Richard Clark wrote in
:

On Sat, 25 Mar 2006 01:53:24 GMT, "W. Watson"
wrote:

Ultimately, I'm trying to comprehend, via a proof, that two receivers
separated by a distance D can act as though they are a single receiver
of size D. Perhaps it can be done by simply considering the Young
double slit experiment. It bothers me that the idea is passed along
without ever proving it. Maybe the proof is trivial.

Hi Wayne,

The two receivers/antennas is called "synthetic aperture." You can
observe the same thing with one antenna that is moving, we commonly
call it "picket fencing." This effect is due to reflections and
direct signals interfering constructively and destructively as you
move through the interference field. The math for that alone is found
in "Fresnel loss."

The Young double slit IS the proof in that it contains all the math
you need. It contains two transcendental operations (sin or cos) as
many thetas as there are phases and distances, some magnitude
information, and the result pops out at you.

In fact, the math is all the same for all of these effects.

It gets a bit interesting to implement, though, if the antennas are 2000
miles apart!

--
Dave Oldridge+
ICQ 1800667

On Sun, 26 Mar 2006 03:48:19 GMT, Dave Oldridge
wrote:

It gets a bit interesting to implement, though, if the antennas are 2000
miles apart!

Hi Dave,

If you mean by interesting, SETI.

73's
Richard Clark, KB7QHC

Richard Clark wrote in
:

On Sun, 26 Mar 2006 03:48:19 GMT, Dave Oldridge
wrote:

It gets a bit interesting to implement, though, if the antennas are 2000
miles apart!

Hi Dave,

If you mean by interesting, SETI.

Naw, just garden variety radio astronomy.



--
Dave Oldridge+
ICQ 1800667
VA7CZ

Please do not think you are getting something for nothing with an
interferometer. In radio astronomy you have a large number of RF sources
(stars and other interesting objects) transmitting at more or less the same
frequencies. The trick is to select the same source signal for phase
analysis.


Bill W2WO

"Bill Ogden" wrote in message
...
Please do not think you are getting something for nothing with an
interferometer. In radio astronomy you have a large number of RF sources
(stars and other interesting objects) transmitting at more or less the
same
frequencies. The trick is to select the same source signal for phase
analysis.


Bill W2WO



Seems to me there are two things of major concern. 1- getting close to the
target and and 2- phase wrap.

Anyway...
How do they actually distinguish phase in the GHz range between two dishes
across the country/world? I heard they use recordings, but that can't be
right since they'd need pico second timing accuracy...

73, Steve, K9DCi

"Bill Ogden" wrote in
:

Please do not think you are getting something for nothing with an
interferometer. In radio astronomy you have a large number of RF
sources (stars and other interesting objects) transmitting at more or
less the same frequencies. The trick is to select the same source
signal for phase analysis.

Yep...it won't give you any louder signals but it will help you ascertain
exactly where they are coming from.


--
Dave Oldridge+
ICQ 1800667

Dear Dave Oldridge (no call sign given):

Interesting? Yes, but it has been done in radio astronomy and many years
ago. Receivers were well over 10 Mm apart and signals were recorded along
with time signals.

73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:

"Dave Oldridge" wrote in message

snip
It gets a bit interesting to implement, though, if the antennas are 2000
miles apart!

--
Dave Oldridge