Seti At Parkes

The Breakthrough Foundation and Yuri Milner have entered into an agreement with CSIRO to use the Parkes Telescope to Search for Extra-terrestrial Intelligence (SETI).

The Breakthrough Listen program will be allocated 25% of Parkes observing time for five years from October 2016. On Feb 29 an enthusiastic group from the Breakthrough Listen program arrived at Parkes, and by March 1 the first rack of hardware had already been installed at the telescope.

In this picture you see (left to right) Jamie Drew, David MacMahon, Andrew Siemion, Danny Price and Dan Werthimer during their visit.

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08.03.2016. 20:57

Scope For Design

One thing I've been needing for a while is a useful oscilloscope for digital and RF work. Having a limited budget and a fair idea of the project I needed to work on I decided to get a Chinese Digital Storage 'Scope with a 50MHz working bandwidth. Quoted as a 500 megasample per second device it should work at well over 50MHz. Ideal for the project in mind.

I ordered it from a Chinese dealer on Ebay and it arrived in about 7 days which was exceptionally good delivery speed through China Post. For a total delivered cost of $300 Au I was very happy. Now to see how well it performs.

I'd looked at a few reviews from various Tech Review sites and while some had commented on it being good value for money, others had remarked on the disappointing performance and low screen resolution. After unboxing and doing some preliminary tests I couldn't really fault it. Even the FFT (time to frequency) Math function worked as advertised.

The Storage Scope is made by Uni-Trend and is probably on the lowest level of quality that is available. Plenty of other Chinese manufacturers make much better quality and designed products but at a much higher price.

Project Skylight - RF design

So the main reason for getting a 50MHz Digital Storage Scope is the design and development of a Low Frequency (0-50MHz) Radio Astronomy Phased Array. Project Skylight has multiple antenna elements as active RF receivers using either an RTL-SDR software defined radio or other radio receiver and doing baseband sampling at the antenna with an analogue to digital converter, putting the raw RF samples into a data stream and, along with time stamping, send them down an Ethernet cable to a central data processing system.

To keep costs low the highest frequency of 50MHz was chosen for the performance of components at the price point. The sweet spot would probably be around 40MHz but the receiver design would be capable of 1MHz to 60MHz.

The design of the whole array allows for easy scaling by just adding Active Antennas. Each antenna has a power usage limit of 500mA and power supply is through the ethernet cable using a 'Power Over Ethernet' type system. The network router can connect up to 24 antennas with total maximum power of 12 Amps (24 x 0.5A).

Each receiver has a Low Pass Filter frontend with a 3dB rolloff at 56MHz. The filter is followed by a 30dB RF gain block using a FET amplifier stage to reduced overload and a MMIC amp with a 50 ohm output impedance. A mixer stage using an SAA612 Double Balanced Mixer is also fed from either a local oscillator using an AD9850 DDS Synthesiser or a buffered RF source fed down a spare twisted pair in the ethernet cable.

By using a common source RF local oscillator to all antenna the phase of the RF signal is the same for all antenna. With the inclusion of a locally generated (in each antenna) RF source each antenna can listen at a different frequency at the same time.

The individual antenna dipoles in the array are arranged roughly in a circle about 30 metres across. Distances between antenna should be unequal.

24.01.2016. 00:06

Radio Sculpture

A sculpture is a physical representation of an idea, a concept or even a feeling. In many ways, anything we can build becomes a sculpture of our thoughts.

Scott Mitchell is a Sculpture Artist and has many works to his name. As an entrant in the Melbourne Prize for Urban Sculpture 2014, Scott set his mind on a sculpture that would divert our attention to the sky. As a propositional work (for a larger version in Melbourne's Royal Park) he decided to build a working Radio Telescope.

Scott approached the Astronomical Society of Victoria and came along to one of the Radio Astronomy section monthly meetings. We spent several hours helping him understand some of the concepts, the science and the electronics behind Radio Astronomy. We also went over the History and the Pioneers of Radio Astronomy. Eventually Scott decided a Horn Antenna would be most appropriate and sculpturally pleasing.

The Horn Antenna has an opening at the wide end to allow radio waves to enter and funnels the waves down to a receiver element at the narrow end, usually just a short wire that is tuned to the particular frequency of interest. Then it connects to an amplifier to greatly increase the signal level. In Scotts design a receiver normally plugged into a computer to pick up Radio and TV signals is used to receive signals on the Hydrogen Line at 1.420 GHz.

The Hydrogen Line is the frequency where neutral Hydrogen atoms emit radio waves and allow us to see into the Cosmos. Other atoms also emit radio waves at different frequencies but Hydrogen is by far the most abundant element and therefore is the easiest to detect.

Scott has named his sculpture 'The Listener' and has thoughtfully provided a pair of headphones as part of the display so that visitors can listen in on the static from the Stars much as Ellie Arroway did in the brilliant movie 'Contact'. The display also has a chart recorder under a perspex cover that draws lines representing the level of radio noise being received. From what I saw, the chart paper is replaced every morning at 10am which will give a permanent record of the two weeks that the display is available for viewing.

I visited the sculpture at Federation Square and took a few pictures. I even chatted with quite a few people that came to find out what it was. Being the friendly and knowledgeable fellow that I am I was more than pleased to tell them. I guess I was happy that Radio Astronomy was on display.



19.11.2014. 05:18