2012 in review


The WordPress.com stats helper monkeys prepared a 2012 annual report for this blog.

Here’s an excerpt:

The new Boeing 787 Dreamliner can carry about 250 passengers. This blog was viewed about 1,500 times in 2012. If it were a Dreamliner, it would take about 6 trips to carry that many people.

Click here to see the complete report.

Simple Ham Radio Antennas–a vertical antenna for 15-meters, post #254


A VERTICAL ANTENNA FOR 15-METERS

 

Now that the New Year is here, why not start the year right by building a simple vertical antenna for 15-meters?  The materials are inexpensive and can be found at the nearest hardware or home improvement store.  If you’re a rf “packrat” like me, most of the antenna is probably stored in your “junk” box.

The 15- and 10-meter bands are some of my favorite hangouts.  When propagation is favorable, dx from my dry spot in the Central Pacific can be exciting.  My qth is located along the Hamakua Coast of Hawaii Island, just about 2,100 miles south west of Los Angeles.  There’s nothing but ocean between my shack and the bright lights of Hollywood and the entire West Coast of the mainland U.S.  Propagation to the northwest and most of northern Asia is a bit hampered by the presence of 13,000-foot Mauna Kea, but not terribly so.  I get plenty of contacts from Japan, Korea, and Asiatic Russia with the simple vertical described below.

MATERIALS REQUIRED:

A 100-foot spool of antenna wire.  Although I prefer #14 AWG household wire or a similar gauge of Copperweld wire, all I had on hand yesterday (Saturday) were several spools of #20 AWG hookup wire.  Since the antenna was going to be only a temporary arrangement, I could get by with what I had in the storage room.

50-feet of coaxial cable.  You can use either 50-ohm coax (RG-58, RG-8, RG-8X) or 75-ohm coax (such as RG-6).  I happened to have some RG-6 from an old studio installation at my former employer (Pacific Radio Group–Hawaii Island).  Earlier, I used two “F” to “UHF” adapters to make the cable usable for my station.  The trusty Drake tuner (MN-4) would take care of the small mismatch present in the antenna system.

A Budwig center coax connector.  The + side would be connected to the vertical element, while the – side would be connected to the elevated radials (4).

A mast of suitable height.  I used a spare MFJ fiberglass mast for the antenna support.   My mast was 33′ tall (approximately 10.01 meters).

A tuner to manage the small mismatch present in the system.

Four insulators and four posts to tie off the elevated radials.

An antenna grounding system to bleed off static electricity and provide some protection from lightning.  Integrated ground and static discharge systems for antennas can be found in the 2012 Fall/Winter AES catalog.

A sturdy post to mount the fiberglass or pvc mast.

Dacron rope to tie off the elevated radials.  The elevated radials can be used to guy the antenna.

BUILDING PROCESS:

I assembled the antenna on the ground.  I measured out and cut the vertical element to a length of 11′ 1″ (3.38 meters). I measured out and cut the radial elements to a length of 11′ 4″ (3.45 meters).  According to Ed Noll, W3FQJ, these lengths would make the antenna resonant at 21.150 MHz.

I attached the vertical element and the radials to the Budwig center connector.  Each connection was soldered, coated with clear fingernail polish, and sealed with vinyl electrical tape.

Dacron rope was fastened to each end insulator of the elevated radials.  The tie offs would be made after I lifted the antenna onto its support stake.

The vertical element was fastened to the fiberglass mast with nylon ties.  The bottom of the vertical element was attached to the mast at mid-point, approximately 16′ or around 5 meters above ground level.

I attached the feed line to the UHF connector on the Budwig center coax connector.

I raised the mast and positioned it on a support stake.

I tied off the four elevated radials to prepositioned ground stakes.

I attached the coax to the static discharge/ground system below the window of the shack and connected the discharge unit to my antenna tuner with a small length of RG-6 coax.

SOME PRELIMINARY RESULTS

Although I’ve had the 15-meter vertical up and running for only two days, results have been encouraging.  Fifteen meters is quite active between 1100-1600 hours local time (2100-0200 UTC).  Most of my contacts have been with the continental U.S. with CW reports ranging from 559 to 579 and SSB reports holding between 54 and 56.  Not too bad for 10 watts.  I’ll leave this “skyhook” up for a few weeks to see if propagation improves.

