Category Archives: Newsletter

Nashua Area Radio Society Newsletter Articles. You can find an archive of our Newsletters on our website.

Using Python to Track Amateur Satellites

Introduction

Recently, it’s been difficult for me to find a solid block of time to go down to the shack and operate. I’ve been looking for other things to do, therefore, to stay relevant in the hobby and always keep my learning vectored forward. Since I have an interest in one day building my own satellite station, and I receive the ARRL Keplerian Data emails via AMSAT (which show the latest Two-Line Element (TLE) sets of all the amateur sats), I thought it would be pretty neat as a first step to use Python and code up a predictive tool to plot the and track the location of all the amateur satellites will be given a UTC start and end time.

There are packages which already do this (much better than my own) such as MacDoppler. The perks are it shows coverage (footprints), orbital tracks, and even compensates your radio’s VFO for the satellite’s Doppler. The downside of this package is it costs money ($98 for a license), and it doesn’t make sense for me to pay for it when I don’t have a satellite station to utilize it. The rest of the functionality, though, I could figure out myself if I have enough time to code. And coding, is something I can very easily do on the couch in between changing dirty diapers. 🙂

There are a fair number of dependencies to this codebase which uses Python 2.7. Installed, you must have:

  • Numpy/Scipy: basic and advanced mathematical functionality
  • urllib2: Opens the websites needed to HTML scrape the satellite TLE’s
  • BeautifulSoup: performs the HTML scraping
  • Basemap: This actually plots the map of the world with the satellites across it
  • Tkinter: Creates the GUI windows to ingest data from the user
  • pytz: A package to get local time at your QTH (may already be installed with most distributions)
  • Pyephem: used for validation of my own answers. Really nice library though to do all things astronomical

If you don’t have Python already installed, I recommend using the Anaconda distribution, especially if you don’t have root access on your machine for whatever reason. This is a self-contained Python environment and it is just like installing everything in your /usr/local account.

Once you have Python and all the dependencies successfully installed, you can obtain the code from the link to the GitHub repo.

Basic Operation

The steps to using the software are relatively simple. The user first runs the main executable at a terminal prompt:

python main.py

From there a GUI window pops up displaying checkboxes next to all the satellites, two entry fields for a start and end UTC time (in 24 hour format), and a Run/Quit button.

The main GUI window for the code. The checkboxes appear next to satellites. The UTC start/end times are entry boxes to the user. REMEMBER TO USE 24 HOUR FORMAT!

Once the Run button is pressed, a map will pop up displaying the satellite track across the Earth for the chosen times. Currently, I would only recommend only plotting 1-2 satellites at a time since the map can become quite cluttered with tracks. Also, I would make the stop time only a few hours different from the start time since many of the satellites will have already executed a complete orbit in that timeframe.

Example output map and track of the ISS

Under the hood

First the software opens the URL of where the latest and greatest satellite TLEs are stored and scrapes them for all the user choices. Next, if the user chooses a UTC time before the most current TLE, the program defaults to using the epoch UTC from the TLE. As for the end date, I wouldn’t go any further than a few days out if you want the results to be fairly accurate.

Once the data has been gathered, internal routines convert the information in the TLE into the needed orbital or Keplerian elements to find the orbital path. Those Keplerian elements then undergo further processing to two different reference frames until finally the latitude and longitude can be extracted. I’d be happy to go into significant detail on what these algorithms are, but I’m pretty sure you probably don’t care! 🙂 Besides, you could easily check out the source code.

To-Do

I do plan on updating this a bit, so be sure to pull down new updates from the repo often. But, I’m actually really looking for feedback from one or two people to tell me what functionality they would like to see. For now, however, what I have planned is:

  • Display satellite footprints to better see when the satellite is up relative to the QTH
  • Have the map run in real time thereby eliminating the entered start/stop time
  • Compute satellite Doppler offsets
  • Have a function to show which satellites will be up relative to your QTH within a given 48 hour period
  • Validate results beyond a few sample cases involving the ISS

So there you have it! Hopefully if I get the above to-do incorporated into the code as well as comms with the rig (to update VFO based on Doppler, for instance), then I should be able to mimic the MacDoppler capability by only paying the price of time. I’d really like this to be an open-source substitute for that software. There’s still much to be done for this to be a really useful tool, but it’s coming along. Also please alert me to any bugs found. I know there are a ton probably. Happy tracking!

73,

Brian, AB1ZO

PTT Router for Satellite Station 3.0

Source: PTT Router for Satellite Station 3.0 | Our HAM Station

Our Portable Satellite Station antenna system uses a pair of Advanced Receiver Research Remote preamplifiers at the antennas to boost weak signals. These preamps have RF sensing and switching to protect…

PTT Router Front Panel
PTT Router Front Panel

Our Portable Satellite Station 3.0 is coming together and has been tested thanks to help from several NARS members. Part of the project is to improve the sequencing system which manages antenna mounted preamplifiers. These improvements involved the design and construction of a simple Push To Talk (PTT) router. The article above explains the design, construction, and integration of this PTT Routing devices. It was a great homebrew addition to our Portable Satellite Station setup.

Fred (AB1OC)

The Very First CQ and QSO…

Who called the first CQ and made the first QSO? Who invented AM radio and made the first broadcast? Who did the first 2-way QSO across the Atlantic (Marconi was one way)? …. posted by Layne AE1N.

You All Know Reginald Fessenden. Who?

