Tag Archives: meeting

Hexagonal Beam Antenna Presentation by Rob Conklin N4WGY

At our last meeting earlier this month, we were treated to an excellent talk about Hexagonal Beam antennas, or Hex Beams,  by Rob Conklin N4WGY. Rob is a local ham, a mechanical engineer, and a home brewer.  He introduced to us what the Hex Beams are, how they perform, and how they are constructed. And he shared his home brewing experience of building one for himself. He showed us how relatively easy they are to build.  It was such a good talk, and a good source of information, that I would like to highlight what he shared.

These are some attractive characteristics of the Hex Beam.

  1. They are relatively low-cost directional antennas compared to the regular multiband Yagis, and don’t require large towers.
  2. Compared to the regular Yagis, their profile provides lower wind loading, and they are relatively more stealthy.
  3. They are relatively light weight (~25 lbs) and small (~22 feet diameter).
  4. They perform well. Their gain and front/back ratio are comparable to the regular 2-element Yagis. They will work well if just above the roof. They are typically HF, and for HF many of the measurements don’t require tight tolerances. They have about a 3 dbi gain over dipoles.
  5. You can buy commercially made Hex Beams.
  6. But they also are very conductive to home brewing.  Good selections of commercial parts and kits are available.  You don’t need fancy tools nor a lot of skill.
  7. You can get up to 6 bands without traps and without a tuner.  They are relatively easy to adjust.

Hex Beam Design

When I first saw Hex Beam antennas, I was confused because I couldn’t immediately distinguish what their many elements were for. But actually their basic plan is simple.

If it is a monoband antenna, it is just a 2-element wire Yagi system, with a driver and reflector. The wires are supported by what looks like an upside-down umbrella structure.  The structure consists of 6 spreader arms mounted radially from a central base-plate, and a straight center post also mounted from the base-plate. The wires mostly follow the spreader arms’ hexagonal shape.  The driven element wires are supported by one half of the upside-down umbrella, the reflector is supported by the other half.  The spreader arms are structurally supported at their open ends by Dacron tension cords connected to the top of the central post.  Two Dacron cords also run between two spreader arms on the front driver side of the antenna, to maintain correct separation.  The central post contains a 50 ohm coax feed.  A mast mounted to the bottom of the base-plate can be rotated to direct the antenna.

Hex Beams are often multi-band antennas, with up to 6 bands. The multi-band antennas have individual 2-element wire Yagi systems for each band, stacked as you go higher up the umbrella. The 6-band Hex Beam that Rob built operates 6, 10, 12, 15, 17, and 20 meters. The shorter wavelength 6 meters antenna wires are the lowest, where the distance between spreader arms is least.  20 meters wires are the highest.

And so unlike the regular Yagis which use trap coils to operate on multiple bands, the Hex Beam design just utilizes separate wire sets for each band.

This is Rob’s antenna on the roof at his home.

Hex beam antenna on Rob's roof.

Hex beam antenna on Rob’s roof. The front driven element side is facing us.  Click to enlarge, click “back” on your browser to return.  [Courtesy N4WGY]

Classic and G3TXQ Hex Beam Versions

Rob discussed two designs of the Hex Beam. The original classic version was manufactured by Traffie Technologies, and then copied by many home brewers. Rob said many hams use it and swear by it. But it has two performance shortcomings.  First, it is narrow banded; that is, if you tuned the antenna length for the SSB portion of the band, its SWR might be too high at the CW end. Second, if front/back selectivity is peaked, the SWR is no longer optimized. And so that front/back selectivity had to be compromised.

The shortcomings were overcome in 2007 by Steve Hunt G3TXQ. After extensive modeling and experimenting, he developed a modified design that corrected both problems and gave the hex beam better performance: The G3TXQ design has good SWR across the full ham bands.  And the peak front/back ratio is at the optimal SWR.  With a slightly simpler wire system, it is also is a little easier to build. Rob built a K4KIO version of the G3GTX design.

