Wednesday, August 28, 2013

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 quarterwave vertical, why devote more time to build a 5/8 wavelength version of an already proven vertical design?

There are two reasons:

Gain.  Even at a level of 1 foot/0.30 meters above ground, the 5/8 wavelength vertical shows a 1.5 dB improvement over a dipole at the same height.  Properly constructed, the 5/8 wavelength vertical will show a gain of slightly more than 3dB over a dipole.

Lower angle of radiation.  According to some antenna experts, the 5/8 wavelength shows a low vertical angle of 16 degrees to the horizon.  Even a half-wave vertical antenna will exhibit a low vertical angle of at least 20 degrees to the horizon. Both antennas have better DX potential than a quarterwave vertical.

I built this highly modified 5/8 wavelength vertical antenna on Sunday, 26 August 2013, and was pleasantly surprised by its performance, considering the generally poor conditions on 10 meters.  I was able to get decent contacts on 15 and 20 meters as well.  Again, thanks to the ladder line, balun, and transmatch.

MATERIALS:

One 33 foot/10.06 meters  MFJ telescoping fiberglass mast.

One 5-foot/1.52 meters wood post to support the mast.

Six, 10-foot/3.04 meters pvc pipes and six, 3-foot/0.91 meters wooden stakes to support the pvc stakes. These posts would support the elevated radial system.  The radials would droop very slightly from the base of the antenna to the support stakes.

Six ceramic insulators to isolate the elevated radials from the support stakes.  One ceramic insulator was attached to the tip of the mast.  This insulator would support the vertical element of the antenna.

Sufficient #14 AWG housewire for the elevated radial system and the main radiating element.

One W9INN 4:1 balun, 50 feet/15.24 meters of 450-ohm ladder line, 25 feet/7.62 meters of RG-8X coaxial cable with UHF connectors, transceiver, dummy load, patch cords, low pass filter, antenna transmatch, and various tools.

ASSEMBLY:

The antenna was assembled on the ground.

Using the general formula for a 5/8 wavelength vertical antenna, 585/f (MHz)=L (ft)/178.308/f (MHz)=L (meters) and a chosen frequency of 28.4 MHz, I cut seven pieces of #14 AWG wire to a length of 20.59 feet/6.28 meters.  Six wires would be used for the elevated radial system.  One wire would be used for the main vertical element.  According to some antenna experts, the formula is about 2 feet/0.60 meters short of resonance.  So, you may want to cut your element lengths closer to 22 feet/6.70 meters.  I chose to leave the length at 20.59 feet/6.28 meters.

The vertical element was attached to the top ceramic insulator,which was secured to the tip of the mast with nylon ties and vinyl electrical tape.

The vertical wire was secured to the mast with nylon ties and run down to a point 12.41 feet/3.78 meters above the ground.

The six radial wires were attached to their pvc posts.

The 450-ohm feed line was attached to the base of the antenna (12.41 feet/3.78 meters above ground).  One wire of the feed line was soldered to the vertical element and the other wire of the feed line was soldered to the elevated radials coming from their support posts.  All connections were wrapped in several layers of vinyl plastic tape.

I hoisted the fiberglass mast onto its support stake, adjusted the elevated radials so they would be symetrical. and led the feed line, which was now about 12 feet/3.65 meters above ground level, to the garage wall where I had previously attached the W9INN 4:1 balun.  Twenty-five feet/7.62 meters of RG-8X coax with UHF connectors were attached to the balun.  The cable was led into the shack through a homemade patch panel in the shack window and then onto the Drake MN-4 antenna transmatch.  Small coax patch cords connected the Drake MN-4 to the Swan 100 MX transceiver, the dummy load, and the low pass filter.

INITIAL RESULTS:

As mentioned previously, there was a slight droop of the radials between the mast and the 10-foot/3.04 meters pvc support stakes.  The elevated radials were generally about 10-feet/3.04 meters above ground level.

With the help of the Drake MN-4, the W9INN 4:1 balun, and the 450-ohm feed line, I was able to get  a SWR of 1.3 to 1 on 20, 15, and 10 meters.  Tuning on 15 meters was a bit touchy.  Although I got some contacts on 10 meters (539 to 559 on Cw and 52 to 54 on SSB), the band was generally in poor condition at my Hawaii Island location.  Contacts on 20 and 15 meters were more consistent and stronger, with CW reports ranging from 569 to 599 and SSB results falling between 55 and 57 on 20 meters.  Fifteen meters picked up a bit by late afternoon with reports of 559 to 579 for CW and 55 to 57 for SSB.  The old Swan 100 MX was running around 25 watts.

