Sunday, December 29, 2013

Simple Ham Radio Antennas--Antenna Resolutions for the New Year. Post #251

The Year 2013 has been an exciting and challenging year for amateur radio operators worldwide.  From earthquakes to tornadoes and from typhoons to floods, the amateur radio community has rendered valuable aid to those in distress.  A special thank you to the "hams" in India and the Philippines who struggled to maintain communications with officials and aid agencies, often without rest and relief.  You have served in the highest tradition of the amateur service.  I also commend my fellow amateurs who kept emergency frequencies free for health and welfare traffic.  I am proud of all of you.  Yes, this past year has been far from dull.

With this in mind, I decided to review my own year in amateur radio to see where I could improve my commitment to my community, maintain a safe, efficient station, and pursue my antenna interests with a minimum of cost.  So, I started making a list of things accomplished and areas where I could do better.

Perhaps my introspective analysis will encourage you to do the same.

First, I thank all those who have responded to my antenna projects.  Your encouragement, corrections, and guidance have proven invaluable in expanding my understanding of "homebrewed" antennas.  Like many of you, my imagination is limitless, but my finances are finite.  Being retired has been a mixed blessing.  I enjoy life a lot more than in my "working" past, especially when my xyl and I continue to find enrichment in our substitute teaching positions at the Laupahoehoe Community Public Charter School.  For the first time in our lives, we have a home in progress on an acre of land--plenty of space for a garden and an "antenna farm." All my years of frugality are finally paying off.  Your tips and suggestions have enabled me to assemble a "ham" station and a set of modest antennas at a relatively modest cost.

Second, a good year from the amateur radio standpoint comes from a rededication to the original "Amateur's Code" conceived by Paul Segal (W9EEA) back in 1929.  The code embodies all that an amateur radio operator should stand for:  An amateur radio operator should be considerate, loyal, progressive, friendly, balanced, and patriotic.  These ideals, while difficult to attain, are at the core of a civilized society.  These are goals worth striving for, no matter what part of the world you call home.  I will try my best to implement these guideposts in my daily life, whether or not I'm on the air.

Third, safety will be a guiding principal of my amateur radio activities, both in my home and at the rig.  Every year I make sure that all safety devices at my qth and in the radio room are working and well-maintained, including the smoke/fire alarms, fire extinguishers, house wiring, and security systems.  At least twice a year, I make sure tree limbs and other debris are clear of utility lines.  On Hawaii Island, the Hawaii Electric Light Company (HELCO) will come to island homes and clear away dangerous limbs from utility lines.  All one has to do is call for help.  In the radio room, I make sure all equipment is clean, dust-free, and maintained to the best of my ability.  I also make certain that there is both an electrical and rf ground system in place.  All electronic equipment, including transceivers, general purpose receivers, television set, stereos, DVD/CD players, and personal computers are hooked up to surge protectors.  When the xyl and I leave the house, we unplug all equipment not in use.

Fourth, all antennas used at the current qth and at the new home site will be better protected against lightning and other storm-related events.  When I finish operating for the day, I disconnect all antennas from the rig and ground the feed lines (coax and ladder line) outside.  My vertical antennas are nested to the ground after use to lessen both the danger of lightning strikes and the discovery by neighbors.  In January, all of my antennas will have a static discharge system in place to lessen inadvertent damage to my solid state equipment.

Fifth, I will expand my alternative power supply for my amateur radio equipment.  Presently, I can operate off the regular electric mains and a backup solar- charged (PV) deep cycle marine battery.  I will convert to a complete "off-grid" power system early next year.  I have enough money to buy some more solar panels, a new deep cycle marine battery, a new trickle charger (if needed), and an inverter.  Also in the works is the purchase of a small Honda generator for additional backup power.

Sixth, I plan to renew my American Red Cross CPR and First Aid Certificates.  I'm also considering taking some CERT or FEMA courses to sharpen my emergency communications skills.  Because of past work requirements and other demands, I was unable to help my community as fully as I wished.  Now, in retirement, I've got the time to become proficient in vital skills and, therefore, a better asset to the local civil defense agency.

Seventh, I will help more people get licensed as amateur radio operators.  I'm a current W5YI Volunteer Examiner and have helped monitor a few amateur license exams.  I plan to do more in this area during 2014.

