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

Building An Amplifier

Elecraft KPA500 Amplifier

Elecraft KPA500 Amplifier

I have been planning to add a medium power HF Amplifier to our station for some time now. The plan was to use an amplifier of this type for two purposes –  as an amplifier for Anita’s (AB1QB’s) position at our home station and to have an amplifier that we could take along on DXpeditions and other portable operations. After doing some research, it looked like the Elecraft KPA500 Amplifier would be ideal for this. It is small in size, can operate using either 120 VAC or 240 VAC power and has a quite reasonable weight of 26 lbs.  After dropping some not so subtle hints, I received a KPA500 kit as a holiday gift.

The Elecraft KPA500 is a no-solder kit and requires 4 – 6 hours to assemble. Just for fun, I decided to make a time-lapse video of the assembly, checkout and an initial QSO with our KPA500.

The assembly of the kit was quite straightforward and I was able to complete it in about 5 hours. The amplifier worked fine after assembly. It  performs well on all of the Amateur Bands from 160m – 6m and delivers its rated output of 500 W with 25-35 watts of drive power. The initial QSO in the video was made using our Elecraft KX3 Transceiver which provides a maximum of 12 watts of drive power to the amplifier. As you can see in the video, the KPA500 produces about 200 w output using the KX3. I have also tested the KPA500 with a 100W transceiver and found that it produces the rated output on all of the bands and runs cool and quiet. Testing with my station monitor as well as on-air reports indicate that the KPA500 produces a clean signal.

I know that some of you may be wondering how I made the time-lapse video included in this post. I found a very good how-to webpage that explains how this is done and includes links to some good software choices to perform the various steps in the process. The software and hardware that I used are listed in the credits at the end of the video for those who are interested.

Time Lapse Video Setup

Time Lapse Video Setup

The basic setup requires a digital camera on a tripod that can take a series of still images at regular intervals. My video was created using a Nikon D7000 which took a still frame  every 5 seconds. The video required a total of about 3,900 individual photos to produce a 24 fps video that is about 2:40 minutes long. A combination of Batch Photo Editing (Adobe Lightroom), Time-Lapse Assembly, and Video Editing (Apple iMovie) tools were used to complete the project.

The plan is to couple the KPA500 with Anita’s new Flex-3000 Software Defined Radio (I got a not so subtle hint too). More on the Flex-3000 and its operation with the Elecraft KPA500 will be the topic of a future post.

– Fred (AB1OC)

Feedline Breakout System

Feedline Breakout System

Feedline Breakout System

Since Anita (AB1QB) and I both want to operate at the same time, we are planning to put two SteppIR DB36 Yagis on our tower. These antennas will be connected to a DX Engineering Stack Matching System so that they can be operated together as a 4 over 4 array. The DXE Stack Match can select either antenna individually and connect it to the feedline associated with the array but it does not provide breakout of both antennas onto separate feedlines. We designed and built a custom feedline breakout system to enable simultaneous breakout of both antennas to separate feedlines. This project involved the construction of both a tower mounted box to house a part of relays and a control box for the shack.

This device is inserted between the Stack Match and the antennas in line with the two phasing lines to each Yagi. It is critical that the breakout device provide identical impedance and phasing effects on both phasing lines if the array is to function correctly. To accomplish this, we selected a pair of Tohtsu Coaxial Relays (Model CX-800N) that have very low SWR impact in the HF bands. These were installed in an outdoor utility box that we got from DX Engineering. Only one relay is used to breakout the lower antenna to a separate feedline as the Stack Match can break out the upper antenna to the main feedline for the array. The reason that two relays are needed is to ensure that RF performance of both phasing lines to the two antennas is identical.

Coaxial Relay

Coaxial Relay

The relays require a 24V source to energize them. I built a simple control box for the shack to provide the needed control voltage. The controller includes three switches so that it can be used for additional 24V relay applications in the future.

