Simple Antennas for Amateur Radio Operators–a continuing series


KH6JRM’s Amateur Radio Blog

Post #177

A modified fan dipole

How would you like to make a simple, stealthy, and inexpensive antenna that covers 80 to 10 meters?  All you need is a local hardware store, some connectors, some RG-8 coax, schedule 40 pvc pipe, some copper plumbing straps, a few bungie cords, and about 250-feet of stranded copper wire.

The details of this fascinating skyhook can be found in the 31 July 2012 edition of eham.net (http://www.eham.net).  Howard Gorman, W6HDG, has writen an article entitled “The Fence Fan Dipole (FFD)–A Quick, Easy, and Inexpensive Multiband Antenna.”

Howard provides detailed instructions and photographs to guide you in completing this project.  Most of the materials for his antenna came from a local Home Depot store.  Howard used a 12-foot fence around an old tennis court to support a 10-foot schedule 40 pvc pipe and ran antenna elements from a special antenna connector atop the pvc pipe.  He used bungee cords to attach the elements for each band.  The antennal elements also served as guy wires for the pvc pipe.  He fed the antenna with one piece of RG-8 coaxial cable.  Howard’s station is modest–a Yaesu FT-857, an Astron 30-amp power supply, and an antenna tuner.

According to Howard, SWR readings for all bands except 15 meters showed SWR at 1.9 or less across each band.  Fifteen meters and portions of 75 meters could be used if an antenna tuner were used to reduce the SWR.

Howard acknowledges the limitations of his creation by noting, “I have no illusions about DX worthiness of this antenna.  The multiband variety of dipole…when well-tuned, should not suffer appreciably in performance over a monoband dipole at similar height.  The advantage of  a single feedline connot be overemphasized.”

Despite the limitations of this antenna, it’s worth a try, especially if you don’t have much real estate to erect antennas.  Howard says the antenna is barely noticeable and blends in well with the environment–something to consider in crowded neighborhoods.  If you follow Howard’s instructions and photographs, you should have little difficulty in building and using this antenna.

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Thank you for joining me today!

Aloha es 73 de KH6JRM–BK29jx15

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Simple Antennas for Amateur Radio Operators–a continuing series


KH6JRM’s Amateur Radio Blog

Post #176

A compact 40-meter vertical

There are times when a small vertical comes in handy.  You could be in a space restricted environment such as I where neighbors are almost back to back or you could be looking for an easily portable antenna useful for mini-DXpeditions or a casual day of operating from a park or beach.  There is a solution to this often vexing problem.

If you have the resources, you may want to consider screwdriver antennas, adaptations of various mobile antennas (ham stick), or event the handy Buddipole sytem.  But if you’re on a restricted budget and willing to “roll your own”, you can find all the materials you need at the nearest hardware store.

What I wanted to build was as a top-loaded “vertical helix” that could be erected in my backyard and easily hidden by bushes and trees bordering my qth.  Based on various readings in antenna literature, I found that if you wound a half-wave length of ordinary AWG #22 gauge hook up wire in a spiral along a pvc or wooden pole, the antenna would behave as a quarter-wave vertical for your chosen frequency.  As in any vertical, a good ground system would be needed.  In my case, I had a 10-foot piece of schedule 40 pvc pipe (2″ diameter) under the house which could be used to wrap the wire.  For my 40-meter helix, I wound 66-feet of #22 wire along the length of the pipe and attached a 4-foot piece of an old CB antenna to the spiral to provide a bit of top-loading.  At the bottom of the pvc pipe, I attached one lead of some 450-ohm twin lead to the spiral or helix and connected the other part of the twin lead to 4, 33-foot radials.  The twin lead ran into a W9INN 4:1 balun, which was attached to approximately 25 feet of RG-6 coax (that’s what I had in my storage box).  The coax was attached to the Drake MN-4 tuner, which was connected by a short piece of coax to the Swan 100-MX.

I adjusted the old Swan transceiver to 7.040 Khz, checked out the signal on the dummy load, used the Drake MN-4 to reduce the swr, and fired off a CQ.  Everything seemed to work alright, although the bandwidth was quite narrow.  From everything I’ve read about HF vertical helices, the impedance of the antenna is around 5 ohms, so this mismatch may preclude the use of coax for multi-band use.  The antenna works on 40, 20, 15, and 10 meters.  Performance does not match what I get from a dipole or inverted “vee”.  But, with ladderline, I can get contacts on those bands, usually a s-unit below what I get on the dipole.  Your results may very, depending on the number of radials you use and the proximity to nearby objects.  As you may have guessed, this system is quite primitive and can use improvement.  The good thing about this antenna is that it’s easy to build and easily hidden.  I plan to attach a better ground system when the weather improves.  I can break up the pvc support pipe into two, 5-foot sections, which fit comfortably into my van for portable use.