Total cost for this project:  $0.00.  I had all of the materials in the storage room, so a trip to my local hardware store in Hilo (30 miles) wasn’t necessary.  Besides, the weather was sunny and I enjoyed the time outdoors.  Listed below are some references that may prove useful in your next “homebrew” vertical antenna effort.

REFERENCES:

Edward M. Noll, W3FQJ.  Easy-Up Antennas for Radio Listeners and Hams.  Limited Edition, 1991.  MFJ Enterprises, Inc. p. 110.

“How to Build an Antenna”.  http://www.ehow.com/how_4617340_build-antenna.htm.

W5ALT.  Indoor Vertical Antenna.  http://www.comporto.com/~w5alt/antennas/index.php?pg=3.

Have a safe and prosperous New Year!

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Until next time,

Aloha es 73 de Russ, KH6JRM–BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.

 

Simple Ham Radio Antennas–the antenna packrat, post #253


THE ANTENNA PACKRAT

I admit it.  I’m an antenna packrat.  If something looks useful for an antenna project, I get it.  That includes packages of nuts and bolts, discarded wire of various types from yard sales, cable installations, and the “public take it” table from the local trash transfer station.  Once I get these “treasures” back to the shack, I catalog and store them in plastic storage bins for future use.

Over the past year, I’ve accumulated the following:

Various lengths of RG-6 coaxial cable  from  local cable installs.  Most of this coax is under 10 feet–perfect for making patch cords.  I’ve also been able to get longer lengths of RG-6 coax from my former employer (Pacific Radio Group) when there’s been a studio rebuild.  With appropriate “F” to “UHF” adapters, this cable is suitable for feed lines or matching sections.  Although RG-6 has a nominal impedance of 75 ohms, a decent antenna matching unit (i.e. tuner) should be able to handle the small mismatches found in a dipole or vertical antenna.  Cost:  $0.00.

Various lengths of #14 AWG household wire from local contractors.  This wire is useful for dipoles, verticals, and loops.  I’ve even made my own “ladder” line from this stuff.  Cost:  $0.00.  I just ask for the stuff.  If I get a “no” to my request, so what.

A good stock of small schedule 40 pvc pipe (under 2 feet in length) in diameters ranging from 1.5 to 2.5 inches.  These pvc leftovers from household or building projects can be used as coil winding forms or end/center insulators for antennas.  Cost:  $0.00.

Various lengths of hookup and speaker wire (#18 AWG to #22 AWG).  When one of the local hardware or home improvement outlets has a sale, I can usually get this type of wire at a reduced price.  This wire can be used for radials or tuned counterpoises in your vertical antenna system.  With care, this light gauge wire can be used as antenna elements if they are tied or taped to a fiberglass or pvc mast.  I carry several spools of light gauge wire in my “go kit” for emergency antennas.  Cost:  varies, but I can usually get several 100-foot spools for under $20.

There are times when going “commercial” saves both time and money.  Although I prefer finding my own antenna wire from local sources, I have a small stock of Davis RF “Poly-STEALTH” high strength antenna wire for antennas designed for permanent use.  This “Copperweld” wire is a little hard to handle because of its “springiness”, but it’s remarkably tough and seems to resist environmental damage for years.   At my qth, light gauge wire is prone to failure after a few months exposure to heavy rain, wind, salt air, and vog (volcanic haze).  This copper coated steel wire is available in a variety of AWG sizes (13, 14, 16, 18, and 26).  In the AES Fall/Winter 2012 Catalog, a 100-foot spool of #14 AWG is priced at $19.99 (page 77).

For emergency antenna use, I’ve assembled an emergency 30-foot mast made from 5-foot sections of schedule 40 pvc pipe.  The pipe sections and joints were bought at a local Ace Hardware Store.  Cost will vary depending on your location.

And finally, what do you do with coaxial cable which has outlived its usefulness as a feedline?  Unless the cable is thoroughly chewed by rodents, at least some of the cable can be added to your vertical antenns’s radial system.  In the past, I’ve cut off the outer insulation, saved the copper braid for grounding applications, and used the solid center wire for receiving antennas or as radial/counterpoise wires.

