The first step in the project was to assemble the antenna and check its SWR on the ground. The elements on an antenna like this typically vary by small amounts and are usually not arranged from shortest to longest. It is important to carefully measure each element during installation to confirm that each element is installed at the correct location on the boom.
The folks at M2 Antenna Systems made up a custom boom support truss for us. This is important given the potential for ice and snow accumulation that we face here in New England. We also made up a section of LMR-600uF coax to connect the antenna to the feedline and preamp system on our tower.
Driven Element Details
The new antenna uses a Folded Dipole style feed point. This system is essentially a T-matching arrangement where the two sides of the driven element are fed 180 degrees out of phase. It is important to set the locations of the shorting blocks carefully to ensure proper operation of the driven element and a resulting low SWR.
Yagi Going Up The Tower
Matt, KC1XX, and Andrew from XXTowers handled the installation of the new Yagi on our tower. The installation involved climbing our 100 ft tower and the 25 ft mast at the top to remove the old yagi and install the new one. Note the careful rigging of the new antenna and associated feedline. This allows the new antenna to be pulled up the tower without damaging it.
Climbing a mast is not for the faint at heart! An installation like this one is clearly a job for experienced professionals. Andrew makes this task look easy. Our tower camera captured some video (click on the image above to play) of Andrew’s handy work.
The new yagi (top antenna in the picture above) is installed on a 5 ft fiberglass mast extension. The extension is used to ensure that the antenna does not “see” a metal mast which would disrupt the antenna’s pattern. The final installed height of our new yagi is a little over 125 ft. Note Andrew’s good work in attaching the feedline to the mast.
432-9WLA Installed SDR – Shack End
With the new yagi installed and hooked up, we made a final check of the end-to-end SWR from the shack. The antenna’s SWR is very good and the 2:1 SWR bandwidth extends from the bottom of the 70cm band to almost 450 Mhz. The new antenna is optimized for weak signal work up through the ATV sub-band and its SWR is below 1.2:1 in this range.
The Nashua Area Radio Society produces similar how-to training materials on almost a monthly basis and we make these materials available to our Members an Internet Subscribers (folks that live too far from our location to be regular members) for a small cost which supports our new Ham development programs and covers the production and storage costs associated with the video material. Here’s a list of the training topics that we’ve produced to date:
2019 Tech Nights
Fox Hunting: Radio Direction Finding for Beginners including a Tape Measure Yagi Build by Jamey Finchum, AC1DC
Surface Mount Technology by Hamilton Stewart, K1HMS
RF Design with Smith Charts, Building a First HF Station, and Begining with CW – Hamilton Stewart, K1HMS; Anthony Rizzolo, KC1DXL; and Jerry Doty, K1OKD
All About Field Day 2019 by our Field Day Planning Team
We recently completed the finishing touches on our new VHF/Satellite Tower. The first step was to install a second set of entry conduits into our shack and a new ground block for our satellite antennas. This involved installing 4″ PVC conduits into our shack. The new entries are very close to the base of our tower and this will allow us to keep our feedlines as short as possible.
Hardline Coax Cables Up The Tower
We also replaced the section of our feedlines which run down the tower with 7/8″ hardline coax. We installed a total of four runs for 6m, 2m, 70cm, and 23cm. The use of hardline coax will help reduce our feedline losses – especially on 70cm and 23cm.
Hardlines at Base of Tower
The new hardlines are connected one of the two entries into our shack. The 6m hardline enters on the side closes to our antenna switching matrix and the 2m, 70cm, and 23 cm hardlines will enter the shack via the newly created entry which will be close to our satellite transceiver.
The next step in our project will be to upgrade our Flex-6700 SDR based Remote Gateway for operation on the satellite bands. You can find other articles about our Satellite Station 4.0 project here:
It is winter here in New England and it is not the best time of year to work outdoors. I have been able to complete a few finishing touches on our new Satellite and 6m Tower.
