nothing. If a high-gain antenna is “off-beam,” even slightly, it won’t work well — you’ll lose your gain, defeating the purpose of having a high-gain antenna in the first place. To spread the beamwidth, or the length of the horizon that an antenna sees, it’s possible to stack directional antennas or to place them stacked and side-by-side in an arrangement called an array. This approach not only in- creases the beamwidth, but the gain of the setup as well. If you generally listen to only two sources, you can use more than one beam antenna, each pointed in the direction of in- terest. It not, you can install a motorized an- tenna rotator to remotely aim your antenna in a 360-degree sweep, which means you can fine-tune the pointing direction to multiple transmission sources. Although directional antennas are the
“mother of all antennas,” you can build non-directional antennas such as ground- plane types that work surprisingly well. These tend to be smaller and simpler, which makes them ideal for portable and mobile applications. Although the reception range of non-directional antennas is typically less than that of a beam or array, they do have the advantage of receiving signals equally in all directions about the antenna as long as the antenna is generally kept vertical. This characteristic obviates the need to aim the antenna, which does away with rotators and related gear. Finally, if you’ve damaged or lost your handheld scanner antenna, you can whip up a suitable replacement that will actually work better than the “rubber duckie” that came with your scanner. In general, due to the nature of VHF radio propagation, the rule of thumb is the higher you can get your antenna, the better. How- ever, keep in mind the coaxial cable you’ll use to interconnect your radio and anten- na (the feedline) has loss — the longer the feedline, the greater will be the amount of signal “soaked up” by the line. You can see that given a long enough feedline, all signal will be lost, completely negating the reason for building and installing an antenna in the first place. To prevent loss, only high quali- ty, low-loss coaxial cable should be used with your antenna. Manufacturers spec their cable loss by the foot. As always, safety should be a top consid-
eration when installing and using anten- nas. If you construct a big enough array, it will bear a surprising amount of wind load during strong breezes, which could cause your setup to crash to the ground, damaging anything along the way. In the worst case, it could fall onto a power line, which presents an electrocution and fire hazard. Because of this, you must carefully consider the locations of power lines and other hazards before you design and install your antenna. If you use a mast-mounted antenna in the field, you must make sure it won’t come near or touch any power lines. You can find out about safe an- tenna construction and installation practices on the web and through books — safety is al- ways covered in detail. Needless to say, if you mount your antenna on a roof or tower, you must carefully consider height and related fall hazards including the sudden stop you’ll experience when reaching the ground. To explore the world of homebrew antenna contruction and installation, I would recom- mend a web search on the topic. There are lit- erally hundreds of antenna construction proj- ects chronicled on the web, from the simple to the complex, i.e., wire antennas to beam
ANTENNA MOBILE GAIN
Tuned to Railroad Band as reviewed in Railfan & Railroad
• Increased range • 5/8 wave, 3db gain • Tuned for optimum Sensitivity, 160-161 Mhz. • Heavy-duty magnetic
$76 mount - other options
PLUS $19 SHIPPING Specify scanner type
Box 38881, Germantown, TN 38183
www.railcom.net
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railcom@aol.com 901-755-1514
Fax: 901-756-8242
MOTOROLA, MOTO, MOTOROLA SOLUTIONS and the Stylized M Logo are trademarks or registered trademarks of Motorola Trademark Holdings, LLC and are used under license. © 2012 Motorola Solutions, Inc. All rights reserved.
B&O Thunder in the Alleghenies
This look at the B&O
This version of the dipole antenna is construct- ed using scraps of solid metal tubing, a wood- en or plastic separator for the two dipole ele- ments, and a wood or metal mounting bracket.
arrays. Some projects are ingenious, such as using a salvaged tape measure and plastic plumbing fixtures, to construct a Yagi-type beam antenna. And if you just want to play around to test the beam antenna concept, you can quickly construct a Yagi antenna using a yardstick, electrical tape, and pieces of salvaged house wiring. I think you will be amazed at how well something so simple and quickly thrown together can work. Along with web-based sources, hundreds
of books have been written on antenna con- struction. Many projects in these publications and on-line are for ham use, but can be easily adapted and scaled for railscanning appli- cations. And, if you don’t want to start from scratch, sources also tell how to adapt exist- ing antennas — such as those for analog tele- vision and for CB radio — for scanner use. If you have any questions, folks on numerous fo- rums will be ready to answer your questions, that is, if you don’t mind putting up with all the egos that typically inhabit such places. Have fun and be safe. Antenna building could easily become the next big facet of your rails- canning hobby!
61
depicts the road’s struggle to master the Alleghenies.
$14.95 Order item CRS-BOTA
877-787-2467 TOLL-FREE 660-695-4433 NON-US
Project4_Layout 1 10/20/14 6:42 PM Page 1
WhiteRiverProductions.com plus S/H
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