Satellite / ISS Ground Station

Satellite / ISS Ground Station

Thanks to a generous grant from the ARDC, W1HLO has a satellite / ISS ground station!  After waiting for components to arrive and waiting for warm, dry days to do roof work, our station is finally operational.  

Background

W1HLO wanted to create a ground station for contacting amateur radio satellites, weather satellites, and the International Space Station (ISS).  We also wanted to create an academic resource that could be integrated into our science curriculum.  Having our ground station remotely controlled was a requirement.  That way, our club members can visit science classrooms and remotely control the station to make satellite radio contacts and download weather satellite images.  With this resource, our science classrooms can:

  • Study Kepler’s Laws to predict and track satellite movements to contact weather/AMSAT satellites.
  • Use live weather satellite data to predict weather patterns on Earth.
  • Use weather satellite data to investigate any correlations between weather patterns and flora and fauna grown patterns in different regions.

Challenges

Identifying the needed equipment, setting up the hardware, and learning how to use SATPC32 were all challenges to this project.  Even figuring out which AMSAT FM repeater satellites are good "birds" (as they're called) to try was daunting.  So I'll tell you right now:  AO-91, SO-50, and the ISS (when its FM repeater is active) are all good satellites to start with!  Another tip: These three birds use a PL tone of 67.0 Hz for repeating your signal.  The only exception is SO-51, which requires you to transmit for about 2 seconds with a PL of 74.4 Hz to activate its repeater.  Then, the repeater is active for 10 minutes of use and you have to switch to a PL of 67.0 Hz for making contacts.

Equipment List

One of our challenges was finding a current list of everything that's needed for a satellite / ISS station.  We also needed to spec a back-up station, which is required by ARISS for scheduled ISS contacts.  Joe Carcia NJ1Q was a big help in getting us started with the equipment list.  His suggestions from his "Go-Kit" as well as experience provided the needed guidance.  Chelsea from the ARDC recommended that we use the ICOM IC-9700 as it has VHF/UHF capabilities, is full duplex, and widely used for satellite work in amateur radio.  Why VHF and UHF?  Many amateur radio satellites use a VHF frequency for an uplink and a UHF frequency for a downlink!  The IC-9700 has separate antenna connectors for VHF and UHF antennas (as well as a third connector for a 1.2GHz antenna).  Ultimately, I put together this equipment list (updated) for ordering components for the station.

Gabe and Andy run the antenna and controller cables into the W1HLO shack. Watch out for falling debris from those ceiling tiles!

The Rotator

The Yaesu G-5500DC presented its own challenges with interfacing to a computer and figuring out how to mount the VHF and UHF yagi antennas.  (Since a satellite has some rotation to it, its antenna polarization is constantly changing and can cause signal fading.  This is why we opted for cross-polarized VHF and UHF yagis.)  Once we verified the rotator was working with the controller, we set the controller to point the rotator's azimuth to south.  Then, we ensured the yagis were pointing south (opposite of true north and not magnetic north) per the instructions.  This was easy enough by placing an iPhone on top of the rotator with the Apple Compass app's "true north" option turned on.  We then had to set the controller to 90 degrees elevation and make sure the yagis were pointing straight UP at the sky.  We then moved the antennas to different positions and made sure that the altitude/azimuth indicators on the rotator controller matched the directions of the antennas.

Since the rotator controller does not have a USB interface, we had to purchase the Yaesu GS-232B, which is an RS-232 (serial) computer interface.  We also had to purchase a USB-to-serial adapter to be able to connect the GS-232B to our computer.  The rotator requires two controller cables: one for the altitude motor and another for the azimuth motor.  We decided on using DX Engineering's DXE-CW8-HD control cable as it has 18AWG wire which is better suited for longer cable runs.  For the VHF and UHF antennas, we ran two LMR-400 cables (one for each antenna).

Gabe and Andy help Dr. Girasoli with running the cables to the antennas with a broom.

Satellite Tracking Software

SATPC32 was ultimately decided upon as our software of choice as it can track amateur radio satellites, weather satellites, and NOAA satellites.  It can also control the ICOM IC-9700 radio to set frequencies, PL's, and adjust frequencies to account for doppler shift.  That's right – when the satellites are approaching you their frequencies shift up and when they are leaving you, their frequencies shift down.  SATPC32 takes care of moving the rotator, changing the frequencies, and predicting a satellite's next pass.