As 2012 ends, I find myself adequately stocked with spare parts, wire, and mast materials.  Most of my “stash” has come from materials found locally.  I’m a frequent visitor to my local hardware or home improvement store.  I also keep an eye out for moving and garage sales.  You never know what will turn up at these events.  Become good friends with your cable or telephone installer.  You may be able to pick up lengths of new coaxial cable at no or little cost.

In the end, I’m still a packrat.  Every six months, I inventory my collection of wire and parts to see if anything is “so far gone that I can’t use it anymore.”  That mentality extends to my vehicles, too.  Before I bought a new Honda van, my trusty 1996 Toyota Tercel racked up 268,000 miles before I sold it to one of the mechanics at my local service station.  The vehicle is now fitted with a surf rack and serves as transportation to the island’s hottest surfing spots.  Although I’m no electrical or mechanical genius, I try to keep my amateur radio equipment clean, covered, and responsibly used.  All of my equipment is on a maintenance schedule, even if its only to clean circuit board contacts, lube mechanical parts, and blow the dust out.

Although this attitude may seem extreme, it works for me.  I’ve been able to enjoy amateur radio at a modest cost.  Thanks to the internet and a small collection of antenna reference material, I’ve been able to build my own antennas, expand my knowledge, and meet some great people in the process.

I hope the holiday season is treating you well.  Be sure to spend some time with your family and closest friends.  These assets are priceless in a world that seems to be “going off the deep end.”  Remember this:  It could be worse.  We could be organized.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Until next time,

Aloha es 73 de Russ, KH6JRM–BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.

Simple Ham Radio Antennas–Antenna Sources, post #252


ANTENNA SOURCES OR ONE PERSON’S JUNK IS ANOTHER PERSON’S TREASURE

Generally, amateur radio antennas fall into two broad categories:

Commercially designed antennas which are marketed and sold through businesses specializing in electronics and communications.

Homebrewed, “roll your own”, and “do it yourself” (DIY) antennas built by amateur radio operators.  Some of these made at home antennas find their way to the commercial market and become the basis of small independent businesses.

Most of the amateur radio operators I know have used both types.  Same here.  Until recently, most of my antennas for mobile operations have been of the commercial variety.  At one time, I used a few commercially made G5RV antennas and verticals for my HF operations.  I have no complaints about the commercially made antennas.  They all worked well, considering my limited real estate.  If you feel uncomfortable about designing and building your own antennas, a commercially made “skyhook” will do the job for you.  This is important when it comes to erecting towers and using multi-element beams.

Now that I’m semi-retired and my income is limited, I’ve found it necessary to build most of my amateur equipment, including antennas.  Although I’ve built a few Heathkits and station accessories, I prefer my rigs to be commercially made.  The newer rigs are truly marvels of engineering.  They’re also expensive.  So, over the  past few years, I’ve put away a few bucks to buy a new rig while I continue to enjoy my near antique transceiver arrangement, including a Yaesu FT-7 (QRP), Ten-Tec Scout, Kenwood TS-520, and the venerable Swan 100 MX.  A new rig is on its way, but not at this time.

Other than making a few simple station accessories, most of my amateur radio “craftsmanship” focuses on designing, building, and using homebrewed wire antennas.  The process is fairly inexpensive, gets you outdoors for some exercise, and gives you the satisfaction of building something you can call your own.

THINGS NEEDED FOR HOMEBREWED ANTENNAS

1.  A good antenna library.  I’ve built up a good number of antenna volumes during my 37 years as an amateur radio operator.  A few posts back I listed a series of books, internet web sites, and magazine articles  which have proven useful in my antenna projects. There is always something new to learn.   If you are an ARRL member, you can access their archives for all kinds of antenna ideas.

2.  A source of wire for your antennas.  I’ve used all sorts of wire for antennas, including copperweld (copper plated steel wire), speaker wire,  #14 AWG house wire, hook up wire (#20 to #28 AWG), magnet wire (very thin stuff), and even aluminum foil.  A good source of antenna wire would be your nearest hardware or home improvement store (i.e. Home Depot).  A farm supply and garden store can be good source of stakes and poles.  Many hardware stores (i.e. Ace Hardware) sell a variety of pvc poles in various lengths and diameters.  It’s fairly easy to assemble a lightweight pvc or fiberglass mast.

