Thursday, May 29, 2014

Simple Ham Radio Antennas: An Extended Double Zepp for 20 meters. Post #277

How would you like to have a simple dipole-like antenna that would give you almost 3dB over over the classical dipole antenna?  You can if you're willing to build a Double Extended Zepp antenna for your favorite amateur radio band.  

Now that I have enough room at my new home-in-progress in the Puna District of Hawaii Island, I decided to make a simple gain antenna for one of my favorite DX bands--20 meters.

I had a spare MFJ telescoping fiberglass mast available, some leftover #14 AWG house wire in the garage, a spare 4:1 W9INN balun, a 50-ft./15.24 length of 450 ohm ladder line, a sturdy Drake MN-4 transmatch ("the tuner"), and 25-ft./7.62 meters of RG-8X coaxial cable with UHF connectors.

I decided to configure the extended double zepp as an inverted V, knowing that its gain would be a bit less than a horizontal arrangement of a half wavelength dipole.

With school over until mid-August, I thought this simple antenna project would give me something creative to do over the summer, in addition to the usual home repairs, yard maintenance, and the various "honeydos" needed to keep domestic bliss.

Before I built this antenna on Wednesday, I did a bit of research and tried to keep construction simple and fairly inexpensive.

Basically, an extended double zepp is a center-fed dipole type antenna consisting of two collinear 0.64 wavelength (5/8 wavelength) elements fed in phase.  Theoretically, this type of antenna gives an approximate 3dB gain over a conventional horizontal dipole designed for the same frequency.  If you will be using this antenna for only 20 meters, you'll need a 1/4 wavelength matching stub in addition to a current balun and an antenna transmatch ("tuner").  Since I wanted to have multi- band coverage from 20 meters through 10 meters, I decided to use a length of 450 ohm ladder line connected to a 4:1 current balun.  A piece of 50 ohm coaxial cable would would then join the balun to the antenna transmatch in the shack.

Using a general formula for an extended double zepp antenna from William K. Hibbert (WB2UVO), 600/f (MHz)= L (ft), each antenna segment worked out to a length of 42.25 ft/12.88 meters.  The total length of the extended double zepp totaled 84.50 ft/25.76 meters.

MATERIALS:

One hundred feet/30.48 meters of #14 AWG house wire for the antenna elements (two equal lengths of 42.25 ft/12.88 meters).  It doesn't hurt to have more wire than you need.

One 33-ft/10.06 meters MFJ telescoping fiberglass mast.

One 5-ft/1.52 meters wooden support stake for the mast.

Fifty-feet/15.24 meters of 450 ohm ladder line.  This would serve as the antenna feed line.  In an article authored by W2HT and IW5EDI, certain lengths of 450 ohm ladder line were  to be avoided because of matching problems.  These lengths include 32-ft/9.75 meters, 64-ft/19.51 meters, 96-ft/29.26 meters, and 124-ft/37.80 meters.  With 50-ft/15.24 meters of 450 ohm ladder line available, matching problems should be reduced.

One "ladder lock" device to secure the ladder line and attached antenna elements to the top of the mast.

Two ceramic insulators and nylon rope to tie off the sloping antenna segments to nearby tree branches.

Two 50-ft/15.24 meters lengths of nylon rope with fishing sinkers attached.  These ropes would be connected to the end insulators of each antenna segment and  tossed over nearby tree trunks to form a slightly sagging inverted V antenna configuration.  The ropes would be secured to branches approximately 10-ft/3.04 meters above ground.

One W9INN 4:1 current balun.

Twenty-five feet/7.62 meters of RG-8X coaxial cable with UHF connectors.

Station equipment, including a Drake MN-4 antenna transmatch ("tuner"), Ten-Tec Argosy II transceiver, low pass filter, Heathkit Cantenna dummy load, and various tools.

ASSEMBLY:

The antenna was built on the ground.  The ladder lock device was attached to the top of the mast.  Each leg of the ladder line was strung through the ladder lock and secured to an antenna element.  All connections were soldered and wrapped with several layers of vinyl electrical tape.

