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:
This article explains how to put a Sat Tracker together.
The information and software described here are provided on an “as is” basis without support, warranty, or any assumption of liability related to assembly or use. You may use information and software image here only at your own risk and doing so releases the author and Green Heron Engineering from any liability for damages either direct or indirect which might occur in connection with using this material. No warranty or liability either explicit or implicit is provided by either AB1OC or Green Heron Engineering.
Now that we have that out-of-the-way, here are the components that you need to build your own Sat Tracker:
The Sat Tracker image includes a display driver for the specific touch display listed above and will most likely NOT WORK with any other touch display. You will also need a Green Heron RT-21 Az/El or a pair of Green Heron RT-21 single rotator controllers from Green Heron Engineering that are properly configured for your rotators.
If you have not worked with the Raspberry Pi before, it’s a good idea to begin by installing NOOBS on your SD card and getting your Raspberry Pi to boot with a USB Keyboard, USB Mouse, and an HDMI display attached. This will give you a chance to get familiar with formatting and loading your SD card with the Raspbian build of the Debian OS for the Raspberry Pi. I’d encourage you to boot up the OS and play with it some to get familiar with the OS environment before building your Sat Tracker.
Etcher Writing Raspberry Pi SD Card Image
The first step in building your Sat Tracker is to put together the hardware and write the image to your SD Card. Use the enclosed instructions or search the web to find information on how to do each of these steps:
Install the Heat Sinks on the Raspberry Pi 3 B+ Motherboard. Make sure your chipset heat sink will clear the back of the case. If it won’t, it’s fine to just install the CPU Heatsink.
Assemble your case to the point where it is built up to support the touch display
Carefully install your touch display on the Raspberry Pi Motherboard
Install the remaining pieces of your case including the nylon screws and nuts which hold the case parts together
Download the SD Card image from the link below, unzip it, and load the image onto your SD card using Etcher
Install your SD card in the slot on your Raspberry Pi Motherboard
Connect your Raspberry Pi to the outside world as follows:
Connect Two USB cables – one end to the Elevation and Azimuth ports on your Green Heron Engineering RT-21 Controller(s) and the other ends to two of the USB connections on the Raspberry Pi
Connect a wired Ethernet Cable to your Raspberry Pi via a common Ethernet Hub or Switch with a PC or Mac that has VNC Viewer Installed. You will need a DHCP server running on the same network to supply your Raspberry Pi with an IP address when it boots. Your router most likely provides a DHCP function.
Connect your USB power supply to the Raspberry Pi Motherboard and power it up
Your Sat Tracker should boot up to the desktop with GH Tracker V1.24 running. The touch display works fine for using GH Tracker but its a bit small for configuring things. To make the configuration steps easier, the image comes up running VNC Server. I like to use VNC Viewer on my PC to connect to the Sat Tracker using VNC to perform the steps that follow. Note that both the Raspberry Pi and your PC must be on the same sub-network for the VNC connection to work. I’ve also included the following commands in the Sat Tracker image which can be run from the Raspberry Pi terminal window to make the configuration process easier:
$ setdisp hdmi # Disables the TFT display & uses the HDMI interface
$ setdisp tft # Disables the HDMI interface & uses the TFT display
$ reboot # Reboots the Raspberry Pi causing
# the latest display command to take effect
If you select the HDMI interface, you will find that VNC Viewer produces a larger window enabling you to perform the following configuration steps:
First, you need to determine the IP address of your Sat Tracker. This can be done via your DHCP server or by touching the network icon (up and down arrows) at the top of the display on the Sat Tracker.
Use VNC Viewer on your PC or Mac to connect to the IP address of your Raspberry Pi. The default password is “raspberry“.
Once you are connected, open a terminal dialog on the Sat Tracker, set your display to hdmi mode via the command shown above, and reboot your Sat Tracker.
Reconnect VNC Viewer to your Sat Tracker and click on the Raspberry button (Start Menu Button) at the top left of the screen, select Preferences, and run Raspberry Pi Configuration. Select Expand Filesystem from the System Tab. This will expand the filesystem to use all of the available space on your SD Card. You can also change the system name of your Sat Tracker and your login password if you wish. When you are done making these changes, reboot your Sat Tracker.
