HFU HF Underground
General Category => General Radio Discussion => Topic started by: Tim Bucknall on April 21, 2019, 1527 UTC
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I almost posted this under sdr software but as this is probably in cloud cuckoo land I thought better of it.
You know how the signals from different radio telescopes are combined together to create the capabilities of a receiving array of huge dimensions. Well can we do this with our reception?
Obviously for run of the mill tropo this would create a confusing pointless mess, but what about for extreme long haul dx maybe even EME on band 2 ?
I could imagine that being useful for transatlantic dx
How do radio observatories combine data streams? Do they use the normal internet to combine signals or some dedicated fibre optic cables with consistent latency they can work around?
Would we be better off recording IQ files and combining them offline?
Problems radio astronomers don’t have that we do: lack of frequencies that are free in multiple locations. The further apart the receivers are the more of a problem this becomes until we end up limited to the bottom of the band.
That could change after The UK switches off analog, assuming we’re not the last country to switch off.
Could some of the sdr units capable of diversity reception be hacked into combining the required inputs?
PS: a Dutch radio amateur posted on a forum in 2016 that his next project would be band II EME.
I tried contacting him via qrz.com but the email bounced. His callsign is PE1BBI
no harm in dreaming right? ;-)
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Heck, someday I'd like to see that taken a step further. It's only a matter of time before we have a Moon base, or even a Mars colony. Wouldn't it be unreal to communicate via amateur radio to them. The Moon wouldn't be too hard to do, but can Mars be done at amateur power levels? Using the technique of a received multiple dish array, that might be possible. Albeit, that 40min RX / TX lag time will be a pain.
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This could be really useful on any frequency low enough to have a fairly stable phase delay between all the stations involved.
for example, if everyone was able to receive wwvb, (or nist corrected GPS) they could open loop record a slice of spectrum that included wwvb and the desired signal, (or record the spectrum of interest with a GPS timestamp).
The next step could take as long as needed, as it is recorded and no longer happening in real time. take an FFT of all the recordings, pick an arbitrary recording as the "master" then adjust the timing alignment until the WWVB signals in all of the recordings are in phase. apply a timing differential based on each stations distance from the transmitter you are trying to receive, and the tiny signals of the desired signals should add when all FFTs are averaged.
as far as implementation, there are probably a thousand ways, but if one is willing to record raw spectrum, and process it later, rather than in real time, this becomes much easier.
if anyone has any additions, subtractions, or criticisms for this idea, I would love to hear them
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The tdoa feature of the kiwi sdrs is kinda a effort in that direction already.