Sunday, June 30, 2013

Antenna Topics: A Junk Box Vertical. Post #206

I've been a "radio junkie" since age 8 when my father and I built a crystal set in the garage.  I was amazed what a Quaker Oats cardboard cylinder, some enameled wire, a crude slider, a piece of pyrite, a "cat's whisker", and a pair of high impedance headphones could do.  With about a hundred feet (30.48 meters) of #14 AWG house wire and a good ground, I was able to capture many AM broadcast stations, many all at once.  The pyrite crystal wasn't too selective, but I did have fun.

From there I graduated to better receivers and some homebuilt Heathkit audio equipment.  Although my father was a "stereophile" and appreciated good jazz and classical music, he never did become an amateur radio operator.  I kept putting off getting my amateur radio license until I left the Air Force and became part of a commercial broadcast station.  One of the engineers at KHLO-AM (Hilo, Hawaii) finally persuaded me to take the novice examination.  Once I got the license, it wasn't long until I became a radio "packrat", collecting all manner of equipment, parts, wire, microphones, and radio books.  That affliction has followed me for over 36 years as a "ham."

When I completed my last inventory of radio equipment, I found a large collection of mobile antenna coils, baluns, various lengths of wire, a box full of RG-8 coaxial cable, some ladder line, connectors, and insulators.  Next to the back wall was my first mobile antenna--a Hustler system consisting of the 54 inch (134.16 cm) mast, a bumper mount, shock-absorbing spring. loading coils for 40, 20, and 15 meters, and a 20-foot (6.09 meters) piece of RG-58 coax with "pigtails."

I put these antenna pieces in the house and began researching ways to convert a mobile HF antenna to fixed station use.  On Friday (28 June 2013) I found an interesting article by R. "Andy" Wiedeman (WA0AW) in the February 2012 issue of QST.  Andy describes how he used pvc mast sections, a small metal plate, a connector with a 3/8 X 24 thread, several Hustler coils, a "stinger", and 4 radials to build a portable antenna that could be used on his recreational vehicle (RV) or at his home qth.

With a few modifications, I was able to adapt my junk box parts to build a compact vertical in my back yard.  With apologies to WA0AW, here's how I used my old mobile antenna for a fixed station antenna.

I have two metal clothes line poles in my back yard, separated by about 16 feet (4.87 meters).  I bolted the bumper mount onto the cross arm of the clothes line pole furthest from my house.  The cross arm is approximately 8-feet ( 2.43 meters) above ground.

I attached the RG-58 coax with the "pigtails" to the mast and the bumper mount, with the center wire of the coax going to the Hustler mast and the braided shield going to four evenly spread out radials which left the the clothesline cross arm at approximately 45-degrees.  Since I was interested in pursuing 20 meter contacts with this modified antenna, I screwed in the 20 meter Hustler coil and its matching wire "stinger."  Each radial was cut according to the general formula 234/f (MHz)=L (ft), giving me an element length of 16.47 feet (5.02 meters).  Many antenna authorities recommend cutting the radials about 5% longer than the normal 1/4 wavelength for each dipole element.  I decided to stick with my original measurements.  Once I spread out the radials, I found that I had to run a portion of the radial length on the ground.

I used a barrel connector (UHF to UHF) to attach the RG-58 coax to 25 feet (7.62 meters) of RG-8 coax.  The RG-8X ran through a panel in the radio room window case and was connected to the Drake MN-4 antenna transmatch.  Small coax patch cords connected the low pass filter, dummy load, and the old Swan 100-MX transceiver to the transmatch.  All antenna connections were soldered and covered with clear fingernail polish.

After a few tests and adjustments, I found the mobile antenna conversion worked about as well as my low home station dipole.  The modified ground plane formed by the slightly elevated radial system performed well.  According to a recent article by Rudy Severns (N6LF), four elevated 1/4 wave radials "will perform about the same as many radials mounted on the ground and far better than using the RV chassis as a counterpoise.  Elevating a horizontal radial system results in an antenna impedance of about 30 ohms, resulting in poor match to a 50 ohm coax.  Sloping radials sloped at 30 to 50 degrees provide an improved match." Since my antenna was lower to the ground than the one described by WA0AW, I had a small mismatch to handle--easily done with the trusty Drake MN-4.

To change bands, I just screw on another loading coil and its "stinger" and add four sloping radials cut for my band of choice.

Since the antenna is mounted at a relatively low height in my backyard, it remains invisible from the street and  the prying eyes of neighbors.

I enjoyed making this antenna.  Other than my own labor and supply of  extra parts, the cost of the antenna was zero.  When I tire of this antenna, I will break it down, clean all the parts, and recycle the components for other antenna projects.

REFERENCES:

Wiederman, R. "Andy" (WA0AW).  "Double Your Mobile Antenna Use." QST, February 2012, pp. 41 to 43.
Steverns, Rudy (N6LF).  "An Experimental Look at Ground Systems for HF Verticals."  QST, March 2010.  pp. 30-33.
Robeson, R (K4YZ).   "One Ham's Fix for Limited Space Antennas."  QST, March 2011.  pp. 37-39.

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

For the latest amateur radio news headlines, check out my news blog--http://kh6jrm.com.  I've listed a few stories following this post.

Aloha from the beautiful Hamakua Coast of Hawaii Island,

Russ (KH6JRM.

BK29jx15.


Wednesday, June 26, 2013

Antenna Topics: Antenna Trimming Shortcut. Post #205

Most of us who use the general formula for a half-wavelength flat top dipole (468/f (Mhz)=L (ft), rarely give much thought on how accurate the dipole length really is.  We cut the dipole to its calculated length, cut the wire in half, attach center connector and insulators, attach a length of 50 or 75 - ohm coaxial cable, suspend the wire between two tall supports, and prepare for a day of radio fun.  In most cases, your dipole will work well, although a little trimming or pruning may be necessary to bring the wire antenna into resonance.

I'll admit to being lazy in this department.  As long as the SWR falls below 1.5 to 1, I don't bother trimming.  Even if the SWR hovers around 1.7 to 2.0 to 1, I always can use my trusty Drake MN-4 to bring the SWR below 1.5 to 1.

