now available as a Kindle ebook for 99 cents ! Get a spiffy ebook, and fund more physics The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems , there seem to be fewer explanations of the procedure for deriving the conversion, so here goes! What do we actually want? To convert the Cartesian nabla to the nabla for another coordinate system, say… cylindrical coordinates. What we’ll need: 1. The Cartesian Nabla: 2. A set of equations relating the Cartesian coordinates to cylindrical coordinates: 3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system: How to do it: Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables. The chain ...
Hamilton: I thik they do matter. Proof of this is what happens when you try to use an HF transceiver from inside a building with a metal or re-bar structure. It is as if you are trying to work from inside a Faraday cage. It doesn't work very well. The same principal applies if you have a building next to your antenna. I have a clear shot at the horizon to the east, northeast and south. To the northwest I have the seventh floor of my apartment building. With a lot of re-bar to ground. This indeed, matters!
ReplyDelete73 Bill
Hi Bill! I believe you. It makes sense. I'm digging through my data. Unfortunately everywhere I've been in a city that I've found so far, there have been buildings in the way of paths to very small numbers of people, or in some cases, no one. The map here is a good example. Yes, all the QSOs are over the park, but also, the bulk of the entire United States is west over that park :)
ReplyDeleteI'll let you know when I find definitive evidence of what I agree must be true.