Finally, I will get on the air more than I have in 2013.  With the house move underway and my teaching commitments, it's been difficult checking into nets and going to Big Island Amateur Radio Club meetings.  That will change now that my teaching schedule is more predictable.  Hawaii Island is fortunate to have several ham radio clubs that are active in ARES and other community-related programs.

For me, and perhaps for you, amateur radio is not a destination.  It's a journey to an expanding universe of knowledge.  Our license is only the first step in seeing the future.  Good luck in the coming year and may the winds of DX blow your way.

Listed below are some of the places where you can get some ideas for 2014:

The Amateur's Code may be found by visiting http://www/qcwa/prg/amateur-code.htm.
http://www.techpodcasts.com/myamateurradio/127182/parp-65-amateur-radio-goals-for-the-new-year.
http://www.arrl.org/Groups-Nebraska.
http://www.humanresources.about.com/od/motivationsuccess3/a/new_resolutions_2htm.
http://www.forums.qrz.com/shorsthread.php?417314-New-Year-s-Resolutions-Become-a-CERT-Leader.

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 es 73 de Russ (KH6JRM)

BK29jx15

Along the beautiful Hamakua Coast of Hawaii Island.




Wednesday, December 25, 2013

Simple Ham Radio Antennas--going stealth mode. Post #250.

For most of my 36 years as an amateur radio operator, I've had to operate under the limitations imposed by HOAs, CC&Rs, and postage stamp sized backyards.  Like many of you, my creativity was sorely tested  as I tried to get reasonably efficient antennas erected for my home station.  In many cases, one antenna had to suffice for multiband operation.  And that antenna had to be inconspicuous, easy to erect and take down, and not present an "eyesore" to the neighbors.

Over the course of those years, I managed to enjoy ham radio despite the highly compromised antennas and low power employed at the shack.  There were a few multiband designs which proved successful for local and occasional DX.  Among them were inverted vees and 1/2 wavelength horizontal dipoles fed by 450 ohm ladder line connected to a 4:1 balun and a Drake MN-4 antenna transmatch.  When I did have a bit more space, I used full wavelength loops fed by ladder line for 20, 15, and 10 meters.  Height above ground was always a problem owing to the lack of nearby trees or other structures.  So, early on I bought several telescoping fiberglass masts which extended to 33 feet/10.06 meters.  These masts were easy to erect, take down, and store.  With a pulley and lanyard system, I could hoist pre-made antennas for single or multiband use in a matter of seconds.  The antennas were nested to ground level after use, lessening the impact on the local "environment."  My antennas were largely "out of sight, out of mind" since I operated mostly at night.

I generally avoided vertical antennas because I lacked sufficient space to lay in a decent ground radial system.  A vertical antenna depends on a ground radial system to function efficiently.

While I did enjoy working on these temporary antennas, I felt the need for more space so I could erect more permanent, full-sized  antennas for the bands I favored.  In May, my xyl and I bought a nice home on an acre of land in the sprawling Puna District of Hawaii Island.  At last, there was sufficient space to erect antennas for each amateur radio band.  The antenna "farm" is slowly taking shape--a project that will take a few months to complete.

Meanwhile, both of us are still living in a nice rental home in Laupahoehoe along the Hamakua Coastline. The house is quite nice, but it's confined by high voltage lines, numerous neighbors, and very little backyard space.  I needed a temporary, largely invisible antenna to continue my amateur radio activities while we gradually moved into the new place.  Most of the antennas I had used here were already packed away and stored at the new qth.

After a few days of research in my antenna books, the ARRL archieves (members only), and some inquiries into a few antenna websites, I found an antenna which is both "stealthy" and useful for my mostly local and regional contacts--a 40 meter full wavelength loop strung under the house and fed by 450 ohm ladder line connected to a 4:1 balun and my trusty Drake MN-4 transmatch.  Last year, I used this low-lying loop to good effect on the local Hawaiian Afternoon Net.  The loop is basically a NVIS (near vertical incident skywave) antenna that puts a strong signal out to about 300 miles/approximately 480 km--more than enough to cover the entire Hawaii Island chain.  So, I decided to reinstall the loop.  I'm glad I did.

