archive: SETI Yet another hair-brained-antenna-idea?

SETI Yet another hair-brained-antenna-idea?
Sun, 6 Sep 1998 16:31:17 EDT

Yesterday, Rich wrote:
< Greetings my fellow Setizens,
< I recently read a paper somewhere that included a list of past SETI
<searches. As I recall, one of those searches was done with a simple
<on 1420 Mhz.

Chip N1IR wrote:
*Uhhh. Which one?

Rich replies:
~ Sorry, I've been reading so many papers and abstracts lately
I can't recall.. It may have been a list on a SETI web site. If you
really want to
know, I'll try to find it and post it..

< Now that I've had some time to think about it, it may not be such
<a bad idea.

* It is not a good idea.

~ Yes I agree. It's not a good compromise. It would be far better if we
all owned 6 meter dishes. (Better for what most of us want to do)..

< A dipole (or a 2 turn LH Helix) could cover a lot of the sky.

*That's not a dipole; its a axial mode Kraus helix with quasi-hemi

~I agree, a helix is not a dipole. But a helix with a small amount of
would be my choice, even if it wouldn't cover the whole sky at once.
(At least a helix pointed skyward wouldn't see as much ground noise).

~I use the term 'helix' because it's shorter. When I last spoke with
he didn't say "axial mode Kraus helix". He just said "Helix".
So if it's okay with the him, it's okay with me.
(Maybe I should be more careful, I hear Uda killed himself after Yagi
got all the credit)..

< A hand held GPS receiver with a small antenna can easily hear
<weak GPS signals from very high orbits.. (Ranges of 20,000
<to 25,000 km). (My BUD could likely hear a GPS in Lunar orbit).

*yes... but not relevant.

~Maybe not so relevant, but maybe interesting to anyone considering
installing a small antenna.

< My Points:
< We don't know the direction of the incoming signal. (a prime
< reason for the Argus project). We don't know how strong the
< signal will be.. It could be very weak or very strong..
< Maybe a low gain antenna could hear it.

* The transmitted power you would need would be outrageously large.

~True, but not too outrageous if the range was short.

< Benefit #1:
<Those folks who can't install a BUD could increase their participation
<in SETI work. If hundreds of coordinated Non-BUD searchers were to take
<part, a few dB of gain could be added to each site as their numbers
<(Still maintaining full sky coverage by using assigned declinations).

* But you still won't search the globe by keeping everyone in the same to speak.

~ If nothing else, some of these low gain stations may eventually
upgrade to BUDs and move themselves off the block a few yl...

< Benefit #2:
< In the event of a very strong short term ETI signal, a few wide field
< stations around the world might record the hit at the same time.
< That would definitely put ARGUS (everyone) on red alert..

< Benefit #3.
<Although less sensitive, continuous full sky coverage might give us
< a better chance of detecting any Probes (see note) in the local solar
< system area.

* I don't follow this; nor the reason why such probes would use microwave
signalling to us.

~ I can think of one reason right off hand. If an ETI probe studying
knew we were listening on 1420.4056 Mhz, and wanted to be heard..
Of course, a probe might not want to signal us at all..
SETI is like fishing, you may never get a bite or you may get yanked
out of the boat..

<In conclusion:
<One point we have all heard, 'Any coverage is better than none'. If a
<signal was very strong and of short duration, chances of hearing it
with a few dozen
<3 meter dishes is small. A few dozen wide field antennas (in the mix)
< give us better odds. If the wide field participants were well
coordinated, (good clocks & LOs)
<their daily data could be collected into one data base and analyzed for
common noise
< peaks & etc. (Who knows what we might find)..?..

*Exceedingly unlikely you will find anything but interference.

~Most of us understand that we are more likely to hit the mega
bucks lottery.. But to be in the pool, you MUST buy a ticket, or the
"Exceedingly unlikely" tends to takes on the value of zero.
(Not that zero is bad mind you.. It's just a little boring)..

~As to interference, it would be great to have the ability to
track down local and orbiting sources of RF inference.
If it worked, this aspect alone might make a low-gain group
a valuable part of the Argus project.

< Note:
<Some Probe theory. Some have estimated that during the next 10 Million
<years, probes (or manned star ships) from Earth could travel to most
<parts of the Milky Way. That is, if they can fly at 0.1 the speed of
<(Plus or minus a few million years for variations in propulsion

< Paradoxically speaking, during in the last 10 Billion years, many
<(thousands?) of ET civilizations should have, 'Been there, done that'.
<As the man said "Where's ETI"? They should be here already!
<So the point is, maybe they are. Maybe there are some
<robotic Probes sitting out there in near-earth space scanning the Earth
<for signs of intelligence. ;-)
<Why have they kept silent? That's a good question, maybe they're on a
<schedule. Maybe they only call us for 3 weeks every 15 years..
<Or maybe LDEs are feelers they put out to see what our reaction will
<(Did you notice the word 'maybe' appears at random in the above text)?
<This could go on for pages & ages.. Time to go, 73 Rich <>

*Richard, you have failed to compare the spatial figure of merit for
low gain/ high gain systems,and looked for the dependence on transmitted
(in the scenario you describe). I will give you a hint: the FOM goes as
SQUARE ROOT of the transmitted power (among other factors)...that's not
for optimism unfortunately.

~Thanks for the F minus. I just hope my blurb was a little better
reading than the spinning
swimming pool full of Jello with BBs (or whatever).

* The Kardashev 1964 paper considers isotropic transmissions and hence
outrageously high powers need for ''Type I,II etc" civs.

~Of course everyone on the list is well aware of Kardashev's 64 (Astron)
However, that Type III stuff seems really unlikely.. (Harnessing the
energy of a
whole galaxy? 4E37 Watts?). Come on already...
Anyhow, from what I've read Stephenson's 1981 paper shows a more
scenario.. And 'isotropic'.. I just don't get it. Why would anyone want
to waste
99.99% of their RF? If I was them, I would get myself a dish. (or a


*Chip N1IR

~Thank you Chip, for expertly pointing out the negative aspects of the
idea. Many of us on the list are not experts (especially me) and need to
reminded of what mother nature will permit. However, this is a place
ideas can be aired, no matter how far-fetched they sound. I just hope
others won't be reluctant to post after seeing my poor grade..
(But please no more Jelly pools).. :-)

~73, RIch NJ1A

Richard Tyndall NJ1A Woburn, MA. USA or
ARGUS Observatory FN42jl

HEY! I just got a hit!
Darn.. GPS again..

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