Raspberry Pi Satellite Rotator Interface

MacDoppler and GHTracker

MacDoppler and GHTracker

We’ve been using our Portable Satellite Station 2.0 for some time now and it works great. One area that can be improved is the interface between the MacDoppler Satellite Tracking program we use and the GHTracker application which controls the Green Heron Engineering RT-21 Az/El Rotator Controller in our setup. Our initial approach was to run the GHTracker app under Windows/VMWare on the same MacBook Air laptop that runs MacDoppler. While this approach works ok, it was more complex and less reliable than we had hoped.

Fortunately, the interface between MacDoppler and GHTracker uses a UDP-based interface which will run over an IP network.

GHTracker Running On A Raspberry Pi 3

GHTracker Running On A Raspberry Pi 3

Anita, AB1QB got great results using a Raspberry Pi 2 with a Touch Screen for her DX Alarm Clock Project so I decided to do something similar with GHTracker. The new Raspberry Pi 3 Model B boards feature a built-in WiFi networking interface and four USB ports which made the RPi 3 a perfect platform for this project. An email exchange with Jeff at Green Heron Engineering confirmed that GHTracker could be made to run under Linux on the Raspberry Pi (RPi).

We wanted a compact package that did not require anything but a power supply to run the final project. There are lots of great choices of parts to build a Raspberry Pi system. Here’s what we used:

Total cost for all of the parts was $120.

Assembly of the case and the hardware was straightforward. The folks at Adafruit provide a pre-built Jesse Linux image for the RPi which includes the necessary driver for the Touch Screen Display.

After a bit of configuration work and the creation of a few shell scripts to make it easy to boot the RPi to a HDMI display or to the Touch Display, we were ready to install the GHTracker App. we also enabled the VNC Server on the RPi so that we could use a VNC Client application on our MacBook Air in place of directly connecting a display, keyboard, and mouse to the RPi. Finally, we installed Samba on our RPi to allow files to be moved between our other computers and the RPi.

GHTracker Running on the Raspberry Pi

GHTracker Running on the Raspberry Pi

Jeff at Green Heron Engineering provided a copy of GHTracker V1.23 and the necessary serial interface library to enable its use on the RPi. Jeff is planning to make a tar file available with GHTracker and the library in the near future. We did some configuration work on LXDE (the GUI interface for Linux that runs on the RPi) automatically run GHTracker whenever the RPi is booted up. We also optimized the GUI for the sole purpose of running GHTracker on the Touch Screen Display. Finally, we configured the Ethernet and WiFi interfaces on the RPi to work with our home network and with our LTE Hotspot modem.

RPi GHTracker Test Setup

RPi GHTracker Test Setup

With all of the software work done, it was time to test the combination with our Satellite Rotator System. The setup worked on the first try using a WiFi network connection between the MacBook Air Laptop running MacDoppler and the RPi. The USB-based serial ports which control Azimuth and Elevation direction of the rotators worked as soon as they were plugged into the RPi. Also, the touchscreen interface works well with the GHTracker App making the combination easy to use.

MacDoppler and GHTracker via VNC

MacDoppler and GHTracker via VNC

The VNC Client/Server combination allows us to work with the software on the RPi right form our MacBook Air laptop. It also makes for a nice display for monitoring the GHTracker App’s operation from the Mac.

Thanks to the help from Jeff at Green Heron Engineering, this project was very easy to do and worked out well. The Raspberry Pi 3 platform is very powerful and relatively easy to work with. It makes a great start for many Ham Radio projects. Also, there is a wealth of online documentation, how-to information, and open source software for the RPi. I hope that some of our readers will give the RPi a try!

Fred, AB1OC

Icom IC-9700 VHF/UHF/1.2GHz Prototype Transceiver

Source: Icom IC-9700 VHF/UHF/1.2GHz Prototype Transceiver

Another new radio from Icom based on their SDR platform. This looks like a great radio for Satellite and EME use. We’re going put in a pre-order for this radio and will plan to include it in our Portable Satellite Station. I’ll post more here as details become available.

Portable Satellite Station Design and Operation

Building and Operating a Portable Satellite Station Presentation

Portable Satellite Station Design and Operation Presentation

Anita and I attended the New England Regional Hamvention this past weekend. We gave a presentation on Portable Satellite Station Design & Operation there. You can view a copy of our presentation here.

