Raspberry Pi Satellite Tracker Interface How To

GHTracker Running On A Raspberry Pi 3

Sat Tracker – GH Tracker Running On A Raspberry Pi 3 B+

I have received several requests to share the image and construction details for the Raspberry Pi Satellite Tracker Interface that we use with MacDoppler as part of the Satellite Stations here. You can read more about the motivation for this project and its initial design and testing 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

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:

  1. 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.
  2. Assemble your case to the point where it is built up to support the touch display
  3. Carefully install your touch display on the Raspberry Pi Motherboard
  4. Install the remaining pieces of your case including the nylon screws and nuts which hold the case parts together
  5. Download the SD Card image from the link below, unzip it, and load the image onto your SD card using Etcher
  6. Install your SD card in the slot on your Raspberry Pi Motherboard
  7. 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:

  1. 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.
  2. Use VNC Viewer on your PC or Mac to connect to the IP address of your Raspberry Pi. The default password is “raspberry“.
  3. 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.
  4. 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.
  5. 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 Azimuth and Elevation connections 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.

    GH Tracker Rotator Configuration

    GH Tracker Rotator Configuration

  6. Configure your Green Heron Engineering RT-21 Controllers to work with your rotator(s). The settings below are the ones that we use with the RT-21 Az/El controller and Alfa-Spid Az/El Rotators that we have here.

    GHE RT-21 Az/El Controller Settings for Alfa-Spid Rotator

    SettingAzimuthElevationNotes
    Park Heading0 degrees90 degreesSet via MacDoppler. Minimize wind loading and coupling to antennas below. Also enables water drainage from cross-boom tubes.
    Offset180 degrees0 degreesAzimuth dead spot is South. Elevation headings are from 0 to 180 degrees.
    Delays6 sec6 secMinimize relay operation during computer tracking
    Min Speed23Creates smooth start and stop for large array
    Max Speed1010Makes large movements relatively quick
    CCW Limit180 degrees355 degreesCCW 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.
    CW Limit179 degrees180 degrees
    OptionSPIDSPIDAlfa-Spid Az/El Rotator
    Divide Hi360360Rotator has 1 degree pointing accuracy
    Divide Lo360360
    Knob Time4040Default setting
    ModeNORMALNORMALDefault setting
    Ramp66Creates smooth start and stop for large array
    Bright22Easy to read in shack
  7. Configure the source of tracking data to be MacDoppler (UDP) from the GH Tracker Source Menu. 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 MacDoppler with UDP Broadcast on and Rotators Enabled to start tracking.

    MacDoppler Tracking AO-91

    MacDoppler Tracking AO-91

  8. 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 BEFORE booting up your Sat Tracker.

Most communications problems can be resolved by initializing your tracking system via the following steps in order:

  1. Start with your RT-21 Controller(s) and you Sat Tracker powered down. Also, shutdown MacDoppler on your Mac.
  2. Power up your RT-21 Controller(s) and let the initializations fully complete.
  3. Power up your Sat Tracker and let it fully come up before enabling tracking in GH Tracker.
  4. 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.

Fred, AB1OC

WSJT-X and FT8 – A Video Introduction

WSJT-X 2.0

WSJT-X 2.0

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

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.

I hope you enjoy the video!

Fred, AB1OC

A First Look at WSJT-X V2.0

WSJT-X 2.0-rc1

WSJT-X 2.0-rc1 Beta Software

It looks like the first Beta Release of WSJT-X 2.0 is available. WSJT-X Version 2.0  includes a number of features to support contesting and longer compound callsigns when FT8 and MSK144 (Meteor Scatter) modes are used. The new features include:

  • Better support for North American VHF Contests with improved handling of grids and /R rover call sign designators
  • Six-character locators and call sign suffix support for portable operators focused on EU VHF contesting
  • Support for ARRL Field Day exchanges
  • Support for ARRL RTTY Roundup exchanges
  • Support for call signs up to 11 characters to support non-standard and compound call signs

The new version extends the length of the messages used for FT8 and MSK144 from 75/72 bits to 77 bits to enable the above features. As a result, there are compatibility issues between the v1.x releases of WSJT-X and v2.0 when FT8 and MSK144 modes are used. More detail about the new features and changes can be found here.

It is expected that the Meteor Scatter community (MSK144 mode users) will rapidly move to WSJT-X V2.0 so no backward compatibility features are provided for MSK144.