Installed IP Camera
The first enhancement is the addition of an SV3C IP Camera. The camera allows us to see what is going on with our antennas. The camera has IR illumination so we can see our antennas when operating at night as well. The camera will also be useful for demonstrations when we operate our satellite station remotely in the future. This camera can use Power Over Ethernet (PoE) for power and is compatible with most popular security and webcasting applications.
The video above is from our IP Camera while our antennas are tracking AO-7 during a high-elevation pass.
The second enhancement relates to VU Mode (or J Mode) satellites such as SO-50 and FO-29 which use a 2 m uplink and a 70 cm downlink. Satellite ground stations are prone to problems with 70cm downlink receiver desensitization when transmitting on a 2m uplink. The symptom of this problem is difficulty in hearing your own transmissions in your downlink receiver while being able to here other operators in the downlink just fine. Our antennas are separated enough here that we have only minor problems with J Mode desensitization at our station. Fortunately, this is not a difficult problem to take care of.
Comet CF-4160N Duplexer
Installation of a good quality duplexer in the 70 cm path between the antenna and electronics such as our 70 cm preamp provides about 60 dB of additional isolation when operating in J Mode. The Comet CF-4160 Duplexer is a good choice for this application.
Duplexer J Mode FIlter Installed In Preamp Box
We added one to the preamp box on our tower to create a J Mode desensitization filter. The duplexer is mounted on the left side of the 70 cm preamplifier which is on the right side in the image above. The 70 cm output of the duplexer connects to the feedline from our 70 cm antenna and the common output goes to the input of our 70 cm preamp. We also added a connector cap to the unused 2 m port on the duplexer to protect it from moisture. You can read more about this approach to J Mode desensitization filtering here.
The next stage of our project will be to add hardlines to our new tower and install a second entry to our shack near our new tower to bring our feedlines and control cables permanently into our shack. These projects will have to wait until spring. For now, we are enjoying operating our new antennas from a temporary station set up in our house. We also have a new IC-9700 Transceiver on the way and we should have it installed sometime during the next couple of months.
You can find other articles about our Satellite Station 4.0 project here:
The Nashua Area Radio Society participated in Winter Field Day for the first time this past weekend. We put up a 40 ft tower and we were QRV on all allowed bands from 160m through 2m and 70cm. Our station was a four transmitter one and we produced a great score during the 24-hour operating period. Winter Field Day presents some unique challenges that we did not encounter during Summer Field Day.
We put together a station for 160m for the first time as well as some other new things. You can read all about our approach to a station and operating for Winter Field Day via the link above.
Sometimes we learn from problems and mistakes. We all go through this from time to time. It is part of the learning aspect of Amateur Radio. My most recent experience came while integrating our new tower-based satellite antenna system. After the antennas were up, initial testing revealed the following problems:
After an initial attempt to correct these problems with the antennas on the tower, we decided to take them down again to resolve the problems. The removal was enabled, in part, via rental of a 50 ft boom lift.
The lift made it relatively easy to remove the Satellite Antenna Assembly from the tower. We placed it on the Glen Martin Roof Tower stand that was built for the Portable Satellite Station 3.0. Once down, the Satellite Antenna System was completely disassembled and a replacement Alfa-Spid Az/El rotator was installed.
Cross Boom Truss System
The photo above shows the reassembled cross boom and associated truss supports. Note the tilt in the truss tube on the left side. This allows the antennas to be flipped over 180 degrees without the truss contacting the mast.
As mentioned in the previous article, polycarbonate reinforcement bushings are installed in the fiberglass parts to prevent the clamps from crushing the tubes. The photo above shows one of the bushings installed at the end of one of the truss tubes.
The bushings are held in place with small machine screws. This ensures that they remain in the correct locations inside the fiberglass tubes.
Thorough Ground Test
With the Satellite Antenna Array back together and aligned, we took a few days to operate the system on the ground. This allowed me to adequately test everything to ensure that the system was working correctly.