Quick, name someone influential in the history of radio. Who do did you think of? Marconi? Tesla? Armstrong? Hertz? Perhaps Sarnoff? We bet only a handful would have said Reginald Fessenden. Fessenden was the first man to make a two-way transatlantic radio contact (Marconi’s was one way) and he was a pioneer in using voice over the radio.

He patented transmitting with a continuous wave instead of a spark, which made modern radio practical. This was unpopular at the time because most thought the spark was necessary to generate enough energy.

Start at the Beginning

Reginald Fessenden was born in Quebec in 1866. Eventually, he would move to New York City hoping to work for Thomas Edison.  Once in Edison’s employ, his math skills and troubleshooting skills led to him quickly rising, finally working directly for Edison in New Jersey as a junior technician.

Armed with practical experience, he found several jobs before winding up as a professor at Purdue. There his work came to the attention of George Westinghouse who personally recruited him to be the chair of the electrical engineering department at the Western University of Pennsylvania in Pittsburgh (now the University of Pittsburgh).

Radio Active

About this time, Marconi was in the news for developing a practical wireless transmission system using spark gaps and coherers to send Morse code. Fessenden started experimenting and realized he could do better. By 1899 he had sent messages between Pittsburgh and Allegheny City, using a receiver he designed.

In a talk in 1899, Fessenden showed three different detectors he had been working on. They were sensitive and able to produce a measure of signal strength. He also understood resonance from experiments he’d conducted earlier with multiplex telegraph systems that use various frequencies. This all sounds ordinary today, but remember, Marconi’s system operated at about 8 Hz and the sparks were throwing lots of harmonics and decaying down to zero on each pulse.

Working for the United States Weather Bureau, Fessenden would invent the barretter detector that demodulated radio waves using a hot platinum wire prepared with acid. He followed this up with the popular (at the time) electrolytic detector that used the same kind of wire, but kept it in the acid during operation.

So What?

More sensitive detectors were crucial in making radio more useful. In addition, these detectors could detect amplitude not just on and off like a coherer. Not only did this enable the scientific measurements Fessenden wanted, it also enabled AM radio. By using a carbon microphone in the transmission line, Fessenden was able to successfully transmit voice on Cobb Island in the Potomac River near Washington DC. The distance was only about a mile and the audio quality was not suitable for practical use, but it is considered the first transmission of speech. The message was reportedly: “One, two, three, four. Is it snowing where you are Mr. Thiessen? If it is, telegraph back and let me know.”

Continuous Wave

Fessenden kept experimenting with alternators that would go as high as 50 Hz, but with no amplification, it was difficult to get good results. There were reports that some of the audio tests were even accidentally heard in the Scottish sister station set up by Fessenden’s new company. By 1906 he patented a system for measuring the distance to icebergs using radio waves — similar to modern radar. It was also used during wartime to detect submarines.

That’s Entertainment

Christmas Eve of 1906, Fessenden’s station at Brant Rock, Massachusetts sent CQ using Morse code. Then, he used a microphone to announce the show followed by a gramophone playing Handel’s Largo. He also personally played the violin, rendering O Holy Night. Then he wished his listeners a merry Christmas. Some others were to speak, but they suffered what could be the first case of mic fright, or so it is reported. That was the first entertainment broadcast known to occur. Between connecting radio and telephone, and using broadcasts for entertainment, you can conclude that our inventor had a pretty good crystal ball. He certainly had a big antenna, as you can see.

You can hear a reproduction of the original Christmas program in this video:

Personal

While Fessenden built much of the foundation for radiotelephony, he didn’t have a lot of financial success. The company that sponsored most of his work dismissed him in 1911, leading to a protracted court battle.  The company was eventually sold to RCA who settled the case. He continued to work, but not on the radio. He wound up with over 500 patents. He also became eccentric, causing Radio News, a magazine, to eventually stop carrying his serialized autobiography.

His burial vault bears the words: By his genius, distant lands converse and men sail unafraid upon the deep.

A great sentiment. A shame so few remember him. On the other hand, he did get his own ballad.

Full article: https://hackaday.com/2018/02/19/you-all-know-reginald-fessenden-who/

Posted in Hackaday.

HAB School Kit Builds

We have started our HAB-3 program and we are working with 4 schools who will be part of the launch.  Two of the schools, Bishop Guertin High School and Merrimack High School have been through the preparation sessions before.  To expand their involvement with STEM activities, the Nashua Area Radio Society has hosted kits builds at both schools.

Fred, AB1OC Elmers the BGHS Kit BuildersFred, AB1OC Elmers the BGHS Kit Builders

The first kit build was held earlier this month with 6 students from Bishop Guertin High School.  They built the 40 meter Pixie Kit QRP radio, the same one the NARS built a year or so ago.

Tech Night Suggestions
Pixie Kit

The students did a great job once they learned to solder and enjoyed the kit build.

Bishop Guertin Students Build the Pixie Kit
Bishop Guertin Students Build the Pixie Kit

The students are also learning morse code and there will be a morse competition in future sessions at both schools, using the Pixie kits built by the students.

Merrimack High School Students build the Pixie kit
Merrimack High School Students build the Pixie kit

Last Friday,  5 club members were Elmers to 18 students at Merrimack High School, who also built the PIXIE kit.  Thanks to Bill, AB1AV, Niece, KA1ULN, Mike, K1WVO, Jamey, AC1DC , Tom, AB1NS, and Fred, AB1OC for helping the kids to have a successful kit build.

Merrimack High School Students Building the Pixie Kit
Merrimack High School Students Building the Pixie Kit

All of the teachers and students had a great time and learned a lot during the kit build.  They are looking forward to the morse code competition.

Anita, AB1QB