The transition for FT8 mode users is a much bigger problem. As a result, it is suggested that users test the new mode on alternative frequencies on the 20m band at 14.078 MHz and on the 40m band at 7.078 Mhz.

WSJT-X 2.0 FT8 Compatibility and Contest Options

WSJT-X 2.0 FT8 Compatibility and Contest Options

The Advanced Tab in the WSJT-X v2.0 settings provides some options to help with compatibility between v1.x and V2.0. One must choose whether to transmit using the shorter v1.x or the v2.0 messages. If you are operating in the above mention “2.0” frequency areas on 20m or 40m, it’s a good idea to transmit using the 2.0 message format (check always generate 77-bit messages).

The new version of WSJT-X can decode both the shorter v1.x and the longer v2.0 messages simultaneously. The decoding will be faster on slower computers if you check the Decode only 77-bit messages option when operating in the v2.0 frequency ranges.

If you want to try the new v2.0 FT8 mode in one of the supported contests, you’ll want to check the appropriate Special operating activity option. If you are not operating in one of these contests, you’ll want to select None.

All you need to do to try the new version is to download and install it and configure the FT8 options. I’ve been running WSJT-X v2.0 rc1 in the 20m band in the 14.078  MHz sub-band this morning and have made about 20 contacts using the new format. The v2.0 software is working well.

There are some additional enhancements which will be included in WSJT-X v2.0. Here’s some information on these features from the WSJT-X v2.0 Quick Start Guide

WSJT-X 2.0 has several other new features and capabilities. The WSPR decoder has better sensitivity by about 1 dB. Color highlighting of decoded messages provides worked-before status for callsigns, grid locators, and DXCC entities on a “by band” basis. Color highlighting can also identify stations that have (or have not) uploaded their logs to Logbook of the World (LoTW) within the past year. The necessary information from LoTW can be easily downloaded from the ARRL website.

Currently, several additional release candidates are planned for WSJT-X v2.0 as follows:

  • September 17, 2018:   -rc1        Expires October 31, 2018
  • October 15, 2018:        -rc2       Expires November 30, 2018
  • November 12, 2018:    -rc3       Expires December 31, 2018
  • December 10, 2018:     GA         Full release of WSJT-X 2.0

Note that the release candidates will expire about 2 weeks after each new version becomes available. Also, its required that anyone who runs the Beta (release candidate) software agrees to report any bugs that they find.

We are looking forward to trying the new FT8 in the next digital contest which allows it.

Fred, AB1OC

Operating FT8 Remote on the 6m Band

FT8 Digital Remote Setup

FT8 Digital Remote Setup

I have been operating using the FT8 digital mode on the 6m band using our remote operating gateway quite a bit this summer. The SDR-based remote operating gateway in our station allows us to operate our station from other rooms in our home as well as from outside our QTH via the Internet. When I’m at home, I have computers set up with outboard monitors to create an operating setup for FT8 digital contacts on the 6m and other bands. The photo above shows this setup. Having the extra screen space and multiple laptops enables control of our station, making and logging QSOs, and checking propagation via Reverse Beacon Networks as we operate.

Radio and Logging System

Radio and Logging System

The main system is a windows laptop. It runs the SmartSDR software which operates the Flex-6700 Radio in our shack (upper right window below).

Flex-6700 SmartSDR and WSJT-X Weak Signal Digital Software

Flex-6700 SmartSDR and WSJT-X Weak Signal Digital Software

This laptop runs the WSJT-X software (left windows above) which conducts QSOs in FT8 and other weak signal modes and the JTAlert Software (lower right windows above) which interfaces WSJT-X to the DXLab logging suite. JTAlert displays all callsigns decoded by WSJT-X and compares them to my log to determine which potential contacts are new DXCC’s, Grids, States, etc. JTAlert adds contacts to my logs in DXLab when a QSO is completed using WSJT-X.

DXLab Suite Logging and Rotator Control Software

DXLab Suite Logging and Rotator Control Software

The windows laptop also runs the DXLab logging suite. DXLab handles logging of QSOs, one-click pointing of our antennas based upon the callsign being worked, and uploading contacts to LoTW, eQSL, and ClubLog for confirming contacts.

Reverse Beacon Network and Station Monitoring Computer

Reverse Beacon Network and Station Monitoring Computer

I like to use the second computer to monitor propagation and strength of my FT8 signal while operating.

