Bora Bora Island DXpedition

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Our QSL Card from Bora Bora

Our QSL Card from Bora Bora Island, French Polynesia

In February of this year, we had the opportunity to travel to Bora Bora Island in French Polynesia. This South Pacific destination is absolutely beautiful! When Anita (AB1QB) suggested that we take a portable HF radio with us, we had no idea what sort of experience we were going to have! We put together a portable HF station and antenna system and obtained licenses from the officials in French Polynesia. I also tested our portable HF setup on business trips to Arizona and Florida in advance of our trip.

Bora Bora Station

Bora Bora Station

Our location in Bora Bora was about 400 yards from the beach and 8 ft above saltwater. Needless to say, this made for some exceptionally good antenna performance and our station worked very well there.

Our Shack in Bora Bora

Our “Shack” in Bora Bora

We took a TransWorld Antennas Vertical dipole (all bands 20m thru 10m) and a two element Buddipole 10m beam with us to Bora Bora. Both of these antennas are good performers and are very portable (especially the Buddipole system which literally fit in the bottom of our suitcase).

Bora Bora Antennas

Bora Bora Antennas

Anita and I had only very limited experience operating a pileup prior to this trip from our participation in the 13 Colonies Special Event as K2K, the New Hampshire, USA digital station. It was quite an experience when we went on the air in Bora Bora for the first time using SSB phone and had at least 50 stations trying to call us at once! Anita (FO/AB1QB) and I (FO/AB1OC) did a little over 1,500 QSOs while on this trip. We earned a Worked All States (WAS) and a Worked All Japan Districts awards based upon our operations there. This trip allowed us to learn a great deal about DXpedition’ing, pileup operations, propagation, portable station design, and QSL’ing for a DXpedition. We are going to be sharing our experience via a presentation at the upcoming Boxboro 2012 Hamfest in Boxboro, MA USA later this month. If you are in the MA/NH USA area, please join us for our presentation at Boxboro 2012 on Saturday, August 25th.

– Fred (FO/AB1OC)

What Are You Interested In?

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We’ve had our Blog in operation for about a week now and I think its a good time to get some feedback on what our readers are finding most interesting. We’ve had the opportunity to participate in a pretty broad range of amateur radio activities in the bit under two years since we have been licensed. I’d like to have our reader’s input on what sort of material might be most interesting to post here. Please take a moment to provide us some input. You may choose your top three items from the following poll and you can use the “Other” choice to add something else that you think would be interesting or useful. Thank you for you time and input.

– Fred (AB1OC)

First Tower Part 8 – VHF/UHF Antenna System Design

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M2 2M Beam

M2 Antenna Systems 2m Yagi

We have an interest in weak signal work on the 2m and 70cm bands. We currently have a vertical ground plane antenna installed at about 50 ft for accessing our local repeaters on these bands but the surrounding tree cover and lack of gain have prevented us from pursuing our interest in VHF/UHF contesting, Grid Square collecting, etc., on these bands. We designed our tower to accommodate long-boom Yagi’s on 2m and 70cm for these purposes, and we have decided to install them as part of our project. I spoke with Jason at M2 Antenna Systems this evening. After some discussion about our goals and the tower and station equipment we have, we decided upon the following antennas and related equipment for VHF/UHF weak system work:

Both antennas have good gain and F/B ratios and very good patterns. Initially, we will drive the system with our Icom IC-9100 Transceiver. This rig provides 100W on 2M and 75W on 70cm barefoot. This should be enough power to have some fun on these bands initially. We plan to add an amplifier on 2m and 70cm, so we selected antennas capable of handling 1KW+ power. We are also having M2 Antenna Systems assemble a custom pre-amp and high-power switching system to mount at the top of the tower, which will accommodate our planned power levels. Both antennas feature rugged construction to help them withstand the winters that we have here in New Hampshire, USA.

M2 70cm Beam

M2 Antenna Systems 70cm Yagi

It is important to pay careful attention to the feedline losses at these frequencies. This is especially important for us as we need 200’+ of coax feedline to get from our shack to the top of the tower/mast where the antennas are located. To ensure good performance, we set a target for the total losses in the feedlines to be no more than 1.5 dB. To meet this goal, we settled on the following configuration:

Both feedlines will have about 1.2 dB of loss end to end using these components. We will place both beams on the 15′ mast above our upper SteppIR DB36 Yagi. We plan to place the 70cm Yagi at the top of the mast and the 2m Yagi between the DB36 and the 70cm Yagi in the middle. This configuration should minimize any interactions between the three antennas.

You can read more about our tower project via the articles which follow:

– Fred, AB1OC

First Tower Part 7 – 100 ft Tower Completed!

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Completed 100 ft Tower

Completed 100 ft Tower

We completed our 100 ft Rohn 55G Tower today! Matt at XX Towers got the second Star Guy Bracket from Rohn, installed it on the top section of the tower and raised the top section into place. After he and Andrew attached the second level of Phillystran guy lines at the 95 ft level, our tower was up.

