Posts

Showing posts from April, 2014

Simple Ham Radio Antennas: A 5/8 wavelength vertical ground plane. Post #272

Image
According to Edward M. Noll (W3FQJ), "The 5/8-wavelength vertical is a preferred length for the best low angle radiation."  For the higher HF bands (20 through 10 meters), this antenna is easily assembled and requires a small quantity of wire, some ceramic insulators, a suitable mast, 50-ohm feed line or 450-ohm feed line, a simple ground radial system, and a sturdy antenna matchbox or ATU.  Multiband use between 20 and 10 meters is possible with 450-ohm ladder line, ATU, and a balun, while good single band use can be obtained with 50-ohm coaxial cable and an inline or base antenna "tuner".

So, let's build a simple 5/8 wavelength vertical for the 10 meter amateur radio band, centering on 28.4 MHz.  This frequency is at the mid-point of the SSB allocation for Technician Class licensees.  The antenna was built at my new home in the Puna District on 18 April 2014.

MATERIALS:

Using the general formula, 585/f (MHz)=L (ft), our vertical element will measure out to 2…

Simple Ham Antennas: The Novice 40 meter delta loop. Post #271

Image
During that brief period between getting my novice amateur radio license and moving on to the technician and general class license (1977-1983), I built several dipoles, inverted vees, and verticals.  All of these antennas worked very well, considering the lack of space I had at the time.  When my xyl and I moved from Honokaa to Laupahoehoe, we occupied a larger home and had more backyard space to place antennas.

Just before I passed the Advanced Amateur License exam, I built what I considered my best and "most forgiving" antenna--a full-wavelength 40-meter loop.  The loop displayed some gain over a dipole at the same height, needed only one tall support, and didn't require a ground radial system to operate efficiently.  Using balanced feed line, a 4:1 current balun, and a Drake MN-4 transmatch, I could cover 40, 20, 15, and 10 meters with one antenna.  Later on, when 30 meters became available to amateur radio operators, I used a MFJ-941-E Versa Tuner II and my spare ri…

Simple Ham Radio Antennas: Time to head for the radio basement? Post #270

Image
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 appropria…

Simple Ham Radio Antennas: The Ghost of Antennas Past--the simple vertical. Post #269

Image
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 system.

To f…