In both the original and G3TXQ designs, the layout of the driven element wires is similar.  The driven element layout is shaped like an “M”, or more precisely like two “V”s.  One end of each “V” starts from the feed connection at the central post, extends to a spreader arm, then continues as a side of the hexagon to the next spreader arm.  Spacer ropes clamped at the spreader arms keep the wires in sufficient tension.

Schematic top view of G3TXQ Hexbeam antenna

Schematic top view of G3TXQ Hexbeam antenna. [Courtesy N4WGY]

The other end of the spacer ropes connect to the reflector wires. The spacer ropes keep a critical separation distance between the driver and reflector elements. The lengths of the wire elements and the spacer ropes are the critical measurements to make for the hex beam.

In the original design, the reflector wires had also followed an “M” shape configuration. In the G3TXQ design, however, the reflector wires follow the hexagonal shape provided by the spreader arms.

Performance

As Rob points out, the G3TXQ design provides good SWR performance across the full range of each ham band. He showed us a spectrum analysis of his antenna.

Full SWR scan of N4WGY's hexbeam antenna, from 1 to 36 MHz (160 to 10 meters ham bands). [Courtesy N4WGY]

Full SWR scan of N4WGY’s hex beam antenna, from 1 to 36 MHz (160 to 10 meters ham bands). The grey columns are the ham bands.  Note the SWR dips where this hex beam is designed for: 20, 17, 15, 12, and 10 meters. The antenna is also resonant for 6 meters (50 MHz), but the analyzer doesn’t reach that high a frequency.   [Courtesy N4WGY]

 The chart shows the SWR performance of his Hex Beam, as the frequency varies from 1 MHz at left to 36 MHz at right.  The shaded columns are the locations of the amateur radio bands.  For the bands not designed for, 160, 80, 40, and 30 meters at left, the SWR values are well above 3:1.  But at 20 meters the SWR dips to about 1.2:1 and is well below 2:1 across that band. The SWR for the other ham bands designed for also remain below 2:1 and in some cases also dip to as low as 1.2:1.   You can click the image to see the details for each band. You can see Rob made his lengths slightly long, but he can adjust that, to better position the dips within the ham bands.

Rob brought in to show us the antenna analyzer he used to scan his antenna and make the chart.  This analyzer connects through a USB cable to a computer, where the scans can be displayed, zoomed in for details, and saved.  The analyzer is made in India as a kit and costs under $60.  The analyzer is called a Fox Delta AAZ-0914Ahttp://www.foxdelta.com/products/aaz-0914a.htm.

Rob mentioned that he can reliably make contacts around the world, when propagation permits.  And he feels comfortable competing with hams with larger antenna systems.

Construction Tips

Rob Conklin N4WGY presenting at our meeting [Photo courtesy NM4T]

Rob Conklin N4WGY presenting at our meeting, here discussing construction details. [Photo courtesy NM4T]

Rob devoted much of his talk to construction details, and much of the Q&A from the group was about components and building. I will mostly defer to the online resources Rob suggested. But Rob did give some additional advice:

  • Don’t use PVC for the center post.  Especially in the South with UV from sunlight, the material will quickly degrade.  Spend the extra money to get UV resistant tubes.  He recommends buying online the mast sold by K4KIO.
  • For the wire sets, he says 14 AWG stranded/plated and uninsulated antenna wire would be best.
  • Telescoping fiberglass poles are recommended for the spreader arms.
  • Do not make the wire elements too tight.

Here are resource links.

Construction plans:

  • http://www.hex-beam.com/ – The K4KIO website with detailed, step-by-step construction plans, similar to what Rob showed us.