Completed 100 ft Tower in Back Yard

Completed 100 ft Tower in Back Yard

Matt placed our 21 ft x 3″ mast inside the tower at the base prior to installing the top section of the tower. This makes getting the mast into place when the rotator goes in much easier!

Mast Inside Tower

Mast Inside Tower

Matt also finished the guy equalizer plates and grounded them. Here’s what they look like.

Guy Equalizer on Anchor

Guy Equalizer on Anchor

As you can see, the Phillystran guy material transitions to Extra High-strength Steel (EHS) guy cable near the ground for safety reasons. Here’s a picture of a portion of one of the Phillystran guy lines on the ground. You can see the transition to the EHS cable at the end.

Phillystran Guy Line

Phillystran Guy Line

The Star Guy system worked out great and should keep the tower from twisting under the torque of rotating two large SteppIR DB36 antennas at the same time.

Two Levels of Star Guys

Two Levels of Star Guys

The tower base is also grounded at this point. We will be adding two additional ground rods on the other two legs and bonding the tower ground to the station ground over the next few days.

Tower Base

Tower Base

We are really happy with the results of our tower project to date. Now we need to get some antennas on our new tower! We are expecting our SteppIR antennas to arrive soon – it sure is tough to wait!

Up The Tower

Looking Up The Tower

You can read more about our tower project via the articles which follow:

– Fred, AB1OC

Tower Layout And Mechanical Analysis

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Tower Layout (Not to scale)

Tower Layout (Not to scale)

Once we determined the height of our tower and the antennas on it, the next step was to determine the location of the tower and the associated guy anchors on our property. Rohn provides specs for guy anchor heights, layout angles and distances for a given tower type and height. Using Rohn’s specifications for a 100 ft 55G Tower, we selected the location for our tower in such a way that the guy anchors were about 100 ft or so from the tower on the edge of our backyard in the woods. These locations allowed the guy lines to rise above the yard enough to walk under them before reaching the edge of our lawn. This layout placed two of the guy wires below the ground level that the base of the tower sits on. To ensure that our guy angles would be as expected, we used a surveyor’s transit to measure the elevation of the guy anchors relative to the tower and to locate them at the required angular separation. A little bit of trigonometry and a spreadsheet allowed us to determine the angle of each guy wire relative to the ground using the following formula:

Guy Angle = arctan( Elevation / Distance ) where:

Guy Angle = Guy angle relative to the ground
Elevation = Total rise of guy wire
(height of guy on tower + distance of guy anchor below tower base)
Distance = Distance from tower to guy anchor

These calculations should be done to determine angles for the upper and lower guys wires at each of the three guy anchor points. As long as the distances and angles are within Rohn’s specifications, the tower layout is ok. We also had a special requirement here because we are planning to rotate on of our SteppIR DB36 beams around the tower using a KoXG rotating ring.

K0XG Ring Rotor

K0XG Ring Rotor

The concern here was that the lower SteppIR DB36 antenna might interfere with the upper set of guy wires as it rotates.

SteppIR Antenna on K0XG Ring

SteppIR Antenna on a K0XG Ring

SteppIR’s specifications for the DB36 indicate that this antenna has a 26 ft turning radius. To allow for the size of the K0XG ring and some margin for error, we settled on a minimum clearance of 30 ft between the lower rotating SteppIR DB36 Antenna and the upper guy lines. Again, some trigonometry and a spreadsheet help us determine if our planned design will work.

Clearance = ( Upper Guy Height – Ant Height ) / tan( Guy Angle )

The Guy Angles are those computed in the previous step. Note that the Upper Guy Height includes both the height of the guy on the tower plus the distance of the guy anchor’s elevation below the base of the tower if any.

We created a simple spreadsheet to calculate the clearance between all three of the upper guy lines and our planned SteppIR DB36 antenna at 65 ft and determined that we had more than the required clearance for all three guy lines.

– Fred (AB1OC)

Tower Wind Loading Analysis

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REV G Wind Speed Map (from Rohn, Inc. Website)

TIA-222 Rev. G Wind Speed Map (from Rohn, Inc.’s Website)

CAUTION – THIS POST IS NOT INTENDED TO BE AN AUTHORITATIVE PROCEDURE OR INFORMATION SOURCE ON WIND LOADING CALCULATIONS OR THE SAFETY OF YOUR INTENDED TOWER AND ANTENNA SYSTEM DESIGN. USE THE INFORMATION HERE AT YOUR OWN RISK AND CONSULT A PROFESSIONAL ENGINEER AS THE FINAL WORD ON WHETHER YOUR TOWER DESIGN AND PLANS ARE SAFE. FAILURE TO PERFORM THESE STEPS CORRECTLY CAN LEAD TO  MAJOR DAMAGE OR FAILURE AND COLLAPSE OF YOUR TOWER AND COULD RESULT IN SEVERE PROPERTY DAMAGE, INJURY AND/OR DEATH! Now that we have the cautions out-of-the-way, I should note that the most important aspect of engineering a tower and antenna system is to ensure that the tower is not overloaded and is safe in the wind (and icing) conditions that may be encountered. The ARRL Antenna Book chapter 26, Appendix A is a source on how to perform a basic form of these calculations. You should also read and understand Rohn’s brief on TIA-222 Rev G before beginning. IN ALL CASES, SEEK THE HELP OF A PROFESSIONAL ENGINEER OR EQUIVALENT SKILLED TOWER PROFESSIONAL TO ENSURE THAT YOUR TOWER DESIGN AND PLANS ARE SAFE.