The ladder line was led down the mast to a point approximately 5-ft/1.52 meters above ground level.  The ladder line was secured with nylon ties.

Each antenna element was attached to a ceramic insulator and to its corresponding nylon rope/sinker combination and shot over nearby tree limbs with a slingshot.

I carefully hoisted the fiberglass mast onto its wooden support stake.

I adjusted each sloping element to form  a uniform V shape and tied off the nylon rope/sinker combination to nearby tree limbs.  The ends of the inverted V were approximately 10-ft/3.04 meters off the ground.

I then led the 450 ohm feed line to the 4:1 balun attached to the garage wall.  The ladder line was not allowed to touch the ground.  The terminal point of the balun was 8-ft/2.43 meters above ground level.  Once the ladder line was attached to the terminals of the balun, I connected a 25-ft/7.62 meters length of RG-8X coaxial cable with UHF connectors to the balun and ran the cable through the patch panel in the window of the shack.  The coax was attached to the Drake MN-4 antenna transmatch.  Short lengths (3-ft/0.91 meters) of RG-8X interconnected the Drake MN-4 to the Ten-Tec Argosy II, the low pass filter, and the Heathkit Cantenna dummy load.

As added insurance against RF entering the shack via the coaxial cable, I attached a "counterpoise bundle" consisting of a 1/4 wavelength of wire for 40, 30, 20, 15, and 10 meters to the ground lug of the Drake MN-4 antenna transmatch.

INITIAL RESULTS:

With the Drake MN-4 in line, I was able to get a 1:1 to 1 SWR across the entire 20 meter band.  The antenna works fairly well on 30, 15, and 10 meters.  With careful adjustment, I was able to get a SWR reading of 1.1 to 1 on 30, 15, and 10 meters.  The antenna also works as a slightly long dipole on 40 meters.  SWR is easily reduced with the use of the Drake MN-4.

Based on a leisurely afternoon of operating, I was able to get multi-band contacts both in Hawaii and the mainland U.S. without any difficulty.  The best band was 20 meters, with CW contacts ranging from 579 to 599 and SSB contacts falling between 56 and 59 with the Argosy II running 50 watts.  Contacts on 15 and 10 meters were a bit spotty because of propagation issues, but even these bands produced solid copy when the bands opened in the early afternoon Hawaii time.

The results from this simple antenna were gratifying.  I had a lot of fun building this "stretched" dipole.  Best of all, I got some modest gain at a reasonable cost.  Most of the materials were in the shack or could have been bought at the nearest hardware or home improvement outlet.

Why not build an extended double zepp for your antenna "farm"?  A 10 meter version will take up less than 50-ft/15.24 meters of horizontal space.  To save space, you could opt for my inverted V design or a sloper tied to a mast or high tree limb.  All you need is a little time, a few feet/meters of wire, some ladder line, a 4:1 balun, a short length of 50 ohm coax, an antenna "tuner", and a tree limb or fiberglass mast.  Have fun!

REFERENCES:

http://www.westmountainradio.com/antenna_calculator_zepp.php.
http://www.iw5edi.com/ham-radio/428/double-extended-zepp-antenna.
http://www.rudys.typepad.com/ant/files/antenna_collinear_zepp.pdf.
http://www.home.frognet/~mcfadden/wd8nf/text/zepp.txt.

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,

Russ (KH6JRM)

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







Enhanced by Zemanta

Wednesday, May 21, 2014

Simple Ham Radio Antennas. A basic 40/15 meter dipole. Post #276

My antenna "farm" at the new QTH finally is taking shape. So far, I've built and used successfully a 40-10 meter inverted V fed with ladder line, a 5/8 wavelength vertical for 20, 15, and 10 meters, a 135-ft/41.15 meters "classic doublet" fed with ladder line that works from 80-10 meters, and a 40-10 meter delta loop fed with ladder line.  I've described these antennas in past posts.  All of them work very well with relatively low power (less than 50 watts) with my older rigs (Argosy II, Swan 100 MX, Yaesu FT-7, and a Kenwood TS-520).

