Posts

Showing posts from July, 2013

Hawaii Island Hams help during tropical storm warning. Post #217

Today at 1700 hours local time, The National Weather Service downgraded Tropical Storm "Flossie" to a tropical depression.  The weakened storm swept over Hawaii Island, leaving heavy showers, gusty winds, high surf, and power interruptions in its wake. Thankfully, no one was injured.  Damage from the storm was minimal.

During the warning period, members of the Big Island Amateur Radio Club stood by to help at Hawaii County Civil Defense, the Hilo Medical Center, and at various American Red Cross stations across the island.

The Hilo International Airport reported winds between 30-35 knots early this afternoon (Monday) with rainfall gauges registering 2 to 4 inches (5.08 to 10.16 cm) of rain.  The situation could have been a lot worse, with early forecasts predicting up to 10 inches (25.4 cm) or more of rain by this evening.

The remaining portions of "Flossie" will move past West Maui, Molokai, Honolulu (on Oahu), and Kauai later this evening.  Rainfall is expected …

A 40-Meter Inverted L Antenna. Post #216

During the past few weeks, I've been experimenting with the versatile inverted L antenna for my small house lot.  I find the antenna simple, inexpensive, and easily concealed.

An inverted L is a bent quarter-wave Marconi vertical fed against a system of surface, buried, or elevated radials.  The vertical segment should be as high as possible, with the remaining length running horizontal to a nearby tie off point.  Coaxial feed line can be used for monoband operation or 450-ohm ladder line can be employed if multiband use is planned.

MATERIALS:

Two vertical structures to support the antenna--one for the vertical segment and the other to tie off the horizontal wire running from the top of the mast.  I had a homemade 20-foot/6.09 meters pvc mast under the house and a convenient Norfolk Pine Tree at the edge of my property to support the horizontal portion of the antenna.

Sixty-six feet/20.12 meters of #14 AWG house wire for the radial system and the antenna element.

Three, 6-foot/1.…

A Multiband "Lazy L" antenna. Post #215

One of my favorite antenna guides is a book by the late Doug DeMaw (W1FB) titled the "Novice Antenna Notebook."  Although it is a slim volume, it contains most of the facts, construction principles, and modifications needed to erect simple, inexpensive, and effective antennas.

I bought the book 25 years ago while I was mentoring (elmering) a newly licensed ham in my neighborhood.  Since I'm not a technical genius, I decided to consult a basic antenna primer that could be used by the new licensee as well as myself.  I wasn't disappointed.  DeMaw's writing is down to earth, clear, and largely without complicated formulas for the beginning ham.  I still have this wonderfully simple volume squeezed in between other antenna tomes, including the ARRL Antenna Book, the ARRL Handbook, and various RSGB publications.

What prompted me to consult DeMaw this late in my amateur radio "career" (I was licensed as a novice back in 1977), was the need to erect a simple …

Ten Basic Antenna Truths. Post #214

Sometimes knowledge comes from the strangest places.  Take today, for instance.

While my van was having a routine maintenance check at my local Honda dealer (I have an Odyssey van), I ran into an Dean Manley (KH6B), one of my oldest friends and former station engineer at Hilo radio station, KHLO-AM.  I worked at this station from 1976 to 2011.  We discussed a variety of antenna ideas, including improving the homebrewed antennas we use at our stations.  I consider Dean an expert in this area.  He has spent many years building and upgrading antenna systems for  AM and FM stations, both commercial and nonprofit.

Anyway, we spent a good half-hour discussing some ideas, including his current project--a 40-meter vertical beam which Dean uses for the Hawaii Afternoon Net.  Before we parted, he gave me a copy of a handout he made for members of the Hilo Amateur Radio Club.  The one-sheet article, entitled "HF Antennas 101" by Van Field (W2OQI), appeared in the September 2004 issue …

A 3/2 wavelength sloping dipole for 20 meters. Post #213.

One of the easiest and least expensive antennas for the amateur radio operator is the sloping dipole or "sloper."  Ed Noll (W3FQJ) defines the sloper as "a slanted half-wave antenna with one end of the antenna attached to (a) mast top and other end near to ground level."  According to Noll, the sloper shows "a modest directivity in the direction of its slope and considerably less signal pickup from its rear."  A well-designed half-wave sloping dipole can fit in a small city lot using a mast between 20 to 30 feet (6.09 to 9.23 meters), two dipole elements cut to your preferred frequency, a few insulators, a couple of tie-down stakes, and sufficient 50/72 ohm coaxial cable to reach your shack.  Multiband operation is possible using 450 ohm ladder line, a 4:1 balun, and an antenna transmatch.

Since most of my ladder line was being used for other antenna projects, I decided to use 50 feet (15.24 meters) of RG-8X coaxial cable with UHF connectors for my feed …

My favorite stealth antenna. Post #212

Amateur radio operators who live in deed restricted homes and apartments face a variety of antenna problems.  The amateur radio press is full of stories describing the "no outdoor" antenna rules of OHAs and CC&Rs.

