Saturday, January 25, 2014

Simple Ham Radio Antennas: Antennas without tuners, part 4. Post #257

So far, the "tunerless" antennas I've built have worked very well.  They have been made with locally available materials from my "junk" box, neighborhood garage sales, and the nearby Ace Hardware Store.  These antennas have consisted of individual dipoles/inverted vees for my bands of preference (40, 20, 15, 10 meters), telescoping fiberglass masts (33-ft/10.06 meters tall), a single RG-8X coaxial feed line, and supporting wooden stakes or tree branches.

Dipoles for each band were built on the ground and were later hoisted into position via a halyard and pulley system.  A "choke balun" made from part of the RG-8X feed line was attached to the mast just below the center connector at the top of the mast.

In my first multiband antenna system, I changed bands by lowering and raising the appropriate antenna into place.  I couldn't change bands by staying in the shack.

My second system was a modified "fan dipole/inverted vee" using multiple dipoles/inverted vees connected to a common connection point at the apex of the mast.  The dipole/inverted vee elements were "fanned" out below the lowest frequency dipole/inverted vee (40 meters).  The 40 meter 1/2 wavelength dipole was nearly horizontal, with subsequent bands run off at an angle below the common connection point.

The third variant of the coax-fed multiband antenna without a "tuner" was a segmented inverted vee, with the main 40 meter elements connected to 20 meter "outrigger" elements by means of clip leads.  The 40 meter segments were cut for the cw portion of the band, allowing for phone (ssb) operation in the upper portion of the 15 meter (21 MHz) band.  The 15 meter antenna would operate on the third harmonic of 40 meters. With the "outrigger" elements connected to the 40 meter elements, the antenna would function as a 3/2 wavelength antenna on 20 meters.  If I wanted to change bands, all I had to do was connect/disconnect the appropriate leads.

Now, for the next phase of the "tuner less" antenna. These next two antennas use both 450 ohm ladder line and 50 ohm coaxial antenna to create a multiband antenna.  Is it possible to do without a "tuner" and still retain the ladder line as a feed line?  Yes, if certain precautions are taken.

Back in 1992, Bill Wright (G0FAH) faced such a problem.  According to Bill, a modified G5RV antenna served as the inspiration for his "tuner less" ladder line/coaxial cable feed system.  I decided to duplicate his efforts at my new homesite in the Puna District.  I found the antenna was useful from 40 through 10 meters, with 40 meter swr measuring 2.4 to 1; 20 meter swr reading 1.5 to 1; and 10 meter swr reaching 2.4 to 1. Bill also had data for 17 and 12 meters, where swrs ranged from 2 to 1 for 18.1 MHz and 1.5 to 1 for 24.9 MHz.  I didn't test these frequencies because my older equipment didn't cover those bands.  I found an antenna transmatch was needed to work 15 and 30 meters.  In essence, I had an antenna which did well on 40, 20, and 10 meters.

I used an inverted vee for this antenna configuration, since suitable trees were not available for this antenna. As with my past antennas, I used several wooden stakes to support the fiberglass mast and to serve as tie off points for the antenna elements.  I managed to find several end insulators, some extra 450 ohm ladder line, an old 1:1 balun, and a good supply of #14 AWG house wire for the antenna elements.

As usual, I built the antenna on the ground and hoisted the inverted vee into position with a halyard and pulley system.

According to Bill here are the general dimensions of the antenna:

94-ft/28.65 meters of #14 AWG wire.  Each element was divided into two equal sections of 47 -ft/14.329 meters.  Ceramic insulators were connected to the end of each element.  A third ceramic insulator would serve as the center connector and support for the 450 ohm ladder line.  Wires connected to the ladder line were threaded through the center insulator and connected to the ladder line.  The connnections were soldered and covered with several layers of vinyl electrical tape.

Then, I rolled out 41-ft/12.50 meters) of 450 ohm ladder line.  The ladder line was soldered to the terminals of the 1:1 balun.

From the balun, I ran 25-ft7.62 meters of RG-8X coaxial cable with UHF connectors to the patch panel in the shack window.  A 6-ft/1.829 meters piece of RG-8X was connected to a Drake MN-4 antenna transmatch in bypass mode.  I would use the "tuners" meter to measure swr and power.  Once that step was done, I would not use the tuner.  The tuner would be available to work 15 meters.  Three-foot/0.91 meters sections of RG-8X would interconnect the Swan 100 MX to a low pass filter and dummy load.

I then hoisted the modified G5RV into position and adjusted the wooden support stakes to give the inverted vee an uniform and balanced appearance.

Test results were good.  I found acceptable swrs on 40, 20, and 10 meters.  The antenna works well and I'm pleased with the mainland U.S. and Hawaii contacts I've received.  Power levels ranged from 20 to 50 watts, cw and ssb.