Now that my vacationing neighbors are scheduled to return on 31 July, it’s time to take down by temporary 40-meter “long wire” (see last post).  This distant cousin of an off-center-fed dipole did fairly well under marginal propagation conditions.  I will roll up the longer 100-foot and shorter 35-foot sections and put them back in the storage chest.

I trust that your weekend was pleasant and that you had some time to work with homebrew antennas–that’s half the fun of amateur radio.

Until next time,

Aloha es 73 de KH6JRM–BK29jx15

Simple Antennas for Amateur Radio Operators–a continuing series.


KH6JRM’s Amateur Radio Blog

Post #175

A “long wire” antenna

One of the joys of being an amateur radio operator is the creation of antennas.  Since I live on a restricted lot surrounded by neighbors and high power distribution lines from the local utility, I have to be creative if I want to get on the air.  Like many of you, I’ve had to live with compromise antennas most of my amateur “career”.  Sometimes, opportunities come along that just beg for experimentation. 

Such was the case today, when several of my neighbors mentioned they would be visiting relatives for several days.  Since my teaching assignments won’t begin until 01 August (or later, if you are a substitute teacher such as I), I offered to keep on eye on their homes until they returned.

Goody!  There are several 30 to 50-foot trees in back of my house on my neighbor’s property that just call out for antenna use.  Oh, well, that must be my imagination.  Anyway, I decided to string up a full-wave 40-meter “long wire” through the trees and tie off the end on a fence post about 100-feet from my qth.  So, using a big slingshot, some fishing line, and a 6-ounce fishing sinker, I launched this skyhook through the trees and tied off the end on the distant post.  Using the top of a spare 32-foot fiberglass pole as the first support, the antenna was run out about 100-feet throught the trees, with about 35-feet running off at a 45-degree angle as a counterpoise.  I attached about 40-feet of 450-ohm twin lead to the top of the fiberglass pole, with one wire soldered to the 100-foot of wire and the other lead soldered to the 35-foot counterpoise.  The antenna resembles a lazy inverted “L”.

The twin lead goes into a 4:1 W9INN balun.  Twenty feet of RG-6 (with suitable connectors) goes to the Drake MN-4.  Three feet of RG-6 attached the tuner to the Swan 100-MX.  The antenna can be tuned from 40 to 10 meters without upsetting the old Drake or the venerable Swan.  I also have an 8-foot copper ground rod outside of the shack which is attached to two 33-foot counterpoise wires running around the property.  The antenna works fairly well, especially since the longer portion of the wire is pointed NNE–that puts most of my signal into the Pacific Northwest of the U.S. mainland.  Reports on cw run between 569 and 589 with 20 watts from the Swan 100-MX.  After Sunday, I’ll have to take the antenna down.  The neighbors are due back on Monday.  In the meantime, I’m having fun.  Once Monday arrives, I’ll return to the inverted “vee” and my two loop antennas.  The antenna was fairly cheap, since I used wire and connectors I already had in storage.  Besides, with all the rain our area has been receiving, I needed to take advantage of whatever sun was available.  Antenna erection day (today) was most pleasant–mostly sunny.  I probably shouldn’t say much, because I see some evening showers coming towards the Hamakua coast.  Such is life.   Enjoy what you can.

Have a good, productive weekend.

Aloha es 73 de KH6JRM–BK29jx15

Simple Antennas for the Amateur Radio Operator–a continuing series


KH6JRM’s Amateur Radio Blog

Post #174

Antennas and Contests

Amateur Radio Operators will have a lot to do during August.  In the August 2012 edition of “QST”, there are at least 33 contests hams can enter.  These contests range from weekly sprints to the ARRL 10 GHz and up Contest.  There is something for everybody in August, even if you aren’t an active contester.  I try to jump in on a few contests (mainly cw and SSB) to see just how good by homebrew antennas work.  Sometimes, my great antenna ideas fall flat–they just don’t perform the way I want them too.  As always, contests give us antenna experimenters plenty of “rope to hang ourselves.”

Now that I’ve installed my garage roof 20-meter loop, I’m anxious to see how this skyhook performs. If performance is not up to expectations, I’ll opt for the 40 to 10 meter inverted vee in the back yard.  That antenna has always done well, propagation permitting, of course.