Suppose you wanted to make your antenna (in this case for 40 meters), as resonant as possible and do without a tuner altogether?  Instead of cutting and trimming, wouldn't it be nice just to cut the dipole length once and come up with a low SWR?

After doing a bit of research in several ARRL documents, I found an article by Joseph H. NeCamp (W4JBQ) in the 11th Edition of "Hints and Kinks for the Radio Amateur" that addresses that issue.  Following Mr. NeCamp's example, I duplicated his pruning example with a temporary 40 meter flat top dipole in my backyard.  I used two 33-foot (10.06 meters) MFJ fiberglass masts to support the antenna.

Like Mr. NeCamp, I cut a dipole resonant at 7.05 MHz using the general dipole formula (468/f (MHz)=L (ft).  The length of the dipole worked out to be 66.4 feet/20.24 meters or 33.2 feet/10.12 meters for each dipole element.  A check with a SWR bridge showed resonance around 7.15 MHz.  Obviously, my original calculated length was off by quite a bit.  I would have to add some more wire to each element to make the dipole resonant.  Here's how  W4JBO adjusted things:

"Multiplying the original 66.4 feet times the actual resonant frequency of 7.15 MHz yields 475, a new constant to use in the formula in this particular installation."  NeCamp continues by saying: "L=475/7.05=67.4 feet.  If the original short dipole is lengthened to 67.4 feet (20.54 meters), the resonant frequency will be very close to the desired 7.05 MHz."

I tried this pruning method and it works.  With each dipole element measuring 33.7 feet/10.27 meters. I had a SWR of 1.2 to 1 at the desired frequency without using the Drake MN-4.  Of course results will depend on your dipole's height above ground, the type of coax used as the feed line, and surrounding objects which could detune the antenna.  I was able to remove the antenna transmatch and enjoyed a casual afternoon of "rag chewing" on 40 meter cw.

REFERENCE:

NeCamp, Joseph H. (W4JBQ).  An Antenna - Pruning Shortcut.  Contained in "Hints and Kinks for the Radio Amateur", 11th Edition. Copyright 1982.  ARRL, Newington, CT, 06111. Page 5-9.

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

For the latest amateur radio news, please visit my news site--http://kh6jrm.com.  I've included a few headline stories at the bottom of this post.

Thanks for joining us today!

Aloha es 73 de Russ (KH6JRM)

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.

Sunday, June 23, 2013

Antenna Topics: Using your mobile station as your base antenna. Post #204

An article by retired ARRLTechnical Editor Joel Hallas (W1ZR) in the July 2013 issue of "QST" offered me another idea of operating in "stealth mode."  Hallas outlines a simple way to use your mobile antenna as a base antenna in areas where restrictive CC&Rs and HOA's prevail.  With a few simple components, you can use your vehicle-mounted antenna as your main antenna when everything else fails.

Thanks to the use of two Bias Ts (devices that allow dc to share a coaxial cable without interferring with the RF), " you can easily supply power from your home shack to the vehicle's antenna system."  Hallas continues by saying that "the bias T at the end of the coax removes the dc.  The dc can either be used to power an automatic antenna tuner, or provide power to run a motorized antenna."  Hallas says "the usual  'monoband' mobile whip, either those with lumped loading inductance or helically loaded types, can be used on lower frequency bands than their self resonant frequency if used with a wide band tuner."

All you would have to do is run coax with the two Bias Ts from your rig's power supply to the automatic tuner or motorized antenna controller in your vehicle.  Now, you're in business.  Be sure to detach the coax before you drive away.  Hallas recommends leaving a reminder in your car and on your home transceiver to coil up the coax after you close out your operating day.

Hallas also describes a modification of this arrangement using the popular "screwdriver" antennas supplied by Tarheel and other manufacturers.  All told, Hallas's article gives several antenna ideas for those caught in the web of HOAs and CC&Rs.

Using Hallas's  general idea, I tried out a slightly different version for my situation.

I had several of those old "Hamstick" helical mobile antennas in storage just waiting for another antenna mission.  I also had an old MFJ mag mount that could be pressed into service.

At 11:30 a.m. local time today (Sunday, 23 June 2013), I drove my van into the back yard where it couldn;t be seen from the street.  I placed a 40 meter Hamstick into the mag mount and positioned the mount in the center of the van's roof.    I attached three 33-foot (10.06 meters) radials to the base of the mag mount with large alligator clips.  Hopefully, these radials would improve antenna performance.

I connected 50 feet (15.24 meters) of RG-8X to the Drake MN-4 antenna match box and ran the cable to the mag-mounted Hamstick.  With the use of the Drake MN-4, I was able to keep the SWR below 1.3 to 1 across the entire 40 meter amateur band.  Running approximately 20 watts output from the venerable Swan 100-MX, I made several local contacts.

I repeated the procedure with a 20 meter Hamstick  using three radials cut for that band and found no problem making contacts with the mag-mounted Hamstick.  I tried the same efffort with 15 and 10 meters.  Those bands were quite noisy, most likely a result of the recent M-Class flare from the sun.

Although performance of the emergency home antenna didn't match what I usually found with the 40 meter loop or the 40 meter inverted vee, I was satisfied that the "home-based" mobile worked well enough for emergency purposes.

If you follow Hallas's instructions, or even my humble efforts, you should be able to continue making contacts despite the restrictions you face.  Hallas concludes his excellent article by saying "In any of these cases, you have the ability to operate from the comfort of your home station with an antenna that works reasonably well."  Remember the old saying:  "Out of sight, out of mind."

REFERENCES:

Hallas, Joel, W1ZR.  "Use Your Mobile Station as a Base Antenna Platform."  "QST", July 2013, pp. 39 to 40.
Ford, S., WB8IMY.  "Short Takes--MFJ Model 4118 Bias Tee Power Injector."  "QST". May 2008, p.54.
Salas, P., AD5X.  "Build a Legal Limit Bias T that Covers 1.8 to 230 MHz."  "QST", Jan. 2013, pp.45-48.

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

Thanks for joining us today!

Aloha es 73 de Russ, KH6JRM

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.



