Job's latest work has seen him detect Pulsar B0329+54 with his 1.9m dish and an RTL-SDR. He writes:
A pulsar is the rapidly spinning and pulsating remnant of an exploded star.
PSR B0329+54 is a pulsar approximately 3,460 light-years away in the constellation of Camelopardalis. It completes one rotation every 0.71452 seconds and is approximately 5 million years old
Everything indicates that I may have been able to detect the pulsar B0329+54 with JRT [Job's Radio Telescope]. This dish has a diameter of 1.9 meters, which would make it the first time (!) this pulsar has been detected with a dish of this size as far as I can tell. This result was obtained thanks to the good help and software of Michiel Klaassen.
A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish or directional antenna and a software defined radio. In the past we've posted a few times about Pulsars, and how the HawkRAO amateur radio telescope run by Steve Olney in Australia has observed Pulsar "Glitches" with his RTL-SDR based radio telescope.
Over in Canada, Marcus Leech has also set up a Pulsar radio telescope at the Canadian Centre for Experimental Radio Astronomy (CCERA). Marcus has been featured several times on this blog for his various amateur radio experiments involving SDRs like the RTL-SDR. In one of his latest memos Marcus documents his Pulsar observing capabilities at CCERA (pdf). His memo describes what Pulsars are and how observations are performed, explaining important concepts for observation like de-dispersion and epoch folding.
The rest of the memo shows the antenna dish and feed, the SDR hardware which is a USRP B210 SDR, the reference clock which is a laboratory 0.01PPB rubidium atomic clock and the GNU Radio software created called "stupid_simple_pulsar". The software DSP process is then explained in greater detail. If you're thinking about getting involved in more advanced amateur radio astronomy this document is a good starting point.
Back in May 2019 we posted about Steve Olney's HawkRAO amateur radio astronomy station which was the only station in the world to capture the 2019 Vela Pulsar "glitch" which he did so using his RTL-SDR as the radio. The astronomy focused podcast "Astrophiz" recently interviewed Steve in episode 95 where he talks about his amateur radio background, his home made radio telescope, his RTL-SDR and software processing setup, and the Vela glitch.
A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish or directional antenna and a radio, like the RTL-SDR. The Vela pulsar is the strongest one in our sky, making it one of the easiest for amateur radio astronomers to receive.
Pulsars are known to have very accurate rotational periods which can be measured by the radio pulse period. However, every now and then some pulsars can "glitch", resulting in the rotational period suddenly decreasing. Glitches can't be predicted, but Vela is one of the most commonly observed glitching pulsars.
The HawkRAO amateur radio telescope run by Steve Olney is based in NSW, Australia and consists of a 2 x 2 array of 42-element cross Yagi antennas. The antennas feed into three LNAs and then an RTL-SDR radio receiver.
Astrophiz 95: Steve Olney: From Ham Radio to Radio Astronomy - "The 2019 Vela Glitch"
Feature Interview: This amazing interview features Steve Olney who has established the Hawkesbury Radio Astronomy Observatory in his backyard. Steve has constructed a Yagi antenna array, coupled it with a receiver and observed a pulsar 900 LY away and generated data that has enabled him to be the only person on the planet to observe Vela’s 2019 glitch in radio waves as it happened.
If you're interested in learning more about Vela, Astrophiz podcast episode 93 with Dr. Jim Palfreyman discusses more about the previous 2016 Vela glitch and why it's important from a scientific point of view.
Pulsars are known to have very accurate rotational periods which can be measured by the radio pulse period. However, every now and then some pulsars can "glitch", resulting in the rotational period suddenly increasing. Glitches can't be predicted, but Vela is one of the most commonly observed glitching pulsars.
The HawkRAO amateur radio telescope run by Steve Olney is based in NSW, Australia and consists of a 2 x 2 array of 42-element cross Yagi antennas. The antennas feed into three LNAs and then an RTL-SDR radio receiver. He has been observing the Vela pulsar for 20 months.
His observations indicate that Vela glitched and spun up by 2.5PPM at 14:09 UTC on Feb 1, 2019. He claims that this glitch detection is a first for amateur radio astronomy as far as he is aware.
If you're interested in Pulsar detection, check out a few of our previous posts on the topic.
A corner reflector antenna is basically a monopole antenna with a metallic 'corner' reflector placed behind it. The reflector helps the monopole collect signals over a wider aperture resulting in signals coming in stronger from the direction that the corner is pointing at. In past posts we've seen a homemade tinfoil corner reflector used to improve reception of the generic stock RTL-SDR monopole antenna, and a larger one was used in a radio astronomy experiment to detect a pulsar with an RTL-SDR.
Recently The Thought Emporium YouTube channel has uploaded a video showing how to build a large 2 meter 3D corner reflector out of readily available metal conduit pipes and chicken wire. While the antenna has not been tested yet, they hope to be able to use it to receive weather satellite images from GOES-16, to receive moon bounce signals, to map the Hydrogen line and to detect pulsars.
Building a Giant 2m Corner Reflector Antenna For Less than $200 (For Goes-16, Pulsars and More!)
Steve Olney VK2XV is the creator and administrator of the Neutron Star Group website which collects a listing of confirmed amateur attempts at pulsar detection, many of which have been made with a humble RTL-SDR dongle. A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR.
Now after more than four years of trying, Steve has finally been able make his own confirmed pulsar detection by using a 42-elment circularly polarized Yagi antenna tuned for 436 MHz and an RTL-SDR. Typically a large dish antenna is used to receive a pulsar, but Steve has instead used a fixed position circularly polarized Yagi antenna, which he writes has an equivalent aperture to a 2.8 meter diameter dish. His antenna can point directly upwards as his target is the Vela pulsar which happens to pass almost directly overhead at his location.