My rental house is built on a pillar and pier system to withstand minor earthquakes and flooding.  The house is approximately 5 feet/1.82 meter above ground.  The loop can be squeezed around the perimeter of the house and part of the garage.  

MATERIALS:

Using the general formula 1005/f (MHz)=L (feet), I cut the 40 meter loop to a length of 142.55 ft/43.46 meters.  I used some #22 AWG hookup wire stored in the garage for the antenna.  The resonant frequency of the loop would be 7.088 MHz, the "watering hole" for the Hawaii Afternoon Net.

A box of push pins to secure the wire to the underside of the house.

One ceramic insulator to support the junction of the loop and the 450 ohm feed line.  The insulator would be attached to the underside of the living room floor about 5 feet/1.82 meters above ground level.  The feed line connections were soldered and covered with several layers of vinyl electrical tape.

Twelve feet/3.65 meters of 450 ohm ladder line.

One W9INN 4:1 balun.

Three feet/0.91 metes of RG-8X coaxial cable with UHF connectors.

Transceiver (Swan 100 MX).

Dummy load.

Drake MN-4 transmatch.

Low pass filter. Some of my neighbors get their television programs over the air.

Various coaxial patch cords to interconnect station equipment.

ASSEMBLY:

The antenna assembly is simple and takes only a few minutes.

I attached the 40 meter loop around the perimeter of the house and part of the garage.  Push pins secured the loop to the underside of the house.

The 450 ohm ladder line was attached to each end of the loop.  Connections were soldered and covered with vinyl electrical tape.

The ladder line was inserted under the back door and led into the living room where it was connected to the W9INN balun. The balun was approximately 3-feet/0,91 meters from the Swan 100 MX transceiver.

A 3-foot/0.91 meters length of RG-8X coaxial cable was attached to the balun and then connected to the Drake MN-4 antenna transmatch.  The Swan 100 MX was connected to the Drake MN-4 along with the dummy load and the low pass filter.

INITIAL RESULTS:

As expected, the under-the-house loop used  in conjunction with the 4:1 balun and the Drake MN-4 transmatch covered all amateur radio frequencies between 40 and 10 meters with a low swr (below 1.3 to 1).  Since the antenna was a NVIS design, most of the signal went straight up and covered the state of Hawaii from Kauai to Hawaii Island with SSB reports ranging from 57 to 59 using approximately 20 watts from the old Swan 100 MX.  In most cases, I will not exceed this power level because of rf and safety concerns.  When I use CW, the power level is held to 10 watts or less.  I've had a few mainland U.S. contacts on 40 and 20 meters with reports running between 55 and 57.

Given the self-imposed height and power restrictions, this low-lying loop is providing the performance I need until my antenna "farm" is done at my new qth.

The under-the-house 40 meter loop supplements the 80-foot/24.39 meters loop I have tacked around the interior of my rental home.  In any case, these antennas, when operated at low power levels, provide many hours of enjoyment without undue interference to computers, televisions, or entertainment systems.  

The new loop is invisible to neighbors, requires no ground system, and easily erected and taken down.

Perhaps a loop antenna is in your future.

REFERENCES:

http://www.g4ilo.com/stealth.html.
http://www.dxzone.com/catalog/Antennas/Stealth.
http://www.arrl.org/shop/Stealth-Antennas.
http://www.sgcworld.com/Publications/Books/stealthbook.pdf.
http://bvarc.org/pdf/HF_Antennas_by_KD5FX.pdf.
http://www.hamlearningnet.org/dl/Stealth_Antennas.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.

Happy Holidays!

Russ (KH6JRM)
BK29jx15
Along the beautiful Hamakua Coast of Hawaii Island.

Friday, December 20, 2013

Simple Ham Radio Antennas: A multiband Inverted-V Antenna. Post #249

One of the most popular amateur radio antennas is the Inverted-V.  This antenna is a first cousin to the half wavelength horizontal dipole whose antenna elements are drooped down so that the included angle between them is between 90 and 120 degrees.  According to William I. Orr (W6SAI) and Stuart D. Cowan (W2LX), the "bandwidth is somewhat lower than for a conventional dipole...Because the wires of the Inverted-V do not lie along one axis, the physical length is somewhat longer than that of a dipole cut for the same frequency."  For general design purposes and allowing for some trimming of antenna elements, you can use the general dipole formula, 468/f (MHz)=L (feet) to compute the total length of the Inverted-V dipole.  Some antenna experts believe the drooping halves of the Inverted-V change the resonant frequency, and, therefore, recommend a slightly different formula be used to calculate the length, such as 464/f (MHz)=L (feet).  I use the 468/f (MHz)=L (feet) formula to establish a general length parameter and use the old "cut and trim" method to bring the antenna to resonance on my chosen frequency.  More often than not, I cut a compromise length and use my trusty Drake MN-4 transmatch to take care of the small SWR found on the feed line.