Although I prefer multiband HF antennas fed with 450-ohm ladder line, I still use a few single or two-band antennas fed with 50-ohm coaxial cable when I wish to experiment on 40 or 15 meters.  Last Sunday, 18 May 2014, I decided to build a simple two-band dipole covering the 40 and 15 meter bands using a single piece of RG-8X coaxial cable.

The dipole would be designed for the lowest frequency range and then use the third harmonic of  that frequency to operate on 15 meters.  There are all kinds of ways to be sure the SWR is good on both bands. You can use capacity hats, "outrigger" add ons using small clips, or design modifications to use CW on 40 meters and SSB on 15 meters.  One can also use an antenna transmatch or "tuner" to bring both bands into resonance.

For this new antenna, I opted to design the 40 meter segment using a design frequency of 7.088 MHz (the "watering hole" for the daily Hawaii Afternoon Net on Lower Side Band), which would put the third harmonic frequency around 21.264 MHz in the 15 meter phone band.

MATERIALS AND OTHER PROCEDURES.

Before we move forward, it may be best to define what a dipole is.  According to James Healy (NJ2L), "a dipole is a balanced antenna, meaning the 'poles' are symmetrical...they're equal lengths and extend in opposite directions from the feed point."  Or, in other words, a dipole "is an antenna made of wire and fed at the center."  The dipole would be cut to a length of 1/2 wavelength for the design frequency.

The first step is to cut the antenna wire into two equal segments.  Most of the antenna was built on the ground to facilitate construction, soldering, and trimming.  Using the general formula 468/f (MHz)=L (feet) or 143/f (MHz)= L (meters) and a design frequency of 7.088 MHz, I came to total length of 66.02 ft/20.13 meters.  Each segment of the dipole would be 33.01 ft/10.16 meters.  These lengths are only approximate.  Please cut a little extra wire for trimming and adjustment purposes.  For the antenna wire, I chose some #14 AWG house wire left over from another project.

Next, I attached one end of each dipole element to a Budwig Hi Que-1 Center Connector.  You can use ceramic materials, hard plastic, wood, or even glass to make your center and end insulators.  Each connection was soldered and wrapped with several layers of vinyl electrical tape.

A ceramic insulator was attached to the far end of each dipole element.

A 75 ft/22.86 meters piece of nylon rope was attached to each end insulator of the antenna elements.  The other end of each rope was attached to a ceramic insulator.  These ropes would be later shot over two tree limbs approximately 70 ft/21.34 meters apart.  The tree limbs were approximately 35 ft/10.67 meters above ground.

With the dipole elements on the ground, I made an eight turn, 6 inch/15.24 cm diameter "choke balun" out of the RG-8X coaxial cable that would serve as the feed line.  Hopefully, this balun would keep rf out of the shack.  The balun was positioned approximately 18 inches/45.72 cm below the center coax connector.  With the balun wound and taped, I attached the free end of the coax to the Budwig Center Connector.

GETTING THE ANTENNA UP

I used a slingshot to fire each nylon rope over its appropriate tree limb.  There was enough overhang to allow me to adjust the antenna.  With the antenna loosely positioned above the ground, I carefully adjusted each nylon rope so the dipole was mostly horizontal.  If you can get your dipole up to 50 or 60 ft/15.24/18.29 meters above ground, your performance should improve.  Antenna experts recommend that you keep your dipole at least 1/2 wavelength above ground for your desired band of use.

Once the nylon ropes were secured to nearby branches, I ran the RG-8X coax to the shack patch panel.  A 6 ft/1.82 meters piece of RG-8X was run into my trusty Drake MN-4 transmatch ("tuner").  Initially, I bypassed the tuner to get a SWR reading from the antenna system without compensating for the small amount of SWR I expected on the line.  My Ten-Tec Argosy II, a Heathkit dummy load, and a low-pass filter were interconnected to the Drake MN-4.

INITIAL FINDINGS

Without the Drake MN-4 in the system, the SWR ranged between 1.4 to 1 and 1.6 to 1 on 40 meters and between 1.6 to 1 and 2.0 to 1 on 15 meters.  I worked several stations on each band without difficulty and the old Argosy II didn't seem to mind the SWR.  When I put the Drake MN-4 into the system, I was able to get a SWR of 1.1 to 1 across the entire 40 meter band and a SWR of 1.3 to 1 across the entire 15 meter band.  Obviously, some trimming has to be done.  But, for now, the antenna works very well for these two bands.  I'll leave the Drake MN-4 in the system to keep this small amount of SWR contained.