PSKReporter RBN Monitoring on 6m

PSKReporter RBN Monitoring on 6m

I use two tools to assess propagation conditions while I am operating. The first is PSKReporter which is a Reverse Beacon Network (RBN) tool that is enabled by WSJT-X and most other digital mode software programs. Each time WSJT-X decodes a stations transmission, it reports the decoded callsign along with location and signal strength information to the PSKReporter website. This website then uses this information to display all of the stations that hear my and other’s transmissions in real-time. The RBN information is used to determine where a given band is open and as a tool to determine how much transmit power is needed to provide acceptable signal strength at stations that I am trying to work.

DXMaps Propagation Report on 6m

DXMaps Propagation Report on 6m

The DXMaps website shows a real-time map view of contacts being made on the 10m and higher bands. This second tool provides a real-time view of band conditions and opening on bands like 6m which have somewhat unpredictable propagation characteristics.

Together, these tools help to determine where to point antennas and what stations we can work on the 6m band.

The second laptop also runs Teamviewer remote control software. This provides access to the antenna switching controls, SWR and power monitoring equipment, station electrical power, and amplifier controls in our shack. These tools are important elements in safely operating and controlling our station when we are not in the same room as the radios and other equipment we are using.

I’ve been using the remote operating setup described here on the 6m band quite a bit over the last few weeks. I hope this post provides some ideas that other can use.

73,

Fred, AB1OC

A 6m Es Season to Remember

AB1OC Worldwide 6m Grids

AB1OC Worldwide 6m Grids

2018 has been a summer 6m E-Skip (Es) season to remember. The Es openings have been strong this year and they are continuing into the second half of July. We are enjoying almost daily openings to Europe and the western USA from here in New England. For fun, I’ve plotted my 6m Grids worked and confirmed to date using WG7J’s GridMapper site.

We got started a little late with 6m Es operations this year but the conditions have really helped our Grids, DXCC’s, and States totals worked on 6m. My totals are currently standing at:

  • 6m DXCC’s – 55 worked
  • 6m US States – 48 of 50 (only AK and HI still needed)
  • 6m Grids – 357 worked

A great deal of this progress has been made in 2018. Here are my 6m worked totals since the beginning of the year:

  • 6m DXCC’s – 48 worked
  • 6m US States – 46 worked (All but AK and HI)
  • 6m Grids – 312 worked
AB1OC Europe 6m Grids

AB1OC Europe 6m Grids

The new FT8 and MSK144 modes has made more difficult 6m contacts much easier. This is especially true for DX contacts into Europe and Africa.

AB1OC Americas 6m Grids

AB1OC Americas 6m Grids

At this point, we have worked most of the grids in the eastern half of the US. There are still some “rare” ones that are needed and a contact with Delaware is still needed for my last state on 6m in the continental USA. Alaska and Hawaii will be a challenge on 6m and I may need to use JT65 and EME propagation to work these states on 6m.

With some work on QSL’ing, the recent 6m activity will add significant progress to several of my operating awards. The new 6m DXCC’s worked recently should enable breaking the 2,000 band point level on my DXCC Challenge Award.

If you are interested in trying 6m operations or perhaps you are a new Technician Licensee or are looking for something new to try, don’t forget about the Magic Band (6m). The availability of FT8 mode has really enhanced the activity on 6m. Give it a try!

Fred, AB1OC

A 40m High Performance Antenna for Field Day

40m V-Beam Wire Antenna at Field Day

40m V-Beam Wire Antenna at Field Day

The Nashua Area Radio Society has been using a 3-element wire beam antenna for Field Day for the last several years. The antenna uses three guyed 50 ft. fiberglass masts from Max-Gain Systems. The antenna uses three inverted-V style elements separated by a little over 50 ft. Since we are in the northeastern United States, we can point the antenna on a fixed, 260° heading and it covers the entire U.S. well.

40m V-Beam - EZNEC Antenna View

40m V-Beam – EZNEC Antenna View

Our 40m V-Beam antenna was initially designed in EZNEC 5.0. It was manually optimized for decent gain and front to back performance and it worked quite well. Recently, we decided to try automatic optimization software on the antenna as part of a tune-up on the design for Field Day 2018. After looking around on the Internet a bit, we discovered a software package called AutoEZ which looked ideal for my project.