Another approach:

For the more adventurous hams among us, an experimental multi band antenna using ladder line, a 1:1 balun, and 50 ohm coaxial cable designed by Cecil Moore (W5DXP) may prove interesting.  Cecil's antenna consists of a 130-ft/39.63 meters dipole at a height of 37-ft/11.28 meters fed with lengths of 450 ohm ladder line arranged in a relay and switching system.  Feed line length varies between 91 and 121-ft (27.74 and 36.89 meters).  Cecil says varying the length of 450 ohm feed line for each band (80 through 10 meters) will produce a low swr and maximum power transfer from your transceiver to the antenna.  He uses something called a "ladder line length selector" which adds or removes lengths of feed line depending on the band in use.  Although I haven't built this system yet, it surely looks interesting.

For now, I'll keep the "fan dipole/inverted vee" as a semi-permanent antenna.  I have multi band use with a single feed line without going outside to switch clips or adjust "outrigger" elements.  I'm not getting rid of my antenna transmatches.  They will be used in further antenna experiments.

Have fun building these antennas.  They are inexpensive, easy to build, and don't require a ground radial system.

RESOURCES:

http://www.w6ier.org/images/Five_Bands_No_Tuner.pdf.  The original article appeared in the June 1995 "QST", number 6.

http://www.w5dxp.com/notuner.htm.

http://www.arrl.org/file/Technology/tis/info/pdf/9401070.pdf.

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Aloha de Russ (KH6JRM).

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


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Sunday, January 19, 2014

Simple Ham Radio Antennas: Antennas without "tuners", part 3. Post #256

In some of my previous posts, I've investigated, built, and used multiband dipole and inverted vees using a single 50 ohm coaxial feed line.  With a telescoping fiberglass mast (33-ft/10.06 meters extended), a simple halyard and pulley system, and separate antennas cut for each band of use (40, 20, 15, and 10 meters), I've been able to change bands fairly quickly by lowering the dipole/inverted vee elements, substituting those of another band, and raising the new antenna.  With each band element cut for the desired frequency, the efficiency is high with low swr for that band.  Since each antenna element is trimmed for the lowest swr at my mast location, an antenna transmatch isn't necessary.  Sometimes, as in the case with the 40 meter dipole/inverted vee, an antenna cut for the cw portion of the 7 MHz band will often work well on the phone portion of 15 meters (21 MHz band). The 15 meter band will operate on the third harmonic of the 40 meter band.

In order to save me a trip outside to change bands, I then made a "fan dipole/inverted vee" with separate dipole elements for each band attached to a common point on the feed line located at the apex of the mast.  The principal band of use (in my case, the 40 meter band) was made as a nearly horizontal dipole with each element attached to tree branches approximately 33-ft/10.06 above ground.  Inverted vee elements were led from the common connection point at the apex of the mast and "fanned out" below the main 40 meter dipole and attached to lower branches, with each end of the antenna element approximately 5-ft/1.82 meters away from the elements above it.

In both of the above antenna projects, a "choke" balun was attached to the mast just below the feed point of the coax connector.  I used an extra Budwig center connector for the common connection point.  You could also use a "homebrew" center connector made from lucite, fiberglass, or teflon.

Both of these antennas work very well with a swr of less than 2:1 across each band.  However, you may want to cut your dipole/inverted vee antenna elements a bit longer than calculated to allow for trimming and swr adjustment.

SEGMENTED DIPOLES--another approach to coax-fed multiband antennas.

Fan Dipoles/Inverted vees are great antennas, but they often are a bit tedious to tune because of the coupling between elements.

A way to avoid the extra work and still get good performance is to design and build a segmented dipole/inverted vee, with the main elements used for your lowest frequency band and segmented dipoles with clip leads to provide coverage on other bands.

When I first started refurbishing my permanent home in the Puna District of Hawaii Island, the first antenna I built (and still use) was a combination 40, 20, and 15 meter segmented dipole using a single telescoping fiberglass mast, a halyard and pulley raising and lowering system, and a single RG-8X coaxial cable with UHF connectors for the feed line.  This antenna didn't require an antenna transmatch or "tuner".

I chose the inverted vee configuration because this antenna used only one tall support and could be raised and lowered by one person.  This antenna didn't require a ground radial system.

MATERIALS:

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

Three, 5-ft/1.82 meters wooden support stakes.  Two stakes would be used to tie off the ends of the segmented inverted vee.  One wooden stake would be used to support the lightweight fiberglass mast.  The antenna elements would also help support the mast and would function as "guy wires".

A total of 125-ft/38.10 meters of #14 AWG house wire for the antenna elements and segments.  I didn't require this much wire, but a little extra would be handy if I miscalculated the length of any element.

Seventy-five feet/22.86 meters of RG-8X coaxial cable with UHF connectors.  This would be the common feed line for the multiband antenna.

Basic tools, including wire cutters, soldering iron, nylon ties, vinyl electrical tape, and assorted items.