This was a fun project at almost no cost to me.  I had all of the materials on hand, so I just used what I found in the store room.  You can also configure this dipole as an inverted V, a sloper, or even as a parallel fed multi-element "fan dipole" antenna.  All of these variations on the basic dipole design work well and will give your hours of on-air fun.  You can also feed your basic dipole with 450-ohm ladder line connected to a 4:1 balun and an antenna transmatch ("tuner") to give you multi-band coverage from one antenna.

Have fun.  Build a dipole.  It's simple, cheap, and quite versatile.

REFERENCES:

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

nathan.chantrell.net/old-stuff/radio/radio-scanning/how-to-make-a-simple-dipole-antenna/

http://www/arrl.org/files/file/Technology/tis/info/pdf/9106023.pdf.

rsgb.org/main/get-started-in-amateur-radio/antennas/your-first-antenna-the-half-wave dipole.

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

Aloha,

Russ, KH6JRM

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.
Enhanced by Zemanta

Wednesday, May 14, 2014

Simple Ham Radio Antennas. A field-deployable 40-10 meter inverted V antenna. Post #275.

GOING TO THE FIELD FOR FUN AND SERIOUS BUSINESS

Considering the amount of natural and human-made disasters making headlines this year, every amateur radio operator should have a "go-kit" should it be necessary to support your community in times of emergency.  Once you have this kit, practice using it so it becomes part of your support package.

A "go-kit" should be portable, easy to set up, and contain the necessary equipment to get an amateur radio station on the air for emergency service.  Your emergency kit should also contain sufficient food, water, clothing, medical supplies, and personal items to last at least three days--more days if you can squeeze more stuff in your vehicle.

So, with this in mind, I took inventory of the "back up station" I alway take with me in my Honda Odyssey van.  The station is simple and functional.  I schedule several portable operations each year to test out the equipment and my ability to operate in the field.  In fact, such impromptu operations are an excellent way of preparing for the ARRL Field Day on 28 and 29 June 2014.  There's nothing like a little practice to keep your radio skills in shape.

When I finished mowing the lawn and cutting back some of the rainforest on my new property in the Puna District of Hawaii Island, I decided to unpack the portable station from the van and set up operations in my expansive back yard.  Everything worked very well, considering what I had available.

Here's what I assembled on Saturday afternoon, 10 May 2014:

One portable inverted V antenna made from a 33-ft/10.06 meters MFJ telescoping fiberglass mast.  The antenna elements were cut for the frequency of the Hawaii Afternoon Net (7.088 MHz), which serves as a call up frequency during emergencies. Each element was cut to a length of 33.01-ft/10.06 meters.  I used #14 AWG house wire for the antenna.

Five, 5-ft/1.52 meters wooden stakes (one to support the fiberglass mast, two for tying off the antenna elements, and two to support the feed line off the ground).

Fifty-ft/15.24 meters of 450 ohm ladder line, one W9INN 4:1 balun, and 25-ft/7.62 meters of RG-8X coaxial cable with UHF fittings.  These elements would allow me to operate on amateur radio frequencies between 40 and 10 meters.

One solar-charged  deep cycle marine battery.

One Yaesu FT-7 QRP 80-10 meters transceiver.  This is an old, dependable rig I was saving for such a purpose.

One W9INN 4:1 balun.

One MFJ air-cooled dummy load.

One J-38 key and a Yaesu microphone (the one that came with the FT-7).

Two folding tables, a folding chair, a beach umbrella for sun protection, a cooler full of iced tea, and my trusty Kenwood TR-2500 2 meter HT for some local repeater contacts.

SET UP:

Once the antenna was assembled on the ground, the wooden support stakes pre-positioned, and the apex of the V antenna attached to the top of the mast with a "Ladder Lock" device, I was set to go.

