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

Re: SETI Yet another hair-brained-antenna-idea?
Sun, 6 Sep 1998 17:04:29 EDT

In a message dated 9/6/98 1:43:26 PM Pacific Daylight Time,

<< Subj: SETI Yet another hair-brained-antenna-idea?
Date: 9/6/98 1:43:26 PM Pacific Daylight Time

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..

**Doesn't sound familiar...might be a Russian effort with very broad
bandwidth. But that was a dipole ARRAY.

< 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)..

** I would be much happier if you all owned 60M dishes:-) from the figure of
merit standpoint.

< 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".

** That's because he didn't want to confuse you with the two other modes. Your
(spring) stubby is a normal (Wheeler) mode 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)..

** The pioneer often gets shafted..

< 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.

** For SETI though? Nah.

< 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.

** If the range is short, then statistically you are demanding that the
density of ET;s is so high that ETI is effectively an infestation in the

< 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...

** Uhh..why?

< 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..

** IF they already KNEW this then they presumably would have other, more
efficient ways of communicating.

<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..

** Gigabucks a better analogy...

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)..

** There are plenty of tickets purchased with bigger pools...

~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.

** RFI tracking is , without doubt, very valuable.

< 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

**LDE's are plasma phenomena and the amateur reports on this (such as dates;
times; and so on) are rife with errors. I know this. See Feb 78 QST for a
great idea obviated by the wrong data (admitted later) published by OZ9CR.

<(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.

** Ideas are wonderful things. But being SCIENTIFIC demands some sifting. This
could have been a fairly simple exercise to work out before extrapolating to

~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).

** Shall I grade? I would say an A-; it indicates that you are thinking but
need just a bit more work to get there...

* 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)

** Are they --really-- or as highly derivative extrapolations?

However, that Type III stuff seems really unlikely.. (Harnessing the
energy of a
whole galaxy? 4E37 Watts?). Come on already...

** Kinda goofy.:-)

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?

** You are asking to waste may 60%....

If I was them, I would get myself a dish. (or a

**Large for the former; LONG for the ladder:-)

* *Regards,

**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 didn't say 'don't air it' What I said was think about whether this made
sense before taking the next step (which you described in some detail).

I just hope
others won't be reluctant to post after seeing my poor grade..
(But please no more Jelly pools).. :-)

**An A- is a poor grade?

~73, RIch NJ1A

*Chip N1IR
Richard Tyndall NJ1A Woburn, MA. USA or
ARGUS Observatory FN42jl

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

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