Transceiver (Swan 100 MX), low pass filter, Drake MN-4 transmatch--I would use the SWR meter on the transmatch to help trim the antenna for the lowest swr, and the trusty Heathkit Cantenna dummy load.  The antenna transmatch would always be available if I chose to use it.  But in this case, I bypassed the "tuner" and just used the SWR meter.

Four ceramic insulators.  These would be used to tie off the ends of each antenna segment.

Four antenna clips to join the main 40 meter inverted vee elements to the 20 meter segments.  Small pieces of dacron rope would be used to tie off the final segments to the end support stakes.

ASSEMBLY:

The antenna was built on the ground.  The antenna elements were cut and attached to the Budwig center coax connector in the garage where I could solder without interference from the wind.

The 40 meter antenna would be cut using the standard dipole formula, 468/f (MHz)=L (feet).  I used a design frequency of 7.088 MHz (the frequency of the Hawaii Afternoon Net).  Wire measuring 66.02 ft/20.13 meters was cut for the 40 meter portion of the antenna.  Although my calculations were fairly accurate for my location, you may want to cut your elements a bit longer to allow for trimming and swr adjustment.  I then divided the dipole into two equal segments, measuring 33.01-ft/10.06 meters each.

Each element was connected and soldered to the center coax connector.  The connection was wrapped with several layers of vinyl electrical tape.  The end of each element not connected to the center connector was attached to a ceramic insulator.  After securing the wire to the insulator, an inch (2.54 cm) of wire insulation was stripped off and soldered to a small battery clip.

At this point, the antenna could be used as a 40/15 meter antenna, with the 40 meter segment cut for the cw part of the band, while the third harmonic of 7.088 MHz could be used in the phone portion of the 15 meter band.  In Hawaii, amateur radio operators can use 7.088 MHz for LSB purposes.  So, this works out rather well for those of us in the Central Pacific.

To use the antenna on 20 meters, an "outrigger" segment must be added to each 40 meter element via a clip lead.  Fortunately, the addition of a 1/4 wavelength element for 20 meters to each 40 meter element will do the trick.  This makes the new 20 meter dipole/inverted vee a 3/4 wavelength antenna for each side of the dipole/inverted vee.  With all segments connected, the 20 meter antenna will function as a 3/2 wavelength antenna on 20 meters.  So, using the general formula 468/f (MHz)=L (feet) with a chosen frequency of 14.200 MHz, the length of the 20 meter segment will be 32.95- ft/10.04 meters or 16.47- ft/5.02 meters for each dipole/inverted vee element.

The total length of the combined 40/15/20 meter inverted vee will be 49.48-ft/15.08 meters per side or a total length of 98.96-ft/30.16 meters for the entire antenna.

Once the 40 meter dipole/inverted vee is made, the 16.47-ft/5.02 meters segments for 20 meters are attached.  The 20 meter segment is threaded through the end insulator of each 40 meter element and connected to a small battery clip.  The connection to the clip is soldered.

With the telescoping mast on the ground, I attached the Budwig center coax connector to the halyard and pulley system.  Just below the center connector, I connected a "choke balun" comprising 8 turns of RG-8X coaxial cable, 8-inches/20.32 cm in diameter to the Budwig center connector.  The "choke balun" is then secured to the mast with nylon ties and vinyl electrical tape.  The coaxial cable feed line is run down the mast to a point 16-ft/4.87 meters above ground level.

I hoist the fiberglass mast onto its wooden support stake and slowly pull up the antenna center connector with the halyard and pulley arrangement.  Once the center connector is at the tip of the mast, I secure the halyard and tie off the ends of the 20 meter segments to their respective wooden stakes.  I adjust the antenna to a uniform and balanced appearance.  The clip leads are easily attached by using a small ladder to connect the segments.  To use the inverted vee as a 40 meter antenna, leave the clip leads disconnected.  To use the antenna as a 3/2 wavelength on 20 meters, connected all clip leads together.

I run the remaining length of RG-8X to a hook on the garage door about 10-ft/3.04 meters above ground.  There is sufficient clearance for a vehicle to pass under the antenna without snagging the feed line.

I then run the feed line through my "homebrewed" patch panel in the shack window into the old Drake MN-4 transmatch.  The "tuner" is bypassed so only the swr meter is used.  A series of short patch cables (RG-8X measuring 18-inches/45.72 cm) connects the Swan 100-MX transceiver to the bypassed "tuner", dummy load, and low pass filter.

Since the terminal point of the inverted vee is around 5-ft/1.82 meter above ground, connecting the segments together for 20 meter operation is easy.  I was lucky to have the 20 meter segment read a swr below 2:1 across the band.  The 40 meter segment was better at 1.6 to 1.  With the Drake MN-4 in line, I was able to get the swr to read 1:1 across both 40 and 20 meters.  On 15 meters, the swr measured 1.7 to 1 with the Drake MN-4 bypassed.  With the transmatch in the line, I was able to get a 1:1 swr.  Obviously, some adjustments must be made.  But, for now, the antenna works very well without the "tuner".  The old Swan 100- MX stays cool running 20 to 30 watts cw and ssb.