I hoisted the fiberglass mast into position, adjusted the V antenna to a uniform shape, and ran the ladder line to the 4:1 balun attached to one of the two folding tables.  Twenty-five ft/7.62 meters of RG-8X was connected to the balun and run into the MFJ-941 Versa Tuner II.  Short patch cables made from RG-8X coax connected the FT-7 and dummy load to the ATU.  I also attached a multiwire "counterpoise bundle" to the ground lug of the ATU.

RESULTS:

This simple antenna gave me several hours of pleasurable operating before I had to "call it a day".  I also made a few contacts on local repeaters with the old, but serviceable Kenwood TR-2500.  Just before sunset, I repacked the portable station in a large Rubbermaid plastic storage bin.  With the second row of seats lowered, I was able to store the folding tables, folding chair, collapsed fiberglass mast, and the marine battery in the back half of the van.  All exposed items were covered by an old quilt. I still had some room left to store some water, snacks, clothing, and the umbrella.

All told, this was a productive, enjoyable day.  This also served as valuable practice for ARRL Field Day, which will be held 28/29 June.

Here are some references that may help you set up your own radio "go-kit":

http://www.emergencyradiogokit.com.

http://www.iw5edi.com/technical-articles/building-a-go-kit.

http://www.races.org/gokit.htm.

http://www.youtube.com/watch?v=gmnnf0xUWNM.

http://www.desotoarc.org/jumpkit.pdf.

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

Until next time,

Aloha,

Russ (KH6JRM)

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

Enhanced by Zemanta

Friday, May 9, 2014

Simple Ham Radio Antennas. A 5/8 wavelength vertical antenna for 20 meters. Post #274

How would you like to have a simple, effective antenna for 20 meters thast will give you some gain over a ground plane antenna and exhibit a radiation angle of approximately 15 degrees?

You can grab more DX (distance) at a modest cost by building a 5/8 wavelength vertical antenna working in conjunction with 1/4 wavelength radials beneath the main radiating element.

I've built 5/8 wavelength antennas for 10 and 15 meters and they work very well.  If you desire multiband performance out of this antenna, you will need a balanced feed line (such as 450-ohm ladder line), a 4:1 current balun, and a sturdy ATU (antenna tuning unit).  If you prefer to use this antenna on one band only, you can establish resonance with a base loading coil that tunes the antenna to 3/4 wavelength  resonance.  Standard 1/4 wavelength wire radials are used with both versions of this antenna.

According to William I. Orr (W6SAI) and Stuart D. Cowan (W2LX), "a 5/8 wavelength antenna provides improved performance DX-wise over the ground plane and is recommended for those amateurs with restricted yard space who have nowhere to go but up."

So, let's get started.  I built and tested this 5/8 wavelength vertical antenna for 20 meters on Friday, 09 May 2014 after I completed my morning yard work.  The process was done at a leisurely pace and took approximately 4 hours to erect and test.

PRELIMINARY WORK:

Using the general formula 585/f (MHz)=L (ft) and a chosen frequency of 14.200 MHz, I cut some #12 AWG house wire to a length of 41.19 ft/12.55 meters.  This would be the vertical element.  Each 1/4 wavelength radial wire (there would be four elevated radials in this system) was cut using the general formula of 234/f (MHz)=L (ft).  Each radial came out to a length of 16.47 ft/5.02 meters.

I had one remaining MFJ telescoping mast in the garage.  The mast was 33-ft/10.05 meters fully extended. Since the length of the 5/8 wavelength vertical exceeded the length of the mast, I would run the required extra length to a nearby tree limb approximately 35-ft/10.67 meters above ground.

I also had a good supply of 6-ft/1.82 meters metal tomato support stakes in the garden storeroom.  Four of these stakes would support the slightly sloping radial wires.

Six ceramic insulators were found in my junk box along with assorted pieces of nylon rope.  Four  insulators and rope would tie off the radial wires to the support stakes.  An additional insulator would serve as the junction/connection point for the 450 ohm feed line and its attachment to the vertical element and the radial system.  A final insulator would be attached to the end of the vertical element.

One 5-ft/1.52 meters wooden support stake for the fiberglass mast.