I'll keep this antenna up for awhile and see what develops on 10 meters.

REFERENCES:

http://www.dx-antennas.com/5-8wavevertical.htm.

http://www.dxzone.com/dx20212/5-8-wave-vertical-antenna-calculator.html.

http://qsl.net/co8tw/vertical.htm.

Noll, Edward M.(W3FQJ).  "73 Vertical, Beam, and Triangle Antennas."  Editors and Engineers.  Seventh Printing. 1979.  Indianapolis, IN, 46268.

You can follow our blog community with a free email subscription.  You can also tap into the blog RSS feed.

Thanks for dropping by!

Aloha es 73 de Russ (KH6JRM).

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


Thursday, August 22, 2013

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.

MATERIALS:

Using the general dipole formula of 468/f (MHz)=L (ft) and a chosen frequency of 7.088 MHz (the frequency of the Hawaii Afternoon Net), I cut a piece of #14 AWG house wire measuring 66.02 feet/20.13 meters.  I rounded off the length to 66 feet/20.12 meters.  I cut the wire into two equal segments for the dipole...each segment measured 33 feet/10.06 meters.

Two ceramic insulators to isolate the segments from the fiberglass masts.

Two MFJ telescoping fiberglass masts...each mast was 33 feet/10.06 meters long.

Two 5-foot/1.52 meters wooden stakes to support each mast.

A homebrewed fiberglass center insulator to support the feed line.  The insulator had a hole drilled in each end to attach the feed line to each dipole segment.

Fifty feet/15.24 metes of 450-ohm ladder line.  This would be the antenna feed line.  The ladder line, used in conjunction with a 4:1 balun, a few feet of RG-8X coaxial cable, and an antenna transmatch would enable me to get multiband coverage from the dipole antenna (40 through 10 meters).

A W9INN 4:1 balun.

25 feet/7.62 meters of RG-8X coaxial cable with UHF connectors on each end.

My old but trusty Drake MN-4 transmatch.

Station equipment, including a Swan 100-MX transceiver, the Drake MN-4, a low pass filter, and a dummy load.

ASSEMBLY:

The antenna was built on the ground and later hoisted into position.

I first attached and soldered each dipole segment to the 450-ohm feedline.

I marked each dipole segment at its 60% distance from the center connector.  In this case for the 40 meter dipole, that length was 19.8 feet/6.03 meters.  The total horizontal span would then be 39.6 feet/12.07 meters.  The remaining segment lengths would be 13.2 feet/4.02 meters for each side.  The space between the ground and the bottom of each dipole segment would be 19.8 feet/6.03 meters.  A ceramic insulator was attached to each bent portion of the dipole.

The bent portions of the dipole were secured to the fiberglass masts with nylon ties.

Each mast was hoisted onto its support stake.  The dipole now conformed to an inverted "U" shape.

The 450-ohm feed line was run to the W9INN 4:1 balun attached to the garage wall.  Twenty-five feet/7.62 meters of RG-8X coax with UHF connector ran from the balun, through the shack window via a homebrew patch panel, and then to the Drake MN-4 transmatch.  Small coax patch cords connected the Swan 100-MX, the dummy load, and the low pass filter to the transmatch.

INITIAL RESULTS:

Thanks to the Drake MN-4 transmatch, I was able to get a SWR of 1.3 to 1 or lower on 40, 20, 15, and 10 meters.  The best bands were 40 and 20 meters, where I received reports on cw ranging from 569 to 599 and on SSB varying between 54 and 59.  I was running 25 watts from the old Swan 100-MX.  Ten meters was very noisy, while 15 meters had a few good contacts in the mid-afternoon, Hawaii time.

The bent dipole performs a bit better than my inverted vee, especially on 20 meters, where my reports were generally about 1 "S" unit more than the signals sent from the inverted vee.

This antenna is uncomplicated and performs better than expected.

REFERENCES:

http://www.hamradiosecrets.com/ham-radio-hf-antenna.html.
http://www.w6ier.org/images/97050561.pdg.
w4rnl.net46.net/uyagi.html.

