Posts

Showing posts from February, 2014

Simple Ham Radio Antennas: An 80-10 meter inverted vee dipole. Post #263

Image
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 simpler th…

Simple Ham Radio Antennas: The 10 meter 1/2 wavelength sloper. Post #262

Image
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 the fibergla…

Simple Ham Radio Antennas: The W3EDP antenna revisited. Post #261

Image
The "classic" W3EDP antenna has been around since March 1936 when Yardley Beers (W3AWH/W0JF) described a multiband antenna built by his friend H.G. Siegel (W3EDP).  Siegel used the traditional method of "cut and try" to arrive at an antenna length that would work satisfactorily on 160, 80, 40, 20, and 10 meters.

Beers remembered that "A length of 84 feet (25.60 meters) seemed to stand out as being the best of all the combinations tried."  A similar "test and tune" method was used to determine a satisfactory counterpoise length of 17 feet (5.18 meters), "as the one working best in combination with the antenna."

Since that time, several variations of this true "Zepp" antenna have been developed to facilitate portable, emergency, and even home use.  Many QRP enthusiasts use some kind of W3EDP-derived antenna for their operations.  The W3EDP antenna is a simple, cheap, and field deployable.  The antenna requires a 1:1 or 4:1 cur…

Basic DX tips. Post #260

Image
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 sea of …

Simple Ham Radio Antennas: A Low HF Band Triangle. Post #259

Image
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 ef…

Simple Ham Antennas: The AG9C Loop Antenna. Post #258

Image
Over the past 37 years as a licensed amateur operator, I've accumulated a wide variety of antenna reference material, including books, magazine articles, and topics discussed on amateur radio forums.  All ARRL members can further augment their antenna research by accessing the digital files of "QST", the offical journal of the ARRL.  All told, there is an almost endless resource of antenna building ideas for most every ham station.

Recently, I began to put some of these "classic ideas" to use on my new property in the Puna District of Hawaii Island.  I now have an acre of space to "plant" my antenna "farm"--quite a change from my present rental home which is hemmed in by neighbors and utility poles.  Although my neighbors have been tolerant of my amateur radio pursuits, I try to keep a low profile.  Namely, my verticals and inverted vees are usually lowered when they are not in use and, because of my part-time employment as a sports announc…