Contacts are being made both locally and throughout the Pacific and mainland U.S.A.  This antenna doesn't outperform a yagi on a 50-ft/15.24 meters tower, but it does do well for what it is.  Because the current maximum is at the tip of the mast, it provides an acceptable match for 50 ohm coaxial cable.  Best of all , I had most of the material on hand and I didn't have to make an extensive ground system.

When I'm done for the day, I lower the antenna with the halyard and pulley system, disconnect the antenna feed line, and ground the antenna system to a ground rod in back of the garage.  Because the antenna is behind my house and is surrounded by trees, it is nearly invisible.  So far, there have been no complaints from my neighbors.

Next time, I'll look at "tuner-less" antennas that use a combination of 450 ohm ladder line, a balun, and coax to attain multiband capability.

RESOURCES:

Noll, Edward M. (W3FQJ).  "Easy-Up Antennas for Radio Listeners and Hams.  MFJ Enterprises, Inc., Mississippi State, MS, 39762.  Limited Edition, 1991. pp. 111-112 and pp. 117-118.

Noll, Edward M. (W3FQJ).  "73 Vertical, Beam, and Triangle Antennas."  Editors and Engineers, Indianapolis, IN, 46266.  Seventh Printing, 1979.  pp. 70-74.

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 de Russ (KH6JRM).

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

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Monday, January 13, 2014

Simple Ham Radio Antennas. Antennas without "tuners". Part 2. Post #255

One of the more popular amateur radio antennas is the multiband "Fan Dipole" and its close relative the multiband inverted vee "Fan Dipole."  According to Howard (W6HDG), the Fan Dipole "consists of  two or more distinct half wave dipoles which are mounted to a common parallel feed point so that a single feed line can be utilized."  With a little ingenuity and careful trimming, it is possible to make a single band dipole antenna work on several bands just by adding half wavelength dipoles for your favorite band to the center coax connector and by "fanning them out" below the dipole for the lowest frequency.  Add a 1:1 balun or a "choke" balun below the center connector, connect some 50 ohm coaxial cable, run the cable to your rig, and you're ready to go on your favorite bands without a "tuner" and a ground radial system.

According to Simone (IW5EDI), "an antenna like this works on multiple bands because the antenna presents a high impedance on the elements that aren't resonate, allowing the resonant elements to radiate ...."

A quick search of the data available, shows there are many approaches to building a "Fan Dipole"--some of them backed by research from the Standford Research Institute and years of individual ham operator experience.

My goal in this antenna project was not to duplicate the plans of these authors or to buy all the necessary auxiliary supplies needed to build these antennas.  All I wanted was to build, erect, and use a simple "Fan Dipole" with the materials I had at the qth or from the local hardware store.    A  secondary purpose was to build an antenna that was portable and inexpensive to make.

MATERIALS:

My property in the Puna District of Hawaii Island is blessed with an abundance of trees approaching 50 feet/15.24 meters in height.  Some of these trees are stately Norfolk Pines which have strong lateral branches every 5 feet/1.82 meters or so.  These trees would make perfect supports for the end of each inverted vee element.

One 33-foot/10.06 meters MFJ telescoping fiberglass mast.  This would be the main support for the multielement inverted vee and the coaxial feed line.

Seventy-five feet/22.86 meters of RG-8X coaxial cable with UHF connectors.  This will be the antenna feed line.

Six ceramic insulators to tie off antenna elements to tree branches.

One 5-foot/1.82 meters wooden stake to support the fiberglass mast.

One Budwig HQ-1 center coax connector.

One 'homebrew choke" balun to keep rf off the feed line and station equipment.

Approximately 150- feet/45.73 meters of #14 AWG housewire for the antenna elements.  You won't need the total amount, but it doesn't hurt to have some extra wire around.

Approximately, 200- feet/60.97 meters of 0.25 inch diameter/0.635 cm diameter dacron rope.

A MFJ antenna analyzer would be helpful for trimming purposes.  Since I didn't have one in the shack, I used the SWR meter in my Drake MN-4 antenna transmatch for any trimming needed.  Clumsy and slow, but it did the job.

ASSEMBY:

The antenna elements were made and connected on the ground.

The inverted vee "Fan Dipole" would cover the 40/15 (shared antenna), 20, and 10 meter bands.

Using the general forumla 468/f (MHz)=L (feet), my antenna elements looked like this:

40 meters (7.088 MHz/21.264 MHz)--33.01-feet/10.06 meters for each element (2).  By cutting the antenna for the cw portion of 40 meters, I could use the antenna on its third harmonic for ssb in the 15 meter band.

20 meters (14.200 MHz)--16.48-feet/5.02 meters for each element (2).