Thursday, June 20, 2013

Antenna Topics: A Simple Multiband Vertical Antenna. Post #203

While I was searching for some antenna projects on Thursday (20 June 2013), I came across an antenna book I bought 25 years ago to help a new amateur radio operator make his first HF antenna.  The "Novice Antenna Notebook"  by Doug DeMaw, W1FB (SK) contains a wealth of simple, effective antenna ideas suitable for any license class.  I was drawn to this book a quarter century ago because it explains complex antenna theory and design in a simple, easy to understand manner.  I've used several of DeMaw's designs for my portable and emergency antennas.  All have worked successfully.

I decided to return to my own novice/technician days (1977-1978) and create one of the simple antennas that got my friend on the air.

The simple multiband vertical antenna described by DeMaw is easily made, cheap, and performs very well.

As DeMaw says, "you may want to keep things simple when you erect your first multiband vertical...simplicity denotes reduced cost for materials, and this is an appealing factor to most of us!"  I thoroughly agree.  So, with that caveat in mind, I gathered the materials needed for this ultra simple vertical antenna.

As designed by DeMaw and modified for my location, here's what I used:

Two 30-foot (9.14 meters) pieces of #14 AWG house wire.  One wire would serve as the vertical element.  The other wire would serve as an elevated radial or counterpoise.  As designed, this antenna would cover from 40 to 10 meters and would be fed with 450-ohm ladder line to a 4:1 balun and an antenna transmatch.

Fifty feet (15.24 meters) of 450-ohm ladder line. This would be the feed line.

Four ceramic insulators.  Two insulators would be for the vertical section and two insulators would be used for the counterpoise or elevated radial.

Fifty-feet (15.24 meters) of monofilament fishing line with sinker attached.  The fishing line would be attached to the vertical element and then shot over the branch of a nearby tree.  The extra fishing line would be secured to the base of the tree to hold the vertical element at a 45-degree angle.  I used a slingshot to place the line at a suitable notch in the tree limbs.



Four 7-foot (2.13 meters) wooden stakes.  One stake would be used as the center tie-off point for the vertical element.  One stake would be used to tie-off the elevated radial.  And two stakes would be used to keep the ladder line off the ground until it reached the 4:1 balun on the garage wall.

One W9INN 4:1 balun.  The ladder line would be connected to the balun.

Twenty-five feet (7.62 meters) of RG-8X coaxial cable with UHF connectors.  The cable would be attached to the balun and would be run into the shack through a plexiglass window pane.  The RG-8X would be connected to a suitable transmatch.

A transmatch.  I use an old Drake MN-4 ATU for my multiband antennas.

Short coax pieces to connect the Drake MN-4 to the Swan 100-MX transceiver, the dummy load, and the low-pass filter.

ASSEMBLY:

Per DeMaw's instructions, I cut two, 30-foot (9.23 meters) pieces of #14 AWG house wire.  I attached insulators to each end of the wires.

I pounded the central wooden stake into the ground with a hammer.  This would serve as the tie-off point for both the vertical element and its elevated radial.

I attached the vertical element to the fishing line and shot the combination through a notch in a nearby pine tree with my slingshot.  The limb was approximately 35-feet (10.67 meters) above ground.  The fishing line was tightened a bit before I tied it off to the base of the tree.  The vertical element was led to the central stake at an angle of 45-degrees.

I attached the elevated radial to the center stake and stretched it out to a nearby wooden stake. I attached one lead of the ladder line to the vertical element and then attached the other lead to the elevated radial.

I led the ladder line to a wooden stake 25-feet (7.62 meters) from the center connection stake.  The ladder line was kept off the ground and eventually was connected to the 4:1 balun attached to the garage wall.

All connections were soldered and wrapped with vinyl electrical tape.

Twenty-five feet (7.62 meters) of RG-8X ran from the 4:1 balun into the shack, where it was connected to the Drake MN-4 ATU, Swan 100-MX, a dummy load, and the low-pass filter.

RESULTS:

For a simple, inexpensive antenna, I have no complaints.  I can bring the SWR down to 1.3 to 1 or less on 40, 20, 15, and 10 meters.  I've enjoyed some excellent contacts on 40 and 20 meters with reports ranging from 569 to 599 for CW and 56 to 59 on SSB.  I've been running the old Swan 100-MX at around 25 watts.  Fifteen and ten meters have been a little weak in my area, but I've manged to bring in some good contacts from Asia and the U.S. mainland.  If I added a few more elevated radials and fanned them out around the antenna, my results would have been better.

This antenna was a joy to build and produced some good contacts.  I will build a few more of DeMaw's novice antennas before summer ends.  These antennas work.

REFERENCES:

DeMaw, Doug, W1FB.  "Novice Antenna Notebook".  American Radio Relay League, Newington, CT, 06111.  First Edition.  Copyright 1988.  pp.60 to 61.

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

For the latest amateur radio news, please visit my news site at http://kh6jrm.com.  I've included a few headline stories at the bottom of this post.

Thanks for joining me today!

Aloha es 73 de Russ (KH6JRM)

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island

Sunday, June 16, 2013

Antenna Topics: A Field Day Dipole. Post #202

One of the simplest and most efficient Field Day antennas is the common half-wavelength flat top dipole or doublet stretched between two trees or portable masts and fed with 50-ohm coaxial cable (RG-58, RG-8, or RG-8X) for single band use or fed with 450--ohm ladder line, a 4:1 balun, and an antenna transmatch ("tuner") for multiband use.  I 've used this type of antenna in various configurations, included the inverted vee and the half-wavelength sloper.  For single band use, I've also employed 75-ohm RG-6 coaxial cable with "F" to "UHF" connectors.  Used with an antenna matchbox, the RG-6 serves as a suitable  feed line if 50-ohm cable is unavailable.

Placed a height of 30 to 50 feet above ground (9.14 to 15.24 meters), the  doublet will give you plenty of local and DX contacts.  Just cut your 2 antenna elements to the lowest frequency of use, feed with ladder line  into an appropriate balun and antenna matchbox, and you have an antenna capable of operating on several bands.

A few years ago, I was part of an antenna raising team that placed such an antenna in use during a Field Day operation at Hilo's Wailoa Visitor Center.  Using a Kenwood 430 (remember those?), our operators ran a hot operation on 40, 20, 15, and 10 meters.

Here's a list of materials our team used for the half-wavelength flat top dipole:

Two 33-foot (10.06 meters) telescoping fiberglass masts.