Among my selected targets will be the North American QSO Party (cw) on 06 August, the Worked All Europe Contest (cw) on 11 August, and the North American QSO Party (SSB) on the 18 August.  Depending on propagation, this could be fun or a real chore.  Over the past few weeks, 20 meters has been fair to poor in the central Pacific.  Of course, my timing may be wrong, too.  I’ve had to take care of a few teaching matters during the day, so I may have missed some good openings.

As for new antennas, I’m in the process of redoing my indoor 40 to 10 meter antenna.  I’ll remove the random wire and counterpoise I installed as an experiment.  The counterpoise was becoming a safety hazard, since it snaked around the floorboards and under the rugs of my qth.  Most likely, I’ll restring a 70-foot loop on the ceilings and feed it with a balun and the Drake MN-4 tuner.  That system worked well a few months ago.  As before, I will run mostly cw and SSB at 10 watts or less to reduce rfi and rf exposure. 

Have a good day and get on the air.

Aloha es 73 de KH6JRM–BK29jx15

Simple Antennas for the Amateur Radio Operator–a continuing series


KH6JRM’s Amateur Radio Blog

Post #173

Friends remembered and a 40-meter vertical for restricted space

This has been a sad week for many amateur radio operators on the Big Island of Hawaii.  Two well-known hams have died and will be missed in our small radio community.

First, Paul Lieb, KH6HME, passed away last week in California.  Paul was best known for his VHF, UHF, and SHF beacons atop Mauna Loa on the Island of Hawaii.  When the tropo was in or a rare ducting across the Pacific Ocean and the U.S. mainland occurred, Paul was on top of the 13,000-foot mountain handling a wave of contacts.  Paul was a friendly guy who always was available to help his community and the Big Island Amateur Radio Club.

Second, Joe Day, NH7LP, died this past Saturday morning following his daily swim in Hilo.  Although he was not too active on the bands, he was always willing to talk “radio” and help others with their licensing efforts.  He remained active on echolink, since he was unable to erect decent antennas at his qth.  He designed and built computers, was knowledgeable in coding, and recently had three books published on Amazon.com.  He pursued the mystery-crime genre after he closed his CPA practice and had plans to go on a major book tour within the continental United States.

I knew both of these gentlemen and considered them close friends.  They will be missed.

Now, on to antennas.  While I was reading about stealth antennas, I came across an article written by Robert Houf, K7ZB, entitled “A 40 meter stealth vertical.”  The article, originally published in antennex in 2001, was republished by Simone, IW5EDI in dx.com.  Basically, the antenna was fashioned out of collapseable aluminum tubing about 35-feet long.  The vertical was attached to the patio (or lanai if you’re from Hawaii) with a homebrew swivel mount.  He fed the 35-foot tube with RG-8 and had two counterpoise wires leading away from the antenna at an angle of about 145 degrees.  The illustrations in the reprinted article are quite good and give you a thorough description of his building process.  At night, Robert would lower the antenna and lie it flat against the floor of the patio.  His bill of materials should be available at most hardware stores.  The antenna apparently does an excellent job and creates a very small footprint on his property. 

My former vertical antenna was patterned after Robert’s, using a 33-foot fiberglass mast to support the wire antenna and one counterpoise running from the base of the antenna.  This antenna worked very well, considering the scarcity of space in my back yard.  And, just like Robert’s antenna, my homebrew vertical could be nested to the ground by a homebrew swivel.  If you would prefer a more sturdy swivel mount, consider the various swivels offered by DX Engineering.  These mounts have received good reviews.

Until next time,
Aloha es 73 de KH6JRM–Bk29jx15

Simple Antennas for the Amateur Radio Operator–a continuing series


KH6JRM’s Amateur Radio Blog

Post #172

A homebrew 20-meter loop

For the better part of two days (Saturday and Sunday), conditions on 20-meters from the Laupahoehoe qth have been poor.  Apparently, a near class X solar flare from our sun has made severe inroads on HF propagation.  So, once my xyl and yours truly finished our daily routines, I decided to work on my modest “antenna farm” in the backyard.

Although my hastily-built 20-meter delta loop worked fine, it was low enough to cause problems with neighborhood pets, wild pigs (we have many here), assorted birds, and other furry creatures (feral cats, goats, and even a lost cow or two).  Living in an agriculture zone does present certain problems.