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.

Friday, August 16, 2013

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 on my lot in the Puna District.  My xyl and I spend the weekends there remodeling our future home.  I'm able to use the various trees on the lot to erect some decent dipoles as well as my successful half square antennas for 40-and 20-Meters.  These antennas will stay because I have adequate space and supports to create a good "antenna farm."

While we're remodeling our new home, I'm still operating my amateur radio station in the confined lot which has been our home for many years.  Because of space limitations and limited areas to run a ground radial system, I've opted to use a full wavelength delta loop for my 40 through 10-Meter activity.

Over the course of the past few weeks, I've modified some of my previous loop designs and have rebuilt a delta loop which performs well, has low SWR, shows some gain over a dipole, and is easy to erect.  To get 40 through 10-Meter coverage, I'm feeding the full wavelength delta loop with 450 ohm ladder line.  The ladder line is coupled to a W9INN 4:1 balun, which is then connected to RG-8X coaxial cable.  The cable enters the shack through a homebrew wooden patch panel in a nearby window.

MATERIALS:

One 33-foot/10.06 meter MFJ telescoping fiberglass mast.  This will support the apex of the delta loop.

Using the general formula for a full wavelength loop (1005/f (MHz)=L (ft) and a chosen frequency of 7.088 MHz, the loop measures 141.78 ft/43.22 meters.  Each side of the equilateral triangle will measure 47.26 ft/14.54 meters.  I used #14 AWG housewire I bought at the Hilo, Hawaii Ace Hardware Store.

Three ceramic insulators to form the equilateral delta loop.

Three 7 ft/2.13 meters wood stakes.  One stake will support the fiberglass mast and the remaining two stakes will support the bottom side of the delta loop.

50 ft/15.24 meters of 450 ohm ladder line. This will be the feedline.

One W9INN 4:1 balun.

25 ft/7.62 meters of RG-8X.

Station tools, transceiver, low pass filter, dummy load, Drake MN-4 transmatch, nylon ties, vinyl electrical tape, soldering equipment, and dacron rope.

ASSEMBLY:

The antenna was built on the ground.  The fiberglass mast was also on the ground.

141.78 ft/43.22 meters of #14 AWG housewire was laid on the ground and passed through three ceramic insulators.  The 450 ohm ladder line was soldered to the bottom left hand section of the delta loop.  That connection was wrapped with several layers of vinyl electrical tape.

I secured the apex of the delta loop and its insulator to the top of the mast with nylon ties and vinyl electrical tape.

I hoisted the mast onto its support stake.  The bottom two insulators of the delta loop were secured to two wooden stakes equidistant from the bottom of the mast.  Dacron rope was used to tie off the bottom of the delta loop.  I made minor adjustments to the loop, so the loop would assume the shape of an equilateral triangle measuring 47.26 ft/14.54 meters for each side.

The ladder line was led to the W9INN 4:1 balun attached to the garage wall.  The ladder line was not allowed to touch the ground.  The height above ground for the ladder line ran from 7 ft/2.13 meters at the support stake to 10 ft/3.04 meters at the balun attachement point on the garage wall.

25 ft/7.62 meters of RG-8X with UHF connectors ran from the balun to the wooden patch panel in the shack window and then onto the Drake MN-4 transmatch.  Small patch cords connected the transmatch to the Swan 100-MX, the dummy load, and the low pass filter.

INITIAL RESULTS:

With the use of the Drake MN-4 transmatch, I was able to get a SWR of 1.3 to 1 across the 40, 20, 15, and 10 Meter Bands.  Using 25 to 50 watts output from the old Swan 100-MX I received reports of 559 to 599 on cw and 55 to 59 on ssb.  The best reports came on 20 meters and 40 meters.  Ten meters was fairly noisy, while 15 meters showed some life in mid afternoon.

I'll be using this loop for a while.  My other antennas have been boxed and stored in the garage.  With only one antenna in the backyard, I'll have some room to experiment with other designs until my xyl and I move to our permanent home.  The antenna performs well and gives me plenty of contacts.

REFERENCES:

http://www.youtube.com/watch?v=JiFllyZzfnUo.
http://www.youtube.com/watch?=7odS9dWcUyE.
http://www.iw5edi.com/ham-radio/?full-wave-loop-antenna,164.
http://www.radioworks.com/nloop.html.