10 meters (28.400 MHz)--8.23 feet/2.51 meters for each element (2).

Each dipole was soldered to the Budwig HQ-1 center connector.

30-feet/9.14 meters of dacron rope was tied to each end insulator of the antenna elements.

A halyard and pulley system would be used to hoist the center connector and antenna elements into position.  I used 50-feet/15.24 meters of dacron rope and a marine pulley from "Ace Hardware" to complete the hoisting mechanism.

A "choke balun" consisting of 8 turns of RG-8X coaxial cable measuring approximately 8-inches/20.32 cm in diameter was positioned just below the connecting point of the center insulator and the coaxial feed line.  You could also use a commercially bought 1:1 balun.  The "choke balun" was taped to the fiberglass mast.  The coaxial feed line was led down to the 16-foot/4.87 meters point on the extended mast.  That part of the coax was taped to the mast and secured with several nylon ties.  The remainder of the coax would be lead off the ground to the patch panel in the shack window.

I slowly hoisted the mast onto its support stake.

I used a slingshot to fire each dipole over suitable branches in the two Norfolk Pine Trees.  The trees were approximately 40-feet/12.19 meters apart.  The top dipole elements belonged to the 40/15 meter antenna, and they were shot through branches approximately 30-feet/9.14 meters above ground.  The top dipole was nearly horizontal. The dipole elements were tied off at lower branches with the leftover rope.  I found my antenna length was pretty much close to what I had calculated, leaving the dipole with a swr of 1.6 to 1.

The 20 meter dipole was led off the center connector at an angle and secured to a branch 25-feet/7.62 meters above ground.  Extra rope was tied off at a lower branch.  The swr of this dipole wasn't too bad--1.7 to 1.  Five-feet/1.82 meters separated the ends of the 40 and 20 meter dipoles.

The 10 meter dipole was led off the center connector at an angle below the 20 meter inverted vee.   The 10 meter elements were secured to branches approximately 20 feet/6.09 meters above the ground.  Extra rope was tied off at lower branches.  The swr for the 10 meter antenna elements was 1.9 to 1.

The antenna  was adjusted so  the appearance of the inverted vees was uniform and balanced.  Before I started on-air contacts, I tested the antenna with the Drake MN-4 transmatch in the system.  I was able to get a swr of 1:1 on all bands. Without the transmatch in the line, the swr measured less than 2:1 across each band preference.

Your results will vary because of local ground conditions, proximity to structures, and space restrictions.  Even if you don't get a great swr, you can use an antenna transmatch to smooth things out. Try to keep the antenna elements separated as much as possible to cut down on coupling.

RESULTS:

Considering the materials available, I am satisfied with the overall results of this inverted vee "Fan Dipole." Running 50 watts from the old Swan 100MX, I had no trouble maintaining solid cw and ssb connections with stations in Hawaii and on the U.S. mainland.  Despite the relative crudeness of this antenna, it has performed very well at my new home site.  The antenna is fed at a current maximum for all bands and does not require a radial ground system.  Most of your material can be found at the nearest home improvement outlet or hardware store.  If you don't have tall trees on your property, you can use several telescoping fiberglass masts to support the antenna.  Be creative, save money, and build it yourself.

REFERENCES:

http://www.hamuniverse.com/multidipole.html.
http://www.hamuniverse.com/kb3pkbfandipole.html.
http://www.hamuniverse.com/ae5jumultibanddipole.html.
http://www.hamuniverse.com/w6hdgfandipole.html.
http://www.iw5edi.com/ham-radio/?20-40-dual-band-dipole0146.

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

Aloha de Russ (KH6JRM

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







Friday, January 10, 2014

Simple Ham Radio Antennas: Antennas without "tuners", part 1. Post #254

Antenna transmatches or "tuners" are wonderful devices that make amateur radio operations easier.  They can help minimize swr on antenna feed lines and extend the band coverage of your present antenna.

However, there are times when such devices may not be needed, especially if you're designing an antenna for a single band or are contemplating an emergency or portable antenna for your "go" kit.  By carefully designing, cutting, and trimming your basic 1/2 wavelength dipole for the lowest swr, you can just connect a good quality 50 ohm coaxial cable feed line and run the band of your choice without much difficulty.

In this post, I will describe a few simple coax-fed dipoles and inverted vees that will serve your favored amateur radio band without the need for an antenna transmatch.  Of course, you could always insert a transmatch into the system to squeeze out the maximum power at the lowest possible swr if you so desire.  These antennas work either way.  For the purposes of this post, I will confine my choice of antennas to dipoles and inverted vees and save vertical antennas and their ground systems for another post.

