Posts

A 30 Meter Sloping Dipole Antenna. Post #236

The 30 Meter Amateur Radio band (10.100 MHz to 10.150 MHz) is territory for the cw and digital enthusiast.  You can find cw operators around 10.105 MHz and many Japanese hams clustering around 10.130 MHz.  In between, you'll find RTTY, PSK 31, FAX, and other digital modes.  If you're a cw operator, 30 Meters can be the place to make new friendships at a leisurely pace while increasing your sending and receiving skills. Antennas for this tiny sliver of the rf spectrum are modest and inexpensive to build with many materials obtainable from the nearest home improvement outlet or hardware store. Over the past few weeks, I've built several 30 Meter antennas for my new house lot in the Puna District, including an inverted vee, a ground plane, a delta loop, and even an inverted "L".  All have worked well. The latest addition to my growing antenna farm is a 30 Meter halfwavelength sloping dipole.  This variation of the basic horizontal, halfwavelength flat top dipo

A modified 30 Meter Ground Plane Antenna. Post #235.

This week, I'm exploring the joys of 30 meters and the antennas that support this intriguing amateur radio band. Last week, I built a simple 30 meter inverted vee antenna which continues to deliver outstanding performance. Today, I decided to try a 30 meter ground plane antenna, consisting of a main vertical element and four sloping radials.  Many antenna experts believe that sloping the radial elements by 45 degrees will produce a better match for 50 ohm coaxial cable feed lines. Although my sloping radials don't come off the connector at 45 degrees,  they do seem to produce a usable match for my RG-8X feedline.  Any mismatch is corrected by my standby antenna transmatch--an old MFJ-941 E Versa Tuner. According to "searchmobilecomputing.tectarget.com", a ground plane "is a variant of the dipole antenna designed for use with an unbalanced feed line such as coaxial cable.  It resembles a coaxial antenna whose lower section consists of straight elements call

A 30 Meter Inverted Vee Antenna. Post #234

The Thirty meter amateur radio band extends from 10.100 MHz to 10.150 MHz.  This sliver of the rf spectrum offers plenty of space for the die-hard cw fan as well as plenty of contacts for those into the various digital modes.  The operators who populate this band are generally friendly and willing to help out those unsure of the digital frontier.  You'll find plenty of action with PSK31 and RTTY as well.  Antennas for this band are simple and inexpensive.  While thirty meters is a good night time DX band, there are some interesting day time opportunities as well, especially towards sunset.  Besides, a few hours on thirty meters will give you some new contacts and an opportunity to improve your cw speed. So, let's build a simple antenna for this band.  I built an inverted vee for thirty meters last weekend after I finished clearing some brush from my new home site in the Puna District.  I chose the inverted vee option because I had a spare fiberglass mast in my garage and did

The K3MT "Grasswire Antenna". Post #233

How would you like to use what I call the "ultimate stealth antenna" at your deed-restricted location?  While I was doing some research for antennas at my new home location in the Puna District of Hawaii Island, I came across a fascinating article by Mike Toia (K3MT).  Over 20 years ago, Mike designed, built, and used something called the "grasswire antenna" which would serve as a  nearly invisible, yet effective antenna while he traveled from his various jobs.  Although the antenna appears to be a lossy dummy load on steroids, the data revealed by Mike show that this unusual antenna does work--not as well a dipole or a yagi, but it does get contacts in difficult operating situations. The antenna is ridiculously simple to build and use.  Mike says his design "is an end-fed, longwire antenna that is laid right in the grass."  This would be perfect for those amateurs that have restrictive HOAs and CC&Rs prohibiting outdoor antennas. Mike's origi

A simple, portable 40-10 meter vertical antenna with counterpoise. Post #232

How would you like to build a 40-10 meter vertical antenna that could be used in portable or emergency situations?  For the relatively low cost of some housewire, a length of 450-ohm ladder line, some clip leads, a few insulators, a 4:1 balun, a small length of coaxial cable, and an antenna transmatch, you could have a simple multiband antenna that will give you hours of fun on your next mini DXpedition to the nearest public park or in your own back yard.  With a  QRP rig, a deep cycle marine battery, and a few solar panels, you can enjoy a few carefree hours without increasing your electric bill. I have such a station placed in my Odyssey van.  I can operate when the mood strikes me or when a local emergency is declared.  During the quarterly break from my teaching duties, I decided to unpack my portable station and give it a brief "shakedown cruise" at my new homesite in the Puna District of Hawaii Island. I wanted to relax a bit after a day's work of clearing t

A radiating dummy load antenna, part 2. Post #231

In my last post, I recounted a conversation I had with Dean Manley (KH6B) on Monday, 30 September 2013 concerning the use of "dummy loads" as emergency antennas.  The conversation centered around Hank Scharfe's (W6SKC/7) attempt to get some power into his 150-ft (45.73 meters) grounded inverted "L" antenna following the failure of his automatic antenna tuner.  Hank was successful in meeting his scheduled nets when he used his Waters dummy load with a "T" UHF connector to feed some rf to his antenna.  Although most of his power was confined to the dummy load, there was sufficient power delivered to his antenna to complete his schedules. Dean and I have made several such antennas for field day and portable operations.  In fact, I mentioned my own experience with a dummy load antenna back in September 2012 when I was a newly licensed novice operator.  That contact surprised me, and that experience has kept me interested in radiating dummy loads ever si

