Swarm-E (formerly known as e-POP)

In the spirit of making data from the Radio Receiver Instrument (RRI) onboard Swarm-E (formally known as e-POP) more accessible to the ham radio community, we have converted RRI's data into a ".raw" format so that it can be ingested into open source software such as Gqrx or GNU Radio.  We have done this for all RRI data related to the 2015, 2017, and 2018 ARRL Field Days.

We encourage everyone to help us identify hams in RRI's signal.  You can use the Gqrx tool discussed here, or you can use your own technique.  If you decode a ham's call sign, if you would like to share your technique, or if you have any comments or suggestion contact us and let us know! 

To help organize your findings, you can download a spreadhseet containing that you can fill out and send to us.  Feel free to create your own spreadsheet or modify this one.  

Swarm-E (e-POP) RRI

Swarm-E RRI is a digital radio receiver with 4 3-m monopole antennas.  In most cases, the monopoles are electronically configured into a crossed-diople configuration.  In this configuration, RRI records I/Q samples for the two dipoles.  RRI has a sampling rate of 62500.33933 Hz, and a ~40 kHz bandpass, and can be tuned to anywhere between 10 Hz and 18 MHz.  More information on Swarm-E RRI can be found in the Swarm-E RRI instrument paper or Gareth Perry's recent Radio Science article.


  • Perry, G. W., Frissell, N. A., Miller, E. S., Moses, M., Shovkoplyas, A., Howarth, A. D., & Yau, A. W. (2018). Citizen radio science: An analysis of amateur radio transmissions with e-POP RRI. Radio Science, 53, 933– 947, https://doi.org/10.1029/2017RS006496.

Data Format

Each data file contains raw 32 bit complex I/Q samples for a given RRI dipole at a given frequency.  The samples are interleaved, e.g., IQIQIQIQ... The data files do not contain any metadata.  Any information regarding the time, frequency, and corresponding RRI dipole is in the file name.  

Filename Format

The filename format gives information about the time and data of the recording, the tuned frequency, and which of RRI's dipoles the recording corresponds too.  For example, gqrx_20150628_011614_3525000_62500_RRI_Dipole1 contains data recorded on Dipole 1, starting at 01:16:14 UT on June 28, 2015, at 3525000 Hz (3.525 MHz), at a sampling rate of 62500 Hz (RRI's 62500.33933 Hz sampling rate).


We have opted to convert the data into the .raw format so that it can be ingested into Gqrx.  There are other ways of analyzing RRI's data; this is just one way which we felt was as easy first step.  We are open to posting about other techniques on the HamSCI site as well.  To help get started with Gqrx, we have developed a How to play an RRI raw IQ file on Gqrx page.

Data Files

The data files may be downloaded directly from the Zenodo repository here


We are looking for presenters for the March 22-23, 2024 HamSCI workshop at Case Western Reserve University in Cleveland, Ohio! The workshop will focus on the theme of Alignments - between the Sun, Moon and Earth; between collegiate amateur radio recreation and STEM curriculum; between data collection and analysis; between professional and citizen science. We are preparing for the solar eclipse of 8 April 2024, for which Cleveland will be in totality. If you would like to present, please visit https://hamsci.org/hamsci2024 to submit an abstract. Abstracts are due by February 10, 2024. Presenters will be notified by March 1, 2024.

By Jonathan Rizzo, KC3EEY

SAQ (callsign SAQ) is a VLF transmitting station located in Grimeton, Sweden and is a UNESCO World Heritage Site operated by the Alexanderson Association. The heart of the transmitter is the Alexanderson Alternator and six antenna towers that are iconic to the site. Twice a year, there is a CW transmission at 17.2 kHz with an inspirational message to listeners all over the world. On Alexanderson Day, July 2nd, 2023, SAQ is scheduled to be on the air. More details can be found here (https://alexander.n.se/en/alexanderson-day-2023/) and contains a tentative schedule and a YouTube live broadcast for those who would like to watch the event live.

Dr. Kristina Collins, KD8OXT, is the lead author on a new paper published in the peer-reviewed journal Earth System Science Data entitled Crowdsourced Doppler measurements of time standard stations demonstrating ionospheric variability. The Grape Personal Space Weather Station is a low-cost, high frequency (HF) receiver designed to make precision measurements of signals received from frequency standards stations such as WWV, WWVH, and CHU. Because these standards stations transmit carriers with atomic-clock grade frequency stability, and the Grape receiver achieves similar frequency stability through the use of a GNSS Disciplined Oscillator, variations in the received signal can be attributed to changes in the ionosphere. The new paper demonstrates this in multiple ways, including showing changes in Doppler frequency due to the dawn and dusk terminators, seasonal variations, wave signatures with Medium Scale Traveling Ionospheric Disturbance periods, and the ionospheric response to solar flares. The paper also explains how to access Grape data and the open-source software used to conduct the analysis. The co-author team consists of professionals, students, and HamSCI volunteers, including Kristina Collins KD8OXT, John Gibbons N8OBJ, Nathaniel Frissell W2NAF, Aidan Montare KB3UMD, David Kazdan AD8Y, Darren Kalmbach KC0ZIE, David Swartz W0DAS, Robert Benedict KD8CGH, Veronica Romanek KD2UHN, Rachel Boedicker AC8XY, William Liles NQ6Z, William Engelke AB4EJ, David G. McGaw N1HAC, James Farmer K4BSE, Gary Mikitin AF8A, Joseph Hobart W7LUX, George Kavanagh KB1HFT, and Shibaji Chakraborty KN4BMT. The Grape receivers are the focus of an NSF-funded experiment to study the upcoming 2023 annular and 2024 total solar eclipses. More information on building your own Grape receiver is available at hamsci.org/grape.