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

Thanks for being with us today!

Aloha es 73 de Russ (KH6JRM).

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

Wednesday, August 14, 2013

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 horizontal phasing line and the two 1/4 wavelength vertical elements.  Using the formula 502/f (MHz)=L (ft) for the horizontal element and 249/f (MHz)=L (ft) for the vertical elements, and a chosen 15-Meter frequency of 21.150 MHz, I came up with the following wire lengths:  Horizontal phasing line--23.73 feet/7.23 meters.  Each vertical element--11.77 feet/3.58 meters.

One Budwig HQ-1 coax center connector.

Two ceramic insulators at the bottom of each vertical element.

Fifty feet/15.24 meters of RG-8X coaxial cable with UHF connectors.  You could also use RG-58 or RG-8 coax.  This cable would serve as the antenna feed line.

Basic tools, nylon ties, vinyl electrical tape

Transceiver, dummy load, transmatch, and low pass filter.  Although the 15-Meter half square had a SWR reading below 1.7 to 1 across the band without the transmatch, I decided to leave my trusty Drake MN-4 in line to improve the match.

ASSEMBLY:

The antenna was made on the ground and later hoisted into position.

I attached 11.77 feet/3.58 meters of #14 AWG housewire to each vertical element.  The wires were secured by nylon ties.

I soldered the left hand vertical wire to the - terminal of the Budwig center connector.  I then soldered the horizontal half wavelength phasing line (23.73 feet/7.23 meters) to the + terminal of the Budwig center connector.  Finally, I soldered the end of the phasing line to the top of the vertical wire running down the right hand mast (11.77 feet/3.58 meters).  A ceramic insulator was attached to the end of each vertical segment.

Before I connected the coax to the center connector, I wound a choke balun out of the coax just before the UHF connector.  The balun would help keep rf off the coax shield and hopefully out of the shack.

Once the antenna was finished, I hoised each mast onto its support stake and adjusted the tension of the half wave phasing line.

The coaxial feed line entered the shack window through a homebrewed wooden patch panel.

INITIAL RESULTS:

With the Drake MN-4 in the antenna system, I had no trouble bringing the SWR below 1.3 to 1 across the 15-Meter band.  Although some adjustments may be needed, I felt the  reading was satisfactory for my purposes.

The 15-Meter band is usable at my location on Hawaii Island between 1000-1700 hours local time.  Sometimes, I can work stations into the early evening if propagation is good.  Most of my mainland U.S. contacts report readings of 569 to 599 for cw and 56 to 59 for SSB.  I generally run between 25 and 50 watts from my old Swan 100-MX.

The half square is easily built, easy to erect, and requires no  radial system. When I'm done for the day, I simply lower the fiberglass masts, disconnect the feed line, and detach the transceiver from the solar powered deep cycle marine battery.

REFERENCES:

http://www.qsl.net/kaidbb/20meterhalfsquare.html.

http://www.antennasbyn6lf.com/2005/04/halfsquare_ante.html.

http://www.hamuniversity.com/wb3agwcurtainantennas.html.

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 from Russ (KH6JRM).

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


Monday, August 12, 2013

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.

Although I used the general dipole formula (468/f (MHz)=L (ft) and the general vertical formula (234/f (MHz)=L (ft) for my first half square, I elected to use slightly different formulas suggested by WB3AYW for the 20-Meter half square.  For the 1/4 wavelength vertical sections, I used 249/f (MHz)=L (ft) and for the horizontal 1/2 wavelength phasing line, I used 502/f (MHz)=L (ft).

For my chosen resonant frequency, I selected 14.200 MHz.  Using the appropriate formulas, my vertical antenna elements worked out to be 17.53 ft/10.77 meters.  The horizontal phasing line came out to 35.35 ft/10.77 meters.

I reused the two MFJ fiberglass masts (33-ft/10.06 meters), wooden support stakes, insulators, Budwig HQ-1 center coax connector,and  RG-8X coaxial cable from my previous half square antenna.

ASSEMBLY:

I built the antenna on the ground and later hoisted each fiberglass mast onto its support stakes.

From the top of each mast, I ran 17.53 ft/10.77 meters of #14 AWG wire down the mast to a little more than halfway down the mast.  A ceramic insulator was attached to each vertical segment.  The wire was secured to each mast with nylon ties.