Satellite Station Portable - Radio and Supporting Equipment

Portable Satellite Station 2.0 at a Recent License Training Class

The Videos from our presentation follow below –



We did two additional talks about the Nashua Area Radio Club’s activities including one on our High-Altitude Balloon Project. You can view those presentations here.

Also, we are planning to have our 2.0 Portable Satellite Station setup at the Nashua Area Radio Club’s upcoming Technician License Class on Sept. 30 – Oct. 1. If you are in the area and would like to see the station in operation, please contact us at activities@n1fd.org to arrange for a visit. If you’d like to register for one of our license classes, you can do that here.

Fred, AB1OC

LEO Satellite Contacts via Easy Sat and Linear Transponder Satellites

Satellite Antenna Details

Satellite Station 2.0 Antennas

We recently did a Tech Night at our club on Building and Operating a Satellite Ground Station. As part of my portion of our Tech Night presentation, I recorded several LEO satellite contacts and made videos showing the operation of the computer controlling our Satellite Station 2.0 during these contacts. These videos give an idea of what its like to operate through LEO satellites.

The video above is a recording of a several contacts through SO-50 – an FM “Easy Sat”.

The next video several contacts made through FO-29, a linear transponder satellite.

The distortion that you hear in my voice is a result of my own voice coming back delayed through the satellites.

We will have our Satellite Station 2.0 setup at Field Day this year. If you are local to Nashua, NH; you are welcome to visit us during Field Day and see our Satellite Station in operation.

You can read more about the station used to make these contacts here on our Blog.

Fred, AB1OC

Nashua Area Radio Society’s 2017 Field Day Station Test

ARRL Field Day is the Nashua Area Radio Society’s largest and most popular activity each year. You can see more about our recent Field Day activities on our Field Day page and on our Blog.

Dave Merchant K1DLM, our Field Day chairman, is bringing some 21st Century radio and computer technology to our Field Day setup this year. There are several aspects to this new component of our Field Day plans including –

  • Two Flex-6700 Software Define Radios running over a network  for our new Digital and enhanced GOTA Stations
  • An on-site WiFi Network to enable using the N1MM+ Logger in network mode for sharing of log information, station activity, real-time scores, and messages
  • A central Score Board and Field Day Information Computer in our public information tent
2017 Field Day Site - Upper Field Layout

2017 Field Day Site – Upper Field Layout

We will again be holding our 2017 Field Day operation at the Hollis-Brookline High School in Hollis, NH. We are planning on using the upper baseball field area as our main operating location. We have decided to add a third tower this year and locate it on a soccer practice field which is situated several hundred feet away from our main operating area. All of our antennas and equipment will lie within the required 1000′ circle but the third tower would situate those operating at that location away from the rest of our group. Dave’s solution to this problem was to set up a network and operate two Software Defined Radios (SDRs) at the lower site remotely from our location on the upper field.

Dave has enlisted Piece Fortin, K1FOP to be our IT Chairman for Field Day this year. Pierce has been instrumental, along with Dave, in the planning and testing of all of this new technology. Pierce and Dave have a great deal of networking and IT experience and knowledge and we could not have put together what is described here without them.

Dave K1DLM, Piece, Hamilton K1HMS, Mike Ryan K1WVO, Anita AB1QB, and I have gotten together multiple times to set up and test all of this new technology. I wanted to share some more about the equipment and the associated testing (which has been staged in the kitchen at our QTH – thank you, Anita!).

We began the testing process by setting up our 20m CW station.

20m CW Station Test

20m CW Station Test

This station uses an Elecraft K3S Transceiver, a K1EL WinKeyer and the N1MM+ Logger running on a Windows 10 Laptop PC. We used this station to get our basic N1MM+ setup including our Field Day CW keying macros right.

40m SSB Station Test

40m SSB Station Test

Next came our 40m SSB station. This setup uses an Icom IC-7300 Transceiver and allowed us to set up and test N1MM+ on the fly audio macro recording and playback. All three of our SSB stations will have on the fly recording and playback capability which will allow each of our SSB operators to record and use a custom set of audio macros.

Digital Station Test

Digital Station Test

Next came our Digital Station. This station uses one of the two remote Flex-6700 SDRs.