Tower Integration Using A 50 ft Boom Lift
With the testing complete, the antennas went back up on the tower, and the integration and testing work resumed. Having the boom lift available made the remaining integration work much easier.
Control Cable Interconnect Boxes On The Tower
There are quite a few control cables associated with the equipment on our new tower including:
The M2 Orion Rotator which turns the mast that holds the 6 m Yagi and the Satellite Antenna Array
A combination of junction boxes near the top of the tower and at the base make connecting and testing of the control circuits easier and more reliable. Tower mounted junction boxes were used to terminate the control cables near the rotators and antennas.
The Preamp System was mounted near the top of the new tower and the feedlines from the 2m and 70 cm Satellite Antennas were connected to it. LMR-400uF coax is run from the Preamp System as well as from the Directive Systems DSE2324LYRM 23 cm Satellite Yagi and the M2 6M7JHVHD 6 m Yagi on our new tower to the station in our house to complete the feedlines. These LMR-400uF feedlines will be replaced with 7/8″ hardline coax to our shack in the spring when warmer weather makes working with the hardlines easier.
Temporary Station Setup
With all of the tower integration work done, we set up the station in our house for testing. This is the same station that is our Portable Satellite Station 3.0 with two additions:
An iMac Computer which replaces the MacBook laptop used in the portable configuration
Both of these additions will become part of the final Satellite Station 4.0 when it is moved to a permanent home in our shack.
The rotator set up on the new tower provides two separate azimuth rotators. The lower one above turns both the 6 m Yagi and the Satellite Antenna Array together. The upper box controls the Alfa-Spid Az/El rotator for the satellite antennas. Using two separate rotators and controllers will allow us to integrate the 6m Yagi into the microHam system in our station and will allow the MacDoopler Satellite Tracking Software running on the iMac to control the Satellite Antennas separately. When we are using the 6 m Yagi, the Satellite Antennas will be parked pointing up to minimize any coupling with the 6 m Yagi. When we are using the Satellite Antennas, the rotator that turns the mast will be set to 0 degrees to ensure accurate azimuth pointing of the Satellite Antennas by the Alfa-Spid Az/El rotator.
PSK Reporter View using the M2 6M7JHVHD 6 m Yagi
So how does it all perform? With WSJT-X setup on our iMac, I was able to do some testing with the new 6 m Yagi using FT8. The IC-9100 Transceiver that we are using can produce 100W with WSJT-X. The 6m band is usually not very open here in New England in January so I was quite pleased with the results. As you can see from the PSKReporter snapshot above, the new antenna got out quite well on 6 m using 100W. I made several contacts during this opening including one with W5LDA in Oklahoma – a 1,400 mi contact. The 6M7JHVHD is a much quieter antenna on the receive side which helps to make more difficult contacts on 6 m.
MacDoppler Tracking AO-91
We’ve made a little over 100 satellite contacts using the new system so far. With the satellite antennas at 45 feet, it’s much easier to make low-angle contacts and we can often continue QSOs down to elevation angles of 5 degrees or less. I have not had much of a chance to test 23 cm operation with AO-92 but I have heard my signal solidly in AO-92’s downlink using the L-band uplink on the new tower. This is a good sign as our IC-9100 has only 10W out on 23 cm and we are using almost 100 ft of LMR-400uF coax to feed our 23 cm antenna.
Satellite Grids Worked and Confirmed
I’ve managed to work 10 new grid squares via satellites using the new antenna system including DX contacts with satellite operators in France, Germany, the United Kingdom, Italy, Spain, and Northern Ireland using AO-07 and FO-29. These were all low-angle passes.
So what did we learn from all of this? Due to concern over possible snow here in New England, I did not take the time to fully ground test the satellite antennas and new rotator before it went up on the tower the first time. My thinking was that the setup was the same as that used on Portable Satellite Station 3.0 for over a year. The problem was the replacement parts and new control cables were not tested previously and both of these created problems that were not discovered until the antennas were at 45 feet. While it would have made increased the risk that the antennas would not have gotten up before the first winter snowstorm here, it would have been much better to run the antennas on the ground for a few days as I did the second time. Had I done this, both problems would have appeared and have been easily corrected.