Despite these reports, many amateurs have been able to build effective indoor and outdoor antennas to pursue their radio interests. From flagpole antennas to attic beams, hams have used creativity and "stealth" to get and stay on the air.

In my case, the adoption of "stealth" antennas was forced on me by natural circumstances and not necessarily by highly critical neighbors.  In fact, my neighbors are good people who tolerate my amateur radio pursuits as long as I don't ruin their television reception or interfere with their entertainment systems.  Although many people in my neighborhood get excellent television via cable television providers, my immediate neighbors get their tv programming over the air using the familiar deep fringe an…

An 80-Meter Vertical Helix

Like many amateur radio operators, I live on a small lot surrounded by neighbors, utility lines, and civic-minded citizens concerned about the "attractiveness" of my community.  Whether by design or outright fear, I've adopted the "stealth" approach to ham radio antennas.  It's the old "out of sight, out of mind" idea applied to amateur radio antennas.

The amateur radio press is full of articles describing the struggle of amateur radio operators to pursue their hobby under the burdensome regulations of CC & Rs, HOAs, and other civic minded citizens who object to antenna farms.  So far, my modest verticals, loops, and inverted vees have blended well with the vegetation and trees bordering my small backyard.  Vertical antennas have always been a problem because of the limited space for a radial system.  There are times, however, where a shortened vertical for the lower HF bands (such as 80/75 meters) is necessary where horizontal space is lacki…

A modified 20 meter extended double zepp antenna. Post #210

How would you like to boost your 20 meter signal by 3 dB with only 84.5 feet/25.76 meters of wire, two supporting masts, some 450-ohm ladder line, ordinary 50-ohm coaxial cable, and a few miscellaneous parts?

Today, I ran across a fascinating article by Paul E. Fuller (N8ITF), who designed a simple data sheet to help you build what is called "an extended double zepp antenna."  The double extended zepp is a dipole type of antenna consisting of two collinear 0.64 wavelength elements fed in phase, providing approximately 3 dB gain over a dipole on its intended frequency.  By following Fuller's advice, you can build an antenna that will give you some gain and more DX in the process.

Although my backyard is a bit cramped, there are numerous tall Norfolk Pine trees in an adjacent lot which could serve as a temporary support system for the 20 meter extended double zepp antenna.

With Fuller's article in mind, plus a few other ideas from several amateur radio operators, I se…

A simple 80 meter inverted "L" antenna. Post #209

Because my back yard is rather small, I haven't been able to erect a decent 80 meter dipole antenna.  In the past, I've used an inverted vee with elements measuring 67 feet/20.42 meters on a side.  Although the antenna worked reasonably well, it barely fit in back of my house and was clearly visible to my neighbors.  Another approach was needed.

I decided to build an inverted "L" antenna, since I had some room to go up (vertical) and some room to go horizontal (flat top segment).  If I used a lightweight wire (#20 or #22 gauge wire) and placed a mast among some trees bordering my lot, I could have a working 80 meter antenna with some degree of stealth.

An inverted "L" is a form of bent vertical, with the vertical section running up a mast for 1/8 wavelength (or more, if possible) and a horizontal wire running for 1/8 wavelength from the top of the mast.  Like all verticals, I would need a ground radial system to maximize efficiency and cut losses.

Althoug…

Antenna Topics: A simple 30 meter vertical antenna

Every now and then I feel the need to get away from the crowded amateur radio bands and just relax with an easy-paced conversation on 30 meters.  The band, which stretches from 10.1 MHz to 10.150 MHz, is quite narrow and is restricted to cw and data transmissions.

The pace of communications is generally more relaxed on 30 meters than in any other amateur radio band.  And since I need more practice in cw, this band is perfect for sharpening my skills.  Along the way I also meet some interesting and helpful people.

In order to use 30 meters, I have to change rigs.  My old Swan 100 MX, Yaesu FT-7, and Kenwood TS-520 don't cover this band, so I rely on another excellent transceiver--the Ten Tec Argosy II.  This rig can run up to 50 watts output, but I prefer the 5 watt setting for most of my cw work.  I can run the Argosy II off my solar charged deep cycle marine battery all day without depleting the battery.

Although I could use my 40-10 meter inverted vee fed by 450-ohm ladder li…

Antenna Topics: Disconnecting equipment for safety. Post # 207

Like many regions of the northern hemisphere summer has come to Hawaii Island.  Although this tropic paradise is known for its gentle climate, there are occasions where severe thunderstorms and lightning plague Hawaiian hams just like our fellow amateur radio operators on the U.S. Mainland.  Every now and then, a small sea-spawned tornado (waterspout) comes ashore in Kailua-Kona and does some minor damage to beach areas.  Most of these unwanted guests arrive on the strong winds of a frontal passage which begins north of Kauai and runs down the island chain to Hawaii Island.  While most of these severe storms occur during the winter months, it's not unusual for a bad thunderstorm to strike in mid-summer and cause damage to utility poles, transformers, and other electrical equipment.

Now that I'm mostly retired, I tend to stay at home and can keep watch on the weather. With adequate warning, I can safely disconnect  my antennas and get my rigs out of danger before any storm str…