On another forum there was debate about whether the requirement of
"near real time" high definition video transmissions was achievable
for a such a low-cost mission.
It would certainly be doable if the receiving antennas on Earth were
the large radio antennas used for space communications with
interplanetary probes or those radio antennas used for radio
astronomy. This is evidenced by the fact that the Kaguya(Selene) lunar
orbiter mission was able to send high definition video to a large
receiving dish radio antenna. And also by the fact that DirecTV sends
high definition video to only 2 foot size antennas from geosynchronous
orbit; so 10 times larger antennas would be able to receive such
signals from a 10 times larger distance at the Moon.
However, I was wondering if it would be possible to detect this using
amateur sized equipment at such a large distance. Usually for
receiving high data rates you used transmissions at very high
frequencies, as higher frequencies can carry more data. For instance
both Kaguya and DirecTV transmit the high def video at gigahertz
frequencies.
However, for the system I'm imaging I'm thinking of using much lower
frequencies, and necessarily longer wavelengths. What I wanted to do
is transmit at decametric wavelengths. High data transmissions rates
would be achieved by making it be pulsed in an on-off fashion at high
intensity but at a rapid rate.
On that other forum the data rate required for high def TV was given
as 256,000 bits per second. So I wanted to make these transmissions be
pulsed at this rapid rate at wavelengths of a few tens's of meters.
My decametric wavelength requirement was because of the fact that
high schools and universities have programs for detecting radio
emissions from Jupiter at these wavelengths:

NASA's Radio JOVE Project.
http://radiojove.gsfc.nasa.gov/

The Discovery of Jupiter's Radio Emissions.
How a chance discovery opened up the field of Jovian radio studies.
by Dr. Leonard N. Garcia
http://radiojove.gsfc.nasa.gov/libra...discovery.html

These school and university receiving antennas on Earth consist of
dozens to hundreds of vertical dipoles of lengths at the meters scale
to correspond to the radio wavelengths. Some questions I had: how
intense would the pulse have to be on the Moon to be detectable from
the Moon above background noise for a detector on Earth of say a few
dozen dipoles? Could this be done for the transmitter of power of say
a few hundred watts for a low cost, low weight lander mission? Could
the transmitter antenna on the moon be only a few meters size for the
low weight requirement?
A secondary purpose I had in mind was a pet project of mine involving
linking these many school receivers to form a global telescope at
decametric wavelengths:

From: (Robert Clark)
Date: 23 May 2001 11:15:06 -0700
Subject: Will amateur radio astronomers be the first to directly
detect extrasolar planets?
Newsgroups: rec.radio.amateur.space, rec.radio.amateur.antenna,
sci.astro, sci.astro.seti, sci.space.policy
http://groups.google.com/group/sci.a...018b68662c14e9

The long wavelengths should make the requirements for accurate
distance information and timing synchrony between the separate
detectors easy to manage even for amateur systems. Using this method
might make the detection achievable even if the power or transmitting
antenna size requirements are not practical for a low cost, low weight
lander on the Moon for an individual detector on Earth.
The recent achievement of real-time very long baseline interferometry
should make it possible to integrate these separate detector signals
in real-time as well:

Astronomers Demonstrate a Global Internet Telescope.
Date Released: Friday, October 08, 2004
Source: Jodrell Bank Observatory
http://www.spaceref.com/news/viewpr.html?pid=15251


Bob Clark

Robert Clark wrote:
On another forum there was debate about whether the requirement of
"near real time" high definition video transmissions was achievable
for a such a low-cost mission.
It would certainly be doable if the receiving antennas on Earth were
the large radio antennas used for space communications with
interplanetary probes or those radio antennas used for radio
astronomy. This is evidenced by the fact that the Kaguya(Selene) lunar
orbiter mission was able to send high definition video to a large
receiving dish radio antenna. And also by the fact that DirecTV sends
high definition video to only 2 foot size antennas from geosynchronous
orbit; so 10 times larger antennas would be able to receive such
signals from a 10 times larger distance at the Moon.

