Tag Archives: antenna

QRP ops on Monte Sano – “Summits on the Air” JT65 Activation, April 2014

By Gary WA2JQZ, with Rob KB5EZ.

On a nice Saturday last April (2014), Rob KB5EZ, Kalen KK4KLT, and I WA2JQZ met at Monte Sano State Park to operate a portable, digital QRP ham radio station. We set up and operated a portable JT-65 station for the international “Summits on the Air (SOTA)” [http://www.sota.org.uk/]. This was the first time a JT-65 operation was tried on Monte Sano — such a first-time activity is called a summit “activation”.

For some this is serious physical sport. As for us, we parked near the ranger office, and hiked a few hundred yards to a clearing on the ridge, which fulfilled the SOTA rules. Monte Sano is on a relatively long and flat sandstone capped plateau ridge, about 2000 feet in elevation. We chose a location near the east edge of the plateau, that was clear and had once apparently been the site of a cabin.

Rob operated JT-65 with his TenTec Rebel and laptop, with some portable batteries. But first we had to erect his EndFedz end-fed 20 meter wire antenna. Using a homebrew slingshot, Rob shot a fishing line over tree branches to raise the antenna. After the end of the fishing line swung over a tree limb and returned to the ground, we attached the antenna’s support cable to the fishing line. Here Rob is reeling back the fishing line, to raise the antenna support cable.

Rob, reeling back the fishing line, to raise the antenna support cable.


Rob reeling back in the fishing line, to raise the support cable for his EndFedz 20 meter antenna.

Readying the antenna support cable.

Rob preparing the antenna support cable. Monte Sano.

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The 20 meter endfedz antenna with balun, deployed, supported by a tension line at this side with the coax feed. The antenna is strung over the tree branches and tied at the other end with another support cable. Monte Sano.

The multi-meter indicated the lowering voltage as the power was used.

Rob KB5EZ set up his laptop to run the digital mode JT-65. A small blue battery and his TenTec QRP Rebel transceiver are behind the monitor. The yellow volt meter was added to monitor the drain on the battery.

We needed shade in order to view the monitor screen.

We needed shade in order to view the monitor screen.

We needed shade in order to view the monitor screen. We therefore chose to set up at this old chimney. The chimney also served to support one end of the wire antenna.

Backup logging of QSOs.

Although Rob’s program logs the QSOs, Rob also used a notebook as a backup logbook. The TenTec Rebel QRP transceiver is visible behind the laptop.

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JT-65 in action…

The program window displays the information we need to have a QSO and monitor other QSOs happening at the same time. The dark colored portion at top left is a “waterfall” display that shows the signals we are receiving (frequency is the horizontal axis) within a 2 KHz-wide range, centered around our set frequency. For 20 meters JT-65, that set frequency is 14.076 MHz. Time is the vertical axis, and the display scrolls downward with time. Therefore each roughly vertical line is the display record of someone’s live JT-65 signal.

We can choose to respond to a signal calling CQ, or find a clear frequency and send out our own signal. Or sometimes, if the situation seems worth the attempt, we could try to call a station that is just finishing a QSO with someone else.

Transmissions are cycled exactly for one minute each, referenced to Greenwich Mean Time. For a QSO, one person sends while the other receives, then the roles switch. The data transmission lasts 47 seconds, and contains a maximum of only 13 characters. During those 47 seconds the message is sent twice, and error checked. The last remaining 13 seconds of the minute are just enough time to read the latest text messages and choose a reply. JT-65 was originally created for EME Moon bounce. Its ability to reliably send short messages as very weak signals makes it a popular amateur mode.

If you look closely, you can see that each JT-65 signal is composed of a base frequency with discreet jumps a few Hz higher, creating the characters.

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The lower left part of the window lists each message transmitted (with a time stamp). If the line is illuminated in green, that message is a CQ call. If the line is illuminated in red, your callsign is in that message!

How do you have a QSO? The lower-middle display lets us choose what message text to send. The standard message exchanges are preset and can be activated with mouse clicks. There is also a field for a 13 character free-text message, which must be typed in.

  • We could call CQ. We first much select a clear part of the spectrum by clicking in the waterfall at the base frequency we want to operate. The red bar at the top of the waterfall indicates the frequency range our transmission will use. In the lower-middle display we then select the “radio-button” to send a CQ message, we choose whether to send during the odd or even minute part of the cycle, and enable transmit. The CQ message will automatically include our callsign with our grid square, e.g.,: “CQ KB5EZ EM64”. We could alternatively call CQ with a text message of our own. Rob sometimes tried “CQ KB5EZ SOTA”.
  • Or we could try to respond to someone else’s CQ. That’s done by double-clicking the text line at left that we want to respond to. The program automatically selects the caller’s frequency, then sends a preset text with our callsign and our grid square, for example, “VE9OK KB5EZ EM64”.
  • The person sending the CQ can acknowledge the response by calling the station back with a signal report (by double-clicking the text line and selecting the “radio-button” for signal report). The message could look like “VE9OK KB5EZ -04”. Then the second person sends a signal report in response. The signal report value is the decibels below the noise floor, and is automatically determined by the program. Afterwards, “RRR” and “73”, or some closing message is sent. And that’s the QSO.
  • If several people respond to a CQ, the caller has the option of which one to respond to. If no one responds, one could continue to call CQ. The programs usually have a counter to call 5 CQs automatically, and then if there is no further action, to stop.