3.  Moving or garage sales.  Sometimes your neighborhood garage sale will net you fixable electronics (radios, computers, printers, etc), old television antennas, and even coaxial cable and tv twinlead.  I’ve made a few 2-meter antennas from old, but serviceable aluminum from discarded television antennas.

4.  Discarded items from around your home.  Old pieces of pvc pipe and discarded prescription pill bottles can be used  for coil forms.  Large pieces of plastic can be used as center or end insulators for dipoles and inverted V antennas.  Old plastic food containers with lids can be used to store components and small parts such as screws, pins, tacks, alligator clips, and connectors.  Large bins made by Rubbermaid and other manufacturers can be used to store coaxial cable, wire, and spare equipment.  Old pillowcases and towels can be used to cover equipment and protect them from dust and dirt.

5.  Discarded coaxial cable from your cable company installer.  Sometimes, installers will give you several feet of perfectly good RG-6 coax after an installation.  It can’t hurt to ask.  During the past few months, I’ve been able to accumulate almost a 100 feet of good RG-6 from cable installs in my neighborhood.  Fitted with UHF adapters, the RG-6 will provide material for free patch cords and even antenna feed lines.  Eventhough RG-6 is nominally rated at 75-ohms, my Drake antenna tuner (MN-4) has no trouble taking care of the small mismatch when I attach the RG-6 to a dipole.  You can also use RG-6 for antenna matching sections.

6.  A PC, Mac, or Laptop computer to run a variety of amateur-related software, including antenna design programs.  This is my one concession to progress.  A home computer is invaluable for the antenna builder and makes your antenna research more efficient.  Besides, there are many amateur reflector sites on the internet that will give you valuable ideas and answer many of your antenna questions.

7.  An open, inquisitive mind.  Don’t be afraid to build and fail.  Some of my antenna projects were both ugly and inefficient.  With more research and practice, I found ways to improve my antennas even when I was met with housing and space restrictions.  I enjoy the process.  I still marvel how a small bundle of energy can span thousands of miles and reach the mind of another radio amateur.  Perhaps it’s all physics and propagation.  Yet, the experience of building something to reach others halfway around the world is truly wonderful–it’s magic in many ways.

There you have it.  The seven things you need to launch your antenna adventure.  If you research carefully and take advantage of the materials available in your neighborhood, you can design, build, and use an antenna you can call  your own.  The cost will be minimal and the experience priceless.

Have fun!

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Aloha es 73 de Russ, KH6JRM–BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.

Simple Ham Radio Antennas–a short indoor 40-meter dipole, post #251


A SHORT INDOOR 40-METER DIPOLE

Merry Christmas and Seasons Greetings from the rain-soaked Hamakua Coast of Hawaii Island!

My scheduled outdoor antenna maintenance day has fallen victim to strong northeast trade winds and heavy, soaking showers.  The erection of a new 40-meter inverted V will just have to wait until the clouds clear.  Actually, the storm clouds are most welcome–Hawaii Island has endured a prolonged drought for the past two years.  On the windward side, precipitation is almost 50 inches below normal, with “normal” being around 130 inches for Hilo. On the Kona side of Hawaii Island, pastures and coffee plantations have been hit particularly hard.  So, every bit of rain we get is a blessing.

While humanity and Nature sort things out, there are still a few antenna ideas I want to try before the New Year.  With that in mind, I began a brief search through some of the ARRL‘s “Hints & Kinks” volumes on the bookshelf.  In the 13th edition of this series, I found an interesting indoor antenna project by Stan Grimes, W7CQB, called “A Short 7-MHz Dipole.”  Steve’s inductively loaded dipole appears  to be a possible solution for those living in apartments or in homes with limited backyard space.

After I read his short article, I decided to duplicate his general design with materials I had in the shack.