Remote Flex-6700 SDRs and Antenna Switch

Remote Flex-6700 SDRs and Antenna Switch

Dave, K1DLM put together a really nice package for the two Flex-6700 SDRs and associated equipment which will be located on the lower field. He used a rack system to mount the two SDRs, power supplies, a three-band Tri-plexor, a set of bandpass filters for 80m, 40m, 20m, 15m, and 10m and a 403A 8×2 networked antenna switch. This setup allows either of the two SDRs to share the tri-band yagi or the 40m and 80m Inverted-V antennas on the tower on the lower field and operate on any of the 5 available HF bands. Antenna and filter switching automatically track the frequencies of the two SDRs making the setup simple to use.

Digital Station Second Display - SmartSDR & More N1MM+

Digital Station Second Display – SmartSDR & More N1MM+

The Digital Station’s remote SDR will be operated using a SmartSDR client running on the Digital Station laptop PC. This station will have a second monitor to better accommodate all of the windows associated with it.

Digital Station Main Display - N1MM+

Digital Station Main Display – N1MM+

The main display associated with the Digital Station will run decoders for all PSK and RTTY modes. The ability to decode multiple PSK signals simultaneously and multiple RTTY decodes are available. The Digital station also acts as the N1MM+ master station in our Field Day setup for all of the other stations which use N1MM+.

Satellite Station Test

Satellite Station Test

Our Satellite Station 2.0 was also added to the test setup. It uses a MacBook Air laptop running MacDoppler to control the antenna rotators and the Icom IC-9100 Transceiver which are part of our Satellite Station. A Windows 10 Surface Pro computer is included which runs N1MM+ and provides logging and other network functionality for our Satellite Station.

GOTA Station Test

GOTA Station Test

We also tested our GOTA station which uses the second Flex-6700 SDR and a FlexRadio Maestro to provide a more conventional “buttons and knobs” interface for our GOTA operators to use. This station will also have a laptop PC running N1MM+ for logging.

Scoreboard Computer

Scoreboard Computer

We also build and tested a Scoreboard PC. This computer will be located in the Public Information tent at Field Day and will be connected to a large display. It will show our real-time score, QSOs being logged as they are made and other useful information about our Field Day operations. This computer will also continuously play videos from our Video Collection and will provide access to IP video cameras which monitor the tower and equipment on the lower field.

Pierce, K1FOP and Hamilton, K1HMS Testing CW Stations

Pierce, K1FOP and Hamilton, K1HMS Testing CW Stations

Our networked N1MM+ testbed contained at least one station of each type (CW, SSB, Digital, Satellite, and GOTA) that will be part of our Field Day setup this year. The Station Masters for the additional CW and SSB stations came by to test their setups using the test bed.

Field Day Networking System

Field Day Networking System

The networking system which Dave and Pierce built is central to all of the technology described here. All of the gear is mounted in a single rack which will be located on the upper field during Field Day. The setup includes a Firewall/DHCP server, a commercial grade outdoor WiFi access point, a 4G LTE modem for Internet access, an Ethernet Switch, and a UPS power supply.

MoCA Data Link Cable

MoCA Data Link Cable

The upper and lower fields at our Field Day site are separated by several hundred feet. A thick line of trees between the two locations raised concerns about connecting the upper and lower sites using WiFi. Pierce came up with a great solution to this problem – we will be using MoCA Data Modems and RG6 Quad Shield 75 ohm Coax Cable to provide a 10 Mbps data link between the two sites. We tested the MoCA link using a much longer run of coax cable then we will need to use at Field Day and confirmed full 10 Mbps throughput.

N1MM+ Talk Window

N1MM+ Talk Window

Our networked N1MM+ setup will allow any station in our setup to send messages to everyone who is operating at Field Day. We can use this capability for important communications like “lunch is ready!” or “I need help from Pierce (our IT chairman) on the 40m SSB station”, or “The 6m band is wide open!”.

Our GOTA and Digital stations will be located together in the same tent and will provide our Field Day 2017 visitors to see and use 21st-century Amateur Radio technology to make contacts. We are expecting young people who participated in our High-Altitude Balloon project and from other local schools where we have done Amateur Radio activities to attend. In additional to being a learning opportunity for all of us in the Nashua Area Radio Society, we hope that the state of the art technology that we are using will generate interest among our visitors. If you are local to the Nashua, NH USA area, come pay us a visit during 2017 Field Day. We’d enjoy providing a tour for you and your family along with a chance to Get On The Air. Hope to see you at Field Day!