The remaining problem to be solved was to reinforce the fiberglass tubes in the Cross Boom and Truss System to prevent the clamps which hold the antennas and other parts in place from crushing the fiberglass tubes. Spencer did an amazing job of making a new center section and polycarbonate reinforcing plugs to provide the needed reinforcements.
Fiberglass Tube Reinforcement Parts
Polycarbonate material was used to avoid adding metal inside the Cross Booms and Truss Tubes near the antennas. Using metal for these parts runs the risk of distorting the antenna’s patterns and causing SWR problems. It was also necessary to keep Truss System parts like eye bolts, turnbuckles, and clamps away from the tips of the antennas for the same reason. As you can see from the photo above, Spencer did an amazing job making the needed parts!
Checking Cross Boom Center Section Run-out
The first step in rebuilding the Satellite Array was to install the new center section in our Alfa-Spid Az/El Rotator. I used a dial indicator to properly center the center section in the rotator. While this level of precision is probably not necessary, I had the tools available and it was easy to do.
Assembled Cross Boom Truss Support
The photo above shows one of the two completed Truss Supports. The trusses support the Cross Boom when it’s either pointing straight up or is flat at 0 degrees on the horizon. It’s important to adjust the horizon truss tube orientation to be slightly tilted to allow the antennas to operate in a “flipped over” configuration where the elevation points 180 instead of 0 degrees. This mode occurs in one of about every 5 to 10 satellite passes to avoid tracking problems with an otherwise south-facing dead spot in the azimuth rotator. Also, note the safety wire on the turnbuckles to keep them from turning after the final adjustment.
Fiberglass Tube Reinforcing Bushings
You can see one of the polycarbonate reinforcing bushings at the end of the horizontal truss tube in the photo above. These are held in place with a small stainless steel set screw at the proper location in the fiberglass tubes. It’s also important to drill small drainage holes in all of the fiberglass pieces so that condensation and water seepage can drain out of the tubes. Without the drainage, water will accumulate, freeze, and break the tubes. I arranged these holes so that the tubes will drain when the antennas are parked in the vertical position.
Satellite Antenna Array Ready to Tram
With everything secured with a combination of tape and large cable ties, Matt of XX Towers rigged a suspension system and tram line to hoist the Satellite Array onto our tower. You can see how well-balanced the antenna system was prior to tramming.
Tramming The Satellite Antennas
The photo above shows the Satellite Array headed up the tram line. The tram line is anchored to a Gin Pole at the top of our tower and to a vehicle on the ground.
Satellite Antennas On The Mast
We removed the rotator and dropped the mast down into the tower to make it easier to get the satellite antennas in place on the top of the mast. Also, note the orientation of the Satellite Antennas – the elements are at 45 degrees to the Cross Boom. This arrangement helps to keep the metal in the ends of the Truss System from getting close to the antenna element tips.
Satellite Antennas Installed On Top Of Mast
Here’s a final photo of the Satellite Antennas with the mast pushed up and the lower rotator back in the tower. You can also see the rigging of the rotator loops for the Satellite Antennas and both the vertical and horizontal Cross Boom Truss supports in place.
M2 6M7JHV HD 6 Meter Yagi
The last step in this part of our project was to place the assembled M2 6M7JHV HD 6 Meter Yagi onto the mast. The 6M7JHV features 7 elements on a 36′ – 8″ boom. The antenna has about 13 dBi of gain and is optimized with a clean pattern to suppress noise from unwanted directions. The antenna was trammed up the tower with a light rope.
Completed Antenna Stack
The picture above shows the completed antenna installation including a second rotator loop around the 6m antenna. The system has two azimuth rotators – one the turns just the Satellite Antennas at the top and a second that turns all of the antennas on the mast together. Our plan is to set the lower rotator to 0 degrees when operating with satellites and use the upper Alfa-Spid Rotator for Azimuth and Elevation positioning. The lower rotator will be used to turn the 6m yagi with the Satellite Antennas parked.