MATERIALS AND ASSEMBLY:

According to Steve, ” the antenna and its two loading coils consist of a total of 60 ft. of no. 14 plastic covered wire”, with the loading coils being wound first on  1.5 inch diameter plastic forms  (old prescription pill bottles can be used).  Each coil is made of 30 close-wound turns of wire on the plastic form.  The remaining length of wire is used to make two sections of antenna, separated by the coil, on either side of the center connector.

For each side of the 40-meter dipole, measure and cut a piece of wire 10 feet long and another 6.25 feet long (6 feet, 3 inches).  The coil will be connected to the end of the 10 foot section and to the beginning of the 6.25 foot section.  The dipole will have two identical sections separated by the homebrewed induction coils.

The total length of the connector with handwound coils will be 32.5 feet (32 feet, 6 inches).

Center connector.  I had an extra Budwig coaxial center connector in the junk box, so I used that to connect the feedline.

Push pins or tape (temporary use only) to support the dipole.  I chose to support the dipole on the shack ceiling.  Steve says you can dangle the 6.25 foot end sections after each coil if you have space problems.  I did.  I let the end pieces run down the wall.

Feed the dipole as close to its center as you can.  You can use either 75 ohm coaxial cable (such as RG-6) or 50-ohm coaxial cable (such as RG-58 RG-8, or RG-8X).   The coaxial cable should leave the center connector at a 90-degree angle.

Just below the center connector, wind approximately 6 feet of the coax into a “choke balun”.  Secure the coil with some nylon ties.  The result is a shield choke balun at the point where the antenna elements connect to the feedline.  This balun will keep reduce feedline radiation and keep rf off your equipment.

Although SWR was fairly low (1.7 to 1), I used my Drake tuner (MN-4) to  keep the SWR as close to 1.1 to 1 as I could.

I received plenty of local (Hawaii) contacts during the day using no more than 20 watts SSB and 10 watts CW.  Steve adds that his antenna system “can handle up to 120 w…it should be exhibit better than a 2:1 SWR from 7050 to 7160 kHz.”

Steve’s antenna also loads up on 15-meters, but the bandwidth is quite narrow.  If you plan to use 15-meters with this antenna, use an antenna tuner to keep the SWR below 2:1.

I’ll continue testing this short dipole.  It appears to be an inexpensive and useful antenna for apartment stations.  I was able to use materials found in my junk box, so the cost was minimal.

Have fun with this project.

REFERENCES:

Stan Grimes, W7CQB, “A Short 7-MHz Dipole”, cited in “Hints & Kinks For the Radio Amateur, 13th Edition”, ARRL, copyright 1992, p.7-27.

Join our blogging community with a free email subscription or by tapping into the blog RSS feed.

Have a happy and joyous holiday season!

Aloha es 73 de Russ, KH6JRM–BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.

 

 

 

Simple Ham Radio Antennas–grounding your amateur radio station, post #250


GROUNDING YOUR AMATEUR RADIO STATION

No discussion of amateur radio antennas would be complete without including a few comments about grounding your shack’s equipment to an actual earth ground.  While power cords with a three-prong plug may offer some protection from static charges and even nearby lightning strikes, your protection will be enhanced by a physical connection to an earth ground through a copper rod driven in the ground.

In previous posts, I’ve suggested how to proactively drain the build-up of static electricity along your antenna and feedlines with various static discharge units (from companies such as AEA and MFJ) connected to ground rods driven into the soil.  Such devices will cut back on line static, reduce the damage from line surges, and perhaps protect your rig from lightning  damage.  Please understand that protection from lightning strikes and surges is an important  part of your initial plan for setting up your radio shack.  But, for the purposes of this brief post, I’ll discuss station grounding as a separate topic.  The resources cited at the bottom of this article will explain lightning and surge protection in greater detail.

To ground the amateur radio equipment in your shack involves the concept of treating your antenna and shack as part of a total system, from ground, to equipment, to the antenna itself.

MATERIALS NEEDED:

A basic understanding of DC and AC currents.  A brief review of these topics in the current ARRL Antenna Book (22nd Edition) will bring you up to speed.

Copper Ground Rods, preferably 8-feet long.  I use one ground rod system for the shack’s equipment.  I use a separate ground rod connected to my 40-meter vertical antenna.