Allowing for some performance shortfalls, the Inverted-V has some definite advantages:

Only one support structure is needed.

No ground radial system is required.

The Inverted-V can be fed with 50 ohm coaxial cable for single band use or fed with 300 ohm television twin lead or 450 ohm ladder line for multiband use.

The Inverted-V is simple to build, inexpensive, and portable.

I've used a variety of single and multiple band Inverted-Vs in my amateur radio "career" with excellent results. Now that I'm moving to a new home site with plenty of room for antennas, I thought a few antenna experiments would be in order.

In previous posts, I've related my adventures with homebrewed delta loops, vertical ground planes, doublets, and even double extended zepp antennas.  All of these antennas have worked very well, even at power levels below 10 watts.

My recent foray into antenna territory has been the construction of a multiband Inverted-V covering the 80, 40, and 20 meter bands.  Unlike some of my other antennas, I didn't use tuned feeders because my stock of 450 ohm ladder line was exhausted.  I did, however, have several 50-foot/15.24 meters lengths of RG-8X coaxial cable with UHF connectors.  Properly designed, a coaxial feed line can be used to cover several bands if "outrigger" segments for each additional band are attached to the main Inverted-V dipole.  Since I would be covering 80 meters as the lowest band, the principal V would be cut for 3.800 MHz.  Subsequent segments would be cut for 40 and 20 meters and connected  by ceramic insulators and alligator clips to constitute a workable antenna for each respective band.

A design attributed to Ed Noll (W3FQJ) provides a series of clip on jumpers for operation of the 80 meter Inverted-V as a 5/2 wavelength antenna on 20 meters and as a 3/2 wavelength antenna  on 40 meters.  The 80 meter antenna is cut as a 1/2 wavelength antenna with various segments added to bring bring each band into resonance.  A single 50 ohm feed line is connected to the top of the mast where the 80 meter elements are attached.

MATERIALS:

The antenna was built on the ground and later hoisted to the top of a mast by means of a pulley and lanyard system.

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

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

Approximately 225 feet/68.59 meters of #14 AWG housewire.  The wire will serve as 80 meter antenna elements and as the 20 and 40 meter outrigger segments.

One Budwig HQ-1 center insulator.

Six ceramic insulators to tie off and join outrigger segments to the main 80 meter antenna.

Four, 5-foot/1.82 meter wooden stakes to support the outrigger segments.

Fifty feet/15.24 meters of RG-8X.  This will be the antennas feed line.

One Drake MN-4 antenna transmatch to handle the small amount of SWR on the feedline.

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

Various 3-foot/0.91 meters lengths of RG-8X cable for connecting equipment to the Drake MN-4 transmatch.

ASSEMBLY:

First, I cut the 80 meter dipole according to Ed Noll's (W3FQJ) instructions. Each dipole element measured 62 feet, 2.5 inches/18.98 meters.  

I attached and soldered the top end of each 80 meter element to the Budwig HQ-1 center connector.

I attached a clip lead to the bottom end of each 80 meter element and secured that connection to a ceramic insulator.

Next, I cut each element of the 20 meter segment to a length of 21 feet, 3 inches/6.48 meters.  I attached a clip lead to each end of the 20 meter segments and threaded them through the end insulators of the 80 meter elements.  I then attached  clip leads to the other end of the 20 meter segments and threaded them through ceramic insulators.

I then cut each element of the 40 meter segment to a length of 16 feet, 0 inches/4.87 meters.  A clip lead was attached to one end of each segment and threaded through the end insulators of the 20 meter segments.

To use 80 meters, I left all clip leads unattached.  To pursue DX on 20 meters, I connected each 20 meter segment to each 80 meter element.  This connection would serve as a 5/2 wavelength antenna for 20 meters.  To chase local contacts and occasional DX on 40 meters, I connected all of the segments together. The arrangement would serve as 3/2 wavelength antenna on 40 meters.