Reconnect to your Sat Tracker via VNC Viewer and select Setup-> Rotator Configuration from the menu in the GH Tracker App. Select the TTY devices (i.e. COM Ports) associated with the Azimuthand Elevationconnections to your RT-21 Controller(s) via the two dropdown boxes. You can also configure the operational parameters for GH Tracker at this time. The ones that I use with our Alfa-Spid Az/El Rotators are shown below.
GHE RT-21 Az/El Controller Settings for Alfa-Spid Rotator
Set via MacDoppler. Minimize wind loading and coupling to antennas below. Also enables water drainage from cross-boom tubes.
Azimuth dead spot is South. Elevation headings are from 0 to 180 degrees.
Minimize relay operation during computer tracking
Creates smooth start and stop for large array
Makes large movements relatively quick
CCW and CW limits ensures predictable Azimuth heading for range around 180 degrees. Elevation limits permit 0 to 180 degree operation. Elevation limits shown can only be set via GHE configuration app.
Alfa-Spid Az/El Rotator
Rotator has 1 degree pointing accuracy
Creates smooth start and stop for large array
Easy to read in shack
Configure the source of tracking data to be MacDoppler (UDP) from the GH TrackerSourceMenu. We use UDP Broadcasts with MacDoppler running on the same Mac with VNC Viewer to run our rotator. Finally, press the Press to start tracking button on GH Tracker and run MacDopplerwith UDP Broadcast on and Rotators Enabled to start tracking.
MacDoppler Tracking AO-91
Once you are satisfied with the operation of your Sat Tracker, use VNC Viewer to access the terminal window on your Sat Tracker one last time, set your display to TFT, and reboot.
The most common problems that you’ll run into are communications between your Sat Tracker and your Green Heron Engineering RT-21 Controller(s). If the Azimuth and Elevation numbers are reversed in GH Tracker, simply switch the TTY devices via the Setup Menu in GH Tracker. Also, note that it’s important to have your RT-21 Controller(s) on and full initialized BEFOREbooting up your Sat Tracker.
Most communications problems can be resolved by initializing your tracking system via the following steps in order:
Start with your RT-21 Controller(s) and you Sat Tracker powered down. Also, shutdown MacDoppleron your Mac.
Power up your RT-21 Controller(s) and let the initializations fully complete.
Power up your Sat Trackerand let it fully come up before enabling tracking in GH Tracker.
Finally, startup MacDoppler, make sure it is configured to use UDP Broadcasts for Rotator Control and make sure that Rotators Enabled is checked.
The VNC Server on the Sat Tracker will sometimes fail to initialize on boot. If this happens, just reboot your Sat Tracker and the VNC Server should initialize and enable VNC access.
I hope you have fun building and using your own Sat Tracker.
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.
Like many memorable events in our lives, our journey towards the Hudson Memorial School ISS Crew Contact began in a modest fashion with a telephone call from Dan Pooler at Hudson Memorial School in Hudson, NH. Dan had been to Space Camp where he heard about an ARISS Crew Contact from … Continue reading Journey to an ISS Crew Contact →
Our project to help the students at Hudson Memorial School in Hudson, NH make a contact with an astronaut on the International Space Station via Amateur Radio is a memory now. The link above is to an article about the more than year-long journey that led to this once in a lifetime experience. I hope that you enjoy it and don’t miss the video of our contact towards the end of the story.
We are just awaiting notification of the final date and time for our contact and we’ll begin final setup and testing at HMS.
We’ve been sharing our progress as we’ve on the Nashua Area Radio Society’s Youth Forum as we have worked through our final preparations. I also would like to share a summary here along with some insights on what we’ve learned along the way.
An ISS Crew Contact is No Small Undertaking …
We have been working for almost a year now to get ready for our contact. We’ve built and tested two space ground stations and we’ve discovered and addressed several performance and reliability issues with these stations during trial deployments at Field Day, Ham Fests, License Classes, and during testing here at our QTH.
Dave, K1DLM who is a member of NARS had extensive professional sound experience and was able to help us with this part of our project.
Dave put together a professional-level A-V system design to support our contact and provided much of the gear to realize the design. His uses a pair of communications microphones, a pro-mixer, and audio interface gear to provide student and radio audio to the sound system in the auditorium at HMS as well as to an array of video cameras. The system makes extensive use of XLR cabling and pro-level devices to ensure clean audio.
Video Presence on the Internet is an Important Element to Draw Interest in a Project Such as Ours…
We Live Streamed some of our Station Testing activities to Facebook and we were amazed at the interest and response that we received. Many folks worldwide followed our progress on Facebook in real-time as we set up and completed our full station test.
