Last Update: June 6, 2025

Polarization and another example of detectable transients was added to the FAQ

The Wow@Home Radio Telescope

This page presents a test of our first Wow@Home Radio Telescope hardware and software configuration (Figure 1). The system is tested for a network of small radio telescopes designed to emulate, as closely as possible, the observation protocol of the meridian radio telescope Big Ear used by the Ohio SETI project in the 1970s. As in the original setup, we use a 10 kHz channel width and a 12-second integration time. However, our initial test system differs in several ways: it has a better frequency and time resolution, and larger sky coverage, but significantly lower sensitivity.

The telescope is fixed at a constant elevation, pointed south, and scans a specific celestial declination over the course of one or more days using a wide field of view of approximately 25° (HPBW or its beamwidth). As the Earth rotates, this configuration allows the telescope to capture a continuous 360° strip of the sky at that declination. After completing three or more full-sky passes, the telescope is adjusted to a new elevation to begin scanning a different declination, gradually building up full-sky coverage over time.

While optimized for educational use, this configuration also yields valuable data on RFI near the H I line in urban environments, helping us assess the likelihood of RFI mimicking a Wow!-like signal. Additionally, it serves as a practical platform for a wide-field search for strong transient events, whether of astrophysical origin or potential technosignatures.

For events that persist longer than a day, multiple observing passes can be used to validate their presence, detect weaker features, improve overall sensitivity, and help distinguish them from RFI. Additionally, simultaneous observations by two or more telescopes pointed at the same location can further aid in rejecting local interference and confirming the reality of signals that last less than 24 hours.

The Wow@Home Radio Telescope operates autonomously, 24/7, as a meridian-style instrument, conducting a continuous all-sky survey for transient events. The hardware required to build these telescopes is both inexpensive and widely accessible, relying on readily available components. The critical element lies in the software, which must be capable of analyzing data effectively, whether from a single station or across a coordinated network of telescopes.

Future expansions could include the integration of multibeam systems to enable simultaneous ON–OFF observations to improve sensitivity, tracking capability to perform targeted observations of specific sources, multi-site detection for signal validation, higher sensitivity, and RFI discrimination, interferometric capabilities for improved angular resolution, and phased array configurations to enhance sensitivity and enable electronic beam steering.

Figure 1: Components of our first Wow@Home Radio Telescope. The Easy Radio Astronomy (ezRA) software is an excellent starter package for getting this configuration up and running for radio astronomy. We plan to test additional configurations in the coming months, including the Discovery Dish, which integrates the frontend into the antenna, and the Airspy Mini as the backend, offering a 12-bit ADC for improved dynamic range.

The Wow@Home Software

The Wow@Home Software is the core of our project. It serves as the data acquisition and analysis platform designed to search for transient events caused by astrophysical phenomena, potential technosignatures, and RFI characterization, using data from any small radio telescope. The software is built on the analysis methods we are developing to detect Wow-like signals in the archive data of professional observatories, as part of our Arecibo Wow! Project. We are currently developing the software in IDL, with example outputs shown in Figures 2, 3, and 4. It will later be translated to Python to ensure cross-platform compatibility and broader accessibility.

Figure 4: In addition to the modern analysis tools available with today’s radio telescopes, we also aim to incorporate into our software the ability to generate a live preview of the data in the style of the original Ohio State SETI project printouts. This feature is intended to provide historical context and connect current efforts to the legacy of early SETI research. Above is an example using the original Wow! Signal data.

Frequently Asked Questions (FAQ)

What’s the main motivation behind the Wow@Home project?

The Wow@Home project is inspired by our ongoing research into the Wow! Signal. We are exploring the possibility that it may have a rare astrophysical origin. While we continue examining archived data from the Arecibo and Big Ear telescopes, Wow@Home allows us to actively search for similar signals and other rare cosmic events, including potential technosignatures, in real time.

To do this effectively, we need a network of small radio telescopes operating 24/7. Large professional telescopes are too few and too busy to continuously monitor the sky for transient signals. This project fills that gap. While small telescopes are only sensitive to strong signals, those are exactly the kind of signals that can make us say, “Wow!”

Is this an interferometer array?

No, the Wow@Home network is not currently an interferometer. While it is technically feasible to turn the array into an interferometer to improve spatial resolution, this isn’t necessary for our main goal: detecting transient astrophysical events. These require broad sky coverage over long periods, not pinpoint resolution.

Adding interferometry would significantly increase system complexity. It demands precise time synchronization, high-bandwidth data transfer, and powerful processing infrastructure, which would raise both technical barriers and costs. Our priority is scalability and continuous monitoring, which small, independent telescopes can achieve efficiently.

Can we measure polarization?

No. While polarization measurements (e.g., full Stokes parameters) would be valuable, incorporating them would increase the system’s cost and complexity. The telescopes are designed to detect transient signals and provide the first alert, enabling larger observatories to follow up and characterize key properties such as polarization, dispersion, source location, and distance.

How much does a Wow@Home radio telescope cost?

A complete setup costs around $500, including a dedicated computer, but we are not selling these systems. Instead, we will provide recommendations for the necessary parts and offer free software to power the telescope and connect it to the Wow@Home network to search for transient events. There are also lower-cost options available, and many online resources can guide you through building your radio telescope.

Some great starting points are the Society of Amateur Radio Astronomers (SARA), the RTL-SDR (Software Defined Radio community), and the Easy Radio Astronomy (ezRA) software, which is excellent for beginners and educational use, especially for studying galactic hydrogen emissions.

How do these telescopes operate?

These are meridian or transit radio telescopes, designed to survey the sky at a fixed declination and do not move. They don’t track specific celestial objects, instead, they rely on Earth’s rotation to scan a full 360° strip of the sky at that declination every day. They operate continuously, day and night, regardless of weather, because they observe near the hydrogen line frequency (in the so-called “water hole”), a part of the radio spectrum that passes through clouds and atmospheric interference.