With the 80 meter antenna and all of its outrigger segments joined by clips and ceramic insulators, I attached the Budwig HQ-1 coax connector to the apex of the mast.  I then hoisted the mast onto its wooden support stake.

Five-foot/1.82 meters wooden support stakes were attached to the insulators joining the 80 and 20 meter segments and the 20 and 40 meter segments.  The wooden stakes kept the outrigger segments off the ground and limited antenna sag.

INITIAL RESULTS:

Without the Drake MN-4  transmatch in the antenna system, I was able to get a SWR of less than 2:1 across all portions of 20 and 40 meters.  Although I was able to get a decent SWR in the neighborhood of 3.800 MHz, it was not possible to cover the entire 80 meter band without the aid of the Drake MN-4.  With the transmatch in the line, I was able to get an acceptable match on most of the 80 meter band.  The transmatch kept the SWR below 1.3 to 1 on the 20 and 40 meter bands. 

As an experimental multiband antenna, the segmented Inverted-V performed well at my home site in the Puna District.  To change bands, all I have to do is lower the Inverted-V and change the clip leads.  Since I had all the antenna materials on hand, my cost was minimal.  You can use this outrigger design for any bands you desire.  Have fun!

REFERENCES:

Orr, William I. (W6SAI) and Cowan, Stuart D. (W2LX).  The Radio Amateur Antenna Handbook.  Radio Publications, Inc.  Lake Bluff, Illinois, 18044.  Seventh Printing, 1988. pp. 131-133.

Orr, William I. (W6SAI) and Cowan, Stuart D. (W2LX).  Simple, Low-Cost Wire Antennas.  Radio Publications, Inc.  Winton, Connecticut, 06897.  Fifth Printing, 1979.  pp.70-86.

McCoy, Lew (W1ICP).  Lew McCoy On Antennas--Pull Up A Chair and Learn From the Master.  CQ Communications, Inc.  Hicksville, New York, 11801.  Second Printing, 1977.  pp. 51-52.

Turner, Rufus P.  The Antenna Construction Handbook for Ham, CB & SWL.  Tab Books, Inc.  Blue Ridge Summit, Pennsylvania, 17214.  Second Printing, 1981.  pp. 91-92.

The ARRL Antenna Book.  American Radio Relay League, Inc.  Newington, Connecticut, 06111.  Fourteenth Edition, Second Printing, Copyright 1983.  pp. 8-9 and 8-10.

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 de Russ (KH6JRM)

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
















Saturday, December 14, 2013

Simple Ham Radio Antennas: A double extended "zep" for 10 meters. Post #248.

From what I've been hearing today (Saturday, 14 December 2013), amateur radio operators are having a good time on the ARRL 10 meter contest.  Although propagation has been variable on Hawaii Island, the band seemed alive with signals.  Ten meters, like its distant cousins at 160 meters and 6 meters, offers plenty of challenges for amateurs new and old.  When propagation is favorable, both local and DX signals are possible with low power and modest antennas that can fit into a small backyard.

Ten meter events are scheduled throughout the year, sponsored by the ARRL, various national amateur radio groups, and the Ten-Ten group, which promotes the use of 10 meters.

Antennas for 10 meters run the gamut from multi-element beams and ground planes to dipoles and full wavelength loops.  Even though the current ARRL 10 meter contest is coming to an end, it's not to early  to think about ways to improve the signal from your 10 meter antenna.

If you want some gain over a dipole and have about 50 ft/15.24 meters of horizontal space, why not build a double extended zepp antenna for your next 10 meter operation?  The antenna traces its ancestry both to the familiar half wavelength dipole and to the trailing antennas used on the Zeppelin airships of the 1920s and 1930s.

The double extended zepp looks like a conventional halfwave dipole fed in the center with 300 or 450 ohm feed line.  But, unlike the horizontal flat top known to most of us, each antenna element is 5/8 of a wavelength long, which produces a gain of approximately 3 dB over a dipole at the same height.  According to Steve Shorey (G3ZPS), this gain is attained when the extended zep is approximately 0.6 wavelength above ground.

