Hack Chat Transcript, Part 1

A event log for DIY Radio Telescopes Hack Chat

Listening to the music of the spheres

LutetiumLutetium 02/12/2020 at 21:050 Comments

de∫hipu11:21 AM
video telescopes are going to kill the radio telescopes

0xCoto11:21 AM
Great! Looking forward. I've also built my own free-to-use open source radio telescope for anyone wishing to observe the radio sky for free without building their own instruments: &

morgan11:29 AM

Joseph Eoff joined  the room.11:35 AM

Joseph Eoff11:37 AM
@0xCoto: That's three now that I've gotten to see. Yours, the one Dr. Aguirre built, and mine.

0xCoto11:37 AM
Awesome, got a link to yours?

Joseph Eoff11:38 AM
Blog posts:

Ethan Waldo11:38 AM
Anybody have any open source plans for a 70m?

0xCoto11:39 AM

Joseph Eoff11:39 AM

Ethan Waldo11:39 AM
You know, like

Joseph Eoff11:39 AM
Software: and

0xCoto11:40 AM
@Ethan Waldo Well I don't have a 70-meter antenna, so...

0xCoto11:40 AM
I also wrote my own software for my radio telescope:

Joseph Eoff11:40 AM
Very few folks have the space for a 70m dish. That's bigger than my house.

Ethan Waldo11:41 AM
My attempts at humor have failed....

Joseph Eoff11:43 AM
@0xCoto: In just the three examples I've seen, there's three different set of hardware. You are working with an SDR and doing frequency analysis. Dr. Aguirre used a commercial RF level detector, and I built my own level detector.

Ethan Waldo11:44 AM
Do you guys do any time coding?

0xCoto11:45 AM
@Joseph Eoff No reason to stick to a radiometer when you can derive the same data and more with a spectrometer. :)

Canadian Centre for Experimental Radio Astronomy joined  the room.11:47 AM

0xCoto11:47 AM
Hey Marcus!

Joseph Eoff11:47 AM
I just find the differences in the concepts between the three rigs fascinating.

Canadian Centre for Experimental Radio Astronomy11:47 AM

Dan Twedt11:48 AM
I just posted in the FB permaculture group about this chat. Anyone here from there?--73 de KK6VDR

Canadian Centre for Experimental Radio Astronomy11:49 AM
We have several DIY radio telescopes. And a technical memo Series about some of them and the techniques we are using.

Canadian Centre for Experimental Radio Astronomy11:50 AM
I wrote one of the first DIY radio telescope articles using RTLSDR several years ago now. On our website.

Canadian Centre for Experimental Radio Astronomy11:50 AM
Radio astronomy at the backyard level is unlike optical. You can’t go to a Walmart and buy a radio telescope.

Steve Bossert (K2GOG)11:51 AM
i hope this hack chat motivates me to get back into radio astronomy. last I experimented with was in August last year. Made a manual picture of the sun on a very overcast day.

jordanbrandes11:51 AM
Now that things like Direct TV dishes are in short supply what alternatives are you guys using?

Gonçalo Nespral11:51 AM
Hey! I also build a small scale radio telescope a couple of years ago, and its on my hackaday page if anyone wants to check it out. I also started building a larger one, able to observe the Hydrogen line, but it got expensive rlly fast haha :( .... I actually got some help from @0xCoto (thanks!)

Canadian Centre for Experimental Radio Astronomy11:52 AM
You can still buy dishes online. 1.5m offset are routinely available on eBay.

Dan Twedt11:52 AM
I wonder if anyone has ever combined a tracking telescope with solar energy collection and/or a dome-shaped greenhouse?

Canadian Centre for Experimental Radio Astronomy11:52 AM
At VHF you can build or buy Yagis

Ethan Waldo11:52 AM
FTA stuff on ebay is 90cm and 1.2m. Kinda small though.

Gonçalo Nespral11:53 AM
Hopefully this hack chat motivates me to get back in radio astronomy

Canadian Centre for Experimental Radio Astronomy11:53 AM
You can still buy larger dishes online, just not on eBay.