Supplies and commercial hex beam kits:

SWR scanner tool:

Addendum

For the close of the talk, Craig Behrens NM4T brought in to show us a light-weight, self-contained, portable G3TXQ hex beam antenna. It is designed and manufactured by a company in Germany called Folding Antennas.  The antenna weighs only 9 pounds, is collapsable to 45 inches, and comes in an easy-to-carry bag. Instead of folding out like an upside-down umbrella, the spreader arms fold out flat.  The flat configuration has much less bending load, and therefore the spreaders are made thinner and lighter.  The wires have special fittings to attach to the poles. The antenna can be assembled by one person in 10 minutes. [See http://www.vibroplex.com/contents/en-us/d3.html. ]

Craig also showed us a prototype TenTech Patriot QRP transceiver.  It operates SSB, CW, and digital modes on 20 and 40 meters at 10 Watts.  Its design was influenced from recommendations by his QRP Skunkwerks group.  During the following week Rob Suggs KB5EZ (one of the members of that group) gave it some field testing.

 

The club again thanks Rob Conklin N4WGY for giving us an excellent practical, educational presentation.  The club also thanks Craig Behrens NM4T.  And thanks to our members and guests for participating.

One of the eQSLs the club recently received shows a hex beam of KL2R, the Two Rivers Contest Club in Fairbanks, Alaska. You can see the wires in front of the aurora.

QSL card we received from KL2R in Fairbanks, Alaska, showing their hex beam at night (with aurora).

QSL card we received from KL2R in Fairbanks, Alaska, showing their hex beam at night (with aurora).

Advertisements

Hex Beam Antenna presentation at our next meeting Oct. 2, 2014

We are delighted to have Rob Conklin, N4WGY, come to talk with us at our next club meeting.  He will share a short slide presentation about his experience in home brewing, mounting and using a K4KIO designed 6 band Hexagonal beam type antenna. After the presentation we’ll have time for Q&A.

Also on our agenda will be the upcoming W1AW/4 week-long operation from Alabama, 15-22 Oct. 2014.

If you have access to the Arsenal, please come join us.

Thursday October 2, 2014, meeting start 4:30 pm
Bldg. 4622, MSFC, Redstone Arsenal, AL
[location on Google maps]

– Gary, WA2JQZ

A good start for 2013

On the heels of a successful January VHF contest, our club has voted to approve a new set of By Laws at our February meeting. These have been sent to the MSFC Exchange Council for their approval. I wanted to take this opportunity to thank everyone for their participation and continued interest in this club. This is how it works ; we want a club, we make it happen. Congratulations to all of us.

While preparing the 2012 Jan VHF Sweepstakes log for submission, I discovered that I had not uploaded any log entries to eQSL since 2010. Duuuuh….
And on top of that, the latest (current) QSL image was not on-line.
So – since I was off today on Holiday – I took care of all that.

the WA4NZD eQSL card

Our eQSL card is updated.

In addition to updating the image, I have uploaded the ADIF files for several recent VHF contests as well as a few Field Day activities. There is now a total of 614 outbound QSL entries on-line. We still need to process the previous STS special event logs into ADIF format so that we can upload those. We have lots of incoming eQSLs that we need to match up and verify with our logs.
This is how our Outbox looks as of now (mid-Feb of 2013)…

eQSL outbox detail

snapshot of eQSL Outbox summary

OK, Thanks again for all the support. This is how fun happens.
Keep up the good work thru 2013, and you will be proud of your club.
Spread the word, we can always find room for a few more new members.

Thanks  /;^)

Simulated Emergency Test 2012

It is that time of year again .!.
Every year the ARRL‘s Amateur Radio Emergency Service conducts a test (SET) of their operational readiness and preparedness plans for managing a communications emergency. This year our test in Huntsville/Madison County Alabama will be in conducted in association with the HMCEMA. We have contacts within many local and regional agencies that would like to participate with us. Our exercise will be held on Saturday, Oct.6 2012 ; starting sometime after 8am, and concluding somewhere around noon. We don’t disclose many details before the exercise, to keep participants prepared for anything.We will toss in a few surprises along the way to add some excitement. We expect to have a picnic downtown in Big Springs Park after the exercise concludes.

The Marshall Amateur Radio Club WA4NZD will participate in this exercise; and fortunately, we have our monthly meeting this Thursday (Oct.4) and can discuss our preparations to ensure that our station is ready for whatever comes. Stop in Bldg.4622 after work and help us prepare for this year’s SET.