Breakout Control Box

Breakout Control Box

I wanted to be sure that the Breakout System had good isolation characteristics between the two phasing lines so that the device did not allow a transmitter using one antenna to interfere or possibly damage a transceiver using the other antenna.. The relays we choose have good isolation characteristics which is a good start. To ensure that we have good isolation at a system level, I used an ArraySolutions Vector Network Analyzer (VNA) 2180 to measure the isolation between the various input and output connections in the Breakout System. The ArraySolutions VNA 2180 uses a PC and software to control a measurement unit which can perform one and two port SWR, impedance, loss and phase measurements (many other measurements are possible as well). In this case, we are making a port to port loss measurement.

Isolation Measurement Setup

Isolation Measurement Setup using a VNA

The VNA 2180 has a dynamic range of about 100 dB which means that it can measure isolation up to this level. As you can see from the following screen shot taken with the VNA software, the isolation of the Breakout System is very close to the limits that the VNA can measure. The worst case isolation measurement is about -97 dB on the 6m band. We also use Bandpass Filters when we are both operating and these filters provide an additional 55 dB or more of isolation which means we have a total of about 150 dB of isolation through this path. In the real world, the antennas themselves will likely have much less isolation between them than this so the isolation performance of the Breakout System should be more than adequate.

Isolation Measurement Results

Isolation Measurement Results

We are making good progress towards the planned installation of three of our Yagis on the tower next week. I will provide some additional posts over the next several days covering additional aspects of the preparation for next week.

– Fred (AB1OC)

Shack Construction – Part 4/4 (Final Setup Of Equipment)

Printer and Phone

Computers, Printer, Phone And Antenna Switching

The final step in the construction of our new shack was to outfit it with all of the infrastructure for power, RF switching and computers and install the radios and related support systems. This post will outline what we did in this area. One of the first things we did was to get the LAN in the shack working and set up our computers (two Windows 7 PCs) and a local printer. We also installed stands to suspend two computer monitors by each of our operating positions and keyboard trays to allow our keyboards and mice to be stored under the desk when they were not in use. The monitor stands were a good idea as they allowed us to place our displays just above our radios at eye level – perfect for the computer aided operating that we often do.

We also installed RF ground blocks by each operating position and terminated the ground connections from outside of our shack on the blocks. The ground blocks act as a convenient single point to connect the grounds for all of the devices in our station.

Ground Block

Ground Block

Desk space is usually at a premium in most shacks and ours is going to be no exception. To make the best use of the available space, we built dolly’s to place our 13.8V and 28V DC power supplies from Astron on the floor along with the main unit for our power amplifier (an Icom PW-1).  The amplifier has a small remote control and meter head which sits on our desktop and takes almost no space there.

Dolly's for Amplifier and Power Supplies

Dolly’s For The Amplifier And Power Supplies

The power supplies are terminated on RIGRunner power distribution panels by each of our operating positions as well as by the construction area. We have 13.8V and 28V DC power distribution blocks installed in these locations so that both voltages are readily available for distribution via Powerpole connections. Some of the 13.8V distribution panels have sensing capability so that when we turn on one accessory at each operating position the distribution panel powers up all of the 13.8V gear in that location – a nice convenience feature. We also added AC power distribution strips at several locations around our operating desk as well as APC UPS Power Supplies on both computers. With all of this infrastructure in place, we were ready to move our radios and related equipment into the new shack and set it up.

DC Power Distribution

DC Power Distribution

The next step in the equipment set up was to connect our antennas to the antenna switching consoles that were built as part of our shack. These devices were all grounded to the ground blocks for safety reasons. The switch panels allow us to assign any of our seven antennas to any of the four radios in the shack. This provides a great deal of flexibility when we are both operating at the same time. With the antenna cabling done, we set up both operating positions. Fred’s position is shown here. You can see the FilterMAX III switchable bandpass filtering systems on the right of Fred’s (AB1OC’s) position which provide needed isolation when both of us are operating on different bands at the same time.

This is Fred's operating position.

