Pulsar array changes shape

We’ve re-jigged the pulsar array again, changing it from a 3 x 3 array to a 2 x 4 array. This geometry is much easier to manage, and it has allowed us to build a better reflector screen under the array, hopefully reducing the amount of ground radiation “seen” by the array elements.

Pulsar array upgrades

We’ve been working to improve the functionality of the pulsar array in order to enhance the reliability and verifiability of ongoing observations of PSRB0329+54.

Gary Atkins and Marcus Leech re-engineered the pulsar array support structure, and have been working on adding a “fence” around the array, to exclude low-angle RFI, which is where most terrestrial interference will be coming from. More work needs to be done to extend the fence around the entire array, but the array is now better-balanced on the support structure.

In addition the front-end electronics have been replaced to improve up-front filtering, using a custom UHF filter provided by Jan Jency in Slovakia. Further versions of this filter will allow us to observe on any of the 3 radio astronomy frequencies in the North American UHF band, while suppressing others.

A peak inside the new front end shows a noise injector, and a new 1/4-wave filter/protector

The noise injector hasn’t been connected yet, but will allow us to do a quick “sanity test” of the entire pulsar system from the comfort of the lab.

Stay tuned 🙂 🙂

Working on improving EMI/RFI suppression

We’ve been working on improving EMI/RFI suppression of our own equipment, to improve the chances of confirming reception of pulsars, and radio astronomy in general.

We’ve added ferrite chokes to all computer cables, etc, and EVERY cable that goes across our bulkhead to the outside world has at least one ferrite choke on it.

We’re working on shielding our window, to reduce the area of radiation leakage from our own equipment to a minimum:

The existing bulkhead has had foil tape added to it, and one of the windows is completely covered with 6mm hardware cloth. The other windows will get a similar treatment.

The walls and ceiling are already fairly good from an RF leakage perspective–50cm concrete on the walls and roof deck, with both mesh and re-bar reinforcement. Given a randomly-chosen building, one couldnt’ ask for much better for doing sensitive radio receiving experiments. The office ceiling (which is dropped only about 20cm below the roof concrete deck) is made from interlocking steel tiles, locked into a steel rail system. Also an excellent serendipity for us.

Success in observing pulsar B0329+54

We have had success in observing pulsar B0329+54 with our pulsar antenna, after making several adjustments both to the antenna structures, and the receiving software.

Here is an averaged, phase-centered, pulse profile, taken over three observing sessions from November 29 until Dec 1.

While it’s still *possible* that this is an RFI artifact, it becomes quickly decreasingly likely as we make more observations.

Adjustments to pulsar array

Marcus Leech went “up top” to make some elevation adjustments to the now-twice-the-size pulsar array,
and added a cross-brace to the “upper” side of the array to stiffen it.

There’s been a fair amount of RFI on the 611MHz radio-astronomy ‘window’, so we’re trying to track it down.

Meteor-cam now in operation on the roof

Gary Atkins moved one of two all-sky camera systems onto the roof late last week. These camera systems are designed for detecting meteors, and we’ll be joining a “network” of such meteor cams around the world.

We’ll have a live feed of the camera pointed to from the website soon–but there are a few housekeeping details that need to be taken care of first.

We may also put a regular webcam “up top” just to show images of the antennae up on the roof. It will be boring, most of the time 🙂

Roof now has 21cm telescope on it as well

Gary Atkins and Marcus Leech moved the 21cm dish “up top” today, so that it can join the pulsar antenna.

We used a rope and brute force. This won’t work for our 1.2m dishes and their mount pods–not without a hoist of some sort.

The next antennae to go “up top” will likely be our UHF interferometer antennae, probably spaced about 30m apart or more.

Pulsar monitor undergoing overnight checkout

The pulsar antenna is now plugged into the pulsar receiver system, which consists of a pair of AirSpy SDR receivers, fed with a high-quality 10MHz OCXO timebase.

We’re running a pulsar-specific flow-graph, written by Marcus Leech, and using Gnu Radio underneath.

There are many unknowns–we don’t know if the ambient noise level is low enough without aggressive filtering, we don’t know if our antenna effective aperture is quite up to the task. This will be a useful test, but a negative result cannot be interpreted to mean “won’t work”.

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