I will not try to repeat the procedure for performing the wind loading calculations here. I do think its important to note the following (all of this is covered in the ARRL Antenna Book):

  • Make sure you select a maximum wind speed target that properly accounts for your location and exposure (how much the tower site will be exposed to the wind)
  • You should do a set of calculations for both ice and non-ice conditions if your location has the potential to experience icing in the winter. Note that icing significantly increases the size and weight of anything that it builds upon and therefore the wind and other loads on your tower!
  • You need to account for all equipment that has a wind profile on your tower. This includes antennas, feedlines, masts, rotators, electronics enclosures, etc. that will be mounted on your tower. The elements beyond the antennas themselves can easily add up to be a big part of the overall wind load.
  • Do not exceed the manufacturer’s specifications for wind loads for your planned tower height, guying arrangement, exposure, etc. All of Rohn’s specifications include this information. DO NOT OVERLOAD YOUR TOWER BY EXCEEDING THE MANUFACTURER’S SPECIFICATIONS.

These calculations are best done by an experienced engineer or tower professional. There are significant variations in the way various manufacturers quote their wind loading specifications so it is best to seek the help of a profession with these steps.

USE THE INFORMATION IN THIS POST AT YOUR OWN RISK! THE AUTHOR ACCEPTS NO RESPONSIBILITY FOR THE CORRECTNESS, USE OR ANY DAMAGES, CONSEQUENCES, OR LOSSES ASSOCIATED WITH THE USE OF THE INFORMATION IN THIS POST.

– Fred (AB1OC)

First Tower Part 6 – We Have A Tower!

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Tower Compete to 90 ft

Tower Complete to 90 ft

Matt and Andrew from XX Towers put most of our tower up today! We had all of the parts needed except for the upper star guy anchor so we were able to get the first 90 ft and the lower star guy (at 50 ft) up today. We will complete the tower to the 100 ft level and add the mast which will extend 15 ft above the top of the tower for a total of 115 ft once the second Star Guy Bracket arrives.

The star guy system is working out great.

Star Guy Bracket

Star Guy Bracket

The first Star Guy system is installed at the 50 ft level on our Tower. The guy material is made of Phillystran which is a non-conducting high-strength fiber-based material. The Phillystran material transitions to standard EHS steel guy wire for a short section at each end of a guy cable for safety.

Star Guy on Tower

Star Guy on Tower

As you can see from the pictures, the tower is shaping up nicely! Here’s a picture of the tower looking from the front of our house.

View of 90 ft Tower from Driveway

View of 90 ft Tower from Driveway

Andrew did all of the work on the tower and Matt and I acted as the ground crew. Andrew and Matt are very accomplished at working on a tower and the entire 90 ft including the guy system was up in less than a day!

Andrew on the Tower

Andrew on the Tower

I will post a second article explaining the entire process to put the tower up soon once we complete the remaining section, mast, and star guy anchor.

You can read more about our tower project via the articles which follow:

– Fred, AB1OC

Safety Equipment For Tower Climbing

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Climbing Safety Harness

Safety Equipment for Tower Climbing – Harness

I will be climbing our tower both to add equipment in the future as well as to maintain it. To this end, I’ve purchased a safety harness and associated equipment and rigging for tower climbing and work. This is perhaps the most important purchase a tower owner will ever make as you are betting your life on the reliable operation of this equipment. I choose a DBI-SALA ExoFit NEX Tower Climbing Safety Harness along with the associated fall arrest and anchor straps. I also purchased a good quality hard hat for myself and for Anita so that she can assist me on the ground. In addition, we purchased ropes, pulleys, carabiners, and various other rigging accessories to allow us to haul materials and tools up the tower to work on it. All of this equipment was obtained from a combination of TowerClimbing.com and Champion Radio Products. I am planning to provide some posts in the future once I have the opportunity to use this gear.

– Fred (AB1OC)

Weather Station On Tower

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Weather Station

Weather Station

We have long wanted to add a Weather Station at our QTH. We attended the Dayton HAM Fest this year and had a chance to talk with the folks at Davis Instruments and to look at their weather stations. We decided to take advantage of their show special and purchase a Vantage Vue Weather system. We also purchased their WeatherLink IP option as well as an additional Vantage Pro2 console for the system. These options will allow us to connect the weather station to the internet so that we can use our iPhones and iPads as well as PCs to monitor the weather at home from anywhere in the world. Finally, we are going to fabricate a custom tower standoff mount for the station. Stay tuned for a future post showing the installation and the final results of our weather station project.

– Fred (AB1OC)