AB1OC Position

Here is Anita’s (AB1QB’s) operating position. Anita currently has a single radio installed but plans to add a second radio soon. She has her own set of bandpass filters on the right of her operating position. The combination of the filtering and antenna switching matrix allows us to operate our station in a multi-SO2R configuration during contests.

This is Anita's operating position.

AB1QB Position

We also set up all of our construction and test equipment in the shack. It is a great convenience to have all of this equipment set up and ready to use for kit building, making cables, and general test purposes whenever we need it.

Electronic equipment for equipment construction and test.

Construction Area

We took good advantage of the storage space in our shack for all of the odds and ends that are handy to have close at hand. This area also provides a nice spot to display some of our operating awards.

Storage and display area

Storage Area

Finally, we set up an A-V area with a TV, audio system and remote control and integrated this equipment into our whole-house A-V network. This allows us to listen to music or watch videos when we are not operating in the shack.

TV and Entertainment Audio Equipment

A-V Area

Here is a picture of our completed shack. We were able to get it into operation in time to use it for the 13 Colonies Special Event in July 2012. This allowed both of use to operate simultaneously as K2K, one of the New Hampshire 13 Colonies Special Event Stations.

Our Shack

We are both really enjoying our new shack and we find that we are operating much now that our equipment and the associated support system are properly set up. We are now working on a significant expansion of our Antenna Farm with the addition of a tower and several new antennas. We will continue to post as we progress on this next phase of our station construction project.

– Fred (AB1OC)

A Tour Of Our Shack

I wanted to share a little more about our new shack which was recently completed. Anita and I each have our own operating positions and both positions are SO2R capable. Anita’s setup consists of a Yaesu FTdx5000 and has provisions to add a second radio in the future. Fred’s position uses an Icom IC-7800 and an Icom IC-9100. Some of the key specifications and capabilities of our shack include:

  • A manual antenna switching matrix which allows us to connect any one of 6 antennas to our radios
  • W3QN bandpass filters systems for each radio to allow simultaneous operation of multiple transmitters at the same time on different bands
  • microHAM MK2R+ and SignalLink USB sound cards to enable digital mode operation
  • Dedicated displays and keyboards for the FTdx5000 and IC-7800 radios to enable better use of their built-in Pan Adapters
  • Icom and Yaesu desk microphones and Heil ProSet headsets with boom microphones
  • Bencher paddle for CW
  • Windows 7 (64-bit) computers with dual monitors for running all manner of HAM software (we mainly use Ham Radio Deluxe at this time – more on software in a future post)
  • An Icom PW-1 Kilowatt Solid State Amplifier

The shack also has 125A of dedicated AC power, 70A of DC power and its own Heat Pump system for heating and cooling. Our house also has a 20 KW automatic generator system which provides emergency power to the shack.

The following are a few pictures of our shack:

This is Fred's operating position.

AB1OC Position

This is Anita's operating position.

AB1QB Position

Our shack also has a dedicated area for equipment construction and test. It sure is nice to have a place where all of our test equipment, etc. can be left connected and setup for immediate use.

Electronic equipment for equipment construction and test.

Construction Area

Our shack includes areas for storage and an A-V area with a TV and entertainment audio. These are all essential items for a complete HAM-cave.

Storage and display area

Storage Area

TV and Entertainment Audio Equipment

A-V Area

Anita and I were able to use our new shack in its multi-op configuration for the 13 Colonies Special Event over the 4th of July. We were both on the air at the same time as K2K New Hampshire and this was the first test of our station in a multi-op configuration.. To avoid audio interference, one of us did SSB phone on one band while the other operated digital modes on a different band. For now, we built a matrix of manual antenna switches which allows any of our four radios to use any of the available antennas. In the future, we plan to automate all of this with a microHAM system.

The work to construct our shack took about 8 months and was quite a bit of work. We started with an unflinished area of our basement and did framing, electrical, HVAC, plumbing, drywall, ceiling, floor, and finish work. We had the help of several great contractors along the way. We plan to do a series of posts sometime in the future to explain a little more about what went into the construction of the room and the systems which support it.

– Fred (AB1OC)