The radiating dummy load. Post #230

On Monday, 30 September 2013, I had the day off from my substitute teaching assignment and I decided to meet with some of my amateur radio friends at the Hilo, Hawaii Jack In The Box Restaurant for informal discussions concerning amateur radio.  The Hawaii QRP Club holds daily meetings at the popular fast food restaurant around 0800 W.  Most of the time, the meetings are concerned with the usual topics of rigs, DX, antennas, and the latest HOA restrictions on ham operators.  Monday's meeting was going to be different. By the time I arrived at 0800 W, most of the group had departed for their jobs and other concerns, leaving only myself, my xyl, and informal club president Dean Manley (KH6B) left to "hold the fort."  Several times in the past I had lamented my fate in using compromise antennas in the various homes I rented while I was fully employed as a news announcer for KKGB-FM and KHLO-AM in Hilo.  Now that I was building a new home on a larger property, I had more s

The W3EDP antenna revisited. Post #229

I'm always looking for interesting antennas to build for my expanding antenna "farm" at my new house lot in the Puna District of Hawaii Island.  Unlike my present location, the new lot has an acre of space to design, build, and locate new antennas.  So, when I take a break from clearing the land of brush and scrub trees, I have time to explore antennas for my modest station. A few days ago, I ran across an interesting article by William McFadden (WD8RIF) on his "Field Deployable Field Antennas" website.  McFadden wrote about an old classic half-wave length antenna called the W3EDP, a variation of the "Zepp" antennas that were popular in the 1930s.  The original W3EDP article can be found in the March 1936 edition of "QST".  If you're a member of the ARRL, you can access the archives and read about this fascinating antenna. According to McFadden, the W3EDP antenna is a "Zepp" consisting of a radiator 85 feet/25.91 meters and

Two Amateur Radio Icons remembered. Post #228

This week, the Amateur Radio Community lost two of its most illustrious pioneers. On Friday, 13 September 2013, Wayne S. Green II, W2NSD ("never say die") passed away at age 91 at his New Hampshire home.  Green was editor of "CQ Magzine" for 5 years, founded "73 Magazine", which ran until 2003, and published some of the early computer magazines, including "Byte". Green was an occasional guest on Art Bell's (W6OBB) "Coast to Coast AM" overnight talk show.  Green expounded on many topics, including amateur radio, AIDS, cancer, and cold fusion.  Although he was a constant critic of the American Radio Relay League (ARRL), he maintained his membership in the organization, urging the national organization for amateur radio to explore new technologies and include more construction projects in its publications. Wayne was frequently witty, sarcastic, and funny.  Wayne, who was often called a gadfly and an irritant,was one of the early

A 10-Meter Half Square Antenna. Post #227

Over the past few weeks, I've been able to erect several antennas on my wife's property in the Puna District of Hawaii Island.  We are remodeling a small home on an acre of land, so there is plenty of space to plant the "antenna farm." All of my antennas are wire antennas, since I'm at the age where building and climbing towers is out of the question.  I did enough tower climbing when I worked at a commercial broadcast station.  So, my antennas were made of locally procured pvc pipe, #14 AWG housewire, spare coaxial cable and 450-ohm ladder line, homebrew insulators, and few Budwig center coax connectors from Fair Radio Sales. Fortunately, there are several tall trees on our property that can serve as antenna supports. To date, my antenna farm consists of an 80-10 meter flat top horizontal dipole (a doublet with two equal segments of 67 feet/20.42 meters).  The dipole is stretched between two Norfolk Pine trees, 50 feet/15.24 meters above ground.  The anten

In Praise of Wire Antennas. Post #226

Every now and then it's good to stand back and analyze what you've done to your antenna farm.  Is your antenna arrangement fitting your goals? How easy is it to build and maintain the structures that connect you to the world?  Is there a way to make your antenna more efficient without spending a lot of money?  I came to such a crossroads this weekend as I surveyed the rural Puna District home my wife and I are remodeling for our permanent home. After years of living in rental apartments and homes with restrictive covenants, I will at last have an acre of land to build some full sized hf antennas.  I will admit that I've learned a lot about stealth antennas and low power operation during my 36 years as an amateur radio operator.  But now, I have some real space to build antennas with real gain. My main problem was deciding whether to buy a tower, a set of mono band beams, and sophisticated antenna rotating equipment or to stick with my faithful wire antennas which have

An Enhanced 40 meter full wavelength loop. Post #225

When I was first licensed as a novice in 1977, I tried all kinds of antennas.  In the space of a year, I must have built and used 10 or more antennas, including verticals, loops, inverted vees, slopers, and half wavelength horizontal dipoles.  I've always been fascinated with full wavelength loops, but, because of limited space, I rarely built loops except for 15 and 10 meters.  I relied heavily on the standard 1/4 wavelength verticals with ground radials and the inverted vee. Now that my xyl and I are remodeling our future home in the Puna District, I had a chance to build a full wavelength 40 meter loop without worrying about nosey neighbors or lack of space.  Our lot is one acre, giving me plenty of space to experiment with a variety of antennas. Over the past few weeks, I've  built and used a half wavelength horizontal dipole and a half square antenna for 20 meters with outstanding results.  Now it was time to rethink the loop I built 36 years ago as a novice operator.

