Simple Ham Radio Antennas

Those of you who follow my Amateur Radio News Blog (http://kh6jrm.com) on a regular basis may be aware of two related radio stories that will have a significant impact on the future of amateur radio and the rf spectrum that we share with other services. The first article relates to comments made by FCC Chairman Tom Wheeler at the annual NAB convention today in Las Vegas, Nevada. In his speech before NAB delegates, Wheeler urged television broadcasters to abandon over-the-air transmissions in favor of streaming over the internet.  Wheeler says the migration to broadband internet would free up spectrum for the ever increasing demands of consumer electronics, from cell phones and iPads to mobile radio and other public services.  Already, VHF analog channels between channels 2 and 13 have moved to higher frequencies and now employ digital signals.  The now vacant channels won't remain idle for long, since these VHF allocations will be assigned to other services. The gradual appro

Over the past few posts, I've been describing some of the antennas I designed, built, and used during my days as a novice amateur radio operator (1977-1978).  Most of the working designs were copied into school theme books and saved for future reference. One of my favorite homebrewed antennas was a simple vertical  antenna supported by a high tree limb terminating with a slightly angled ground plane consisting of 10 radials.  The antenna was designed for 40 meters and worked very well for contacts throughout the Pacific Rim and the mainland United States . Last weekend, I decided to duplicate that antenna with some spare wire, ceramic insulators, coaxial cable , and basic tools. As mentioned earlier, the process of moving to a new home often uncovers items you once thought were lost.  Such was the case here when I found several 50-ft /15.24 meters rolls of #14 AWG house wire in the garage.  That wire would serve as the vertical element and the rudimentary ground radial sys

Like many amateur radio operators, I've collected many boxes of electronic parts, various lengths of coaxial cable , and assorted rigs over the past 38 years.  I suppose my "shack" is testament to my "pack rat" tendencies.  I rationalize this collective habit by saying all of this material will become useful some day.  That some day was Thursday, 13 March 2014.  I had several lengths of RG-58 coaxial cable that had seen better days.  The assorted 100-ft/30.48 meters and 50-ft/15.24 meters lengths were gathering dust in the corner of the garage serving as the storeroom for my radio room.  The connectors were in good shape and the vinyl covering was intact, although a bit grey from sun exposure.  I wanted to find a use for the old cable ,now that it had been "retired" from active service. Why not use the old coax as a low noise receiving antenna for 80 meters, which was a very noisy band even in my remodeled home in the Puna District of Hawaii Islan

A few days ago I read a fascinating antenna article by Cecil Moore (W5DXP) on the http://www.eham.net website.  Cecil described what he called a " Multi-Band 33-ft dipole" that works on 20, 17, 15, and 10 meters without an antenna "tuner" (i.e. transmatch ).  The secret to this outstanding antenna was the use of 450 ohm ladder line in conjunction with a series of switches and relays that selected the proper length of ladder line used to feed the antenna.  Depending on the band of use, Cecil could insert and remove sections of ladder line with his relay/switch system so that swr across his chosen band remained low.  By carefully selecting which section of feed line to add or subtract, he got a decent performing antenna without having to resort to a transmatch or "tuner." Cecil's idea got me thinking of ways to improve the dipoles I'm using at my new home site.  Although his idea has a lot of merit, I felt the need to build something a bit simpl

The sloping 1/2 wavelength dipole is one of my favorite antennas.  "Slopers" are good antennas for restricted space areas.  They are simple to build, inexpensive, and exhibit some directivity in the your chosen direction. According to VK6YSF, VE2DPE, and other amateur radio operators, a properly designed 1/2 wavelength sloper radiates energy at low angles relative to the horizon with vertical polarization.  Slopers don't require a ground radial system and can be fed with a good grade of 50 ohm coaxial cable.  A sloper antenna only requires one tall support (tree, mast, edge of a roof, etc.) and occupies less space that a 1/2 wavelength horizontal dipole. So, let's build one of these simple, effective antennas for the 10 meter band , centering on 28.4 MHz --right in the middle of the techncian class phone band. MATERIALS: One tall support.  In my case, I used a 33-ft/10.06 meter MFJ telescoping fiberglass mast.. One 5-ft/1.52 meter wooden stake to support