Five, 5-ft/1.52 meters wooden support stakes to keep the ladder line off the ground until it reached the shack.

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

One W9INN 4:1 current balun attached to the outside shack wall (i.e. the garage).  The balun was approximately 8-ft/2.43 meters above ground.

Twenty five feet/7.62 meters of RG-8X coaxial cable.  The cable would lead from the 4:1 balun, through the window patch panel, and onto the Drake MN-4 transmatch or ATU.

One "counterpoise bundle" consisting of 1/4 wavelength pieces of #12 AWG household wire for 20, 15, and 10 meters.  This "counterpoise bundle" would be clipped to the Drake MN-4 ground lug.  The station grounding system was also attached at this ground lug.  The ground system consisted of copper braid from an old piece of RG-8 coax attached to a ground rod and 3 buried radials (each being 33-ft/10.06 meters long).

Short pieces of RG-8X coaxial cable would connect the station transceiver (Ten-Tec Argosy II), Heathkit Dummy Load, and Low-Pass filter to the Drake MN-4 ATU.

ASSEMBLY:

The antenna was built on the ground.

I extended the mast to its full length of 33-ft/10.06 meters.  Since I wanted an elevated radial system (ground plane), I attached the bottom of the 5/8 wavelength vertical to a point 16-ft/4.87 meters from the base of the mast.  The antenna element was threaded through the eyelet at the top of the mast and drawn out to its full length.  I then attached a ceramic insulator to the top end of the vertical element. The remaining 25.19 ft/7.67 meters of the vertical element would be attached to 100-ft/30.48 meters of nylon cord and shot over a nearby tree limb approximately 35-ft/10.67 meters above ground.  The antenna would be partially vertical and partially horizontal.

I joined the bottom of the vertical element and the four-wire radial system to the 450 ohm feedline with the help of  a ceramic insulator, with one leg of the feed line soldered to the vertical element and the other leg soldered to the four, slightly sloping radial segments.

I carefully hoisted the mast onto its support stake.  The dangling remainder of the 5/8 wavelength vertical (25.19 ft/7.67 meters) element was attached to a ceramic insulator, a nylon cord and fishing sinker, and shot over a nearby tree limb with a slingshot.  I pulled the nylon rope until the top portion of the 5/8 wavelength vertical element was nearly horizontal.  The rope was tied off to a bolder.

The 1/4 wavelength radial wires were led off at a slight angle from the the 16-ft/4.87 meters spot on the mast to four, prepositioned metal stakes, approximately 5-ft/1.52 metes above ground.

The 450 ohm feedline was attached to five, 5-ft/1.52 meters wooden stakes with thumbtacks and led to the W9INN 4:1 current balun on the garage wall.  The feed line was kept at least 4-ft/1.21 meters above ground until it reached the wall-mounted balun.  A 25-ft/7.7.62 meters length of RG-8X coaxial cable ran from the balun, through the shack window panel, and onto the Drake MN-4 transmatch.  Small lengths (3-ft.0.91 meters) of RG-8X coax with UHF fittings connected the Argosy II, dummy load, and low-pass filter to the Drake MN-4.  I also connected the previously mentioned "counterpoise bundle" to the ground lug of the Drake MN-4 transmatch.

PRELIMINARY RESULTS:

With the Drake MN-4 transmatch in the antenna system, I was able to get a 1:1 SWR across the entire 20 meter band.  With careful adjustment, the antenna can also be used on the 15 and 10 meter bands.  After construction, I was able to work both mainland U.S. and Hawaii stations with ease.  SSB reports varied between 57 and 59, while CW contacts ranged from 579 to 599+.  The old Argosy II was running 50 watts. Not bad for few hours work.

References:

The ARRL Antenna Book.  ARRL.  Newington, CT, 06111.  Fourteenth Edition, copyright 1982. pp. 8-8 to 8-30 and 13-12 to 13-13.

Hood, William.  "Home Brew Hf/VHF Antenna Handbook."  Tab Books, Inc.  Blue Ridge Summit, PA, 17214.  First Printing, October 1977. pp. 152-153.