Detection of a pulsar involves determining its rotational period from the regular wideband noise pulses that they produce. Pulsar detections with large aperture dish antennas can easily be confirmed due to high SNR, but smaller weaker detectors require some use of some mathematical techniques to confirm a positive detection. This is especially important as it’s possible for terrestrial signals to mimic a pulsar.
In order to detect and confirm the pulsar detection from a weak signal, Steve uses a technique called epoch folding, which makes use of the fact that the period of pulsar pulses are extremely regular. To verify the results he also makes use of techniques such as folding at the predicted period, de-dispersion and plotting daily results against the predicted results. These techniques are explained in more depth in his results post.
Earlier in April we posted about Hannes Fasching (OE5JFL)’s work in detecting pulsars with an RTL-SDR. Thanks to Steve Olney (VK2XV), administrator of the Neutron Star Group for pointing out that there are actually several amateur radio astronomers who are using RTL-SDR dongles for pulsar detection.
A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR. Pulsars create weakly detectable noise bursts across a wide frequency range. They create these noise bursts at precise intervals (milliseconds to seconds depending on the pulsar), so they can be detected from within the natural noise by performing some mathematical analysis on the data. Typically a few hours of data needs to be received to be able to analyze it, with more time needed for smaller dishes.
One problem is that pulsar signals can suffer from ‘dispersion’ due to many light years of travel through the interstellar medium. This simply means that higher frequencies of the noise burst tend to arrive before the lower frequencies. Mathematical de-dispersion techniques can be used to eliminate this problem enabling one to take advantage of wideband receivers like the RTL-SDR and other SDRs. The more bandwidth collected and de-dispersed, the smaller the dish required for detection.
Over on the Neutron Star Group several amateur pulsar detection projects are listed, and entries denoted with the “^” symbol make use of the RTL-SDR. Below we show a brief overview of those projects:
Andrea Dell’Immagine (IW5BHY)– Based in Italy Andrea often uses a 3D corner reflector antenna which is equivalent to a 2.5 meter diameter dish to observe pulsars in the 70cm band (~420 MHz). The antenna is in a fixed position so he can only detect pulsars that drift into the beam width of the antenna. With this antenna, a 0.3dB NF LNA, an RTL-SDR and de-dispersion techniques he’s been able to detect the Pulsar B0329+54 which is 2,643 light years away with an integration time of about 3 hours.
Hannes Fasching (OE5JFL) – Based in Austria Hannes has a 7.3M dish that he uses for pulsar detection with his RTL-SDR. With this large dish he’s been able to receive 22 pulsars at both 70cm (424 MHz), and 23cm (1294 MHz) frequencies. With such a large dish, detecting a strong pulsar like B0329+54 only needs less than a minute of integration time.
Mario Natali (I0NAA) – Based in Italy Mario uses a 5M dish to observer pulsars at both 409 MHz and 1297 MHz. Combined with a low noise figure LNA and his RTL-SDR he’s been able to receive the B0329+54 pulsar with an integration time of about 2 – 2.5 hours.
Michiel Klaassen – From the Dwingeloo Radio Observatory in the Netherlands Michiel has used their large 25M dish and an RTL-SDR to detect B0329+54 at 419 MHz.
Peter East & Guillermo Gancio–Peter and Guillermo have used the large 30M dish at El Instituto Argentino de Radioastronomía (IAR) in Argentina and an RTL-SDR to detect the Vela pulsar (B0833-45) at 1420 MHz.
In terms of hardware required, from the above projects we see that you’ll need an RTL-SDR dongle (other more costly SDR’s could also be used), a dish as large as you can get (along with some sort of dish pointing system), a low noise figure amplifier (0.5dB or less is desired) to be placed right by the dish, a few line amps if the cable run is long and perhaps a filter if you are seeing interference from terrestrial signals.
An overview of software for detecting pulsars with the RTL-SDR can be found over on the Neutron Star Groups software page. Essentially what you need is an analysis program which can work on the raw IQ data that is collected by the RTL-SDR and dish antenna. This software ‘folds’ the data, looking for the regular noise bursts from the pulsars. The output is data that can be used to create a graph indicating the spin period of the pulsar, and thus confirming the detection.
Back in September 2015 we made a posted that discussed how some amateur radio astronomers have been using RTL-SDR’s for detecting pulsars. A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR.
In their work they showed how they were able to detect and measure the rotational period of the Vela pulsar, one of the strongest and easiest to receive pulsars. They also noted how using several RTL-SDR dongles could reduce the required satellite dish size.
Antenna: 7.3m homemade offset dish, OE5JFL tracking system Feeds: 70cm (424 MHz) dual-dipole with solid reflector, 23cm (1294 MHz) RA3AQ horn Preamplifiers: 23cm cavity MGF4919, 70cm 2SK571 (30 years old!) Line Amplifier: PGA103+ Interdigital filter: designed with VK3UM software, 70cm 4-pole, 23cm 3-pole Receiver: RTL-SDR (error <1ppm), 2 MHz bandwidth Software: IW5BHY, Presto, Tempo, Murmur
Furthermore, from looking at the Neutron Star Group website, it seems that the majority of amateur radio astronomers interested in pulsar detection are currently using RTL-SDR dongles as the receiver. Some of them have access to very large 25m dishes, but some like IW5BHY, IK5VLS and I0NAA use smaller 2.5m – 5m dishes which can fit into a backyard.
If you are interested in getting into amateur pulsar detection, check out the Neutron Star Group website as they have several resources available for learning.