Canadian Centre for Experimental Radio Astronomy11:54 AM
Lots of Big Ugly Dishes sitting in people’s back yard having not been used since 1995. joined  the room.11:54 AM

Canadian Centre for Experimental Radio Astronomy11:56 AM
An advantage of an FFT approach is that you can apply a spectral mask prior to computing total power even if you’re not doing spectral work.

Frank joined  the room.11:56 AM

Dan Maloney11:57 AM
Greetings, all! Welcome to the Hack Chat. Not sure if Dr. Aguirre is logged in yet - he said he had a meeting just before this, so he should be along soon. We'll kick off when he logs on. Until then, enjoy the pre-chat!

Brian Shen joined  the room.11:58 AM

Dan Twedt11:59 AM
Ty. (FFT=Fast Fourier transform)

Steve Bossert (K2GOG)12:00 PM
I went on a binge on Facebook Marketplace and Craigslist looking for dish's for an "art project" this part summer. Ended up with an overwhelming response of dish donation options. Scored some nice Wildblue dishes which were popular in my area for satellite based internet back in the day. Moral = Free dishes are there for the asking!

Dan Maloney12:01 PM
You can even offer to take old ones off of roofs, although that's tricky if you don't know what you're doing - could result in leaks.

morgan12:01 PM
yeah, I see DISH network ones on the side of the road *all the time*

Dan Twedt12:02 PM
I would like to get a "Big Ugly Dish" and a big round trampoline frame free for the hauling somewhere.

morgan12:02 PM
^ that too, easy, just take the dish and leave what ever it's attached too

Steve Bossert (K2GOG)12:02 PM
@Dan Maloney or an injury not covered under insurance :)

kjansky1 joined  the room.12:02 PM

James Aguirre joined  the room.12:03 PM

Dan Maloney12:03 PM
IIRC, the installer puts a "pitch pad" down under the bracket that seals the holes made by the mounting screws

Dan Maloney12:03 PM
Hello @James Aguirre ! Welcome to the Hack Chat!

James Aguirre12:03 PM

jordanbrandes12:03 PM
I tried that once lol found it on Facebook Marketplace. Spent an hour with a random family trying to get the dish off and it never came off.

Allan joined  the room.12:04 PM

Dan Maloney12:04 PM
We can get started now, although we've been having a great chat on sourcing Dish network antennas.

Mike Weilbacher joined  the room.12:04 PM

James Aguirre12:04 PM
Great! Dish network or DirectTV is what I've been using

Dan Maloney12:05 PM
Can you perhaps kick us off by telling us a little about your background and how you got interested in homebrew radio astronomy?

James Aguirre12:05 PM
Hi everybody!

Dan Twedt12:05 PM

Gonçalo Nespral12:05 PM

Brian Shen12:05 PM

Joseph Eoff12:05 PM

James Aguirre12:06 PM
I'm potentially going to embarrass myself because this is - more or less - what I do professionally, but of course at a completely different scale.

Allan12:06 PM
Hi Dan - I'm a radio ham in Cape Town South Africa and I've been following the progress of the KAT project

kjansky112:06 PM

Allan12:06 PM
My apologies - but just a novice who's keen to learn and spread the word

jordanbrandes12:07 PM
I'm with Allan but I'd love to be on the level you are James

James Aguirre12:07 PM
I'm a professor at the University of Pennsylvania and have been building various kinds of telescopes at non-optical wavelengths for about 20 years, but I wanted to do something small scale that I could use to teach and show students how it all works

Dan Maloney12:07 PM
@James Aguirre - true, but that leads to interesting questions about the differences between the "big stuff" and what you can accomplish at home

James Aguirre12:07 PM
@Dan Maloney these days, the gap is narrowing! :)

gaa joined  the room.12:07 PM

James Aguirre12:07 PM
is the _the_ Karl Jansky @kjansky1?

James Aguirre12:08 PM
@Allan one of the projects I work on is quite close to KAT at the site in the Karoo

David Prutchi joined  the room.12:08 PM

kjansky112:08 PM
His alter ego unfortunately!