One of my favorite pursuits in amateur radio is chasing DX (distance) contacts with hams living or visiting in remote places of the world, be they small nations, islands, or even mountain tops.  Each contact is a small adventure to a place I may never see. For the dedicated contester or DX enthusiast, there are many attractive awards (i.e. DXCC , WAS, WAC, etc.) to pursue. I'm more of a "casual" DXer , squeezing in contacts when house building or part-time teaching permit.  For those moments when I'm free of family responsibilities, I enjoy listening and working exotic, far off places.  Since I live on Hawaii Island , I'm often the "target" of DXers...a task I thoroughly enjoy. During my 37 years as an amateur radio operator, I've experienced both the joy of making a rare contact and the frustration of losing some elusive call in a rush of QRM.  Such is the DX experience. There must be an easier way of making DX contacts than wading through a

Over the past few years, I've built a variety of HF antennas for my amateur radio station.  All of my verticals, inverted vees, dipoles, and loops have been a learning experience, especially when I've been faced with limited resources and space.  Operating from an apartment or a home governed by CC&Rs and HOAs has been a challenge. Now that I'm slowly moving into a full acre of space in the rural Puna District of Hawaii Island, my space restrictions are gone and there are no committees to oversee my antenna activities.  I count this as a definite blessing.  For the first time in many years, I can build full sized dipoles, verticals with a decent ground system, and large full-wave loop antennas without interference.  Since my new property is surrounded by tall trees approaching 50 feet/15.24 meters, my antennas are well shielded from prying eyes.  When I operate out of my rental home in Laupahoehoe, I'm still hemmed in by utility poles and neighbors.  My antenna

So far, the "tunerless" antennas I've built have worked very well.  They have been made with locally available materials from my "junk" box, neighborhood garage sales, and the nearby Ace Hardware Store.  These antennas have consisted of individual dipoles/inverted vees for my bands of preference (40, 20, 15, 10 meters), telescoping fiberglass masts (33-ft/10.06 meters tall), a single RG -8X coaxial feed line , and supporting wooden stakes or tree branches. Dipoles for each band were built on the ground and were later hoisted into position via a halyard and pulley system.  A "choke balun" made from part of the RG-8X feed line was attached to the mast just below the center connector at the top of the mast. In my first multiband antenna system, I changed bands by lowering and raising the appropriate antenna into place.  I couldn't change bands by staying in the shack. My second system was a modified "fan dipole/inverted vee" using mul

In some of my previous posts, I've investigated, built, and used multiband dipole and inverted vees using a single 50 ohm coaxial feed line .  With a telescoping fiberglass mast (33-ft/10.06 meters extended), a simple halyard and pulley system, and separate antennas cut for each band of use (40, 20, 15, and 10 meters), I've been able to change bands fairly quickly by lowering the dipole/inverted vee elements, substituting those of another band, and raising the new antenna.  With each band element cut for the desired frequency, the efficiency is high with low swr for that band.  Since each antenna element is trimmed for the lowest swr at my mast location, an antenna transmatch isn't necessary.  Sometimes, as in the case with the 40 meter dipole/inverted vee, an antenna cut for the cw portion of the 7 MHz band will often work well on the phone portion of 15 meters (21 MHz band). The 15 meter band will operate on the third harmonic of the 40 meter band . In order to save

Antenna transmatches or "tuners" are wonderful devices that make amateur radio operations easier.  They can help minimize swr on antenna feed lines and extend the band coverage of your present antenna. However, there are times when such devices may not be needed, especially if you're designing an antenna for a single band or are contemplating an emergency or portable antenna for your "go" kit.  By carefully designing, cutting, and trimming your basic 1/2 wavelength dipole for the lowest swr, you can just connect a good quality 50 ohm coaxial cable feed line and run the band of your choice without much difficulty. In this post, I will describe a few simple coax-fed dipoles and inverted vees that will serve your favored amateur radio band without the need for an antenna transmatch .  Of course, you could always insert a transmatch into the system to squeeze out the maximum power at the lowest possible swr if you so desire.  These antennas work either way.  

Nowadays, the antenna transmatch ("tuner") is an integral part of many amateur radio stations.  With this device, a ham can match the output of his/her transceiver with the often unknown impedance of the antenna itself.  With a suitable balun (balanced to unbalanced) transformer, it is possible to use one antenna to cover several HF bands, especially if you're facing space restrictions on a small lot or have  to operate in "stealth" mode because of HOAs and CC&Rs.  This situation applies mostly to the use of 300 ohm tv twin lead and 450 ohm ladder line, which require a balun (1:1 or 4:1) and antenna transmatch to operate as feed lines in a multiband, single antenna system. There are times when you may not have an antenna "tuner" at your disposal, especially if you're operating in portable or emergency situations.  In my case, I remove my Drake MN-4 and MFJ 941-E transmatches from the antenna system for routine maintenance several times a