Ground Bus Bar, flat braided ground strap, isolated grounding bar, and an Alpha Delta Universal Copper Ground Rod Clamp (see p. 99 of the AES Fall/Winter 2012 Catalog).

Copper ground wire.  Copper is expensive, so carefully estimate what you need.

GROUNDING THE SHACK

Follow the instructions contained in the grounding kit you have assembled.  Understand that the actual earth chosen as the grounding site must conduct electricity.  If your grounding site is dry most of the time, water the area around your ground rod occasionally.

Be sure to keep the ground wire from the station bus bar as short as possible.  Be prepared for a more complex ground installation if your station is far away from the ground.  You may have to install a tuned counterpoise to your antenna tuner to keep rf from entering your shack.  Since every antenna and grounding system is different, you may have to consult the ARRL Antenna Book to optimize your particular ground configuration.

Be sure the spot chosen for the ground rod is free from foot-traffic, lawn furniture, or other impediments.  Depending on your soil and lawn conditions, you may have to dig a hole for the ground rod or even bury radial wires at a shallow depth.  If you want to attach buried radial wires to the ground rod, make them as long as the antenna.  Because my yard is small, I was able to install only four, 32-foot radials from my station ground rod.

Together with my static discharge system and ground rod installation, I feel my antenna system and rigs are well-protected from power surges and lightning strikes.  Of course, natural forces can outwit humans, so no system is perfect.  That’s why I always  disconnect and ground all antenna feed lines when my operating day is done.  I also unplug all power supplies and computers when it’s “time to call it a day.”

If you feel you lack the skills necessary to install a ground system, please ask for  help from your local amateur radio club or a nearby ham friend.

Keep safe and stay alive.

REFERENCES:

“Antenna Ground”–American Radio Relay League (ARRL), QST, February 1984, pp. 15-18, republished as http://www.arrl.org/anenna-ground.

“How to Ground a Ham Radio,” http://www.ehow.com/how_2042174_ground-ham-radio.html.

“Ground Systems–Antennas”, Tom Rauch, W8JI, http://www.w8ji.com/ground_systems.htm.

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AES Ham Radio Catalog, Fall/Winter 2012, p.99

ARRL Antenna Book, ARRL, Newington, CT, 06111, 22nd Edition.

Until next time,

Aloha es 73 de Russ, KH6JRM–BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.

Simple Ham Radio Antennas–a short vertical helix for 40-meters, post #249


A SHORT VERTICAL HELIX FOR 40-METERS.

In an attempt to reduce the visual impact of my 33-foot 40-meter vertical, I decided to build a shorter, and hopefully useful antenna, for my 40-meter activities.  I needed the 33-foot MFJ fiberglass mast for another project and felt some shorter pvc pipe under the house could serve my purpose as an alternative mast. Since my “antenna farm” is a very small backyard, I’ve  grown accustomed to compromised antennas and some of their quirks.  Although I have an in-house loop mounted on the ceiling, I prefer an outdoor antenna because of rf exposure and potential interference issues.

From what I’ve read in various ARRL antenna publications and the selections found in http://www.dxzone.com/catalog/Antennas/Verticals, a short, vertical helix antenna could be built with local materials and a few hours of casual labor.  The general consensus of many articles on short verticals was that a half-wavelength of sturdy wire (i.e. #12 to #14 AWG  household wire) spirally wound on a wooden or fiberglass pole would be the rough equivalent of a quarter-wavelength of wire at the desired  frequency taped to a mast.  The only other thing that bothered me about the project was the restricted area for radials.

However, an article written by Ralph Holland, VK1BRH (see references at the end of the article) convinced me that a modest elevated radial system could work well.  Holland said “under certain conditions, a vertical antenna with one radial was substantially more efficient than an antenna with any other number of radials.”  He continues by adding that “such a hybrid antenna has been studied before and has been applied in marine and land-based systems.”  Because my yard is limited, I opted for one, tuned elevated radial/counterpoise for my vertical helix.

MATERIALS NEEDED:

One 16-foot, 2-inch diameter pvc pipe.  I had such a piece under the house.  It was left over from a plumbing project and just “begged” to be used before the landlord took it to the recycling center.

One wooden stake to support the hollow pvc mast.  I found guy ropes weren’t necessary for this installation.