Allan12:08 PM
Well I hope you can stand the heat

James Aguirre12:08 PM
It's called HERA

James Aguirre12:09 PM
I've not been there in some years - I'm due for a trip back

0xCoto12:09 PM
Oh awesome project.

Allan12:09 PM
Thanks James - I'll take a look

Frank12:09 PM
Curious if you'll get to this, but what are your thoughts on the potential impact of large numbers of "small scale backyard units" that are knit together into a cooperative network.... kind of like what SATNOGS did (build a backbone network of lots of "small scale" observers)

James Aguirre12:09 PM
A lot of the work has been software: we generate something like 2 TB of data a night, and we're not at full scale yet

James Aguirre12:10 PM
@Frank googling SATNOGS now ...

Dan Twedt12:10 PM!

t.w.otto12:10 PM
@Frank that would be awesome,

Allan12:10 PM
"I'm due for a trip back" - excellent - look forward to seeing you

Frank12:11 PM
oh, basically they democratized ground stations for VHF and UHF (and some S-band) for anyone flying "amateur" science payloads on cubesats, etc...

Dan Maloney12:11 PM


Ground Stations Are Just The Beginning: The SatNOGS Story

When you think of satellites, you may think of the Space Shuttle extending its robot arm with a huge piece of high-tech equipment waiting to pirouette into orbit. This misconception is similar to picturing huge mainframes when thinking about computers. The future (and arguably even the present) reality of satellites is smaller, cheaper, and more prolific.

Read this on Hackaday

Ethan Waldo12:11 PM
yes, but basically telemetry instead of signal combining

kjansky112:11 PM
At what redshift frequency would you think that the reionization band will occur?

0xCoto12:11 PM
@Frank The problem is combining the signals requires top-notch equipment since timing information (for proper phase correlation) is crucial.

Frank12:11 PM
the biggest benefit is that hey have a coordinated network to bring the vast numbers (~400+) of observers into some form of cohesive value.

Allan12:12 PM
Can I put a question on the table?

Allan12:12 PM
What sort of hardware are you looking at to network and harvest the data?

Frank12:13 PM
@0xCoto yup... but there too there can be effort to sync with GPS (and other) 1ppm accuracy... or is that not sufficient ?

Steve Benesko joined  the room.12:13 PM

James Aguirre12:13 PM
right - so if you just want to monitor satellites, then each antenna can be "independent" and it's just a question of putting all that data in one place to be useful. @0xCoto is right that actually combining the signals as an interferometer (like HERA or EHT) is a whole other kettle of fish ...

0xCoto12:13 PM
Timing accuracy depends on the frequency of operation.

Dan Maloney12:13 PM
@allan - Take a look at this for a primer:

Dan Maloney12:13 PM


A Miniature Radio Telescope In Every Backyard

You probably wouldn't expect to see somebody making astronomical observations during a cloudy day in the center of a dense urban area, but that's exactly what was happening at the recent 2019 Philadelphia Mini Maker Faire.

Read this on Hackaday

James Aguirre12:14 PM
@kjansky1 the rest frequency of the hydrogen emission is 1420 MHz, and it gets stretched by a factor of about 10 in coming to us, so we're looking at around 150 MHz

0xCoto12:14 PM
If anyone's interested, I've written a guide on building your own radio telescope from scratch:

jeremy.lusk joined  the room.12:14 PM

Allan12:15 PM
cool - thanks Dan

Dan Maloney12:15 PM
And rest assured that I'll be posting a transcript after the chat in case you need to refer back for links and such

James Aguirre12:15 PM
I'll just add that I've got (some) more practically useful info and software at

Frank12:15 PM
throwing out the "Deeper and Deeper down to wonderland"... White Rabbit ? sync at sub nano done at looong baselines.

James Aguirre12:16 PM
There's a definitely a lot missing but the goal is to eventually have enough info there that anyone could copy what we've done

Dan Twedt12:16 PM
Do DIY Radio Telescope people cross over into SETI/CETI activities much?

Canadian Centre for Experimental Radio Astronomy12:16 PM
Http:// has a lot of info as well.

James Aguir