Three 7-foot (2.13 meters) wooden stakes.  Two stakes would support the fiberglass masts.  The remaining stake would be used to provide some strain relief to the center of the dipole and the feedline.

Fifty-feet (15.24 meters) of 450-ohm ladder line.  This would be our feedline and our ticket to running several bands off one antenna.

Three ceramic insulators.  One  insulator would be at the end of each dipole element.  The third insulator would serve as the center junction of the ladder line and the two dipole segments.

One 4:1 balun.  I had an extra W9INN balun for this purpose.

One Drake MN-4 antenna trasmatch from my shack.  I still have this "tuner".  It works very well.

Twenty-five feet (7.62 meters) of RG-8 coaxial cable.

Sufficient wire to make the dipole antenna.  We chose to design the antenna for 7.088 MHz, the frequency of the Hawaii Afternoon Net.  With the ladder line in play, the antenna could be used from the lower portion of 40 meters through the limits of the 10 meter band.  Using the general formula 468/f(MHz)=L(ft), we cut each dipole element to a length of 33.01 feet (10.06 meters).  The wire used for the antenna was #14 AWG house wire.

150-feet (45.73 meters) of dacron rope to support the fiberglass masts.  The rope would serve as "guy wires" for the masts.

Six plastic tent pegs to support the guy ropes.

A basic operating position, consisting of a covered lanai (porch), table, two chairs, logs, and various other record keeping items.

A 10 kw gasoline powered generator and extra fuel.

Assembly of the doublet antenna:

The antenna was built on the ground and later hoisted into position, with one team raising one mast and the other team raising the second mast.

Insulators were attached to the end of each dipole element and were tied off to the tip of each mast.  The center insulator was used to support the 450-ohm ladder line, one line of each was soldered to each antenna element.

Three guy ropes were attached to the mid-point of each mast (16-feet/4.87 meters above ground).

The masts were hoisted onto their support stakes and the guy ropes were attached to each tent peg (3 tie-offs for each antenna mast).

The ladder line dropped from the center insulator to a 7-foot (2,13 meters) wooden stake below the center connection.  The ladder line was tightened slightly, allowing a bit of "sag" in the doublet.  The 450-ohm ladder line was secured to the wooden stake with nylon ties. Then, the ladder line was led to another 7-foot (2.13 meters) stake, allowing the feed line to remain above ground level.

The ladder line was secured to the 4:1 balun on the stake.  Twenty-five feet (7.62 meters) of RG-8 coaxial cable went from the 4:1 balun to the Drake MN-4 antenna matchbox.  Several short pieces of RG-8 coax connected the Drake MN-4 to the Kenwood-430 and the dummy load.

Results:

For a quickly-made 40 through 10 meter antenna, the doublet did very well.  The antenna was used throughout the day and night to contact stations on the mainland U.S., Canada, and Asia.  Most of the time, the old Kenwood 430 ran approximately 75 watts output.

After the Field Day exercise ended, the antenna was broken down and stored away in less than 15 minutes.

If you have only one tall support, try the doublet as a half-wavelength sloper or an inverted vee.  If you wish to include 80 meters in the mix, cut each dipole element to 66.85-feet (20.38 meters).  That should put your antenna resonance at 3.500 Mhz--perfect for some cw DX.

REFERENCES:

http://www.youtube.com/watch?v=8KHzsKYsZL0
http://www.hamuniverse.com/easydipole.html.
http://hamuniverse.com/multidipole.html.
http://www.ehow.com/how-4530-build-dipole-antenna.html.
en.wikipedia.org/wiki/Dipole-antenna.

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

You can leave comments on the form at the bottom of this post.

For the latest amateur radio news, please visit my news site--http://kh6jrm.com.

Thanks for joining us today!

Aloha from the Big Island of Hawaii,

Russ Roberts (KH6JRM)

Bk29jx15--along the beautiful Hamakua Coast.


Wednesday, June 12, 2013

Antenna Topics: A Field Day Vertical with elevated radial system. Post #201

With the ARRL Field Day coming on 22-23 June 2013, there are plenty of antenna ideas floating around cyberspace.  Part of the fun of Field Day is the erecting of familiar antennas such as dipoles, verticals, loops, and hexbeams.  Now and then, a three or four element beam is pressed into service thanks to a generous club member, some fiberglass and metal tower sections always seem to appear, or even a "cherry picker" truck loaned by a service-minded company such as a tree trimming business, the telephone company, or the local cable company makes an appearance.  A good antenna raising team can put a formidable tower and beam into the air in a matter of a few minutes.

But what happens when you operate a Field Day station as a single operator, single transmitter entry with no other team members to help you?  You are the antenna raiser, the cook, the tent builder, and the over taxed operator.  Don't dispair.  With a little planning, you can pre-assemble a simple antenna that can be erected, used, and taken down easily.  If you use a telescoping fiberglass mast from MFJ, Jackite, or any of the surplus outfits selling used military fiberglass or pvc mast sections, most of the battle is won.  All you have to do is make a simple vertical and ground system to attach to the mast and you're ready to go.

During my last few posts, I've described some of the simple Field Day antennas I use for my portable and emergency operations.  Most of these antennas are either inverted vees or loops, since these antennas are easily made and require no ground radial system.  Fed with 450-ohm ladder line and connected to a 4:1 balun and antenna matchbox (tuner), these antennas can cover several bands with low SWR.

Just for the fun of it, I decided to use one of my old vertical antennas from my novice operator days (1977 to 1978).  Since 1/4 wavelength verticals require a substantial ground radial system to work properly, I had visions of laying out 16 to 30 quarterwave radials below the vertical...not an enjoyable experience, since my backyard is quite small.  There must be a better way to get a vertical antenna to perform.

Back in those days, I heard a lot about raised radial systems and how they could be used to replace a large number of buried or on-surface radial wires.  Some writers called these elevated wires a "counterpoise".  According to several experts in the field, including Oliver Duffy (VK1OD) and the late L. B. Cebik (W4RNL), there is a lot of misinformation about what comprises a counterpoise. For VK1OD, a counterpoise "means all things to all people...it is used inconsistently...it doesn't have a really acceptable meaning."  Cebik also notes the "use" and "abuse" of the term "counterpoise."