At the top of the left hand mast, I attached a Budwig HQ-1 coax center connector.  The connector was secured to the top of the mast with nylon ties.  The vertical element was soldered to the - terminal of the coax connector.

I then soldered the horizontal 1/2 wavelength phasing line (35.35 ft/10.77 meters) to the + terminal of the coax connector.  The horizontal line was secured to the top of the right hand mast with nylon ties.

The horizontal phasing line was soldered to the remaining vertical element.

Before I attached the coaxial feed line to the coax connector, I made a simple choke balun out of the coax just before the UHF connector.  The balun would help keep rf off the coax shield and hopefully out of my shack.  I then attached the coax to the Budwig HQ-1 connector.

I led the RG-8X coax away from the antenna at a 90-degree angle.  The coax entered the shack via a homebrew patch panel in the shack window.  MFJ sells a commercial version of a patch panel that can fit into your shack window.

INITIAL RESULTS:

Although the antenna can be used without a transmatch on 20-Meters, I preferred to leave my trusty Drake MN-4 in the line.  I was able to get the SWR down to 1.1 to 1 across the entire 20-Meter band.

Results were most satisfactory.  With the half square positioned NW to SE, most of my 50 watts from the Swan 100-MX was aimed for the mainland U.S. and Australia (the antenna is bidirectional).  My receive signal from both areas was about 1 to 2 "S" units above my low-slung dipole and multiband inverted Vee antennas.  Transmitted signals also showed some improvement.  CW reports varied from 569 to 599, with SSB contacts reporting 55 to 59.

When I'm done for the day, I just lower the masts and disconnect the RG-8X coax feed line.  I'm pleased with this simple, inexpensive antenna.  Best of all, I don't have to spend time establishing an extensive ground system.

Later, I plan to build half squares for 15- and 10-Meters.

If you want to build an antenna with some gain over a vertical or a dipole, the half square may be worth trying.

REFERENCES:

http://hamuniverse.com/wb3aywcurtainantenna.
http://www.qsl.net/ka1dbb/20meterhalfsquare.html.
http://www.antennasbyn6lf.com/2005/04/halfsquare_ante.html.

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 end of this post.

Aloha es 73 de Russ (KH6JRM).

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

I



Friday, August 9, 2013

A Simple 40-Meter Half Square Antenna. Post #219

On Friday, 09 August 2013, I built my first 40-Meter Half Square Antenna.  Several hams I know have used this simple antenna to increase their contacts on 80 and 160 meters.  The antenna provides some gain over a single vertical antenna and offers some signal rejection off the sides.

According to my preliminary research, the half square is a wire antenna with 2 vertical elements fed in phase.  One quarter-wave vertical is fed at a  top corner where its attached by a coaxial center connector (such as the Budwig HQ-1).  The other end of the coaxial connector is attached to a horizontal half-wave phasing line and then connected to another quarter-wave vertical aiming down to the ground.  Both vertical segments are insulated from ground.  The vertical elements are supported by masts or other objects such as trees.  With the antenna being fed at a top corner, the current portion of the antenna is high with a good match to 50-ohm coaxial cable.  No ground radial system is required.

According to some antenna experts, the half square is essentially broadsided, bidirectional, and exhibits between 4 to 5 dB of gain over a single vertical radiator.  The antenna can be built at low cost and offers a low angle of radiation--perfect for DX activity.

MATERIALS:

Two supporting masts.  I had two 33-foot/10.06 meter telescoping MFJ masts that would work for this project.

Support stakes for the masts.

One Budwig coaxial center connector.

Fifty-feet/15.24 meters of RG-8X coaxial cable for the antenna feed line.

Two ceramic insulators.  These insulators would be attached to the bottom portion of each vertical element and insulate the radiators from the ground.

Sufficient #14 AWG house wire for two vertical elements and one half-wave phasing line.  Using the general formula 468/f (MHz)=L (feet) and the chosen frequency of 7.088 MHz, I cut wire measuring 66.02 feet/20.13 meters.  This length of wire would be the half-wave phasing line.  Each quarter-wave  vertical element would be half of this amount, or 33.01-feet/10.06 meters.  There are formulas specifically designed for the half square antenna. These formulas would make each of my elements a bit longer.  But, in the interest of simplicity and testing, I decided to use the standard dipole and vertical equations.