AutoEZ Antenna Modeling and Optimization Software - Wires Tab

AutoEZ Antenna Modeling and Optimization Software – Wires Tab

AutoEZ is a collection of Visual Basic code and Microsoft Excel macros that act as a front-end to EZNEC 5.0 and later. AutoEZ provides a number of very useful enhancements to EZNEC including:

  • Ability to use formulas and variables to construct and modify EZNEC wire models
  • A Test Case generator and execution environment to vary model parameters and graph the results calculations run by EZNEC
  • An automatic optimizer that can adjust the parameters of an antenna model in EZNEC to optimally meet a defined set of performance goals
  • Harnesses the full power of Microsoft Excel formulas for trigonometry, logical, and other mathematical capabilities for use in EZNEC modeling
AutoEZ Antenna Model Variables

AutoEZ Antenna Model Variables

The first step in the project was to rebuild the EZNEC model that I already had for our 40m V-Beam antenna in AutoEZ. I began by defining several AutoEZ Variables and Excel Formulas in the AutoEZ Variables Tab that enabled me to easily modify the design of the antenna and to optimize it. Some of the basic variables included the target design frequency for the antenna, the height and separation of the antenna elements, the distance to the element anchor points, and the length of the element wires.

AutoEZ Antenna Model Variables (Formulae View)

AutoEZ Antenna Model Variables (Formula View)

The image above shows the model variables in “Formula View”. You can see some of the math and trig functions that were used to compute values for some of the variables. AutoEZ can only optimize variables that do not contain formulas so I was careful to ensure that the base separation between the elements and the length of the element wires were constants as these are the parameters that I wanted to optimize later.

AutoEZ Antenna Modeling and Optimization Software - Wires Tab

AutoEZ Antenna Modeling and Optimization Software – Wires Tab

Excel Trig formulas and the Variables were used on the Wires Tab to determine the coordinates of the wires in the antennas. There are a total of 7 wires in the model. Six are the two ends of the three inverted-V elements. The Seventh wire is a short 4″ section in the middle of the Driven Element to allow a current source to be inserted to drive the antenna there. I was careful to create an accurate model of the wire gauge, insulation, and loss that we are using for our V-beam

Model Variables to be Optimized

Model Variables to be Optimized

With the model built, it was back to the Variables Tab to select the parameters to be optimized. Optimization is best done as a multi-pass process and I did this in two steps. The first set of runs included optimization of both the element spacings and their lengths. This led me to conclude that the mast spacing of 27 ft (Driven to Director) and 28 ft (Driven to Reflector) were the best choices. I then set these as fixed values in the variables tab and ran the optimizer a second time with some starting element lengths to optimize the element lengths by themselves.

Optimizer Objectives

Optimizer Objectives

One must create a set of frequencies and objectives for the optimizer before running it. This is done in the AutoEZ Optimize Tab. The antenna is being used for SSB on 40m so I choose a range of frequencies that covered the SSB sub-band on 40m. Note that I weighted the center frequency heavier than the edges by including it more times in the optimizer’s list. The use of the Optimization Objectives and their associated weights and values are well covered in the AutoEZ documentation so I won’t cover them in detail here. The parameters above were chosen to create a reasonable balance between SWR values across the 40m SSB sub-band, good Front/Back and Front/Side performance from azimuth values ranging from 60º to 300º, and a reasonable amount of forward gain for a 3 element antenna of this type.

I expected that the final impedance of the antenna would be a typical value for a yagi in the 20 to 30 ohm range. Thus, I set the SWR calculations based upon a 25 ohm target impedance. More on the matching of the resulting design later…

Element Optimization Results

Element Optimization Results

It took several runs of the optimizer with different sets of Optimizer Objectives to get the final results I was looking for. The Optimizer tried 130 combinations of element lengths to arrive at the final lengths shown above. Note the improvements in SWR (1.6 -> 1.04), Forward Gain (+1 dB), Front/Back (+4.2 dB) and Front/Rear (actually Front/Side) performance that the Optimizer was able to achieve over my manual, trial and error optimization.

Post-Optimization Model Variables

Post-Optimization Model Variables

Next, I rounded the optimized element lengths and plugged them into the Variables Tab.

Post Optimization Azimuth Pattern

Post Optimization Azimuth Pattern

The image above shows the optimized Azimuth pattern for the antenna as generated by AutoEZ and EZNEC. A very clean result!

Post-Optimization Elevation Pattern

Post-Optimization Elevation Pattern

And here’s the optimized Elevation pattern near the center of the SSB sub-band. This antenna is a little low for 40m but the resulting maximum gain at a 35º angle should work well for US contacts during Field Day.

