When one mulls the possibility of detecting pulsars, to the degree that one does, thoughts turn to large dish antennas and rack upon rack of sensitive receivers, filters, and digital signal processors. But there’s more than one way to catch the regular radio bursts from these celestial beacons, and if you know what you’re doing, a small satellite dish and an RTL-SDR dongle will suffice.
Granted, [Job Geheniau] has had a lot of experience exploring the radio universe. His website has a long list of observations and accomplishments achieved using his “JRT”, or “Job’s Radio Telescope.” The instrument looks like a homebrewer’s dream, with a 1.9-m satellite TV dish and precision azimuth-elevation rotator. Behind the feedhorn are a pair of low-noise amplifiers and bandpass filters to massage the 1,420 MHz signal that’s commonly used for radio astronomy, plus a Nooelec Smart SDR dongle and an Airspy Mini. Everything is run via remote control, as the interference is much lower with the antenna situated at his family’s farm, 50 km distant from his home in The Hague.
As for the pulsar, bloodlessly named PSR B0329+54, it’s a 5-million-year-old neutron star located in the constellation of Camelopardalis, about 3,500 light-years away. It’s a well-characterized pulsar and pulses at a regular 0.71452 seconds, but it’s generally observed with much, much larger antennas. [Job]’s write-up of the observation contains a lot of detail on the methods and software he used, and while the data is far from clear to the casual observer, it sure seems like he bagged it.
We’ve seen quite a few DIY radio astronomy projects before, both large and small, but this one really impresses with what it accomplished.
[via RTL-SDR.com]
“the data is far from clear to the casual observer”. No kidding!
The link doesnt seem to work..
I guess you need the patience of Job.
B^)
This is very cool! Just curious: is there any Actual Science these backyard dishes could contribute to, the way amateur scopes do? Or are they purely for fun/because-I-can projects?
I’m kind of wondering about the bits of screen added along the edges of the dish … extension panels maybe? I don’t see how they could be placed accurately enough to help. At 1.42GHz, the wavelength is about 20cm, and these have to randomly move back and forth at least a few cm whenever the wind blows or the antenna tilts… so ….
The bits of screening are to block the LNB’s view of the ground.
The ground is warm and therefore radiates at microwave frequencies. The LNB “sees” over the edge of the dish and picks up extra noise from the ground.
The pieces of screening block that view of the ground, reducing the received noise a little bit.
Wire doesn’t radiate that well. It also has a smaller surface area. The wire grid blocks radiation with a wavelength longer than four times the grid width. The combination reduces the noise that the LNB picks up.
I don’t know how much difference it makes. I have a similar setup. I’ll have to measure it and see sometime.
Depends on the feed geometry and how it’s matched to the dish. Obviously, if the feed doesn’t illuminate the dish entirely you don’t need a ground screen. But the ground’s waay hotter than the sky once you get even into UHF (basically anything past 250 MHz or so, once the galactic noise falls away), so even a little spill kills you.
Building a radio telescope with a system noise temp under 100K isn’t terribly difficult, so spilling bits of 300K can have a very big effect.
Awesome work, Job!!!
I so wish I was intelligent enough to understand how to interpret the signals from this system. I have to use my RTL-SDRs for things I do understand, aircraft ADS-B transmissions!
Ok, author, seriously “Bloodlessly named”? Did you get a thesaurus or your birthday or something? Talk about ‘imma use big word, sound smart on nerd site’ vibes, man… Sorry not every star can have a cool name. Most of them are just whatever catalog number they got for whatever survey they were discovered or classified in. How about we just call it “Writer douchebag star”? When writers do that crap it really undermines the legitimacy of their works. Leave your word a day calendar words and opinions about the WELL KNOWN systems for star ‘names’ (more accurately catalog numbers, not names) out of your journalism. Though calling what this site has become ‘journalism’ is a bit of a stretch….like calling most the regurgitant on this site ‘hacks’….
This used to be a good site…..and then the nerdchic hipsters took over. Can yall move on to the next pop culture thing already and let us tinkerers get back to the real hackery?