In most cases, the dipoles and inverted vees cited in this article have been tested by me in both home and portable operations. Most of these antennas are single band affairs, unless stated otherwise.  However, by connecting a series of spaced dipoles to a single coax feed line, you can get multiband coverage.  Sometimes, this arrangement is called a "fan dipole."  As with the monoband dipole, an antenna transmatch can be used to remove any swr on the feed line.  So, if your design shows a bit of swr, insert the antenna transmatch and adjust accordingly.  I'll be covering the "Fan Dipole" in a later post.

The antennas I've built exhibit a swr of 2:1 or less across the band of choice.

MATERIALS NEEDED:

Depending on the amount of structures, trees, and masts available, you can build a standard 1/2 wavelength horizontal dipole or its close cousin the inverted vee.  The inverted vee requires only one tall structure, a wooden stake to support a telescoping fiberglass mast, and two end stakes to support the ends of the drooping antenna elements.  In my situation, I opted for the inverted vee designed for 40 meters.  By cutting the antenna for the lower end of 40 meters (below 7.080 MHz), I can use the third harmonic of this frequency to operate in the phone segment of 15 meters (21 MHz).

Sufficient wire to make two equal dipole elements.  Using the general formula 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 AWG #14 housewire for the antenna elements measuring 66.02 ft/20.13 meters.  Each antenna element would be one-half of the dipole length or 33.01 ft/10.06 meters.  There are some antenna experts that believe a better forumla to use for the inverted vee is 464/f (MHz)=L (ft).  In any case, cut your antenna elements a bit longer than these numbers to allow for trimming and low swr.  I was lucky to have my calculations result in an swr around 1.7 to 1.  A little trimming would be done later.  The antenna would use the third harmonic of 7.088 MHz for the SSB portion of 15 meters.

One 33-ft/10.06 meters MFJ telescoping fiberglass mast.  Try to get your antenna feed point as high as you can.

One 5-ft/1.82 meter wooden support stake for the mast.

One Budwig HQ-1 center coax connector.  You could also make a center connector out of pvc pipe or stiff plastic.

Two ceramic insulators for the element ends.

Two 10-ft/3.04 meters pvc pipes to support the drooping ends of the inverted vee.  Nearby structures such as fences, gates, or even tree limbs could be used.  The insulators would be tied off with pieces of dacron rope.

Fifty-feet/15.24 meters of RG-8X coaxial cable with UHF connectors at each end. This will be your feed line.

This completes the basic materials list for the 40 meter/15 meter inverted vee.

A similar materials list would be used to make separate inverted vee/dipole elements for 20 meters, 30 meters, and 10 meters.  Other than separate center coax connectors, the new elements would share the same mast, pvc support posts, and coax feed line used in the 40/15 meter inverted vee.

To change bands, I would only have to lower the mast, switch out the center coax connectors, attach the new dipole/inverted vee segments, raise the mast, and begin operating on the new band.

Once I had the original 40/15 meter inverted vee antenna built, I made dipole elements for 20 meters (14.200 MHz--16.47 ft/5.02 meters for each element), 30 meters (10.125 MHz--23.11 ft/7.04 meters for each element), and 10 meters (28.4 MHz--8.23 ft/2.51 meters for each element).

ASSEMBLY:

A separate dipole was made for the bands of my choice (40/15 meters, 30 meters, 20 meters, and 10 meters).

Depending on the band chosen for the day, I just attached the coax connector with its elements to the apex of the mast and secured it with nylon ties.  I hoisted the mast onto its wooden support stake, tied off the drooping elements so that the included angle between the elements ranged from 90 to 120 degrees, and ran the coax feed line to the window patch panel.  A short piece of RG-8X (3 feet/0.91 meters) ran to a SWR meter and then to my Swan 100 MX transceiver.  I bypassed the Drake MN-4 antenna transmatch for this direct feed.  I was lucky to find the swr for each separate antenna to be 2:1 or lower across the band of interest.  By inserting the antenna transmatch, I could get the swr down to 1.1 to 1.

So, there's one way to bypass an antenna "tuner" if you have to.  By using separate dipole elements cut for each band of choice, you can get an antenna that performs well without excessive swr.  Of course, a piece of equipment such as the MFJ antenna analyzer would make the task easier.

This is the system I use for my portable and emergency antennas.  To change bands, all I have to do is lower the mast, choose the appropriate antenna, raise the mast, and begin operating.

Next time, I'll describe another way of getting multiple band coverage out of one coaxial feedline without the use of a "tuner".  This antenna will be our friend the "Fan Dipole."

REFERENCES:

http://www.youtube.com/watch?v=8KHzsKYsZL0.
http://www.youtube.com/watch?v=IBncfqEORGM.
http://www.youtube.com/watch?=fyOWRTWdDKM.
http://www.hamuniverse.com/easydipole.html.
http://www.eham.net/articles/24060.
http://www.arrl.org/files/file/Technology/tis/info/pdf/9106923.pdf.

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, de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii.
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Wednesday, January 8, 2014

Simple Ham Radio Antennas: When to use antenna tuners. Post #253.