We are planning to have two IP Video Cameras Live Streaming to Facebook during our contact. One in the room to provide video of the students as they talk with the astronaut on the ISS and a second on our antennas as they track the ISS.
Its Critically Important to Test the Complete Station Ahead Of Time – New Challenges Emerged when we Mixed Audio and Radio Gear…
We set up the full station (Primary and Backup) along with all of the Audio and Video Gear about 3 weeks prior to our contact for a complete system test. We learned a great deal in doing this and we encountered several problems which we have since corrected.
The most important issues did not show themselves until we made some contacts with all of the A-V gear in place. We had problems with RF aggravated ground loops in the radio microphone circuits during the initial test. These problems did not show themselves until we added the audio mixer and sound system into the station.
These problems were easily corrected by adding Audio Isolation Transformers into the radio microphone circuits.
We also solved some potential issues related to level differences between line and microphone audio circuits using Audio Attenuators.
These problems were not difficult to solve but they would have seriously degraded our contact if we had not discovered them early while there was still plenty of time to secure parts and retest.
Data Networks in Schools and Public Places Require Configuration Adjustments to Support Contact Elements…
Schools and other public places typically do a good job of protecting their data networks and users from threats from both the Internet and within the venue. Tracking Programs, IP Cameras for Live Streaming, and other contact support gear are not typical devices that would be in operation on such networks. Also, many public venues rely almost exclusively on WiFi for access to the Internet and typically prohibit or severely limit client devices from communicating with each other.
WiFi can often suffer from RF interference issues when many devices like Smart Phones are located together in a small area. This situation is common in large gatherings.
Data System for ISS Contact
We had quite a bit of experience with these problems as part of other school projects we’ve done. We worked closely with the IT staff at HMS to plan for and create a network design to support our contact. We opted to use a wired network approach with a local Ethernet switch to implement the IP communications between the elements in our stations and the associated IP Cameras.
The IT team at HMS configured their network to ensure that the IP addresses of our devices were fixed in DHCP and that devices that needed access to the Internet had the access that they required. The IP cameras where the most challenging elements here.
Packed and Ready to Go…
Well, all of our gear is packed and ready to go for setup on-site at HMS. The next article in this series will cover the on-site set up for our contact.
Our planned ISS Crew Contact is almost here! It will take place sometime during the first week of December (December 3rd – 8th) at the Hudson Memorial School (HMS) here in Hudson, NH. I am planning a series of articles here on our blog to explain the process for preparing our ground station(s) and making our contact.
Dan Pooler, AC1EN who is a teacher at HMS began this process almost a year ago by reaching out to the Nashua Area Radio Society. Dan wanted to do an ISS Crew Contact at his school and asked if we would help him with the Amateur Radio elements.
We decided early on that we wanted a Direct contact (one which uses an on-site Amateur Radio Ground Station).
Transceiver with 50–100 W output, 1 kHz tuning steps, and 21 memories capable of storing split frequencies
Low-loss coax (such as 9913 or LMR-400)
Mast mounted receive pre-amplifier
14 element yagi antenna with switchable circular polarity
Antenna rotators for azimuth (0–360°) and elevation (0–180°), with an interface for computer control
Computer running tracking software for antenna control (including flip mode operation)
The ARISS approach is to used a series of “secret” uplink frequencies which are determined and provided only to the contact operators before each contact. Doppler correction is not required on the 2m band where the crew contacts take place.
Our 2.0 Station has an 8 element yagi with fixed polarity. This requirement turned out to have a much more significant impact on the design of the Primary Ground Station than just changing the antenna and ultimately led to the construction of our Portable Satellite Station 3.0. More on this in a minute…
The Backup Station
The backup station requirements are as follows:
Transceiver with 50–100 W output, 1 kHz tuning steps, and 21 memories capable of storing split frequencies
Power amplifier with 100–200W output (optional)
Mast mounted receive pre-amplifier
Omnidirectional antenna, either vertical (preferred) or eggbeater style
Uninterruptible power source (UPS or battery)
After consulting with the ARISS folks and some thought, we decided to use the then current Satellite Station 2.0 as the Backup Station and build a new Satellite Station 3.0 for use as the Primary Station. This approach also involved installing a larger rotator to accommodate the larger antenna and a heavier fiberglass cross-boom. The 3.0 station would also receive a more capable antenna for the 70 cm band and add a 23 cm antenna for a third band.