Installation is similar to setting up a satellite TV dish: once pointed correctly, they only require power and internet to run. Each telescope can be monitored via Wi-Fi from any computer. Once a day, the telescope uploads its data to the Wow@Home network, where it joins observations from other telescopes in the system.

What makes this project unique?

It's a scalable network of small, low-cost radio telescopes working collaboratively to continuously monitor a wide region of the sky for transient radio events. By combining observations from multiple stations, the network significantly improves both sensitivity and rejection of RFI.

The project’s distributed design also spreads out the computing, hardware, and operational costs, making it a highly cost-effective solution for sustained sky coverage and signal verification. This collaborative approach brings capabilities once limited to large observatories within reach of a broader scientific community.

Can small radio telescopes detect interesting signals from space?

Absolutely! For example, in November 2020, a powerful Fast Radio Burst (FRB) originating from the Galactic magnetar SGR 1935+2154 was independently detected by two instruments: the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Survey for Transient Astronomical Radio Emission 2 (STARE2). These professional telescopes happened to be observing the right region of the sky at just the right time. The burst was so strong that it would have been easily detectable by a small radio telescope in the Wow@Home network.

In May 2025, a new class of long-period radio transients (LPTs) was announced, characterized by emissions lasting thousands of times longer than those of typical radio pulsars. These emissions were also just above the detection threshold in the radio spectrum for our network of small telescopes.

In fact, it’s entirely plausible that a historical event like the Wow! Signal could have also been captured by a similar distributed system. This highlights a critical limitation in traditional radio astronomy: we are likely missing many compelling signals simply because telescopes aren’t watching every part of the sky simultaneously.

What radio frequency range will we observe?

The telescopes will observe from 1419 to 1421 MHz, centered on the hydrogen line at 1420.4 MHz. This frequency range is of particular interest to both radio astronomy and the search for extraterrestrial intelligence (SETI). The 1420 MHz hydrogen line is a natural spectral feature emitted by neutral hydrogen, the most abundant element in the universe. Because it is both astrophysically significant and relatively quiet in terms of human-made interference (due to international protection), it has long been considered a prime frequency for SETI searches as well.

However, many electrical devices can still emit unintentional interference in this frequency band. Such signals are typically broadband and can be distinguished from the narrowband signals, but the Wow@Home project is interested in both types of signals.

What type of signals are we searching for?

We are searching for broadband and narrowband signals lasting from seconds to days. Broadband signals are typically associated with astrophysical events, such as flares, bursts from stars, magnetars, or other extreme cosmic phenomena. These signals span a wide range of frequencies and are often linked to energetic, natural processes.

Narrowband signals, on the other hand, are highly concentrated in frequency and are less likely to occur naturally near the hydrogen line. These are the types of signals often associated with the possibility of extraterrestrial communications, such as the Wow! Signal. However, it’s important to note that astrophysical explanations for transient narrowband signals are also possible and under active investigation.

Can these telescopes detect signals from extraterrestrial civilizations?

We don't know. We know that a planet with technological civilizations capable of transmitting radio signals into space can exist in the universe, and Earth is the proof of that. The search for other intelligent civilizations is therefore a search for just a second example, and in science, we often find that nature tends to repeat itself. That said, the immense scale of space and time makes it difficult for two technological civilizations to overlap and detect each other, at least with current technology. Still, it is a question worth pursuing.

In any case, the Wow@Home network would only be capable of detecting the strongest signals, especially those intentionally directed at Earth, such as from powerful masers or radio beacons. However, it’s also possible that advanced civilizations avoid actively targeting others out of caution or ethics, after all, they might also consider it rude to point a "laser" at others.

What else can be studied with these radio telescopes?

In addition to detecting neutral hydrogen, small radio telescopes operating near the 21 cm line can be used to study a variety of astrophysical phenomena. For example, they can be used to measure the Galactic hydrogen column density, analyze Doppler shifts to determine gas velocities, and investigate the large-scale structure of the Milky Way. These instruments can also monitor solar radio activity and estimate the radio brightness temperature of the Moon, which also serves as a useful calibration source.

For a solid technical foundation in radio astronomy, a highly recommended reference is Essential Radio Astronomy by James J. Condon and Scott M. Ransom, which is available online.

How many telescopes are needed to cover the entire sky?

At least 114 are required for basic full-sky coverage. However, to enable effective RFI rejection and improved sensitivity, each region must be observed by at least three telescopes. This raises the requirement to approximately 342 telescopes, distributed globally. Assuming a very conservative estimate of 100,000 amateur astronomers worldwide, if just 1% contributed a telescope, this goal could be easily surpassed. Even more remarkable is that deploying all 342 telescopes would cost less than $200,000, excluding power and internet requirements. In contrast, professional astronomical facilities typically cost millions of dollars.

What’s the plan?

Right now, we’re focused on developing the software and testing various hardware configurations. Our goal is to identify the simplest and most effective setup for fully autonomous operation. We aim to release our first hardware recommendations and the initial version of the software by August 15, 2025, in celebration of the 48th anniversary of the Wow! Signal. To mark this milestone, we’re also planning our first local star party, combining both optical and radio telescopes, on August 23, 2025.

How can I help?

We welcome help, especially from those with experience in RFI shielding, software GUI, and App development. Your expertise could make a big difference as we refine both the hardware and user interface. While we’re actively pursuing funding to support the project long term, any assistance now would accelerate our progress and broaden the impact of Wow@Home. Whether it’s technical support, outreach, or collaboration, your contribution matters.

For more information, contact abel.mendez@upr.edu.