"Louis Scheffer" <lou@cadence.com> wrote in message
news:40ab046d$1@news.cadence.com...

"Rob Dekker" <rob@verific.com> writes:

I actually think that this idea (10Billion small transmitters in a phased
array) is pretty cool !

The technical challenges of keeping so many transmitters in phase for the
super-narrow
beams we want is obviously a technical challenge of the first order.

Actually, we have plenty of technology for this already.

One thing will remain unchanged : You need a lot of real-estate for
micro-wave beaming !
I did not do the calculations, but the size of your array is probably

close

to a small continent....

Nah, just a few km on a side.

Cool !

But here is an idea : If we were to spread these billions of small
transmitters across
the planet, would be theoretically be able to create a planet-sized

phased

array transmitter ?

Sure, there is no physics barrier to this.  We make planet size receiving
telescopes quite frequenntly.

Yeah, but these are interferrometers. They provide resolution, but also have
massive amount of side-lobes, so they dont have the sensitivity.

If the technical difficulties are overcome, would it essentially be

possible

that anyone
who would like to join in beaconing can buy and connect a small
transmitter/antenna in his/her/it back-yard ?

Actually, a next generation or so cell phone would be about right.
If it contained an improved GPS such as Galileo, the location could be

known

to a few cm.  If then the phase was adjuseted properly, a large
array of cell phones could make a very effective transmitter.

Mmm. nice !
However, if the transmitters are scattered around the globe, and not
clustered on your few square km, then we have the same problem as
with interferrometers : side-lobes. The more scattered the transmitters,
the narrower the beam(s), but the more uncontrollable side-lobes too.

Doesn't that waste energy beyond belief ?
(Or if used as a receiver, we receive noise from uncontrollable directions).

Just like all of our SETI@homers now analyze signals received, we could

have

a TETI@home
(Transmit for ETI) program where you hook your transmitter to internet,

and

join in the global transmission !
Might even use less energy than SETI@home uses now...

Are there any theoretical limitations to that idea ?

No, it's quite possible....

Except for the side-lobes if we spread out the transmitters....Right ?