Cebik, citing the Frank C. Jones "Radio Handbook", 1937, p. 9, says the elevated radial system "acts as a condenser plate with high capacity to earth, with the result of lower loss in the antenna system.  For this reason, the counterpoise should be fairly close to ground...i.e. 6 to 10 feet (1.82 to 3.04 meters) above ground."  An elevated radial system, even a single radial, can improve antenna efficiency.

That's what I was looking for.  Something reasonably efficient and simple that wouldn't require a lot of digging and stringing of wire in a confined space.

As for the definition of "counterpoise", I deferred to the IEEE Standard Definition of Terms.  According to that standard, a counterpoise is "a system of conductors elevated above ground and insulated from ground, forming a lower system of conductors for an antenna."

With that in mind, I built a simple vertical antenna covering 40 through 10 meters using one elevated radial (or counterpoise) in my backyard.  The antenna worked amazingly well for the time and materials invested.

MATERIALS:

A 33-foot/10.06 meters MFJ telescoping fiberglass mast.

Two, five-foot/1.52 meters wooden stakes.  One stake would support the fiberglass mast.  The other stake would support the elevated radial above ground.

One ceramic insulator to tie-off the elevated radial.

One ceramic insulator to attach to the top of the fiberglass mast.  This insulator would support the vertical element of the antenna.

Two equal lengths of #14 AWG house wire.  One piece would be the vertical element.  The other piece would be used for the elevated radial wire.  Using the general formula for a dipole (468/f(MHz)=L(ft) and a chosen frequency of 7.088 MHz (the frequency of the Hawaii Afternoon Net), I cut each wire to a length of 33.01 feet/10.06 meters.

Fifty-feet/15.24 meters of 450-ohm ladder line.

A W9INN 4:1 balun.

An antenna transmatch (Drake MN-4).  The combination of the balun, transmatch, and the ladder line would let me use the antenna from 40 to 10 meters.  The old Drake MN-4 had no trouble bringing the SWR to 1.5 to 1 on all bands of interest.

Twenty-five feet/7.62 meters of RG-8X coaxial cable with UHF connectors.  The cable would run from the 4:1 balun to the Drake MN-4.  Simple patch cords would connect the "tuner" to the dummy load, low pass filter, and to the Yaesu FT-7 QRP rig.

A deep-cycle marine battery charged by two solar panels would provide power for the station.

A 5-foot/1.52 meters piece of dacron rope to tie off the end insulator of the elevated radial wire.

A 5-foot/1.52 meter support stake near the operating position.  The stake would support the ladder line off the ground until it reached the 4:1 balun near the portable table I used for a desk.

Small table and chair to serve as the operating site.

Small tool kit, logging materials, food, and water.

ASSEMBLY:

I built the antenna on the ground.  I taped the vertical element (33.1 feet/10.06 meters) to the fiberglass mast, attached a ceramic insulator to the antenna, and secured the insulator to the top of the mast with nylon ties.  One wire of the ladder line was attached to the bottom of the vertical element.  The other part of the ladder line was attached to the elevated radial wire (also 33.1 feet/10.06 meters).  All connections were soldered and wrapped with vinyl electrical wire to protect the system from the weather.

The elevated radial wire was led off from the base of the antenna at a slight angle to a 5-foot/1.52 meters wooden stake, approximately 38 feet/11.58 meters from the base of the antenna.

Once I assembled the antenna, I hoisted the mast onto its support stake.

I led the ladder line to the the support stake.  I attached the W9INN 4:1 balun to the stake.

I connected the 25-foot/7.62 meters RG-8X coaxial cable to the balun and ran the cable to the Drake MN-4.  Small patch cords connected the Yaesu FT-7 to the dummy load, the "tuner", and a low pass filter.

RESULTS:

Considering that this hastily made antenna used only one elevated radial (or "counterpoise", depending on your definition), I was satisfied with the contacts I made last Saturday (08 June 2013).  Like my initial work with this antenna back in 1977 and 1978, I was able to keep SWR below 1.5 to 1 on 40, 20, 15, and 10 meters, thanks to the ladder line, the balun, and a good transmatch.  Of course, I couldn't use 20 meters as a novice operator in those days.  Once I passed my general license exam, this antenna gave me good service in the 20 meter band.

Will this antenna match the performance of a beam on a 50-foot/15.24 meters tower?  No.  But it will get you on the air quickly with low SWR.  I've received CW reports ranging from 559 to 599 and SSB reports of 54 to 57, depending on band selection and propagation.  Not bad for 10 watts output from an old rig.

The addition of several elevated radials would undoubtedly improve the efficiency of this antenna.  But, for now, this simple vertical with one elevated radial works fairly well.  The antenna can be erected and taken down quickly.  The antenna can be packed in my van with no problems.  Most of the materials can be obtained at the nearest hardware or home improvement center.  You can also use pvc pipe for the mast and ordinary #14 AWG house wire for the antenna elements.  450-ohm ladder line can be ordered from the major amateur radio supply houses (HRO, AES, Ham Station, etc.).  There are a variety of suppliers for RG-8X coaxial cable.  In an emergency, I've even used RG-58 from Radio Shack, although there are quality issues with some of the coax sold by the "Shack".

REFERENCES:

http://www.w0uce.net/K2AVantennas.html.
http://www.sgcworld.com/radialtechnote.html.
VK1OD.net/antenna/misc/CounterPoise.html.
IEEE. 1993. IEEE standard definition of terms-IEEE std 145-1993. New York:  IEEE.
http://www.antennex.com/shack/Dec06/cpshtml.
Straw, Dean, ed. 2003. The ARRL Antenna Book, 20th ed. Newington, CT. ARRL. 27.25-27.32.
Also, check out articles by L. B. Cebik (SK), W4RNL.

Have fun this Field Day!

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

You can leave comments on the form at the bottom of this post.

For the latest amateur radio news, please visit my news site--http://kh6jrm.com.  I've added a few news stories at the bottom of this post.

Aloha es 73 de Russ (KH6JRM)

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.

Sunday, June 9, 2013

Antenna Topics: A modified inverted v antenna for Field Day. Post #200.