50-feet of 450-ohm ladder line.  Since I planned to use the vertical helix from 40- to 10-meters, ladder line would be better able to handle the wide range of SWR presented by the vertical as I changed frequencies.  You could also use 50-ohm coaxial cable (RG-58, RG-8, RG-8X) if you preferred to use the helix on 40 and 15 meters.

Three ceramic insulators.  One would support the antenna wire at the top of the pvc pole; one would be used to attach the vertical element and the tuned counterpoise wire at the center of the system; and one would support the counterpoise element at the tip of a 5-foot wooden stake.  The feed line and counterpoise would be attached approximately 5-feet off the ground.  Eleven feet of the pvc pole would be used to support the helix.

An 18-inch whip would be attached at the top of the 16-foot pvc pole to provide some top loading.

My chosen 40-meter frequency was 7.088 MHz–the place where the Hawaii afternoon net usually meets.  A half-wavelength of wire at this frequency was determined from the general formula, 468/f (MHz)=l (length in feet).  That came out to 65.39 feet or approximately 65-feet, 5 inches.  The counterpoise was cut to 32.69 feet or approximately 32-feet, 8-inches.

Once I spirally wound the helix, attached the 18-inch “stinger” to the top of the mast, connected the 450-ohm feedline, and attached the counterpoise, I lifted the 16-foot pvc mast into position.

PRELIMINARY RESULTS:

Because vertical helix systems are less efficient, Ralph Holland, VK1BRH, advises amateurs who use such antennas to have some form of ATU at the base of the antenna, because “a short radiator has a very high base impedance, caused by its capacitive reactance and that the voltages at the base are very high.”

With that in mind, I expected less than stellar results from my new system.  Nonetheless, I ran the 450-ohm feedline to the remotely located W9INN 4:1 balun on the garage wall.  I attached a short piece of thick copper braid from the ground lug of the balun to an 8-foot copper ground rod near the garage.  I then ran a short length of RG-8X coaxial cable to the Drake tuner (MN-4) and then connected the tuner and dummy load to the Swan 100-MX with another short piece of RG-8X coax.

After a few hours of casual operating, I was satisfied that the antenna worked without causing any problems to my tuner or the old rig.  I kept power below 50 watts and enjoyed several cw and SSB contacts within the islands and across the “Big Pond” to California.  The bandwidth of this vertical helix is quite narrow on all bands from 40-to 10-meters, but the tuner handled the mismatches without difficulty.  My best results were on 40-and 15-meters.  Most of my contacts on cw were in the 569 to 589 range, while the SSB contacts were 55 to 57…not terribly impressive, but usable.

I’ll leave this vertical helix up for a few weeks and see what a little “tweaking” can do.  Generally, I’m satisfied with the performance of this reduced size antenna.  Unlike my former quarterwave length 40-meter vertical, this antenna is nearly invisible from the street.  The house and surrounding vegetation shield the mast from view and the light-colored antenna wire blends in with the bushes and shrubs surrounding the lot.

For a compromise antenna, the vertical helix does a fairly good job at a reasonable price.  There’s no doubt that more radials and a little less foliage would improve performance, but, for now, I’m satisfied that this short vertical is working out alright.  Fortunately, I had all of the antenna material on site.  Most of the wire, pvc pipe, and insulators can be found in your local hardware or home improvement store.  Most of the Amateur Radio supply houses (HRO, AES,  HamPros) carry a variety of coax cable and 450-ohm ladder line.  You can always make your own ladder line out of plastic straws and #12 AWG wire.  I’ve done it, but the process is tedious.

REFERENCES:

“Short Vertical Antennas and Ground Systems”, Ralph Holland, VK1BRH (http://www.dxzone.com/cgi-bin/jump2.cgi?ID=920).

“Quickie Vertical”, Ray Jurgens, KQ6RH (http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=3875).

The “ARRL Antenna Compendium”, volumes one through five, ARRL, Newington, CT, 06111.

http://www.dxzone.com/catalog/Antennas/Verticals.

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Aloha es 73 de Russ, KH6JRM–BK29jx15–along the beautiful Hamakua Coast of Hawaii Island.

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