Don't forget that DirecTV radiates a LOT more power than a typical deep
space probe. AND they often have a higher gain antenna. A geosync relay
satellite might have 96 TWTAs, each several hundred watts, on it,
feeding a very clever multiple feed dish which is many meters in
diameter (look at Thuraya, for instance).

However, I was wondering if it would be possible to detect this using
amateur sized equipment at such a large distance. Usually for
receiving high data rates you used transmissions at very high
frequencies, as higher frequencies can carry more data. For instance
both Kaguya and DirecTV transmit the high def video at gigahertz
frequencies.

There's a moderately active Amateur DSN group that listens for things
like Chandrayaan or MRO using relatively small dishes (1-2 meters).

The choice of higher frequencies isn't because it carries more data.
It's because a higher frequency allows you to get more gain with the
same physical antenna size. Double the frequency, and your antenna gain
goes up by a factor of 4, at both ends of the link.. a total of 12 dB
improvement in SNR, for the same transmitter power and receiver noise
figure. And, there's more spectrum available up high.

However, for the system I'm imaging I'm thinking of using much lower
frequencies, and necessarily longer wavelengths. What I wanted to do
is transmit at decametric wavelengths. High data transmissions rates
would be achieved by making it be pulsed in an on-off fashion at high
intensity but at a rapid rate.

How high a data rate? If you're at 30 MHz (10m lambda), you're not
going to be pulsing at 10 MHz, or you're going to be generating a signal
that extends from 20 to 40 MHz (and then some). You need a low symbol
rate with lots of bits per symbol, which in turn means you'll need lots
of SNR.


On that other forum the data rate required for high def TV was given
as 256,000 bits per second.

HDTV, as carried on broadcast TV, is 19.8 Mbps. If you're happy with a
lower frame rate, or can do a lot of frame/frame compression, you can
get it lower.



So I wanted to make these transmissions be
pulsed at this rapid rate at wavelengths of a few tens's of meters.
My decametric wavelength requirement was because of the fact that
high schools and universities have programs for detecting radio
emissions from Jupiter at these wavelengths:

NASA's Radio JOVE Project.
http://radiojove.gsfc.nasa.gov/


These school and university receiving antennas on Earth consist of
dozens to hundreds of vertical dipoles of lengths at the meters scale
to correspond to the radio wavelengths.

Any one school only has a couple dipoles up.. the gain is quite low.

Some questions I had: how
intense would the pulse have to be on the Moon to be detectable from
the Moon above background noise for a detector on Earth of say a few
dozen dipoles? Could this be done for the transmitter of power of say
a few hundred watts for a low cost, low weight lander mission? Could
the transmitter antenna on the moon be only a few meters size for the
low weight requirement?

How technical do you want to get? There's a book about space
telecommunications system design available for downloading from JPL
(http://descanso.jpl.nasa.gov/ somewhere on that site)

Here's some basic numbers you'll need:

Free space path loss in dB = 32.44 + 20*log10(distance in km) + 20
*log10(frequency in MHz)
That's between isotropic antennas (0dBi)..

Antenna beamwidth is 70 degrees/ (diameter of antenna in wavelengths)
Antenna gain is 27000/(beamwidth^2)

A typical receiver noise figure (after figuring in losses in
coax/waveguide, etc.) is probably 3dB.

kTB noise is -174 dBm/Hertz * 10*log10(bandwidth in Hz)





A secondary purpose I had in mind was a pet project of mine involving
linking these many school receivers to form a global telescope at
decametric wavelengths:

Coherent combining would be a challenge, because of ionospheric
variability at HF, not to mention the other challenges.

Look up LOFAR or the SKA (Square Kilometer Array) for a fairly well
funded scheme.