The next step of our project will be to install all of the control cables, satellite receive preamplifiers, and feed lines on the tower and test our new antenna system with the rest of our Satellite Station. You can read about other parts of our project via the links below.
The first step in the project is to put up a second, 35′ house bracketed tower. Our new tower will also feature a new 6m yagi along with a permanent installation of our Satellite 3.0 Antennas. The first step in the project was to secure a building permit and prepare the footing for our new tower. Using Rohn’s specifications for the 45G Tower that we are using calls for the first section of the tower to be placed 4′ below ground in a concrete form. It’s important to place a foot or so of stone at the base of the footing and to ensure that the legs of the tower remain open so water can drain. Failure to do this part of the preparation properly will result in water freezing in the Tower Legs which will split them open and ruin the tower.
Also, note the rebar reinforcing material in the hole around the tower and the bracing to keep the first section of the tower level and plumb. The folks at Form King did an excellent job in preparing and pouring the footing for our new tower.
The picture above shows the completed tower base. We’ve also installed a lightning ground on each of the three legs of the tower and the ground are bonded to each other and to the rest of our station’s ground system.
Tower Section on Gin Pole
With the base complete, Andrew and Matt from XX Towers helped me to put the tower up. Here Andrew is using a Gin Pole to hoist a section of the 45G Tower into place.
With a few sections of the tower in place, it was time to install the house bracket. The bracket needs to be reinforced with blocking material on both sides of the wall. The blocking and the bracket are held together with 10″ galvanized bolts.
Rotator and Mast
We chose a 2″ x 25′ Chrome Molly Mast for our tower. We wanted to have about 10′ of mast above the top of the tower. Rather than cut the mast, we choose to keep the mast full length by setting our M2 Orion Rotator down a section and a half from the top of the tower. This is a good thing to do for several reasons. First, it makes the rotator easier to access for service. Also, the mast can twist a bit to absorb the torque on the rotator when the antennas start and stop moving.
The combination of the 25′ tower and the 10′ of mast above top will place our Satellite Antennas at a height of about 45′. This will provide additional clearance above the trees in our backyard for low angle satellite contacts.
The next step in our project will be to rebuild and reinforce the Satellite 3.0 Antenna Cross Boom and rotator system, build our new 6m yagi, and install the antennas on our new tower. You can read about other parts of our project via the links below.
We installed a 75m loop for SSB operation on our tower when we built it. The loop is full size and is diamond shaped so that our lower SteppIR DB36 yagi can rotate inside of it. The loop is fed at the bottom corner about 20 ft up from the ground. It works great for SSB operation on 75m but we have often wished we could use it across the entire 80m band. This goal led to a project to create a matching system for the antenna. The idea was to use a set of loading coils in series at the feed point create a good match in all segments of the 80m band.
EZ-NEC Model for 75m Loop
The first step in the design of our 80m matching system was to build a model of our current loop using EZ-NEC. The model was then used to determine the correct values of a set of series loading inductors to match different segments of the 80m band.
Matching System Design Analysis
We also considered how likely different segments of the 80m band were to be used by profiling historical spotting data from DXSummit. All of this analysis led to the creation of a final design which is captured in the spreadsheet shown above. The final design requires our current 75m loop to be shortened a bit to work well at the very top of the 80m band.
Modeled Loading Coil Inductance Values
A set of 5 different inductor pairs can be used in series with the loop’s feed point to create a good match across the entire 80m band. The modeled values for the series matching inductors is shown above.
Matching System Modeled SWR
Our microHAM control system can easily implement the switching of the various inductance values based upon the frequency that a radio using the antenna is tuned to. Result modeled SWR for the final 80m loop and match combination is shown above. The design should achieve an SWR < 1.5:1 across the entire 80m band except for the very top where the SWR remains < 2:1. Also, the design optimizes the system’s SWR in the important CW DX, SSB DX, and Digital windows on the 80m band.