Fred, AB1OC

A Portable Satellite Station Part 4 – 2.0 Station First Contacts!

Station Packed and Ready for Transport

Station Packed and Ready for Transport

With our new 2.0 Satellite station built, tested, and packed; we were ready to try it in a portable environment. Fortunately, the Nashua Area Radio Club had a Technician License class coming up and we thought that the new station test would be a great way for our students to learn about Amateur Radio Satellites.

Satellite Status from AMSAT Website

Satellite Status from AMSAT Website

Final preparations included checking the operational status of potential satellites on the AMSAT website. The page shown above is like a spotting cluster for LEO Satellites – it shows satellite activity as reported by HAM satellite operators. Using this information, we configured MacDoppler to track the active satellites.

Satellite Pass Predictions

Satellite Pass Predictions

Next, we used MacDoppler to generate pass predicts for the weekend of our Technical Class. We assembled this data for all of the potential satellites and color-coded the available passes to identify those which had the best chance of producing contacts.

With this done, we loaded our portable tower, antennas, and all of the rest of the gear into our pickup truck and transported it to the class site.

Sateliite Antennas Setup Portable

Satellite Antennas Setup Portable

The first step at the class site was to unload all of our gear and move the portable tower to a suitable location. We used a compass to orient the tower to true north and leveled it. We used the weight bags that we made up to anchor the tower securely and then installed the antennas, rotator loops, and control cables. The antenna system worked out very well in the portable environment and was easy to set up.

Satellite Antenna Details

Satellite Antenna Details

Here’s a closer to look at the LMR-400 UF coax cables which connect the antennas to the rest of the system. The loops just behind the antennas are necessary to keep the coax from affecting the pattern of the antennas. The coax cables shown were made long enough to allow the antennas to be rotated through their full travel in the azimuth and elevation directions without binding.

Satellite Station Portable - Radio and Supporting Equipment

Satellite Station Portable – Radio and Supporting Equipment

The final step in the portable setup was to put the IC-9100 Transceiver and Supporting Equipment together in the building and check everything out. As soon as we got everything hooked up and working, we heard an ON4 station through FO-29 which was near the end of a low angle pass. A very good sign!

We took some time to fine-tune the calibration of our rotators and to check the operation of the computer controls – everything checked out fine. The video above shows MacDoppler controlling the Azimuth/Elevation rotator and the IC-9100 Transceiver during the testing.

First Contact using New 2.0 Station (AO-85)

First Contact using New 2.0 Station (via AO-85)

With all the setup done, it was time to try to make our first contact. Fortunately, we did not have long to wait. We caught a medium angle pass of AO-85, a U/V Mode FM Easy Sat. With MacDoppler setup and tacking, we immediately heard contacts being made through AO-85. I gave a whistle and adjusted my uplink VFO until I heard my signal coming back through AO-85. I gave a quick CQ call and immediately got a response from Jonathan, NS4L in Virginia, USA! It took on a few seconds to exchange call signs and grid squares and our first contract with our new station was in the log.

Explaining Satellite System to License Class

Explaining Satellite System to License Class

Our Technician License Class students were very interested in the station. We spent some time explaining the setup and demonstrating how it worked. We made more contacts between our class sessions using AO-85 and FO-29 (a V/U Mode Linear Transponder Satellite). Our most interesting contact was with Burt, FG8OJ in Guadeloupe through FO-29. It was great to work DX using the new station during the first time we used it.

We learned several things during our first use of the new station. First, while the 35 ft. maximum separation allowed between the antenna system and the rest of the station is adequate in many applications, the antenna system’s close proximity to the building we were in blocked passes to the west of us with this separation. We have subsequently made up an additional set of feed lines using a pair of 100 ft. long 7/8″ hardline coax cables to allow for a greater separation in portable deployments such as this one.