An antenna transmatch to compensate for the small amount of SWR found in my system.  If other, more specific equations are used, the 40-Meter half square can be used without a transmatch.  

Transceiver and associated equipment.  In my case, I used my old Swan 100MX, a dummy load, and a low pass filter.

ASSEMBLY:

I built the antenna on the ground.  Before I attached the RG-8X coax to the Budwig coax connector on the top of the left mast, I wound a choke balun out of the coax near the connecting point.  The choke would cut off any stray rf running down the coax shield.

I secured the wire to the first vertical element (33.01-feet/10.06 meters) and soldered the coax connector to the wire.  A ceramic insulator was attached to the bottom of this element to keep it off the ground..

I next connected the half-wave phasing line (66.02 feet/20.13 meters) to the other end of the Budwig coax connector.  That connection was soldered.

I finished the antenna by attaching the final 33.01-feett/10.06 meters) to the horizontal phasing line and passing that line down to the bottom of the second mast.  As with the first mast, the vertical element was secured by nylon ties to the MFJ fiberglass mast.  A ceramic insulator was attached to this vertical element to isolate it from ground.

Once the antenna was hooked up, I hoisted each mast onto its wooden support stake, adjusted tension on the horizontal phasing line, and ran the coax to my Swan 100-MX.

INITIAL RESULTS:

Considering the liberties I took with the general dipole formula, the antenna proved remarkably successful.  With two vertical elements fed in phase, I experienced very little noise coming in from the side of the antenna.  I oriented the half square antenna NW to SE, with the main lobe of radiation aimed at the mainland U.S. and other lobe in the general direction of Australia.  I received contacts from both areas during the early evening hours.  Using about 50 watts output from the old Swan 100 MX, I got 569 to 599 reports on CW and 55 to 59 on SSB.  Received audio was about 1 to 2 "S" units louder than my 40-Meter Inverted Vee.

I kept the Drake MN-4 transmatch in the antenna system to take care of the small SWR expected from this experimental antenna.  With the Drake MN-4 in line, I was able to keep SWR 1.3 to 1 over the entire 40-Meter band.  I probably should have made the antenna elements and horizontal phasing line a bit longer, but, for my purposes, the antenna was satisfactory.

I had fun building this antenna.  The half square can improve your signal with very little financial expense.

REFERENCES:

http://www.hamuniverse.com/wb3aywcurtainantennas.html.

http://www.angelfire.com/electronic/hypower/webdoc7.html.

http://www.va7st.ca/home.com/ant/files/antenna_halfsquare_broadband.pdf.

rudys.typepad.com/ant/files/antenna_halfsquare_array.pdf.

McCoy, Lew (W1ICP).  Lew McCoy On Antennas--Pull up a chair and learn From The Master.  Second Printing, 1997.  CQ Communications, inc., Hicksville, NY, 11801. pp. 54-55.

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Aloha es 73 de Russ (KH6JRM).

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


Sunday, August 4, 2013

An 80 through 10 Meter doublet antenna. Post #218

Sometimes the simple things in life are best.  This reasoning can be applied to amateur radio antennas, where cost and ease of assembly are factors for your "antenna farm".

As much as I like towers and 4-element monoband HF antennas (I've used them during Field Day events), the cost of such structures can really ruin my retirement income.  So, as I've done in the past, I've designed and built simple antennas that "do the job" without depleting my bank account.  In most cases, limited funds, restrictive operating conditions, lack of space, and proximity to neighbors have dictated easily built antennas such as verticals, inverted vees, delta loops, and small flat-top dipoles.

Recently, my xyl and I were clearing some of her property in the Puna District when I saw two Norfolk Pine Trees separated by approximately 120 feet/36.58 meters.  There was a branch on each tree approximately 50-feet/15.24 meters above ground.  These branches would make a suitable support for an 80-10 Meter half-wave doublet or flat-top dipole.  The extra length needed to make the antenna "work" on 80 Meters could be suspend from each branch, with most of the length going from tree to tree.

A basic doublet is a half-wave dipole cut for the lowest frequency of use (in this case 80 meters), fed with 450-ohm ladder line, connected to a 4:1 balun.  A length of 50-ohm coaxial cable would run from the balun to the shack antenna transmatch and then on to the transceiver.  You could also use coaxial cable for monoband operation on the frequency of your choosing.

