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Amateur Seti "may be feasible"

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Conundrum

Sat Aug 18 2012, 05:47PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Hi all.
It seems that many people are using modified satellite LNB's and 3 metre dishes (!) as a way to do home SETI.

Due to recent work done on extending the habitable zone, it seems that white dwarves could have stable, viable near Earth-like planets that have migrated inwards towards the star during its size change.
These planets could then have liquid water and only 1.68* solar UV flux which is survivable with relatively minor modifications consistent with Darwinian evolution.

Said planets could in fact be substantially more stable than the "classic" Sun-type stars for potentially tens of billions of years.
If so then *any* star with over 30% metallicity (ie most second generation) could sustain life.

Does this line of reasoning make any sense?
If so then the Wow! signal may not in fact have been a fluke, it could really have been from the alien equivalent of some radio amateur sending out signals to nearby systems "just to see what happens".

This makes the original transmission date assuming the home system is one of the white dwarves near where the Wow! signal appears to have originated around 1922 to 1935.

An alternate possibility is that the transmission on 1420.356 MHz was as a result of a malfunction on their equivalent of GPS which makes sense as if the satellite lost orientation due to a meteor impact but the transmitter stayed working then it would spin round covering a random area of the sky.
It would also explain the lack of a repeating signal as they probably turned the transmitter off once the problem became obvious.

For comparison:-
"two frequencies are utilized; one at 1575.42 MHz (10.23 MHz Ã— 154) called L1; and a second at 1227.60 MHz (10.23 MHz Ã— 120), called L2."

Note the similarity in frequencies, so a sensible band to also listen to would be 1420.356-347.82 MHz i.e. 1072 MHz.
This is quite feasible with homemade devices and has the advantage of being "radio quiet" at least for now.
Well away from harmonics from the popular comms bands and 2.45 GHz magnetrons.

Comments?

-A

Mattski

Sat Aug 18 2012, 08:03PM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

Our GPS bands were allocated so that they share a common 10.23MHz precision time base. It doesn't make sense to assume a pair of extraterrestrial radio sources would be separated the same spacing when they don't have 10.23MHz as a common denominator.

Far more interesting is the proximity of the Wow signal to a hydrogen resonance line.

Steve Conner

Sat Aug 18 2012, 08:47PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The big problem with SETI has always been what sort of signal to look for.

One interesting trend I see is that, as radio technology evolves, the signals get harder to tell apart from noise. We got encryption ("scrambling") of voice signals, then spread spectrum with pseudo-random coding, and now UWB is coming.

The distinction between signal and noise is really quite subtle and has more to do with philosophy than engineering, but to cut a long story short, the system that detected the Wow signal was basically a spectrum analyser sensitive to steady narrowband transmissions, and modern digital radio signals could well slip right by it.

I remember the "Arecibo signal" which was designed to be self-documenting in a way obvious to any "intelligent lifeform". More like an exercise in human vanity.

Conundrum

Sat Aug 18 2012, 09:43PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Yeah, this is indeed a problem.
It could be that the L in the Drake equation is too small thanks to the switch to compressed/encrypted communications.
Interesting work is now being done with neutrinos, including using sensitive isotopes such as manganese which appear to be reacting to the passage of the neutrinos indirectly through an as yet unknown force carrier particle.

If this system is indeed able to detect neutrinos then a device not much bigger than a 3G stick could essentially replace WiFi, 3G, 4G and still have bandwidths in the hundreds of MBits/sec.
Needless to say this would make the Earth "radio quiet" in short order.

Chris Russell

Sun Aug 19 2012, 08:09AM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

That's the problem with SETI. It makes too many assumptions about technology to be very useful. The total amount of time we spent broadcasting narrowband UHF signals was relatively brief, and even with an Arecibo-sized dish, Earth wouldn't have been visible from very far. In order to detect distant civilizations, we pretty much have to assume that they want to be found, and not only that, they want to be found by someone at roughly our technological level.

I don't see home-based SETI changing that. Yes, we could look at more of the sky at once, and yes, we could look at more frequencies at once. But it still assumes that someone out there is intentionally transmitting a narrowband carrier with an ERP in the gigawatt range, aimed at us. How many neighboring star systems have we sent such a signal to?

An alternate possibility is that the transmission on 1420.356 MHz was as a result of a malfunction on their equivalent of GPS which makes sense as if the satellite lost orientation due to a meteor impact but the transmitter stayed working then it would spin round covering a random area of the sky.
It would also explain the lack of a repeating signal as they probably turned the transmitter off once the problem became obvious.

Not a chance. Even *if* a satellite happened to be pointed at us, and even *if* for some inexplicable reason their GPS satellites operate with an ERP of many gigawatts, there's no way a tumbling satellite remains steadily pointed at Earth for 72 seconds.

Conundrum

Mon Aug 20 2012, 07:01AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Thanks for that Chris, however it is interesting to discuss the possible explanations for the Wow! "signal".

One theory put forward at the time which was later falsified is that it was simply a pulsar whose signal was deflected into line of sight with the Earth by a nearby black hole.

-A

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