Calculated Performance for the Optimized Antenna

Calculated Performance for the Optimized Antenna

The final step in the optimization process was to calculate a full set of performance calculations for the antenna using the Calculate Tab. AutoEZ makes it very easy to generate a set of Test Cases for incremental frequencies in the SSB sub-band on 40m. Note the setting of the Elevation angle of 35º to match the maximum gain angle for the optimized antenna. Also, note the parameter settings for Ground Type and Characteristics. I set these to model the less than ideal soil conditions that we have here in New England.

Performance Plots for the Optimized Antenna

Performance Plots for the Optimized Antenna

AutoEZ provides several nice graphical capabilities via the Patterns, Triple, Smith, Custom and Currents Tabs.  I used some of them to plot the data from the performance calculations. These graphs help to visualize the results of the optimization to verify that the design objectives for the antenna have been met.

1:2 Matching Balun (25 ohm to 50 ohm)

1:2 Matching Balun (25 ohm to 50 ohm)

I am using a 1:2 matching Balun from Balun Designs at the feed point of the antenna to transform the antennas final 25 ohm feed point impedance to 50 ohm to match our coax feed line.

40m V-Beam Antenna

40m V-Beam Antenna

We are looking forward to using the optimized version of our 40m V-Beam at Field Day 2018. It took me a couple of days of time to read all of the AutoEZ documentation and learn to use the excellent tools it provides. I don’t think I will build another EZNEC antenna model without using AutoEZ. Even without the optimization features, AutoEZ makes the construction and modification of an antenna model in EZNEC far easier than it would be using EZNEC alone. I hope that you’ll give AutoEZ a try for your next antenna design project.

Fred, AB1OC

 

Receiving SSTV From The ISS

Portable Satellite Station Additions - Digital and Packet

Portable Satellite Station With Additions For Digital and Packet

We’ve recently upgraded our Portable Satellite Station 2.0 to add digital and packet capabilities. The upgrade was pretty simple – we added a SignaLink USB Soundcard and a Windows Laptop PC. Most of the software for packet and digital Amateur Radio communications is written for the Windows OS so using a separate laptop running Windows 10 was the simplest way to go. Another benefit of the second laptop was added screen space to use when doing packet communications via satellites and the International Space Station (ISS).

SSTV Image From The ISS

SSTV Image From The ISS

We recently learned that the ISS was going to be again transmitting SSTV images worldwide. This provided a perfect opportunity to work with the digital additions in our satellite setup. We downloaded and installed MMSSTV on our Windows laptop and set the audio levels on the Windows PC and our SignaLink Sound card to properly receive SSTV signals. The MMSSTV application can decode several different SSTV formats including the PD120 format used by the ISS. The ISS transmits SSTV on a 2m FM voice channel. We configured MacDoppler to track the ISS and perform doppler correction on the 2m ISS 2m downlink and began to listen.

The video above was made during the reception of an SSTV image from the ISS during a pass over the United States. The video gives a good idea of what its like to receive SSTV from the space station.

Another SSTV Image From The ISS

Another SSTV Image From The ISS

We were able to receive several different images from the ISS during the period that it was transmitting SSTV worldwide.

A Third SSTV Image From The ISS

A Third SSTV Image From The ISS

It was pretty easy to capture the SSTV transmissions from the ISS with our Portable Satellite Station 2.0 setup. The signals were strong and I would imagine that the SSTV transmission could have also been received with a simple portable satellite setup with a hand-held yagi antenna.

We hope that the ISS will send SSTV images again in the near future. It was fun receiving them.

Fred, AB1OC

DX Alarm Clock Part 2 – Hardware

The DX Alarm Clock

The DX Alarm Clock

I recently wrote a blog article about the DX Alarm Clock software – here is Part 2 of the Series on the how I built the hardware for the DX Alarm Clock.

DX Alarm Clock Hardware Components

The DX Alarm Clock is based on a Raspberry Pi 3 computer and an Adafruit Pi-TFT Touch Screen Display.  The list of components, along with links is below.  Since I built the Raspberry Pi almost a year ago and technology is always advancing, some of the parts are no longer available or have better replacements available.  I’ll provide information on what I used and a recommended replacement.  Approximate prices are included.

 

Rapberry Pi 3

Rapberry Pi 3

 

Motherboard: Raspberry Pi 3 ($35) – includes a 1.2 GHz 64-bit quad-core ARM CPU, Build in WiFi, Ethernet, 4 USB Ports, an HDMI port and audio port (3.5″) and Bluetooth.