Just before the ARRL 10 meter contest, I built a crude replica of a double extended zepp at my future homesite in the Puna District.  So far, the antenna works very well and gets better reception reports than my 10 meter ground plane.

Here's what I did to make the antenna:

Using the formula 599/f(MHz)=l (ft) supplied by Steve (G3ZPS), I cut two equal lengths of #14 AWG housewire for a chosen frequency of 28.400 MHz in the 10 meter band.  This frequency is quite busy, with many newly licensed technician class licensees testing the waters of SSB operation.  These contacts are always interesting and remind me of the time I first ventured into a "phone" band.  Based on this general formula, each element of the zepp measured 21.09 ft/6.43 meters.

Once I had cut the wire, I began to assemble the antenna on the ground.

I used three MFJ telescoping fiberglass masts to support the antenna.  One mast would support the center connector and the 450 ohm ladder line, while the other two masts would support the zepp elements.

The masts extended out to 33 ft/10.06 meters.  At this height, the zepp would be more than 0.6 wavelength above ground and should give me about 3 dB gain over my 10 meter inverted vee and ground plane.

Three, 5-ft/1.52 meters wooden support stakes for the masts.  Each mast had a halyard and pulley system which would allow me to hoist each section of the antenna to its proper height.

I attached a ceramic insulator to each end of the elements.  A short piece of dacron rope would be used to tie off the insulator to each mast.  The tie off rope was approximately 3 ft/0.91 meters long.  The center connector was the "ladder lock", a device that allows you to attach each wire of the feed line to its respective antenna element.

The ladder lock was secured to the center mast with nylon ties and duct tape.  The ladder line was run down to the midpoint of the center mast (16.5 ft/5.03 meters) and secured to the mast with nylon ties.  All antenna connections were soldered and covered with several layers of vinyl electrical tape.  

I attached each element of the antenna and the center connector to its respective pulley and halyard system.

After each mast was hoisted into position on its support stake, I raised each antenna element to the apex of its mast and tied off the halyard to the base of each mast.  To make adjustments, all I would have to do is raise or lower each element with the halyard and pulley system.

Once I had the masts in place, I ran 50 ft/15.24 meters of 450 ohm feed line to a W9INN 4:1 balun attached to the garage wall (approximately 16.5 ft/5.03 meters above ground at the peak of the garage roof).  The only dangerous part of this installation was using a ladder to get the balun near the top of the roof peak.  A neighbor, who doesn't mind about my amateur radio operations, steadied the ladder while I attached the feed line to the 4:1 balun and ran 25 ft/7.62 meters of RG-8X coaxial cable with UHF connectors through the patch panel in the shack window.

The balun was wrapped in thick plastic to protect the device from the weather.

Once the coax was safely inside the shack, I hooked up the Drake MN-4 transmatch, the Swan 100 MX transceiver, and the dummy load to complete the project.

Based on just a few contacts  Friday (13 December 2013), the double extended zepp works very well with SSB reports running between 56 and 58, using approximately 50 watts output from the old Swan 100 MX. The antenna was oriented northwest to southeast, giving me some decent coverage of the U.S. mainland.

As an added bonus, the ladder line/balun/transmatch combination allows me to transmit a usable signal with low SWR on 20, 15, and 10 meters.  While not a competition grade antenna, it does perform better than my reference 10 meter ground plane and gives me some gain to mainland U.S. areas.  I can change the directivity of the signal by moving the masts, so that the broadside pattern and its lobes reach other parts of the compass.

If you need a new antenna for 10 meters, try a classic double extended zepp.  It's cheap, easy to make, and produces results at modest power levels.

REFERENCES:

home.comcast.net/~n8itf/doublezepp.htm.
http://www.g3zps.com/Page4.htm.
myplace.frontier.com/~nb6z/nb6zep.htm.
rudys.typepad.com/ant/files/antenna_colinear_zepp.pdf.

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

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

Thanks for being with us today!

Aloha de Russ (KH6JRM)

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




Friday, December 6, 2013

Simple Ham Radio Antennas--a multiband indoor loop antenna. Post 247

Over the past few posts I've been recounting the joys of erecting antennas with no space restrictions.  On my new property in the Puna District of Hawaii Island, I have an acre of land with few close neighbors and a comfortable distance from the Keaau to Pahoa Highway and all of the power lines following that road.