Turner, Rufus P.  "The Antenna Construction Handbook for Ham, CB & SWL."  Tab Books, Inc.  Blue Ridge Summit, PA, 17214.  Second Printing, January 1981.  pp. 141-143.

Orr, William I. (W6SAI) and Cowan, Stuart D. (W2LX).  "Simple, Low-Cost Wire Antennas For Radio Amateurs."  Radio Publications, Inc.  Box 149, Wilton, CT, 06897.  Third Printing.  pp. 115-116.

Orr, William I. (W6SAI) and Cowan, Stuart D. (W2LX).  "The Radio Amateur Antenna Handbook."  Radio Publications, Inc.  Lake Bluff, IL. Seventh Printing, 1988.  pp.108-109.

Thanks for joining us today!  You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Aloha,

Russ (KH6JRM)

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


Enhanced by Zemanta

Monday, May 5, 2014

Simple Ham Radio Antennas: A 5/8 wavelength vertical for 15 meters. Post #273

Over the past few weeks, I've been experimenting with a 5/8 wavelength vertical antenna for 10 meters.  The antenna is a marked improvement over my 1/4 wavelength ground plane vertical for 28.400 MHz.  Some antenna experts believe the 5/8 wavelength vertical can deliver a 3 dB gain over the conventional vertical presented in most antenna books.  According to William I. Orr (W6SAI) and Stuart D. Cowan (W2LX), the "5/8-wave vertical provides improved performance DX-wise over the ground plane antenna and is recommended for those amateurs with restricted yard space who have 'nowwhere to go but up.'"

With that in mind, I spent part of Saturday, 03 May 2014, building a 5/8 wavelength vertical for the 15 meter amateur radio band, with a preferred frequency of 21.260 MHz in the phone (SSB) portion of the band.  The antenna was simple, requiring some wire, a few wooden support stakes, some ceramic insulators, a "ladder lock" support for the feed line, a length of 450-ohm ladder line, a 4:1 current balun, a length of 40-ohm coaxial cable with UHF fittings, a sturdy ATU (antenna tuning unit or transmatch), a transceiver, and related station equipment.  With the use of a balanced feed line, this antenna can be used on 20, 15, and 10 meters.

If you prefer single band operation and plan to use 50-ohm coaxial cable as your feed line, you can bring the 5/8 wavelength antenna into  resonance by "the addition of a small tapped coil at the antenna base.  The number of turns in the coil is varied to provide a low value SWR on the transmission line...." (citing Cowan and Orr in this case).

Since I try to make my antennas serve several bands, I opted to use 450-ohm feed line, an ATU, and a balun to connect the antenna to the shack's transceiver.

MATERIALS:

For ease of construction, I built the antenna on the ground, attached it to a fiberglass mast, and hoisted the assemblage into position.

1.  One 33-ft/10.06 meters MFJ telescoping fiberglass mast.

2.  Five, 5-ft/1.57 meters wooden support stakes.  One stake would support the mast, with the remaining four stakes used to tie off the slightly sloping radial elements.

3.  Approximately, 75-ft/22.86 meters of #14 AWG house wire.  One wire would serve as the vertical element, with the remaining wires to constitute the radial system.

4.  One "ladder lock" balanced line support block.

5.  50-ft/15.24 meters of 450-ohm ladder line.  This would serve as the antenna feed line.

6.  Four ceramic insulators with small lengths of nylon rope to tie off the sloping radials to pre-positioned wooden support stakes.

7.  One W9INN 4:1 current balun.

8.  One Drake MN-4 ATU.

9.  Twenty-five ft/7.62 meters of RG-8X coaxial cable with UHF fittings.  This cable would connect the balun to the Drake MN-4.

10.  Several 3-ft/0.91 meter patch cords made from RG-8X coaxial cable to interconnect station equipment to the Drake MN-4 ATU.

11.  Ten-Tech Argosy II transceiver.  I usually run the rig at the low power setting (05 watts).  But, for this test, I ran the Argosy II at the higher power setting (50 watts).

12.  One Heathkit Dummy Load.  Transceivers should be adjusted off the air.

13.  One low pass filter.  Some of my new neighbors receive over-the-air television signals.  Cable tv penetration at my new Puna District home is sparse.  Many folks still get their programs from tv repeaters in Hilo.  A few neighbors subscribe to Dish TV and other satellite services.

