Surplus PrimeStar Dishes => Radio Telescope Array?

Sean Clifford asks: "Anyone have suggestions on how to get started setting up an amateur radio telescope array using a ton of old PrimeStar dishes? I've read a couple of articles like this one, that makes this idea seem good in theory. Adapting some gear for RVs to steer the dishes should be simple, but does anyone know of good open source software for controlling them? And *nix software for collecting, filtering, and analyzing the data would be sweet too. I've got a couple of hundred dishes in the back yard at work that are screaming for some type of use other than recycling. I'm already adapting a couple for a wireless network, but would like to see what I can do with the rest."

Comments

Phasing

[Detritus]

I'm not an RF guy, but I work around microwave antennas and receivers. Combining multiple feeds, from one antenna or multiple antennas, is tricky, esp. at microwave frequencies. For the frequency of interest, the feeds must be in phase with each other. You need to be able to adjust the phasing for maximum output from the combiner. If you want to do interferometry, it gets a lot more complicated.

Moon bounce receive, Weather imaging, Microwave

[QuietRiot]

Being a licensed radio amateur (holding a General ticket), this post interested me in that respect.

A quick google search for "dish array" took me here which explains some of the basics of dealing with dish arrays.

One thing I was considering is not using the dishes to look randomly to space hoping to sniff some martian communications, but to somehow extract some known low level signal from somewhere - how about the moon? Amateurs sometimes bounce signals off the moon for communication. Really! Do a search for moon bounce, find out the frequencies often used, and see if you can construct an array.

I know I made that sound _really_ simple, but I'm sure it wouldn't be. I think the frequencies involved would significantly complicate using those small dishes and the supplied LNBs (or whatever the receiving elements they use these days are called). Anyway, it's something to look into.

I'd also suggest looking into ways in which you could turn an array into some sort of radar receiver. Lay them out correctly pointing to the sky and bathe some clouds with radar signals. Try to image the cloud densities, determine their height, etc.

Put them on the wall of a high building for weak-signal microwave receive.

Just some ideas...

Bandwidth

[Technician]

Bandwidth of the dishes is going to be a problem. Much of the search is in the 150 MHZ and up spectrum. The smaller dishes can not focus a signal much larger than 10 cM. They are limited mostly to the microwave band above 1GHZ. They will not work well in the 100 Mhz to 1GHZ band. Phasing an array for a large effective apature is not childs play at these frequencies. Temprature changes change the geometry of the feedlines. Microwaves have a very high attenuation in coax. To get past just these limitations would almost require downconverting. To maintain signal phase, the downconversion would have to be done with very low jitter phase locked downconverters tied to a master clock. Last time I checked a phase locked downconverter was >$1200.00 US. (I installed one for a radio station to receive a subscription CANA feed on C-band)