Showing posts from December, 2013

Simple Ham Radio Antennas--Antenna Resolutions for the New Year. Post #251

The Year 2013 has been an exciting and challenging year for amateur radio operators worldwide.  From earthquakes to tornadoes and from typhoons to floods, the amateur radio community has rendered valuable aid to those in distress.  A special thank you to the "hams" in India and the Philippines who struggled to maintain communications with officials and aid agencies, often without rest and relief.  You have served in the highest tradition of the amateur service.  I also commend my fellow amateurs who kept emergency frequencies free for health and welfare traffic.  I am proud of all of you.  Yes, this past year has been far from dull. With this in mind, I decided to review my own year in amateur radio to see where I could improve my commitment to my community, maintain a safe, efficient station, and pursue my antenna interests with a minimum of cost.  So, I started making a list of things accomplished and areas where I could do better. Perhaps my introspective analysis wil

Simple Ham Radio Antennas--going stealth mode. Post #250.

For most of my 36 years as an amateur radio operator, I've had to operate under the limitations imposed by HOAs, CC&Rs, and postage stamp sized backyards.  Like many of you, my creativity was sorely tested  as I tried to get reasonably efficient antennas erected for my home station.  In many cases, one antenna had to suffice for multiband operation.  And that antenna had to be inconspicuous, easy to erect and take down, and not present an "eyesore" to the neighbors. Over the course of those years, I managed to enjoy ham radio despite the highly compromised antennas and low power employed at the shack.  There were a few multiband designs which proved successful for local and occasional DX.  Among them were inverted vees and 1/2 wavelength horizontal dipoles fed by 450 ohm ladder line connected to a 4:1 balun and a Drake MN-4 antenna transmatch.  When I did have a bit more space, I used full wavelength loops fed by ladder line for 20, 15, and 10 meters.  Height abo

Simple Ham Radio Antennas: A multiband Inverted-V Antenna. Post #249

One of the most popular amateur radio antennas is the Inverted-V.  This antenna is a first cousin to the half wavelength horizontal dipole whose antenna elements are drooped down so that the included angle between them is between 90 and 120 degrees.  According to William I. Orr (W6SAI) and Stuart D. Cowan (W2LX), the "bandwidth is somewhat lower than for a conventional dipole...Because the wires of the Inverted-V do not lie along one axis, the physical length is somewhat longer than that of a dipole cut for the same frequency."  For general design purposes and allowing for some trimming of antenna elements, you can use the general dipole formula, 468/f (MHz)=L (feet) to compute the total length of the Inverted-V dipole.  Some antenna experts believe the drooping halves of the Inverted-V change the resonant frequency, and, therefore, recommend a slightly different formula be used to calculate the length, such as 464/f (MHz)=L (feet).  I use the 468/f (MHz)=L (feet) formula to

Simple Ham Radio Antennas: A double extended "zep" for 10 meters. Post #248.

From what I've been hearing today (Saturday, 14 December 2013), amateur radio operators are having a good time on the ARRL 10 meter contest.  Although propagation has been variable on Hawaii Island, the band seemed alive with signals.  Ten meters, like its distant cousins at 160 meters and 6 meters, offers plenty of challenges for amateurs new and old.  When propagation is favorable, both local and DX signals are possible with low power and modest antennas that can fit into a small backyard. Ten meter events are scheduled throughout the year, sponsored by the ARRL, various national amateur radio groups, and the Ten-Ten group, which promotes the use of 10 meters. Antennas for 10 meters run the gamut from multi-element beams and ground planes to dipoles and full wavelength loops.  Even though the current ARRL 10 meter contest is coming to an end, it's not to early  to think about ways to improve the signal from your 10 meter antenna. If you want some gain over a dipol

Simple Ham Radio Antennas--a multiband indoor loop antenna. Post 247

Over the past few posts I've been recounting the joys of erecting antennas with no space restrictions.  On my new property in the Puna District of Hawaii Island, I have an acre of land with few close neighbors and a comfortable distance from the Keaau to Pahoa Highway and all of the power lines following that road. However, for most of my 36 years as an amateur radio operator, I've had to erect compromise antennas because of space limitations, proximity to high voltage power lines, and the eyes of suspicious neighbors.  Most of these antennas worked very well, considering the space restrictions of my rental housing.  One thing I did discover is just how good a basic 1/2 wave length horizontal dipole or inverted v performs when you use a moderate length mast (33 ft/10.06 meters) coupled with 450 ohm feed line, a 4:1 balun, and a decent transmatch.  This combination gives you multiband capability with the design frequency being the lowest band you wish to use. I've also