Nowadays, the antenna transmatch ("tuner") is an integral part of many amateur radio stations.  With this device, a ham can match the output of his/her transceiver with the often unknown impedance of the antenna itself.  With a suitable balun (balanced to unbalanced) transformer, it is possible to use one antenna to cover several HF bands, especially if you're facing space restrictions on a small lot or have  to operate in "stealth" mode because of HOAs and CC&Rs.  This situation applies mostly to the use of 300 ohm tv twin lead and 450 ohm ladder line, which require a balun (1:1 or 4:1) and antenna transmatch to operate as feed lines in a multiband, single antenna system.

There are times when you may not have an antenna "tuner" at your disposal, especially if you're operating in portable or emergency situations.  In my case, I remove my Drake MN-4 and MFJ 941-E transmatches from the antenna system for routine maintenance several times a year and must make do with no transceiver matching devices.  Are there times when you can still operate without a "tuner" and not endanger your transceiver with high SWR and possible damage?

The answer is a qualified "yes."  I faced this problem over the New Year's holiday when I took my Drake MN-4 "tuner" off line for maintenance and was looking for ways to work my limited amateur radio schedule while fixing the old Drake.  I ran across an article by Steve Ford (WB8IMY) in the January 1994 issue of "QST", pp. 70-72.

Ford says the first step is to determine if you need an antenna "tuner" in the first place.  He says a "tuner" is needed if you find yourself in these situations:

1.  Your antenna is fed with open-wire.  A suitable balun and antenna transmatch is needed to form a "bridge" between balanced feed lines and the unbalanced output (usually 50 ohms) from your transceiver.

2.  When you use your antenna on bands other than the frequency range you prefer.

3.  Your antenna has a narrow SWR bandwidth.

Ford says a "tuner" may not be necessary if the following conditions exist in your station:

1.  If your SWR is less than 1.5 to 1 or less on the frequencies you use.  This is most noticeable on 40 meters, where, if you cut the antenna for the lower part of the band (below 7.050 KHz), you can operate on the SSB portion of 15 meters.  In this case, the antenna will work on the third harmonic of 40 meters.  A similar situation can work for an 80 meter/10 meter combination.  The assumption here is that you're using a good grade of 50 ohm coaxial cable for your feed line.

2.  You have high SWR at VHF and UHF frequencies.  Although "tuners" for these bands exist (i.e. several from MFJ), Ford recommends you "correct the mismatch of the antenna by adjusting whatever type of mechanism it provides."  You can also check for cable defects and make sure the cables have been installed correctly.

3.  You're interfering with TV, telephones, and electronic entertainment devices in your neighborhood.  Although antenna "tuners" may reduce harmonic radiation, some RF problems will remain.  These problems might be caused by fundamental overload and the poor design of entertainment devices.  Many electronic devices don't contain any rf filtering devices at all.  Some interference may be picked up indirectly by cables and speaker leads.  About all you can do in these cases is reposition your antenna, reduce power, and use digital modes such as cw and PSK-31.  You may have to shift your operating hours to avoid interfering with your neighbors.  

So, there are times when an antenna "tuner" may not be needed.  If this is the case, what kind of antennas can we use to "fill the gap" until the antenna transmatch is repaired?

I've found two multiband antenna designs that don't require antenna "tuners".  I've built both antennas and found that they work very well with SWRs below 2:1 on several amateur radio bands.  That will be the subject of the next few posts.  So, stay with us.

REFERENCES:

http://www.arrl.org/file/Technology/tis/info/pdf/9401070.pdf.  (originally published in the January 1994 issue of "QST", pp. 70-72.

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

Aloha de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.
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Thursday, January 2, 2014

Simple Amateur Radio Antennas: Your first antenna. Post #252

The New Year is the time of new beginnings.  It's time to try new modes, perhaps a new rig, and even a new antenna.  At the KH6JRM ham shack, the new year got me thinking about the first antennas I built as a novice operator back in 1977.  Some of those halting first steps were a disaster--high swr, no contacts, rf in the shack. You name it, I had it when it came to homebrewed antennas.

Perhaps those of you who are recently licensed can understand my frustration when my knowledge fell a little short in the antenna department.  Thankfully, there are a variety of books, internet sites, and amateur radio clubs that can help the new operator with antenna questions.  But, back in the days when I lived in a fairly isolated location on Hawaii Island, about the only thing I could refer to was the ARRL Antenna Book and my own experimentation.  After a while, my antenna notebooks showed some improvement as I finally understood how antennas are built and used.  Keeping an antenna notebook is a good way to gauge the progress you've made in amateur radio.

All of my early failures and occasional successes were made with simple wire antennas.  As George Woodward (W1RN) mentioned in a June 1983 "QST" article, wire antennas are "easy to build, easy to install, easy to disguise and easy to modify."  Being a man with limited physical dexterity and even lesser financial resources than some, I've stuck to Woodward's advice.  During my 37 year amateur radio "career", wire antennas have served me well. Besides, they are fun to make and relatively inexpensive compared to commercial antennas made of aluminum.