I took down the delta loop and looked around for an alternative location–not an easy task on a small lot.  While I was creating my replacement antenna scheme, I glanced at my wooden garage.  It measured 17-feet by 16-feet, if I included the laundry room.  Aha! Why not draft the wooden panels beneath the roof for an antenna support?  The roof was 10-feet above ground level–not ideal, but it could work.  I measured and cut a loop of 66-feet for the antenna, using AWG #22 gauge hookup wire I found in my junk box.  At 66-feet, the loop would be about 3-feet short according to formulas found in several antenna books.  However, my Drake MN-4 would be up to the task if I used 450-ohm ladder line and a 4:1 balun. 

After I tacked the loop onto the roof boards of the garage, I ran 20-feet of ladder line to the balun and then used 10-feet of RG-6 coax to connect the MN-4.  Three feet of RG-6 cable attached the system to the Swan MX-100.  I used RG-6 (with suitable connectors), because that’s what I had on hand.  Wonder of wonders, the loop worked.  The swr is a little high on the lower portion of the band (antenna is a bit short), but the SSB part of the band can be managed nicely.  I expect to add 3-feet of wire to the loop so I can reach the bottom portion of the band without creating distress for the Drake MN-4.  Under the current configuration, the tuner doesn’t get hot or arc-over.  Presently, I running about 20-watts output on SSB and CW.

Best of all, the loop is invisible to passers by.  I can use the loop on 20, 15, and 10 meters.  Like my other loop (the full-wave 40-meter loop under the house), the antenna is quiet and unobtrusive.  So far, I’ve made only local contacts in Hawaii.  Once conditions improve, I’ll give the antenna a few more tests.  This is not an ideal antenna, but it works and blends it the environment.

The 40-meter inverted vee along the mountain side of the qth continues to perform well.  The antenna is presently nested to the ground because of a few thunderstorms last night.

Until next time,

Aloha es 73 de KH6JRM–BK29jx15

Simple Antennas for the Amateur Radio Operator–a continuing series.


KH6JRM’s Amateur Radio Blog

Post #171

ANOTHER APARTMENT ANTENNA

Thanks to some good weather today, I was able to get out of the house and work on my modest antenna farm in the backyard.  In my last post, I described a hastily built 20-meter delta loop fed by RG-6 coax.  The loop is working fine and I plan to keep it up for awhile.  Later, I will connect the loop to my station with 450-ohm ladder line, so I can use the antenna for 15 and 10 meters.

After that small antenna project, I was once again on the lookout for other simple antennas that even I could build.  It’s true…I’m not the sharpest tool in the shed when it comes to building things, but I do better with each new project.  My fingers have solder burns to prove it!   Anyway, I wanted to improve my emergency indoor antenna without creating problems with RF emissions or TVI.  As I was searching antennas through the internet, I came across an article by Zachary Flemming entitled “How to make an indoor random antenna.”  At the time of the article (06 January 2010), Flemming was a PhD candidate at the University of California, Santa Cruz and had apparently devised an antenna that gave him many contacts over the years from his small apartment.

Basically, Flemming ran 50-feet of Radio Shack wire around the ceilings of his apartment and fed the antenna into a RBA 1:1 balun attached to a LDG Z-100 automatic tuner.  He didn’t say if a counterpoise was used.  Without a counterpoise, that antenna would “bite” a bit when you used a microphone.  Anyway, assuming he had a decent ground and a working counterpoise, the arrangement proved to be quiet effective in pulling in contacts. 

Here is his list of materials:

50 feet of wire, pushpins to hold up the wire along the ceiling, automatic antenna tuner (LDG Z-100 or equivalent), RBA 1:1 balun, short pieces of RG-8 or RG-58 to connect the transceiver to the antenna and tuner, and a low pass filter to reduce TVI.

Flemming advises those who wish to duplicate his success to run low power (below 100 watts), use digital modes (including cw), and reduce RF exposure and electronic interferrance (TVI) with low pass filters.

As an experiment, I made a similar antenna using 50-feet of wire with one end of some RG-6 coax connected to the wire and the other end of the coax connected to a counterpoise of 50-feet, which snaked along the floor panels and rugs in the qth.  I had an old 1:1 balun in the junk box which I interspaced between the coax and the Drake MN-4 tuner.  I had no RF feedback or “bite” when I used the microphone.  I also had my station ground connected to an 8-foot ground rod outside of the bedroom window.  The indoor antenna worked pretty well, as I received 569 to 579 reports on bands between 40 and 15 meters.  My trusty Yaesu FT-7 with its 10 watt output provide the RF source. 

Perhaps you can use Flemming’s original idea for your apartment.  The antenna works given its limitations.  The important thing is getting on the air safely.

Until next time,

Aloha es 73 de KH6JRM–BK29jx15

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