Learning how to use SATPC32 was a BEAR to understand (it's a New England expression...) but we figured it out.  You have to make sure your computer's time is correct – we didn't realize that our computer's clock was off by an hour and couldn't figure out why we weren't making any contacts!  This was, of course, because SATPC32 is making predictions of satellite passes based on your location and the correct time of day.  

We followed Bruce MacAlister W4BRU's Installation & Setup of SatPC32 & SatPC32ISS instructions.  These were invaluable as they provided step-by-step directions on how to set up USB configurations for the ICOM IC-9700 and the Yaesu GS-232B.  To select a list of FM repeater satellites, you have to click on the blank area to the left of the frequency display in SATPC32.  Then, you can select a group of satellites (such as "FM Repeaters").  Along the bottom of the SATPC32 window are letters, each one representing a satellite.  If a satellite is in range, the letter will have a white background.  Click on each letter to activate a satellite in SATPC32.

To turn on CAT control of the IC-9700 for automatically changing the frequencies, click on the "C-" in the upper left so that it becomes "C+".  To turn on the rotator, click on the "R-" so that it becomes "R+".  Lastly, when using satellites like AO-91, SO-50, and the ISS, you need to turn on the PL tone.  To do so, click on "T0" (which means no PL tone) so that it becomes "T1" (a 67.0 Hz PL tone).  For SO-50, since you have to send a 2-second transmission with PL 74.4 Hz to activate it, click on "T1" and it will change to "T2".  This is the 74.4 PL tone.  Transmit for a couple of seconds.  Then, click on "T2" to change it to "T0" and then click again to change it to "T1" for the 67.0 PL tone.  Additionally, at the bottom of the window, "AOS" means "Acquisition of Signal" and "LOS" means "Loss of Signal."  These two indicators give a window of when you can contact the satellite.  However, the window can be a bit smaller than this if there is high terrain around you.

I also found that you need to update your Kepler data when you first use SATPC32 and every few days.  You can do this for each group of satellites by going to the Satellites menu option and clicking on the "Update Keps" button.  Then, you can click on a source file (like the URL "amateur.txt" for the amateur satellites and "nasa.txt" for the ISS) and click on the "Download" button.  Do this for each group of satellites you're planning on contacting.

With the ISS, there are a few frequencies to choose from.  If you want to use the ISS's repeater on the Columbus Module, you have to select the correct frequency pair in SATPC32.  To do so, with the ISS selected, click on "CAT" in the menu bar.  Then, choose the repeater frequencies (145.990 MHz up [PL 67] & 437.800 MHz down) by double clicking on them in the list.  For me, this frequency pair was incorrect in the list of frequencies.  To edit the list of frequencies, you will need to go to (in the menu bar): ? -> Auxiliary Files -> Doppler.SQF.  Then, find the ISS line that has the incorrect frequencies and correct them such as:

ISS,437800,145990,FM,FM,NOR,0,0,Cross band repeater

Exit and safe the file.   You'll probably have to add a PL tone, too, for the ISS as my default configuration didn't have one.  To do so, go to: ? -> Auxiliary Files ->  SubTone.SQF.  Create a new line with the following:

ISS,67.0,$3F,1

Save and exit the file.  Then restart SATPC32 for the changes to take effect.  Now you'll have the correct frequencies and PL tone for the ISS repeater.

What's Next

We've applied for an ARISS contact with the astronauts on the ISS for a school-wide event.  We discovered that the IC-9700 can't receive out-of-band for the weather and NOAA satellites around 137 MHz.  So, we've been using another VHF radio that can receive on this frequency to download the images and decode them with APTDecoder.  We'll most likely replace this with an RTL-SDR receiver so that we can receive the satellite images remotely.  We are also in the process of putting together an installation in our library to showcase our new station and allow students to explore amateur radio and space.  A big thank you to the ARDC for funding this project and making amateur radio and space science more accessible to our students at Norwich Free Academy!