Antenas Vswr

HamNet Antenna Tutorial - Part 1-4
Through the courtesy of the Teleconference Radio Net and net manager Rick Whiting, W0TN, we’ve received a transcript of the June 2nd Teleconference by Joe Reisert, W1JR. Joe spoke on the subject “Antennas and Antenna Systems, Where is the State of the Art Going?” Joe’s talk did an excellent job of covering the whole spectrum of antennas - from HF through UHF -and made heavy use of references in the amateur and professional literature. For the next couple of weeks, we’ll be serializing Joe’s talk here in the Ham Radio Tutorials section of the Message Board. The initial series of messages will be left shortly - to be followed by four remaining sections of the talk in the coming weeks. After the series is presented on the Message Board, it’ll also befound archived away in the XA7 database - so that you’ll be able to readily refer back to it in the future. We hope you find the series interesting and useful. It covers a broad range of technical material on a subject of interest to all amateurs. Your discussion of the Joe’s text is welcomed!

PART I - Overall Summary and Definitions
Good evening, my fellow amateurs. It is a great pleasure to behere tonight. I feel honored to be selected to speak at this very large and possibly largest ever teleconference. Many thanks go to the Honeywell Amateur Radio Clubs and, in particular, Dave Meldrum, KA1MI, and Rick Whiting, W0TN, for the confidence they have placed in me and also for their helpful hints and suggestions to make this presentation a success. Tonight my talk will be about “Antennasand Antenna Systems, Where is the State of the Art Going?” I will divide the talk into four separate segments. The first part will deal with general terms and definitions which will set the stage for the rest of the talk. The other three segments will be the “low HF” (40 through 160 meters), the “middle HF” (10 through 30 meters) and finally VHF/UHF and EME antennas. In most cases I will be talkingabout the top of the line, state of the art or future antennas and antenna systems. There is probably no other amateur radio topic that inspires such a vigorous line of conversation as the subject of antennas. Virtually every amateur has some interesting story to tell about his or her favorite antenna or antenna system or one yet to be fully tested. In reality there is no better place to spend youtime improving the performance of your station since if the same antenna is used for transmitting and receiving, every dB of improvement in gain yields a two dB overall station improvement, one dB on transmit and one dB on receive. The old saw still stands... “If you can’t hear them you can’t work them.” If there is one big complaint that can be leveled against the amateur community it is thatthey almost never use true gain standards when evaluating antenna performance below 30 MHz. Typical performance is measured in dBs above my last antenna or above a long wire in the trees of how many guys I beat out in the pile up on XZ2XX. Seldom regarded are changes in radio propagation, power of the competition, or operator savvy not to mention good luck in being at the right frequency or timingof the call. Another problem is the sheep following the wrong leader copying an antenna that Joe Blow uses because he works more DX than I do without regard for his physical setup, power or operating ability. The trouble with this kind of approach is that you never really know what you have. You even may have built a real good antenna and replaced it with a poorer one. The situation I’ve describedis not hopeless or beyond even the novice doing antenna tests if you understand your limitations and make a few basic tests. Typical amateurs can only measure a few antenna parameters such as VSWR and in the case of a rotary beam, front to back ratio. Therefore, the commercial manufacturers make sure that these parameters are good. Let me be more specific about these parameters and first look at...