Phil Bull

(Left): Dimensions of the pyramidal horn that was selected as the reference design. The flare section has an aperture of 7.3 x 6.0 m, an edge slant length of 5.099 m, and an overall vertical height of 4.3 m. The rectangular waveguide section has an aperture of m and a height of 2.997m. The horn will be static, pointing at zenith, and will have a welded mesh conductive surface. The location of the feed is marked on the waveguide. (Right): Detailed design drawing showing the multipanel construction, consisting of 2.4 x 1.2 m mesh panels cut to size/shape and welded into steel angle frames. These are then bolted together to form a self-supporting structure.

Published in #RASTI RAS Techniques & instruments: "RHINO: a large horn antenna for detecting the 21 cm global signal", Bull et al. This is Fig. 1: to read the paper please visit academic.oup.com/rasti/articl... @oxfordacademic.bsky.social @royalastrosoc.bsky.social

The horn is starting to take shape...

I love it when people in my group listen to me about getting a website :) The most recent convert is Mike Wilensky, who is looking for postdocs in radio/21cm this cycle! mwilensky768.github.io

They Studied Dishonesty. Was Their Work a Lie? Dan Ariely and Francesca Gino became famous for their research into why we bend the truth. Now they’ve both been accused of fabricating data.

“We were, like, Holy shit, there are two different people independently faking data on the same paper.”

Excellent reporting from the New Yorker! 🧪

www.newyorker.com/magazine/202...

Radio telescope using gardening methods...

One of the four trapezoidal horn segments, now covered in wire mesh. It is lying on the ground on top of some weeds.

I also did some meshing today. 3/4 segments complete, but ran out of staples 😐
Rolls of mesh really don't want to lie flat.

Electronics: two RF boards plugged into an Arduino. With glowing blue lights.

Well it ain't pretty, but we now have a (monitored) continuous wave source! This is an Arduino Due controlling an ADF4350 wideband synthesiser and monitoring an AD8317 logarithmic power detector.

Honestly, I could make an entire account dedicated purely to matplotlib tips that I've picked up over the years 😂 🔭

For instance: ax.set is SO MUCH EASIER than setting parameters one by one:

RF electronics laid out on a metal plate.

The frames are done and just need meshing now. How we get a nice, solid, conductive join on the mesh is a hot topic over here.
I've also started positioning the electronics gubbins in the box (which John Edgley kindly donated from his stash). Forgot to buy a splitter I need though, whoops.

There is also Chanty.

We need to build a waveguide segment next, but I'm prevaricating on how long to make it. Another opportunity to break out the mitre saw at least.

Hugh Garsden standing next to the three completed horn panels. They are partially meshed.

Today we used a grand total of 200 screws (a whole box) to get 3/4 of the main horn panels constructed. Hugh went nuts with the electric stapler to get some mesh installed. And we blagged a tiny office from the JBO folks in which to store our junk (a.k.a. highly sensitive radiometer hardware).

The shed of dreams.

Horns offer more control over the beam shape, chromaticity, sidelobe and backlobe levels, and naturally offer some shielding from the environment. You can predict the beam shape quite accurately with EM simulations. They do, however, need to be several wavelengths in size 😬

Why a horn antenna? Well, most 21cm global signal experiments have gone for compact antennas, which are much smaller, but are more sensitive to their environment, incl. via chromatic sidelobes and backlobes. They often also develop resonances/standing waves etc. All difficult to calibrate out.

The experiment is called RHINO. The full size horn antenna will be something like 15m tall (operating at ~70 MHz). The prototype is 5:1 scale, so about 3m (operating at ~350 MHz).

Some of the trapezoid segments of the prototype horn frame. It's made of wood! The conductive surface will be made of 13mm square welded mesh. The joy of working at 80cm wavelength is that this is fine :)

Panel of horn antenna frame propped up against a shed at Jodrell Bank. The Mark II is in the background.

I'm going to start off on the right foot and spend most of my time posting about the prototype 21cm global signal horn we're building at Jodrell Bank. Here's one of the 4 main panels.