The ARRL's Field Day is coming Saturday and Sunday, 22-23 June 2013.  Thousands of amateur radio operators in the USA and Canada will be trying to establish contact with fellow amateurs around the world in one of the oldest emergency communications exercises in existence.

Although many amateur radio operators will be joining their clubs at public parks, schools, and public safety buildings for the exercise, many amateurs, including yours truly, will be operating from our homes and even our work sites.  For those of us running in the single operator, single station category, our Field Day group belongs to us only...we are responsible for everything in our portable or home stations.  That means all antenna, cooking, and sleeping responsibilities fall on us.  Although I enjoy working with my amateur radio club (The Big Island Amateur Radio Club), there are times when I can't  drive out to the Field Day site and must work alone.

With that in mind, it pays to "pre-arrange" your portable station ahead of time, so you can spend the maximum time allowed pursuing those elusive Field Day contacts.  I have a small portable station packed in my van, consisting of a Yaesu FT-7 QRP rig (10 watts), a J-38 hand key from my military service days, a collapsible 33-foot (10.06 meters) MFJ fiberglass mast, 100-feet (30.48 meters) of #14 AWG housewire, 50-feet (15.24 meters) of RG-6 coaxial cable with "F" to "UHF" connectors, a Drake MN-4 antenna transmatch ("tuner"), various tools, wooden stakes, tape, nylon ties, ceramic insulators, and various center connectors (I prefer the Budwig HQ-1 center connector).  To power my low-profile station, I use a deep-cycle marine battery charged by a set of small solar panels.  I also have 100-feet (30.48 meters) of 450-ohm ladder line and a W9INN 4:1 balun if I want to use one antenna for several bands.

I've used this portable station many times, using a dipole antenna configured in either an inverted v or sloper arrangement.

Although I prefer the sloper for portable operations, I decided to try out another design that I once used back in 1980 when I was a fairly new operator (I got my novice license in 1977 and was a general class operator by 1980).  This antenna would be an inverted vee with separate antennas cut for 40, 20, 15, and 10 meters.  A pulley was attached to the top of the mast and was used to raise and lower each separate antenna as the band conditions changed.

The antenna consisted of four separate dipoles cut for 7.088 MHz (the frequency of the Hawaii Afternoon Net), 14.200 MHz, 21.250 MHz, and 28.400 MHz (in the middle of the novice/technician class 10 meter phone band).  I used #14 AWG house wire for the antenna elements.

Each antenna was attached to a separate Budwig HQ-1 center connector and tied off to a ceramic insulator.

Using the general formula, 468/f (MHz)=L (ft), the lengths of each dipole element became:

7.088 MHz--66.02 feet/20.13 meters.  Each dipole element was cut to 33.1 feet/10.06 meters.

14.200 MHz--32.95 feet/10.04 meters.  Each dipole element was cut to 16.475 feet/5.022 meters.

21.250 MHz--22.02 feet/6.71 meters.  Each dipole element was cut to 11.01 feet/3.35 meters.

28.400 MHz--16.47 feet/5.02 meters. Each dipole element was cut to 8.23 feet/2.50  meters.

Each separate antenna had its own Budwig HQ-1 center coax connector and end insulator for tie-off purposes.

I used three 5-foot (1.52 meter) wooden stakes for the antenna system.  One stake would support the fiberglass mast.  The other stakes would serve as tie-off points for the inverted v antenna elements.

I attached a brass, marine pulley to the top of the mast.  I ran a 50-foot/15.24 meters piece of dacron rope from ground level through the pully and back down the mast.  The rope would be tied to each antenna segment as I needed it.  Each segment could be raised or lowered depending on the band of choice.

Two additional pieces of dacron rope (50 feet each/15.24 meters each) were used to tie off insulators belonging to each antenna element.  The rope length could be adjusted depending on which antenna segment was chosen.

ERECTING THE ANTENNA:

I assembled each antenna segment on the ground--two segments for each band (40, 20, 15, and 10 meters).

Antenna elements were soldered to each  Budwig HQ-1 center connector.  All connections were wrapped with vinyl electrical tape to protect the connections from the weather.  In the end, I had four separate dipole elements ready to be used.

I first attached the 40 meter dipole elements to the "pull-up" rope, connected the RG-6 coax (with a choke balun), and raised the antenna segment to the top of the mast via a pulley and dacron rope.  The rope was secured to the bottom of the mast to keep the antenna element fixed at the top of the mast.

I hoisted the fiberglass mast on its wooden support stake and secured the inverted vee elements to their respective stakes.

To change bands, I lowered the 40 meter antenna and disconnected it from its wooden tie-off stakes.  I then connected the 20 meter element, attached the coax, raised the antenna to the tip of the mast with the rope and pulley combination and tied-off the antenna elements to the wooden stakes.

A similar procedure was used for the 15 and 10 meter bands.

In most cases, the antennas exhibited a SWR between 1.6 and 1.8 to 1 without the Drake MN-4 in the feed line. With the Drake MN-4 in the system, I was able to keep SWR below 1.3 to 1 on each band.

As I found out back in 1980, a bit of trimming was necessary to reduce the SWR.  I decided to leave the antenna elements unaltered and used the Drake MN-4 to manage the small mismatch.

This antenna works very well for an inverted v.  Raising, lowering, and changing bands are quite easy with the rope and pulley system.  Although I'm partial to tuned feeders, I found this approach workable and simple to use.  Although the RG-6 has a nominal impedance of 75 ohms, it seemed to match each antenna segment without problems.  The Drake MN-4 handled the small mismatch without causing any difficulties.  I used RG-6 because that's what I had stored in the shack.  "F" to "UHF" connectors are available at Radio Shack.

This antenna is simple, efficient, and requires no ground radial system.  Most of the materials are available at the nearest hardware store or home improvement outlet.  Have fun!

REFERENCES:

http://www.hamuniverse.com/dipival.html (antenna calculator).
http://www.youtube.com/watch?v=fyOWRTWdDKM.
http://www.k7mem.com/Electronic_Notebook/antennas/inverted_vee.html.
http://www.arrl.org/files/Technology/tis/info/pdf/0683033.pdf.

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

For the latest amateur radio news, visit my news site--http://kh6jrm.com.  I've included a few headline stories at the bottom of this post.