We were glad that we had the Heil Pro 7 Headset with us and we used it for most of our contacts. The separate speaker allowed our students to hear the contacts well and the boom microphone on the Pro 7 Headset eliminated feedback due to our own voice coming back through the satellites. We improvised a mono to stereo converter cable to connect the Heil Pro 7 Headset to one of the two speaker outputs on the IC-9100 Transceiver. This allowed the radio to drive the separate speaker and the headphones at the same time.

We were glad to have the low-noise preamps available. These were especially useful during low-angle satellite passes and the sequencing setup that we built worked well.

All in all, our first test of our new 2.0 Portable Satellite station was a success. Our license classes students enjoyed learning about Amateur Satellites and had fun along with us making contacts through a few of them. Our next goal will be to get packet modes and APRS working with our setup. We plan to do another article in this series when this part of our project is completed. Other articles in this series include:

We are planning to add larger antennas and switchable polarity to our portable satellite station in the near future. This will enable us to make contacts with Satellites and the ISS in more difficult conditions.

You may also be interested in the satellite station at our home QTH. You can read more about that here.

Fred, AB1OC

A Portable Satellite Station Part 3 – 2.0 Station Radio and Supporting Equipment

Satellite Station Transceiver and Related Equipment

Satellite Station Transceiver and Related Equipment

With the Antenna System for our 2.0 Portable Satellite Station complete, we turned our attention to assembling the Transceiver and supporting equipment. The equipment used for this part of the project includes:

The Icom IC-9100 provides 100W on 2M and 75W on 70 cm which is more than enough power for our application. It also has some nice satellite features such as support for synchronized VFO tracking between the 2M and 70 cm VFOs in the radio. This radio also uses a single USB connection to allow computer control of the radio and creation of a sound card interface on the host computer. A Heil Pro 7 Headset will be used for operator audio to avoid feedback due to our audio coming back from the satellite. The Icom SP-23 speaker is included to allow observers to hear satellite contacts while they are in progress.

Radio Management via MacDoppler

Radio Management via MacDoppler

The MacDoppler software provides automated control of the IC-9100 including mode selection and automatic correction of both VFOs for doppler shift. These features greatly simplify the operation of the radio, especially when satellites with SSB/CW transponders are used.

The video above shows MacDoppler’s management of the IC-9100 Transceiver during a pass of AO-73. The constant adjustments of the VFOs takes care of doppler shift correction and ensure that our signal stays at a fixed position in the transponder passband of linear transponder satellites.

Preamp Sequencers and Output Monitoring

Preamp Sequencers and Output Monitoring

M2 Antenna Systems S3 Sequencers are used to provide control of the Advanced Receiver Research low-noise preamps on our portable tower. One of the nice features of the Icom IC-9100 is that it can be configured to provide separate keying lines for the 2M and 70cm VFOs. This allows a preamp to remain enabled on the receive VFO while the other VFO is in transmit mode with its preamp shutdown by the sequencer. This arrangement is very useful during tuning when one needs to hear your own signal coming back from a satellite. A custom-made cable assembly was made to interconnect the S3 Sequencers with the ACC socket on the IC-9100, the Weatherpack connector on the tower preamp control cable, and DC power.

We used the excellent WaveNode WN-2 Wattmeter again in our portable satellite setup. This is a modular output monitoring system which has sensor for VHF/UHF use as well as voltage, signal quality and other monitoring functions.

DC power for the setup is provided via a Powerwerx SS-30DV Power Supply and a RigRunner 40007U distribution unit. We use this power supply in all of our portable setups. It is light weight, provides plenty of power for a 100W station and accessories, and is quiet from an RF perspective.

Equipment Packing and Protection

Equipment Packing and Protection

With the transceiver test of the station complete, we turned our attention to transporting the setup. Proper protection of the equipment during transport was provided via a large case from Pelican. We combined this with a roller bag and an inexpensive storage bin for documentation and accessories which are not very fragile. We also included our RigExpert antenna analyzer in the setup to make testing of the station during setup in a portable environment easier.

Station Packed and Ready for Transport

Station Packed and Ready for Transport

With all of the assembly and testing of the components of our 2.0 Portable Satellite Station complete, we packed up all the components. We used an inexpensive furniture dolly to allow us to roll the tower around to load and unload it.

We are ready to test our new station in a portable application. More on that in the final article in this series. Other articles in the series include:

You may also be interested in the satellite station at our home QTH. You can read more about that here.

Fred, AB1OC