A 5/8 wavelength vertical for 10 meters. Post #224

How would you like to build a 10 meter vertical with some gain and a lower radiation angle than the usual quarterwave vertical?  You can realize this goal by building and using a 5/8 wavelength vertical antenna on the popular 10 meter amateur radio band. If you use 50-ohm coaxial cable as your feed line, you'll need a matching device at the base of the antenna to make the antenna work correctly.  However, you can simplify the matching problem by using 450-ohm ladder line, a 4:1 balun, and a short piece of 50-ohm coaxial cable connected to the antenna terminal of your antenna transmatch.  The 5/8 wavelength vertical also requires a ground radial system to realize its full potential.  The radial system needn't be an extensive affair buried in the ground.  I used six elevated 5/8 wavelength radials for my antenna.  Thanks to the ladder line, the 5/8 wavelength vertical also is usable on 20 and 15 meters. Faced with a more complicated construction project than the usual quarte

The Bent Dipole or Inverted "U" antenna. Post #223

Have you ever wanted to erect a full half wave dipole antenna for your favorite amateur radio band, but just didn't have enough horizontal space to put the antenna?  This could be a problem for 80 and 40 meter dipoles, which can stretch out to 135 feet/41.15 meters (80 meters) and to 67 feet/20.42 meters (40 meters). According to an article by Claude Jollet (VE2DPE), most of the rf radiated and received by a dipole is concentrated "in the middle 60% or so of the antenna...the ends can be dropped down from the horizontal without much adverse effect." That was great news to me, since my back yard has a maximum length of 50 feet/15.24 meters bordering the rear of my house.  So, if I bent the horizontal dipole at the 60% part of the flat top and let the remaining length hang down well above ground, I should still retain most of the dipoles good qualities. I decided to erect a quickly built bent or inverted "U" dipole to see what results I could get. MATERIA

A Full Wavelength Loop for 40 through 10 Meters. Post #222

Having built a series of verticals, inverted vees, half squares, and loops for my amateur radio activities, I decided to "thin the heard" of my less than successful antenna efforts and concentrate on a few antennas that have given me the most contacts and overall satisfaction. Although I love the ease of assembly and portability of homebrew vertical antennas, I just don't enjoy the labor involved in putting in a ground radial system.  The elevated counterpoise systems I've used have been less labor intensive than the buried radial approach, but, still, there is a lot of wire running around my property which is a safety hazard for children and pets. The inverted vee antennas are being kept for portable and emergency use.  I have a few telescoping fiberglass masts which make raising these antennas an easy task. Since I lack the space to erect a 80-Meter horizontal 1/2 wavelength flat top dipole (the familiar "doublet" antenna), I have put that antenna o

A 15-Meter Half Square Antenna. Post #221

Now that my 20-Meter half square antenna is performing well, it's time to build its companion for 15-Meters. The half square antenna is a basic 2-element wire array using two 1/4 wavelength vertical elements connected at the top by a horizontal 1/2 wavelength phasing line.  The antenna is fed in phase and shows bidirectionality, modest gain, and some immunity from noise on its sides.  A ground radial system isn't required. By feeding the half square in one of the upper corners, we find the current maximum and a fairly good match to 50-ohm coaxial cable. MATERIALS: Since my two MFJ fiberglass masts were already being used by the 20-Meter half square antenna, I decided to make two new masts out of those 4-foot/1.21 meters surplus military fiberglass poles you see advertised in the Amateur Radio magazines.  I had enough mast sections to make two, 20-foot/6.09 meters masts. Two 7-foot/2.13 meters wooden support stakes for the masts. Number 14 AWG housewire to make the

A simple 20-Meter half square antenna. Post #220.

I thoroughly enjoyed my first half square antenna during this past weekend.  Built for 40-meters, the easily assembled antenna exhibited a bidirectional pattern, offered some gain, required no ground system, and was fairly immune to noise and qrm from the sides.  I disassembled the antenna on Monday and stored it for future use. Now, I wanted to build a similar antenna for 20-Meters, one of my favorite DX bands.  I generally followed the pattern of the earlier half square with a few modifications. In general terms, the half square antenna is a basic 2-element wire array fed in phase using two 1/4 wavelength verticals connected by a 1/2 wavelength horizontal phasing line running from the top of each vertical element.  According to Rudy Stevens (N6LF), "the theoretical gain over a single vertical is 3.8dBi."  The half square is fed at the top of one of the verticals, where the current is at a maximum.  This arrangement is a good match for a 50-ohm coaxial feed line. Alth