Since I had the necessary equipment in my "go kit", I could build a simple dipole fed with ladder line and get on the air without much difficulty.

MATERIALS:

100-feet/30.48 meters of 450-ohm ladder line.
One homebrew center connector.
Two ceramic insulators.
150-feet/45.73 meters of #14 AWG housewire for the dipole antenna.  I always measure out more wire than I need.  Actually, you could use any gauge wire for a temporary antenna.  I've found that #12 or #14 AWG wire is tough and will stand up to most weather conditions.


25-feet/7.62 meters of RG-8X with UHF connectors.
One W9INN 4:1 current balun.
One antenna transmatch.  My "tuner" was the classic Drake MN-4.
Two, 60-foot/18.29 meters of monofilament fishing line tied off with sinkers.
One WalMart slingshot.  The slinghshot would be used to launch the dipole into the trees.
One deep cycle marine battery with solar panel charger.
One folding table and chair.
Note paper, pen, calculator, sunshade.
A 7-foot/2.13 meters wooden stake to support the ladder line as it came off the center connector.
ASSEMBLY:

Since I wanted to cover amateur radio bands from 80 to 10 Meters, I cut the dipole for my chosen frequency of 3.500 MHz.  With the ladder line, balun, and antenna transmatch, I could work all bands without worrying about the severe mismatch that would occur on certain frequencies.

Using the general formula 468/f (MHz) = L (feet), I cut the dipole to a length of 133.71 feet/40.76 meters.  The dipole was cut into two equal parts measuring 66.85-feet/20.38 meters.

I connected the 450-ohm ladder line to my homebrew center connector.  I then soldered each segment of the dipole to the ladder line held by the center connector.  Each connection was wrapped in several layers of vinyl electrical tape.

Ceramic insulators were attached to each free end of the dipole segments.

Monofilament fishing line (with a sinker attached) was attached to each ceramic insulator.

A slingshot was used to launch each end of the dipole to a corresponding tree limb on each tree.  Since the distance between trees was not 133-feet/40.54 meters, there was approximately 13-feet/3.96 meters of antenna wire hanging down the tree in addition to the fishing line and sinker.

The monofilament fishing line, sinker, and extended piece of antenna wire were secured to each tree with a little "slack" in the dipole to accommodate the effect of wind on the trees.

One the dipole antenna was stabilized, I ran the 450-ohm ladder line to a 7-foot/2.13 meters stake near my operating table.

A 4:1 balun was attached to the ladder line.  A 25-foot/7.62 meters piece of RG-8X was connected to the 4:1 balun and terminated at the Drake MN-4 antenna transmatch.  Several small coaxial patch cords connected the Drake MN-4 to the dummy load and Yaesu FT-7 QRP transceiver.  Once the deep cycle marine battery was attached, I had power to run this portable station.

INITIAL RESULTS:

Thanks to the trusty Drake MN-4, I was able to get a SWR of 1.1 to 1 across 80, 40, 20, 15, and 10 meters.  Tuning was a little "touchy" on 20 meters.  With a power of only 10 watts, I was able to make several contacts on 80 and 40 meters and a few contacts on 20 and 15 meters, both CW and SSB.  Ten meters was quite noisy on Friday afternoon, so I didn't attempt much on that band.

For a simple antenna, the multiband doublet with ladder line does an excellent job.  Even with a bit of antenna wire hanging vertically down the tree support, performance has been quite good.  Antenna experts recommend that a doublet be erected as high as possible, preferably above 60-feet/18.29 meters.  Although my antenna height was below 60-feet/18.29 meters, it provided me with many contacts and an enjoyable few hours on a late Friday afternoon.

When I was done for the day, I cut off the sinkers from the fishing line, collected the collapsed dipole, rolled up the feed line and coaxial cable, and stored the old Yaesu FT-7 in the "go kit" behind the driver's seat of my minivan.  The Drake MN-4 and the 4:1 balun would be taken home for use in the shack.

Try a doublet with ladder line, balun, and a transmatch.  You'll have lots of fun with an antenna your built yourself!

REFERENCES:

http:www.hamuniverse.com/hfdoublet.html.
http://www.eham.net/Reviews/detail/255.
http://norcalqrp.org/norcaldoublet.htm.
http://pc5e.nl/downloads/wireantennae.pdf.

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Aloha es 73 de Russ (KH6JRM).

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