Posts

Ten Basic Antenna Truths. Post #214

Sometimes knowledge comes from the strangest places.  Take today, for instance. While my van was having a routine maintenance check at my local Honda dealer (I have an Odyssey van), I ran into an Dean Manley (KH6B), one of my oldest friends and former station engineer at Hilo radio station, KHLO-AM.  I worked at this station from 1976 to 2011.  We discussed a variety of antenna ideas, including improving the homebrewed antennas we use at our stations.  I consider Dean an expert in this area.  He has spent many years building and upgrading antenna systems for  AM and FM stations, both commercial and nonprofit. Anyway, we spent a good half-hour discussing some ideas, including his current project--a 40-meter vertical beam which Dean uses for the Hawaii Afternoon Net.  Before we parted, he gave me a copy of a handout he made for members of the Hilo Amateur Radio Club.  The one-sheet article, entitled "HF Antennas 101" by Van Field (W2OQI), appeared in the September 2004 iss

A 3/2 wavelength sloping dipole for 20 meters. Post #213.

One of the easiest and least expensive antennas for the amateur radio operator is the sloping dipole or "sloper."  Ed Noll (W3FQJ) defines the sloper as "a slanted half-wave antenna with one end of the antenna attached to (a) mast top and other end near to ground level."  According to Noll, the sloper shows "a modest directivity in the direction of its slope and considerably less signal pickup from its rear."  A well-designed half-wave sloping dipole can fit in a small city lot using a mast between 20 to 30 feet (6.09 to 9.23 meters), two dipole elements cut to your preferred frequency, a few insulators, a couple of tie-down stakes, and sufficient 50/72 ohm coaxial cable to reach your shack.  Multiband operation is possible using 450 ohm ladder line, a 4:1 balun, and an antenna transmatch. Since most of my ladder line was being used for other antenna projects, I decided to use 50 feet (15.24 meters) of RG-8X coaxial cable with UHF connectors for my feed

My favorite stealth antenna. Post #212

Amateur radio operators who live in deed restricted homes and apartments face a variety of antenna problems.  The amateur radio press is full of stories describing the "no outdoor" antenna rules of OHAs and CC&Rs. Despite these reports, many amateurs have been able to build effective indoor and outdoor antennas to pursue their radio interests. From flagpole antennas to attic beams, hams have used creativity and "stealth" to get and stay on the air. In my case, the adoption of "stealth" antennas was forced on me by natural circumstances and not necessarily by highly critical neighbors.  In fact, my neighbors are good people who tolerate my amateur radio pursuits as long as I don't ruin their television reception or interfere with their entertainment systems.  Although many people in my neighborhood get excellent television via cable television providers, my immediate neighbors get their tv programming over the air using the familiar deep fringe

An 80-Meter Vertical Helix

Like many amateur radio operators, I live on a small lot surrounded by neighbors, utility lines, and civic-minded citizens concerned about the "attractiveness" of my community.  Whether by design or outright fear, I've adopted the "stealth" approach to ham radio antennas.  It's the old "out of sight, out of mind" idea applied to amateur radio antennas. The amateur radio press is full of articles describing the struggle of amateur radio operators to pursue their hobby under the burdensome regulations of CC & Rs, HOAs, and other civic minded citizens who object to antenna farms.  So far, my modest verticals, loops, and inverted vees have blended well with the vegetation and trees bordering my small backyard.  Vertical antennas have always been a problem because of the limited space for a radial system.  There are times, however, where a shortened vertical for the lower HF bands (such as 80/75 meters) is necessary where horizontal space is lack

A modified 20 meter extended double zepp antenna. Post #210

How would you like to boost your 20 meter signal by 3 dB with only 84.5 feet/25.76 meters of wire, two supporting masts, some 450-ohm ladder line, ordinary 50-ohm coaxial cable, and a few miscellaneous parts? Today, I ran across a fascinating article by Paul E. Fuller (N8ITF), who designed a simple data sheet to help you build what is called "an extended double zepp antenna."  The double extended zepp is a dipole type of antenna consisting of two collinear 0.64 wavelength elements fed in phase, providing approximately 3 dB gain over a dipole on its intended frequency.  By following Fuller's advice, you can build an antenna that will give you some gain and more DX in the process. Although my backyard is a bit cramped, there are numerous tall Norfolk Pine trees in an adjacent lot which could serve as a temporary support system for the 20 meter extended double zepp antenna. With Fuller's article in mind, plus a few other ideas from several amateur radio operators,