Our challenge is that we operate at very low power. Most other stations operate with more. A station that we hear very weakly will probably hear us even more weakly or might not hear us at all. If they do notice us, they might easily choose to respond to a stronger signal. We’re competing with stronger signals.

And so a rule of thumb, for better success operating at low power, is to call CQ to seek others to contact us, rather than compete with responding to other stations. In other words, if we call CQ, we have the chance to get several callers at once. If we respond to someone else’s CQ, the odds are strongly reversed against us.

However, if we still do respond to another CQ, then it is best to respond to the stronger signals. Chances are better those stations will hear us as a strong signal too, and therefore would more likely respond to us.

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Rob KB5EZ and Kalen KK4KLT.

During the afternoon we had 3 QSOs in reply to our CQs. We also succeeded in replying to 3 other stations that called CQ. We had a total of 6 QSOs.

JT-65 is a slow-paced mode in which to make contacts. With the challenges of operating QRP in the field, this is even more so. Nonetheless, as Rob pointed out at his presentation at the 2014 Huntsville Hamfest, you then have time for other things. You can really enjoy your outdoor environment. You can talk with your friends. And you can easily attract non-ham visitors who pass by. You have lots of time to show and tell with them, to have a relaxed chat and to share the enjoyment.

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Rob KB5EZ and Kalen KK4KLT

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Rob KB5EZ and Gary WA2JQZ

As you can see, we had an enjoyable outing!

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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).

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

6m antenna is ready

Wednesday afternoon I took some more time to visit the club station at Bldg 4622, and finish the connections for the 6 meter antenna.

antenna at MSFC 4622

Our 5 element 50 MHz antenna on the rotor deck

The coax is secured and weatherproofed, the rotor and thrust bearing is intact. Inside you can see my Yaesu FT-897D from home, along with my MFJ antenna analyzer. The SWR is a respectable 1.8:1 at a resonant frequency of 50.150 … I called CQ on 50.125, but had no response. A short time later tho I did hear someone else, and moved the antenna rotor to improve the signal. I had a brief chat with Ed – K2LCK, who lives on Long Island in New York (FN30)… only 850 miles or so with 50 watts – I thought that a good indicator of success.

WB5RMG's FT-897D at MSFC 4622

FT-897D listening on 50.125 MHz

Even tho I messed up on the date, and we missed the ARRL June VHF Sweepstakes – there is a SMIRK contest this weekend on 6 meters. I came out Saturday morning about 8am, but have only worked two stations so far. First was Barry – KJ4UGO, over in Trinity, AL (EM64). Then just now I worked Don – KC2AQU in Tuckerton, NJ (FM29). I have heard some others down in the noise today, so I suspect the band is gonna be up and down. I may come back out later this afternoon or evening and listen some more.

There is currently some undetermined issue with my outbound email, so any information I sent out last night about my activities here today have not made it to the YahooGroup. Anyway, I’ll try to listen on the 147.100 repeater this afternoon in case anyone is trying to get me there. You can try me on my cell phone once I leave here for lunch, but I’m using it here as a modem to get on the internet to post this…

Thanks  /;^)

My Bad : VHF QSO Party was last weekend ..

Oops – I slipped a week there somewhere and missed the contest. Arrrrrgh !.

Well at least I got the rotor under the beam, and connected to the controller.
That is a good thing because there is actually a different contest this weekend. This one is even a 6 meter contest – SMIRK !! SMIRK.ORG

I’ll post more on this shortly, but wanted to announce my mistake in case anyone was planning to participate, or even just to watch. This SMIRK event runs from 7 pm CDT Friday evening, thru 7 pm Sunday evening.
But don’t just take my word, go check that website.
Apparently I am not always paying attention.
Maybe . . . ?

Thanks  /;^)

VHF rotor update

Last week I found the time to look at the VHF rotor.
This is the one mounted on the antenna deck that we moved to the west side of the building. I believe it had  been used by KB5EZ in his meteor-scatter research, so the expectation was that it might still be usable. I removed the 4 bolts that held the motor to the deck, and took it inside to clean it up a bit.

temporary connection for test

testing the VHF rotor

After removing the leftover pieces of the control cable Continue reading

BYO lunch Nov.1

We had a bit of an antenna party after the meeting in early October, and now have the new 160 meter dipole hanging from the pole (the 80m dipole is still there too). We haven’t had much opportunity to check out this new antenna, so some of us are meeting at 4622 during lunch Nov 1st. This off-center-feed dipole (also known sometimes as a Windom) is 264 ft of good stranded copper, and signals seem noticable stronger. We also mounted the 6 meter beam on the new antenna deck, and need to get that rotor connected…

Plenty of stuff to consider and plan our strategy around. Bring your lunch out and join in on the fun. We expect to start about 11am, and will likely be there for a few hours (I need to start my day early for STS-133 launch support, so I’ll be done for the day by lunchtime). Come on down ..!..

/;^)