The plan included upgrading the 2.0 Station Antennas to include switchable polarity and the addition of a 200W power amplifier for 2 m to compensate for the reduced gain of the smaller 8 element yagi in the 2.0 station.
Building The Primary Station
The construction and testing of the 3.0 Station are well covered in articles on our Blog so I’ll just share a little information about the final result. The new antenna system used the same ground-based roof tower arrangement that worked so well for the 2.0 station. The larger 3.0 antennas are center mounted on a fiberglass cross boom to prevent the boom from affecting the antenna patterns. We’ve also added a 23 cm loop yagi for a third band. The 3.0 antenna system also uses a more powerful Azimuth-Elevation Rotator from Alfa-Spid.
The new 2 m and 70 cm antennas use relays at their feed point to enable remote switching of the antenna’s polarity between Left-Hand and Right-Hand circular polarity.
The upgraded 3.0 ground station adds a control console for switch the polarity of the antennas and a custom built PPT Router Device to manage PTT sequencing of the radio and the pre-amplifiers at the antennas.
We continue to use the excellent MacDoppler software to control tracking and Doppler correction in the 3.0 Station.
Building The Backup Station
The upgrades to the 2.0 Antenna System involved the installation of Polarity Switching relays in the feedpoints of the 2.0 antennas. This upgrade was a fairly straightford one.
The ground station side was more involved as we needed to build a complete, second station. I was able to purchase an Icom IC-910H radio used in good condition for this purpose. The rest of the station components were similar to the Primary Station.
We tested the Backup Station at our Fall Technician License Class and it worked great! several of our class students used the station to make their first satellite contacts.
I am currently working on adding the 2 m amplifier and improving the PTT sequencing system on the Backup Station and I plan to post more about these upgrades in here in the near future.
Audio System for Our Contact
Our contact will take place in the auditorium at HMS. The room has a high-quality sound system and mixing board for audio.
Dave, K1DLM is part of our ISS Crew Contact Team, and he has quite a bit of pro-level audio experience. He has put together the following plan for our Audio System. His design allows us to smoothly transfer audio to and from either the Primary or the Back Stations. We are also planning to record video and Livestream video to the N1FD Facebook page during our contact, and his design supports these elements as well.
The final element in our plan is the Data System. The network at HMS is very tightly controlled from a security point of view and this makes it difficult to use for contact critical functions like access to up to date Keplerian Elements for our straightforward. Dave has an LTE-based Internet Access System that we have used in the past and we’ve elected to use this to support our stations. We are planning to use the HMS network to transport the Livestream video from our contact. We’ll be using a Mevo Internet Camera for this purpose.
A Million Details…
As you can probably imagine, there a many details that go into making a project like this possible. Here’s a rough timeline of some of the major remaining steps from a Ground Station point of view:
Assemble both stations at our QTH with the 2m amplifier and the final 215′ control cables and feed lines – In progress, should be complete in a few days.
Full Station Test – add the Audio and Data System components and test the full station at our QTH – Within a week.
Configure and Test Data Network Access – for Live Streaming Video and computers and HMS.
Setup Ground Station at HMS and perform Dry Run Test – Complete by December 1st.
Dan and the HMS faculty team are also very busy finalizing the student’s questions and handle press related activities.
We hope our readers will join us via the Livestream video for our contact. We’ll post more on this as we get closer to our contact!
The Nashua Area Radio Society recently held a Tech Night on WSJT-X: FT8, WSPR, MSK144, and More. This Tech Night was recorded and provides a good starting point for folks who want to understand what the WSJT-X software can do, how to use it, and how to integrate it into their station.
August 2018 Tech Night – WSJT-X: FT8, WSPR, MSK144, and More
The video from our Tech Night includes lots of information about how to get started as well as some recorded demonstrations of FT8 and Meteor Scatter contacts.
Topics Cover During WSJT-X Tech Night
Our Tech Night also covered tools like PSKreporter and JTAlert that can be used with WSJT-X. Finally, we spent some time on using WSPR to evaluate your station’s performance and how you can use the software to do more “exotic” QSOs such as Meteor Scatter on 6m.
Nashua Area Radio Society members have access to our full library of over 30 Tech Night Video on a wide range of topics for both beginning and advanced Hams. You can see the list of what is available on the Nashua Area Radio Society Tech Night page.