Your comments are always welcome.

Aloha es 73 de Russ (KH6JRM)

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.

Wednesday, June 5, 2013

Antenna Topics: A Field Day Delta loop. Post #199

Over the course of the next few weeks, I'll be describing some of the simple amateur radio antennas suitable for the ARRL 2013 Field Day Communications exercise.  These antennas will be transportable for remote operations, easy to build, easy to take down, and will offer good performance under "field" conditions.  Most of the materials for these antennas can be found in the nearest hardware or home building supply outlet.

When you are done using these antennas for field day, store them in your shack for future use.  If these antennas perform well for you, consider erecting them on your property for regular contacts with your ham friends.

In my last post, I described a sloping dipole fed by 450-ohm ladder line.  Along with its associated 4:1 balun and a hefty antenna transmatch ("tuner"), this antenna rendered service on 40, 20, 15, and 10 meters.  I still use my sloping dipole when I operate on the weekends at a public park or some deserted pasture above my home QTH.

My next Field Day antenna suggestion is the versatile and quiet delta loop which can be horizontally and vertically polarized  to fit your requirements.  Unlike the half-wavelength designs common to dipoles, inverted vees, and slopers, the delta loop is a full-wavelength antenna, which can be fed with 50- ohm coaxial cable for single band use or with 450-ohm ladder line for multiband use.  If ladder line is used, a 4:1 balun and an antenna transmatch are required.

Like the verticals, slopers, and inverted vees I've used in the past, the  delta loop needs a mast to support the apex of the triangle-shaped antenna and three support stakes--one to support the mast and two for tie-off points for the delta loop.

One of the first steps involved in the construction of this determine the lowest band of operation for the delta loop.  All bands above the lowest chosen frequency can be used if a 4:1 balun and an antenna transmatch are part of the antenna system.

My original delta loop was designed to be used from 40 meters through 10 meters, with the chosen resonant frequency of 7.088 MHz (the frequency of the Hawaii Afternoon Net).  Using the trusty Drake MN-4 and a W9INN 4:1 balun I was able to get a SWR of 1.5 to 1 across 40, 20, 15, and 10 meters.

So, let us begin:

MATERIALS:

A length of #14 AWG house wire suitable for a full-wavelength delta loop at the chosen frequency of 7.088 MHz).  Using the general formula, 1005/f (MHz)=L (ft), the delta loop would measure141.78 feet/43.22 meters.  I rounded off the length to 141 feet/42.98 meters.  Each side of the triangle would measure 47 feet/14.32 meters.

A telescoping  33-foot/10.06 meters fiberglass or pvc mast.  I had a spare MFJ mast in my garage that fit the specifications.

Three ceramic insulators.  One would support the apex of the delta loop at the tip of the mast.  Two would be used as tie-off points for the bottom element of the delta loop.

Short pieces of dacron rope would be used to tie-off the bottom portion of the delta loop to two, 5-foot/1.52 meters, wooden stakes.

One 5-foot/1.52 meters wooden stake to support the mast.

One 5-foot/1.52 meters wooden stake to support the feed line before it reached the operating position.

Three ceramic insulators.

Nylon ties, vinyl electrical tape, basic tools.

One 4:1 balun.  I happened to have a spare W9INN balun in the shack.  I've also used baluns from DX Engineering.  These baluns are well-made and will last a long time.

Fifty-feet/15.24 meters of 450-ohm ladder line.  This would be the antenna feed line.

Twenty-five feet/7.62 meters of 50-ohm coaxial cable (RG-58, RG-8, or RG-8X).  The coax would run from the 4:1 balun into a suitable antenna transmatch.  I used the Drake MN-4 from my home QTH.

Short pieces of coaxial cable to connect the Drake MN-4 to my Yaesu FT-7 QRP rig.

A dummy load for tuning the Yaesu FT-7.

A deep-cycle marine battery.

Some small solar panels to keep the battery charged during daytime operations.

A small table for the transceiver.

A comfortable chair or portable seat for the operator.

Survival supplies, including food, water, insect repellant, and a first aid kit.

Logging materials.

ASSEMBLY:

I built the antenna on the ground.

I laid out a full-wavelength of #14 AWG wire (141 feet/42.98 meters) on the ground and passed the wire through each ceramic insulator.

I attached the top insulator to the tip of the fiberglass mast. At the top insulator I attached each side of the apex to the ladder line, with one line running down to the right and the other line running down to the left.  I secured the ladder line to the mast with nylon ties.  The ladder line was run down to the mid-mast position (approximately 16-feet/4.87 meters).  The ladder line would then run through the middle of the delta loop to a nearby wooden stake and be tied off at the 4:1 balun.  A twenty-five foot/7.62 meters piece of RG-8X with UHF connectors would go to the Drake MN-4 antenna transmatch.  Short pieces of coax would connect the Drake MN-4 to the dummy load and the Yaesu FT-7.

I then hoisted the fiberglass mast onto its support stake, "evened out" the delta loop, and tied off the loop to its wooden support stakes.

RESULTS:

When I tested this antenna last month at a spot above my home QTH, I got good reports on both CW and SSB despite the relatively low power of the Yaesu FT-7 (about 10 watts).  With a more modern rig, such as a K-3, Yaesu 817 ND, or even an ICOM-703, your results will be better.  With the Drake MN-4 in the line, I was able to keep SWR below 1.5 to 1 on 40, 20, 15, and 10 meters.  Generally, I was satisfied with the performance of this quickly-made antenna.

REFERENCES:

http://www.youtube.com/watch?v=kmdQMgBHeT0.
http://www.youtube.com/watch?v=WF1Tlfbl8Xo.
http://www.youtube.com/watch?v=ettbawdhqLc.
http://www.hamuniverse.com/kl7jrdueldelta1012.html.

Have fun!

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

For the latest amateur radio news, please visit my news site...http://kh6jrm.com.  I've included a few items of general interest at the bottom of this post.

Thanks for joining me today!

Aloha es 73 de Russ, KH6JRM

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.