However, for most of my 36 years as an amateur radio operator, I've had to erect compromise antennas because of space limitations, proximity to high voltage power lines, and the eyes of suspicious neighbors.  Most of these antennas worked very well, considering the space restrictions of my rental housing.  One thing I did discover is just how good a basic 1/2 wave length horizontal dipole or inverted v performs when you use a moderate length mast (33 ft/10.06 meters) coupled with 450 ohm feed line, a 4:1 balun, and a decent transmatch.  This combination gives you multiband capability with the design frequency being the lowest band you wish to use.

I've also used a variety of indoor antennas, ranging from the commercially bought MFJ-1622 vertical with tapped coil and counterpoise to homebrew loops fed with 300 ohm tv twin lead or 450 ohm ladder line.  I was able to get many contacts with these antennas, despite their small size and proximity to electronic devices in my former homes.

While I'm moving to my new location (it will take a few months in between teaching assignments), most of my backyard antennas at my Laupahoehoe qth have been lowered, packed away, and taken to the new home site.  The under-the-house 40 meter loop is still available for local and statewide contacts.

Until I get all of my antennas erected at the new location, I'll have to make do with some temporary antennas.  Since I've had good results with HF loop antennas, I decided to make another HF loop to supplement the existing loop under the shack.  This time, I put the loop inside the house, tacked to the ceiling of the living room and fed with 450 ohm ladder line into a 4:1 balun connected by a short piece (3 ft/0.91meters) of RG-8X coaxial cable to my trusty Drake MN-4 antenna transmatch.  For reasons of rf exposure and safety, I decided to use my portable qrp rig (Yaestu FT-7) as the transceiver.

ASSEMBLY:

Using valuable information from "Yukon John" (KL7JR) and Scott (K2ZS), I decided to use an 80 ft/24.39 meters loop fed by ladder line into a 4:1 balun and a sturdy antenna transmatch (Drake MN-4).  The antenna would give me 20 through 10 meter coverage at minimal cost and reduced rf exposure.

I had some spools of #22 AWG hookup wire in the garage, a package of  push pins in the shack desk drawer, 10 ft/3.04 meters of 450 ohm ladder line in the desk drawer, a W9INN 4:1 balun on the workbench, and the Yaesu FT-7 in the van.

In his article on stealth loops, K2ZS suggested a length of 70 to 90 ft/18.29 to 27.43 meters for the indoor loop.  I chose a compromise value of 80 ft/24.39 meters because that fit the dimensions of my large living room.

Using a small ladder for support, I used push pins to attach the loop to the living room ceiling.

The 450 ohm ladder line was soldered to each end of the loop.

The ladder line was dropped straight down to the floor.  The ladder line was connected to the W9INN 4:1 balun.  Three feet/0.91 meters of RG-8X coaxial cable with UHF connectors was attached to the balun and run into the Drake MN-4 transmatch.  Short patch cores made from RG-8X coaxial cable (about 2 ft/0.06 meters long) were used to connect the dummy load, low pass filter, and transceiver to the antenna transmatch.

To minimize rf interference to our home computer and entertainment systems, I only operate during the afternoon or late evening when our use of the entertainment equipment is minimal.  I also keep the power below 10 watts and operate primarily CW.  So far, I've encountered no rf problems in the house.  I do have a good supply of torroids to use on power and computer cables should the need arise.

RESULTS;

The indoor loop works very well on 20 through 10 meters.  My CW reports range from 549 to 579 depending on propagation.  On the occasional SSB contact, I get reports between 54 and 57.  My low power signal won't break a DX pileup, but, for casual contacts and local rag chews, the indoor loop is adequate until my final move out to the Puna District.

Best of all, I don't need a counterpoise to run along the baseboards of the floor. 

I'll try out this indoor loop during the upcoming ARRL 10 meter contest (14-15 December 2013).

This indoor antenna was fun to build and cost me practically nothing.

REFERENCES:

http://www.hamuniverse.com/kl7jrindoorloop4010.html.

http://www.arrl.org/indoor-antennas.

http://www.k2zs.com/indoor-antennatips.

http://www.iw5edi.com/ham-radio/?hf-ham-radio-antennas-for-apartments%2C53.

http://www.g4ilo.com/stealth.html.

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.