14.  Various tools, including soldering equipment, vinyl electrical tape, nylon ties, pliers, wire cutters, etc.

ASSEMBLY:

1.  Using the general formula for a 5/8 wavelength antenna (585/f (MHz)=L (ft), I cut the vertical element to a length of 27.51-ft (27 ft, 6.1")/8.40 meters.  This would resonate the vertical element of a frequency of 21.260 MHz.

2.  I extended the MFJ fiberglass mast to its full length on the ground (33-ft/10.06 meters).

3.  I attached the tip of the vertical element to the apex of the mast with nylon ties, ran the wire down the mast, and brought the wire to a point approximately 6 ft/1.82 meters from the bottom of the mast.  The vertical element was secured to the mast by nylon ties.

4.  Four 1/4 wavelength radial wires were cut to frequency (21.260 MHz).  Each radial segment measured 11.00-ft/3.35 meters.  A ceramic insulator and nylon tie off rope were attached to one end of each radial wire.

5.  The 450-ohm ladder line was attached to the "ladder lock" support device and a wire from one leg was soldered to the vertical element, while the four radial wires were soldered to the other leg of the ladder line.  The "ladder lock" connector was affixed to the mast by nylon ties.  The junction was approximately 6-ft/1.82 meters from the bottom of the mast.

6.  I carefully hoisted the fiberglass mast onto its wooden support stake.  Each radial was carefully led to a prepositioned wooden stake, with the end of each radial wire being tied off at a height of 4-ft/1.21 meters above ground.

7.  The ladder line was led to the W9INN 4:1 balun attached to the garage wall.  The balun was approximately 8-ft/2.43 meters above ground.  The ladder line had a very slight sag leaving the lower portion of the mast, but it didn't touch ground.

8.  A 25-ft/7.62 meter length of RG-8X coax with UHF fitting was led through a window patch panel and then connected to the Drake MB-4 ATU.  I attached a "counterpoise bundle" consisting of wires 33-ft/10.06 meters, 16.5-ft/5.03 meters, 11-ft/3.35 meters, and 8.23-ft/2.51 meters long to the ground lug of the Drake MN-4.  I also had a station ground consisting of a ground rod driving into the soil with four 33-ft/10.06 meters radial wires attached.

9.  Several small RG-8X coax patch cords were used to connect the Ten-Tec Argosy II transceiver, the Heathkit Dummy Load, and the Low-Pass filter to the Drake MN-4.

INITIAL RESULTS:

With the Drake MN-4 in the line, I was able to get a 1.2 to 1 SWR across the entire 15 meter band.  Also, the antenna loaded fairly well on 10 meters and 20 meters.  For now, I'll just use the 5/8 wavelength antenna for 15 meters.  No sense putting additional strain on the aging Drake MN-4.

So far, results have been good.  Depending on propagation and time of day, my cw reports range from 579 to 599+, while SSB varies between 55 to 59.  I'm running the little Argosy II at 50 watts.  Now that I know the antenna works properly, I'll cut back my power to between 5 and 10 watts.

This was an enjoyable and fun project, since I had all of the necessary components in my "junk box."  And best of all, the antenna works and gives my hours of pure fun--as long as 15 meters stays open.

Next on the agenda, a 5/8 wavelength vertical for 40 meters.  For this project, I think the tall Norfolk Pine Tree in the back yard and my trusty WalMart slingshot will come into play.

Thanks for being part of our day! You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Aloha,

Russ (KH6JRM)
BK29jx15--along the beautiful Hamakua Coast.

REFERENCES:

Orr, William I. (W6SAI) and Cowan, Stuart D. (W2LX).  The Radio Amateur Antenna Book.  Radio Publications, Inc.  Box 149, Wilton, CT, First Printing, 1978.  pp.108-109.

Noll, Edward M. (W3FQJ).  73 Vertical, Beam, and Triangle Antennas.  Editors and Engineers.  Indianapolis, IN, 46268.  pp. 29-36.