While I was paging through my 1977 antenna notebook, I rediscovered one of my more successful antennas--an antenna I still use today at my home in progress in the Puna District.  For the sheer ease of construction, you can't beat the 40-10 meter Inverted Vee dipole fed with 450 ohm ladder line fed into a 4:1 balun and connected to an antenna transmatch.  This antenna requires only 1 supporting mast and two equal antenna segments cut for the lowest frequency of use.  The ladder line allows you multiband performance with a minimum of materials.

So, during the week preceding the Christmas Holiday, I remade the 40-10 meter Inverted Vee used during my novice license days (1977-1978).  You'll find this antenna produces plenty of local, regional, and DX contacts with power levels below 100 watts.

MATERIALS:

One 33-ft/10.06 meter telescoping fiberglass mast.  I used a spare MFJ mast for this project.

One 5-ft/1.82 meter wooden stake to support the fiberglass mast.

Two ceramic insulators for the ends of the antenna elements.

Fifty feet/15.24 meter of 450 ohm ladder line.

One homebrew center connector for the ladder line.  I made the center attachment from a piece of pvc tubing.

Two antenna elements of equal length for my frequency of choice.  Using the general formula 468/f (MHz)=L (feet) and a chosen frequency of 7.088 KHz (the meeting place of the Hawaii Afternoon Net), the total antenna length came out to 66.02 ft/20.13 meters.  Cutting this length into two equal antenna elements, each segment of the Inverted Vee worked out to 33.01 ft/10.06 meters.  As in my novice Inverted Vee, I used #14 AWG house wire for the antenna elements.

One W9INN 4:1 balun.

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

One Drake MN-4 antenna transmatch.  I've used this piece of equipment for 37 years without any problems.

Several 3-ft/0.91 meters lengths of RG-8 coaxial cable with UHF connectors for interconnecting station equipment.

My old Swan 100-MX transceiver.  The original Heathkit HW-101 I had as a novice has been gone for many years.

A small step ladder to tie off the antenna elements to nearby trees.




ASSEMBLY:

The antenna was built on the ground.

I attached and soldered each antenna segment to the 450 ohm ladder line.  End insulators were attached to each element.

I attached the homebrewed center insulator to the apex of the fiberglass mast.

I ran the 450 ohm ladder line down the mast to a point 16 ft/4.87 meters above ground level.  The ladder line was secured to the mast by nylon ties.

I hoisted the mast onto its wooden support stake.  The ends of the Inverted Vee were tied off at tree branches near the antenna.  The tie off points were approximately 10 ft/3.04 meters above ground level.  I used a small step ladder to reach the tree branches.

Ideally, the angle of the Vee should be between 90 and 120 degrees.  My angle appeared close to that figure.

I ran the ladder line to the W9INN 4:1 balun, which was attached to the side of the garage, approximately 8 ft/2.43 meters above ground level.

Twenty-five feet/7.62 meters of RG-8 coaxial cable was connected to the balun and then run through a window patch panel in the shack and then connected to the Drake MN-4 antenna transmatch.  Small patch cords interconnected the Swan 100-MX to the Drake MN-4, a low pass filter, and the dummy load.

INITIAL RESULTS:

The 40-10 meter Inverted Vee performed just as well this time as it did back in 1977.  With the Drake MN-4 in the system, I had multiband coverage with an swr below 1.5 to 1 on all bands from 40 through 10 meters.  Reception reports ranged from 56 to 59 on SSB and from 579 to 599+ on CW, depending on the band and time of day.  I was running approximately 25 watts from the old Swan 100-MX.  If I wanted to add 80 meters to the antenna, I could simply add another 33 ft/10.06 meters segment to each element and connect the elements together with clip leads.  Additional supports would be needed to keep the 80 meter segments off the ground.

As a general purpose antenna, the multiband Inverted Vee performs well at a modest cost.  Since I had most of the materials at home, my extended cost was minimal.  As is my usual practice, I nest the antenna mast to ground level when I'm done operating for the day.  This keeps the antenna out of site and reduces the risk of a lightning strike.  All feed lines are disconnected and grounded outside of the shack as well.

If you need an easy, simple, and inexpensive antenna to launch your first signal of the new year, consider the basic Inverted Vee.   You won't be disappointed.

REFERENCES:

Woodward, George.  "Your First Antenna."  QST, June 1983. pp. 33-38.

http://www.arrl.org/your-first-antenna.

http://www.arrl.org/files/Technology/tis/info/pdf/0683033.pdf.

http://www.iw5edi.com/ham-radio/420/a-novice-multiband-vertical-antenna.

http://www.hamuniverse.com/40mcwnvis.html.

Thanks for joining us today!

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

Until next time,

Aloha de Russ (KH6JRM).

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