Simple Ham Radio Antennas

KH6JRM's Amateur Radio Antenna Topics A limited space 40 meter dipole. The half-wave length dipole fed with 450-ohm feedline (the classic "doublet") is a basic antenna that will give you hours of enjoyment and plenty of DX if the flat top is at least 30 to 50 feet (9.14 to 15.24 meters) above ground.  Even at lower elevations, this simple, inexpensive antenna will provide strong local and regional coverage with a minimum of effort. But, for those of us who face space restrictions (not enough back yard or oddly shaped house lots), getting a    horizontal flat top working can be a problem.  Like many amateur radio operators, my backyard is small and erecting two masts approximately 66 feet apart (20.12 meters) is not feasible.  Is it possible to shorten the horizontal length a bit and drop off the remaining portion of the dipole perpendicular to the flat top and still get decent performance? According to Joel R. Hallas, W1ZR, you can modify the horizontal...

A SLIGHTLY NEW BEGINNING: Welcome back to my original Amateur Radio Blog, which has been retitled:  KH6JRM's Amateur Radio Antenna Topics. This blog has been idle since late 2012 because of my changing job situation and the expansion of my original blog topic to include the latest Amateur Radio News. The news blog began early this year using my original title: KH6JRM's Amateur Radio Blog (http://kh6jrm.com). When I started reporting Amateur Radio News, I found the task complicated by an oversupply of information and a lack of time to follow my experimental antenna ideas.  The reaction to my news blog has been gratifying and I refer those interested in the latest Amateur Radio developments to access that site. I've also received some notes about my neglect of simple antenna ideas--a subject that was the original focus of this antenna blog.  So, I've split my interests into two blogs that will hopefully answer both inquiries.  My revised antenna blog will be ...

KH6JRM's Amateur Radio Blog Post #182 Stealth and hidden antennas One of my favorite interests within the Amateur Radio hobby is hidden, disguised, and "stealth" antennas.  I'm amazed at the creative ways amateur radio operators stay on the air despite severe space limitations, restrictive housing regulations, and proximity to power lines.  I'm one of the lucky ones--I do have a backyard.  It's small, but it does allow me to keep most of my HF and VHF antennas outside.  I'm always a little uneasy about using indoor antennas.  There are interference and rf exposure issues indoors which are sometime difficult to solve. Whenever I feel the need to design a concealed antenna, I often refer to the work of Simone, IW5EDI, an Italian ham residing in the beautiful city of Florence.  Ham radio aside, Florence is a true wonder of the world.  I was in that city many years ago and was impressed with its cultural and historical background, parks, and natur...

KH6JRM's Amateur Radio Blog Post #181 A small loop antenna for limited space--the MFJ-1788 Super Hi-Q magnetic loop. I'm a huge fan of loops.  They are quiet and can be hidden if creatively designed.  These antennas can be fed with either coaxial cable, ladder line, or ordinary 300-ohm television twin lead for a simple, effective antenna.  Loops do have their drawbacks.  A full-size 40-meter loop can be large--with a total length of approximately 141 feet.  In my situation, a large full-wave 40-meter loop fits under my house which is raised off the ground by pier and post construction.  A 20-meter full-wave loop is fastened under my garage roof.  Both of these antennas are invisible from the street or from nearby neighbors.  Since these loops are fairly low to the ground, they serve as NVIS (near vertical incident skywave) antennas, which give me strong signals out to 200 to 300 miles.  That range is perfect for afternoon nets and...

KH6JRM's Amateur Radio Blog Post #180 Mars and beyond--some random thoughts about the Red Planet. I was truly astounded as I watched the descent and successful landing of the "Curiosity" Mars Rover on Sunday evening, 1938 hrs local Hawaii Standard Time.  Of course, some of this was computer animation, but when those first grainy, black and white 64 X 64 pixel landing shots were received, all of the animation made sense.  The sophisticated cable release system did its job as the one-ton vehicle reached its intended landing zone.  Now, the testing and hard work begin.  As a sidenote, one of the 2004 rovers is still performing some of its mission, eventhough one of its wheels is stuck in sand.  It is continuing to send photographs of its surrounding environment despite the harsh martian conditions.  The American taxpayer has surely gotten a good return on those two earlier vehicles, as well as the intial data bank sent back by the two Viking l...

KH6JRM's Amateur Radio Blog Post #179 Portable antennas for the unexpected I've made it a habit over the past few years to keep an emergency "go" kit in my van in case I'm needed to provide communications backup for our local civil defense agency and the Hilo office of the American Red Cross.  Other than the 11 March 2011 tsunami (the one that damaged Japan and its Fukushima nuclear reactor), I haven't used my portable equipment that much, except for weekend operations in a local park or beach area.  When I worked at Pacific Radio Group, I kept an old Kenwood TS-520 and a Kenwood HT at the station for emergency backup to the Hawaii County Civil Defense office in Hilo.  But, since I retired, my forays into portable operation have been subject to personal whim or to opportunities I get handed to me. Such is the case this weekend, where I revert to my 22nd year as the tower announcer for the Big Island Auto Club's monthly points meets.  I'm under...

KH6JRM's Amateur Radio Blog Post #178 Portable antennas One of the things I like to do when the weather is nice (such as today) is to drive my van up an old sugar plantation road and set up a low-power emergency station at a clearing above Laupahoehoe town.  At an elevation of 1,200 feet on the east slope of Mauna Kea, I have a clear view of the Pacific Ocean off to the northeast and a fairly good shot at Japan over the summit of Hawaii Island's largest mountain. Once I reach the clearing, I retrieve my homebrew 40-meter helix (see last post), 50-feet of 450-ohm ladder line, a 4:1 balun, the trusty Drake MN-4 tuner, about 10-feet of RG-6 coax, and the venerable Yaesu FT-7 qrp rig, which can be used for both cw and SSB contacts from 80 meters to 10 meters.  The vertical helix is comprised of two, 5-foot schedule 40 pvc pipes, which are joined by a pvc connector.  Sixty-six feet of #22 gauge hookup wire is wound in a spiral to the top of the vertical pole.  A ...