Saturday, June 1, 2013

Antenna Topics: A Simple Field Day Antenna

The ARRL (American Radio Relay League) 2013 Field Day is set for Saturday and Sunday, 22 June through 23 June 2013.  This is one of the biggest emergency communications exercises in the country and it attracts thousands of amateur radio operators to field day sites throughout the United States and Canada.  Many DX stations around the world participate in this event, so, if it's DX you're looking for, Field Day may just be the place for you.

Because of work or family responsibilities, many amateur radio operators can't join their clubs at a Field Day site.  Instead, these amateur will operate from their homes, using a variety of emergency power configurations, ranging from generators to solar-charged batteries.  Amateur radio operators specializing in emergency communications will run stations from civil defense headquarters, police stations, and even public schools.

Field Day will give you a taste of an intense, but fun operating experience without the comforts of home.  In years past, I've fought off mosquitoes, assorted insects, thunderstorms, and crowds of curious onlookers as I tried to communicate with fellow amateur operators thousands of miles away.

One of the interesting and intriguing parts of any Field Day experience is the "antenna farm" which is raised when the event begins.  Antennas range from telescoping towers topped with 4-element monoband beams to   vertical beam antennas and oddly-configured loops.  Those amateurs into satellite operations often bring an array of homemade and commercial antennas designed to contact these elusive, fast moving space "birds."

All of the group comraderie, antenna raising, and operating is quite an experience.  But, what do you do if you can't join a club at a Field Day site?  Do you avoid the event?  Of course not.  You dig in and run as a single operator at your home qth, a favorite public park, or at your chosen camp site using emergency power such as solar-charged batteries or a genertor.

What about an emergency Field Day antenna?  Why not make your own portable antenna and take it with you to your special site?  That's what I'm planning to do.

On Field Day weekend, I'll be announcing the June Points Meet for the Big Island Auto Club at the Hilo Drag Strip.  Since the races will run into the evening, I won't be able to spend much time at my club's Field Day site at the Wailoa Visitors Center in Hilo.  So, I'm bringing my emergency portable station with me in the Odyssey van and will operate after the evening's racing program is done.  I'll be spending the night at the track with the security team, so, at least, I'll have company and perhaps a few converts to amateur radio.

Here's my equipment list for my 1E (single operator, emergency power) station:

A Yaesu FT-7 QRP (10 watts) rig that covers 80 through 10 meters (no WARC bands).

A deep cycle marine battery charged by solar panels.  I'll charge the panels during the day and operate battery power after the races are done for the evening.

A "homebrew" 40 through 10 meter half-wave sloping dipole, consisting of two equal lengths of #14 AWG housewire.  I cut the wire for 7.088 MHz.  Using the general formula, 468/f (MHz)=L (ft), the total dipole length measured 66.02 feet/20.12 meters.  The dipole was cut in half to provide a 1/4 wavelength section for each half of the sloping dipole.  Each antenna element measured 33.01 feet/10.06 meters.

Fifty feet (15.24 meters) of 450-ohm ladder line.  This would be my antenna feed line.


One 33-foot (10.06 meters) MFJ telescoping fiberglass mast.  The mast collapses down to a small package and fits comfortably in my van.

Two ceramic insulators...one for each antenna element.

One, five-foot (1.52 meters) wooden stake to tie off the sloper.  The post can be moved to change the directional pattern of the sloper.

One, five-foot (1.52 meters) support stake for the mast.

One large hammer to set the support stake.

Various tools, such as screwdrivers, portable drill, pliers, wire cutters, vinyl electrical tape, nylon ties.

One Drake MN-4 antenna transmatch.

One W9INN 4:1 balun.  The balun and transmatch are needed for the feed line to work properly.

A 25-foot (7.62 meters) piece of RG-6 coaxial cable with "F" to "UHF" connectors.  This cable would run from the 4:1 balun to the Drake MN-4 antenna transmatch.  Small coaxial patch cords would connect the Drake MN-4 to the Yaesu FT-7 QRP transceiver.

One Yaesu FT-7 QRP rig.  You will probably get better results with a more modern rig such as the Yaesu 817ND or an ICOM 703.  I had the FT-7 in the shack as a backup rig.  I use this rig for my portable operations.

Headphones, notebook, pencils, pens.

One deep cycle marine battery and small solar panels for battery charging.

ASSEMBLY:

I built the antenna at home and had it ready for the Field Day weekend.  The antenna is now in the back of the van ready to be used.  I tested the antenna before I packed it away in the van.



All I had to do was attach the 450-ohm ladder line to each antenna element.  One lead went to the top element.  The remaining lead went to the lower element.  All connections were soldered and wrapped with several layers of vinyl electrical tape.

End insulators were attached to each antenna element.

I hoisted the antenna on a temporary wooden stake and attached the lower end of the sloper to a pre-positioned stake facing Northeast.

I ran the feed line to the W9INN 4:1 balun.  Twenty-five feet (7.62 meters) of RG-6 coaxial cable ran from the 4:1 balun to the Drake MN-4 antenna transmatch.  A short length of RG-6 ran from the Drake MN-4 to the Yasesu FT-7 QRP transceiver.

Thanks to the Drake MN-4, I was able to keep SWR below 1.5 to 1 on 40, 20, 15, and 10 meters.  I received acceptable reception reports during my initial tests (559 to 599 on CW and 54 to 57 on SSB, depending on propagation and time of day).

Satisfied that the antenna was working well at 10 watts from the Yaesu FT-7, I disassembled the antenna, collapsed the mast, packed the battery and solar chargers in two large plastic bins, rolled up the feed line, packed the rig and Drake MN-4 in two padded boxes, and put the system in the van.

When Field Day comes, I'll have an emergency antenna that will be easy to erect, tune, and take apart during the event.  The antenna will become part of my permanent emergency "go" kit for HF operations.

If you're going solo during Field Day, you may want to try this simple antenna.

REFERENCES:

http://www.hamuniverse.com/ae5jufielddayantenna.html.
http://www.hamuniverse.com/klybobfielddayant.html.
http://www.kn5l.net/fdantenna/
http://www.k9jy.comblog/2008/05/14/field-day-antennas-5-considerations.

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

If you want the latest amateur radio news, check out my news site...http://kh6jrm.com.  I've added some recent stories at the bottom of this post.

You can leave comments on the form at the end of this post.

Thanks for joining me today!

Aloha es 73 de Russ, KH6JRM.

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.