Layout of Components in Enclosure
With the design completed, we choose an enclosure and all of the components. Here are the details of what we used:
The first step in the construction was to layout all of the components in the enclosure. Attention was paid to keeping the two series inductors at right angles to avoid coupling and to keep RF connections as short as possible. The relays were arranged to keep the leads connecting to the coils of roughly equal length. Finally, the control circuitry was kept as far removed from the RF leads as possible.
Enclosure Mounting Ears and Clamps
The matching system attaches to a tower leg via saddle clamps. We fabricated a set of mounting ears and spacer blocks to position the enclosure far enough away from the tower so that the antenna connections do not interact with the tower.
80m Matching System Construction
A summary of the completed matching system construction is shown above.The design uses a set of four double-pole double-throw relays to switch in different coil taps which selects the loading inductance provided by the matching system.
We did a set of calculations and found that our relays would be subjected to a worst case peak-peak voltage of about 2.1 KVp-p at the coil tap points.
The relays are arranged such that two sets of contacts have to be traversed to select any given coil tap. The relays we are using have a third pole which we are not using. We disassembled each relay and removed the internal contact wiring for the center pole which improves both the coil to contact voltage rating and the isolation values of the relays.
These steps combine to improve the voltage rating of the system. This is an important design element given that the match will operate at legal limit power.
Completed RF Deck
The completed RF deck and control circuitry is shown above. The enclosure we choose came with a removable plastic plate that made mounting and wiring all of the components simple.
Loading Coil Mounting and Taps
The loading inductors are mounted using nylon hardware with the ends connected to the two antenna terminals on the sides of the enclosure. The coils use movable tap clips to allow us to fine-tune the match once the system is installed with the antenna on our tower. The initial clip locations are set to create the inductance values modeled during the design phase.
Relay Control Circuit Connections
The relay control leads use twisted pair wiring to minimize RF pickup. The control leads are routed away from the RF connections to minimize potential RF coupling.
Relay Control Circuit Details
The control circuits for each relay use a combination of a Diode, a Varistor (MOV) and a filter capacitor in parallel to avoid relay coil switching interference and to suppress control line noise.
1.5 to 1 Matching Balun
The matching system is designed to operate at 75-ohms which is pretty close to the resonant impedance of our 75m loop. The current antenna uses a 1.5:1 Balun to match the loop to our 50-ohm coax feedline. We disassembled an identical matching balun (actually a 75-ohm balun plus a 1.5:1 unun) and used it without its enclosure to create a final 50-ohm match.
MicroHAM Setup to Control 80m Matching System
The final step in the construction of our matching system was to program our microHAM antenna switching system to properly configure the relays in our matching system. This was quite simple to do using microHAM’s frequency dependent antenna control capabilities. The microHAM system automatically operates the appropriate relays to create the best possible match as the radio which is using the matching system is tuned across the 80m band.
Unfortunately, we are in the middle of winter here in New England so I will have to wait for warmer weather to install our new matching system on the tower and make the final adjustments. I am planning another article here when the final integration steps are done to cover the performance of the completed project.
Anita, AB1QB and I have spent a good deal of time this past year helping the Nashua Area Radio Club here in Nashua, NH USA as a way to give back to the Amateur Radio Service. Our work with the Nashua ARC has produced some of the most enjoyable and memorable times of our Amateur Radio experience.
Teaching Nashua Area Radio Club Hosted License Classes
In particular, our contributions to the work that our club is doing around helping people to earn licenses and introducing young people to the Amateur Radio Service has been most rewarding.
Abby, KC1FFX Operating our GOTA Station during Nashua ARC Youth Day
We recently produced a 2016 Highlights video about our Club’s activities and the club’s contributions to the Amateur Radio hobby. We thought that some of our readers here might enjoy the video. You can view it on our club’s home page here.