One teaser, to help encourage folks to participate, is this ‘proposed plan‘ of how we might coordinate multiple agencies and individuals over a large area, utilizing multiple frequencies. Of course, the details are somewhat masked, as this is a work in progress, and we want to observe how our multi-talented pool of resources will evolve into meeting our needs for the exercise.

how to coordinate a communications emergency

brain-storming a messaging network

Be thinking about how we structured our support last year after the tornadoes, and throughout that week-long power outage. What worked well, what might have helped. Bring your good ideas, and a desire to help to the annual SET.
We will figure out what works, and what doesn’t.

Thanks  /;^)

Meeting with Kotrous

On May 3rd, 2012 we had a very productive meeting with Brian Kotrous, an Emergency Manager from NASA Protective Services. With 10 MARC members in attendance, we discussed our role in Emergency Preparedness at MSFC.

photo by WL7C

Kotrous from the Marshall EOC visits the MARC station

Here is a brief summary presented for inclusion into the Center Notes :

NASA’s Emergency Communication Service recommendations (Draft Rev.13) suggests that in addition to official staffing, volunteer support from the Amateur Radio Service can be enlisted. This prompted Brian Kotrous, an Emergency Manager from NASA Protective Services, to attend a meeting of the Marshall Amateur Radio Club (MARC) on May 3, 2012. After describing his mission objectives and some brief discussion, Kotrous invited the membership to participate in future MSFC emergency preparedness exercises. Several MARC members are planning to participate in the upcoming Severe Weather exercise planned for June 14, 2012.

A distinct benefit of utilizing ham radio volunteers, is that many are already connected to and familiar with local and regional agencies such as the Huntsville-Madison County EMA, and the National Weather Service. In addition to providing alternate path communication services, the MARC membership also provides a pool of experienced radio operators that can augment the Center’s capabilities in an emergency.

An example of this type of  service the MARC can provide, was actualized on May 23, 2012 – when KHA945 (MSFC-EOC) was able to check into a regional shortwave radio “net” using equipment at the MARC radio station in Bldg. 4622. This is a weekly radio coordination test conducted by the National Communications System (NCS), for Shared Resources (SHARES). The MSFC EOC has been recently relocated and their HF (shortwave radio) system antenna is not available currently. The MARC will gladly continue to help facilitate this routine testing of operational readiness.

The Marshall Amateur Radio Club is looking forward to becoming more involved in the Center’s Emergency Preparedness activities, and is well positioned to provide additional communication support. More information can be found on the club’s blog https://wa4nzd.wordpress.com .

Feels like summer

I don’t know where the time goes, but the last post here was back in January. We all have so many more projects than time to make progress . . . This time last year MSFC was closed for nearly a week, as we had been saturated with storm damage after a major tornado outbreak – and most of north Alabama had no electricity. Many of us were helping friends and neighbors clean up. On this anniversary, we re-visit these events in our minds to remember the lives lost, and to pay tribute to the first-responders and the recovery teams that helped our community.

20110430_5405ac2

Anderson Hills Tornado 20110427

This response and recovery effort was enhanced by the participation of hundreds of Amateur Radio operators, that jumped at the chance to fill in where ordinary lines of communications were not available. This is an aspect of ham radio that Continue reading

Now we have 2012

Time to start another year .!.

Sometimes it seems like we didn’t do much as a club, but just look back on this last year in the blog, and you will find NanoSail-D, VHF contests, Field Day, the Final Shuttle Launch Special Event, and points in between. We have come a long way in bringing the MARC back to life, and can be proud of that. We logged over 250 HF contacts during the STS-135 commemorative, and have sent certificates to all stations who sent us a SASE. The eQSL logs for this last year’s events will be uploaded before long, so please be patient.  /;^)

Sure we have a ways to go – but we already have plans in place to replace the HF beam rotor, and get our satellite tracking hardware back into operation. We need to focus our attention and get our Continue reading