Also you will need a power adapter  ($10) and Class 10 Micro SD card ($15) for the Raspberry Pi.  Ours is a SanDisk Ultra 64GB Micro SD Card.

Pi-TFT Touch Screen Display

Pi-TFT Touch Screen Display

Display: Adafruit Pi-TFT 2.8″ Display with Capacitive Touch Screen ($45).  A slightly larger, 3.5″ display is now available.

PiBow Case

PiBow Case for Raspberry Pi and Touch Screen Display

Case: Pimoroni PiBow Case for Raspberry Pi and Pi-TFT Display($20)

Kinivo Speaker

Kinivo Portable Speaker

Portable Speaker:  Any small portable/rechargeable speaker will do.  Mine is a Kinivo, but it is no longer available.  Any small speaker will do as long as it is Bluetooth or has a 3.5″ stereo connector.

 

Raspberry Pi Development Environment

Raspberry Pi Development Environment

Raspberry Pi Development Environment

After constructing the Raspberry Pi, case and TFT Display, the next step was to connect it to a monitor via the HDMI port, a mouse via one of the USB ports and to a Bluetooth keyboard.   Then I loaded the Raspbian Operating System onto the Raspberry Pi via the micro SD card.  I first copied the OS to the Micro SD card using a PC or Mac and then inserted the card into the Raspberry Pi and booted from it.  You can find a good tutorial on how to do this at https://www.raspberrypi.org/learning/software-guide/quickstart/

Once Raspbian is installed, you will have a windows like GUI (Graphical User Interface) environment with a web browser, and a number of additional applications included.

This gave me a development environment that I could use to build and test the DX Alarm Clock software.  I used the Python language to develop the software.  I used the Python IDLE development environment, which is included in the Raspbian OS.

Interested in Raspberry Pi Amateur Radio Projects?  See the article on a Raspberry Pi Satellite Rotator Interface.

Meteor Scatter Rocks! – Work’in the Orionids

AB1OC 6m USA Grids

AB1OC 6m USA Grids

I’ve been pretty active on the 6m band the past few years. As you can see from the image above, we’ve worked most of the grid squares in the eastern third of the United States on 6m. I use a mix of modes on 6m including SSB Phone, CW, JT65, FT8, and MSK144. The addition of the MSK144 mode for Meteor Scatter contacts has been a lot of fun and has added some new grid squares to my total.

Orionid Meteor Shower Forecast

Orionid Meteor Shower Forecast

One of the fall Meteor Showers, the Orionids, occurred not too long ago and I decided to focus on MSK144 during the Orionids to see how many grid squares I could work. The shower mast most active over a 3-day period (Friday, Saturday, and Sunday).

MSK144 QSO with WA3LBI Using WSJT-X

MSK144 QSO with WA3LBI Using WSJT-X

The latest WSJT-X software supports a relatively new digital mode for Meteor Scatter contacts – MSK144. A Meteor Scatter contact made using MSK144 is shown above.

Meteor Scatter Pings Detected via MSK144

Meteor Scatter Pings Detected via MSK144

Meteors create short propagation enhancements when they burn up in the atmosphere. These short propagation bursts enable very brief (approximately 1-5 second) propagation on the 6m band.

The video above shows an example of an MSK144 Meteor Scatter QSO using WSJT-X.

6m MSK144 QSOs During Orionids

6m MSK144 QSOs During Orionids

So I bet you may be wondering how many 6m QSOs and grid squares was I able to work during the Orionids? I made a total of 23 Meteor Scatter QSOs using MSK144 during the 2017 Orionids. The image above shows the 16 grids that were worked using MSK144 during the three-day period. A few of these grids were new for me on 6m.

I used our Flex-6700 SDR, our SteppIR Yagis, and about 200w of power to make these contacts. It was a lot of fun making contacts using MSK144 Meteor Scatter on 6m. I am looking forward to future Meteor Shower activity!

Fred, AB1OC

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 an HDMI display or to the Touch Display, we were ready to install the GH Tracker 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 V1.24 and the necessary serial interface library to enable its use on the RPi. Jeff is planning to make a tar file available with GH Tracker 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 GH Tracker whenever the RPi is booted up. We also optimized the GUI for the sole purpose of running GH Tracker 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 GH Tracker 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.

You can find information about how to build your own Raspberry Pi Sat Tracker Interface here.

Other articles in the Portable Satellite Station series include:

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

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