Jim Lux wrote:

Don't forget that DirecTV radiates a LOT more power than a typical deep
space probe. AND they often have a higher gain antenna. A geosync relay
satellite might have 96 TWTAs, each several hundred watts, on it,
feeding a very clever multiple feed dish which is many meters in
diameter (look at Thuraya, for instance).


Wow. 96 TWTs with several hundred watts each. From a satellite. And
what's the efficiency?

So these are powered by what? Small nuclear reactors?

Certainly not solar panels.

tom
K0TAR

"Jim Lux" wrote in message
...


Snip

HDTV, as carried on broadcast TV, is 19.8 Mbps. If you're happy with a
lower frame rate, or can do a lot of frame/frame compression, you can
get it lower.

Yes. OP said "near real time," which I take to mean "OK to drop some
frames," like the satellite video phones the reporters use from the
boondocks. Thus, high-def can be confined to a lot lower bandwidth if you
don't mind seeing compression artifacts as each frame is being built on the
screen.

I have a contemporary example: KABC-DT, Channel 7 Los Angeles is high-def
on 7-1 AND high-def on 7-2, with a service called Living Well. See
http://livingwell.tv/Welcome.html.

Living Well is apparently getting a skimpy bitshare, as compression
artifacts are obvious, especially on scene changes and motion, whereas ABC
programming on 7-1 is just beautiful. Living Well is very good, sharp HD,
but you can see details being "painted in" for a quarter-second after a
scene change.

"Sal"

On Jun 16, 8:06*pm, tom wrote:
Jim Lux wrote:

Don't forget that DirecTV radiates a LOT more power than a typical deep
space probe. AND they often have a higher gain antenna. A geosync relay
satellite might have 96 TWTAs, each several hundred watts, on it,
feeding a very clever multiple feed dish which is many meters in
diameter (look at Thuraya, for instance).

Wow. *96 TWTs with several hundred watts each. *From a satellite. *And
what's the efficiency?

So these are powered by what? *Small nuclear reactors?

Certainly not solar panels.

tom
K0TAR

Not all will necessarily be on at the same time.
Typical narrow band coupled cavity TWTAs can get over 50% efficiency
(DC in to RF out)
Yes Solar Panels..10kW would not be unusual.

See, e.g., http://en.wikipedia.org/wiki/ASTRIUM_E3000 ... 14 kW of
power from 45 m^2 of solar panels and 4500kg of satellite..

This is so far beyond what is used in the scientific space program
it's mind boggling. But, hey, out of the $1-2B cost, the TWTAs are
probably only 5-10% of the total, and there are definitely quantity
discounts.

On Tue, 16 Jun 2009 15:57:38 -0700, Robert Clark wrote:

On another forum there was debate about whether the requirement of "near
real time" high definition video transmissions was achievable for a such
a low-cost mission.
It would certainly be doable if the receiving antennas on Earth were
the large radio antennas used for space communications with
interplanetary probes or those radio antennas used for radio astronomy.
This is evidenced by the fact that the Kaguya(Selene) lunar orbiter
mission was able to send high definition video to a large receiving dish
radio antenna. And also by the fact that DirecTV sends high definition
video to only 2 foot size antennas from geosynchronous orbit; so 10
times larger antennas would be able to receive such signals from a 10
times larger distance at the Moon.
However, I was wondering if it would be possible to detect this using
amateur sized equipment at such a large distance. Usually for receiving
high data rates you used transmissions at very high frequencies, as
higher frequencies can carry more data. For instance both Kaguya and
DirecTV transmit the high def video at gigahertz frequencies.
However, for the system I'm imaging I'm thinking of using much lower
frequencies, and necessarily longer wavelengths. What I wanted to do is
transmit at decametric wavelengths. High data transmissions rates would
be achieved by making it be pulsed in an on-off fashion at high
intensity but at a rapid rate.
On that other forum the data rate required for high def TV was given
as 256,000 bits per second. So I wanted to make these transmissions be
pulsed at this rapid rate at wavelengths of a few tens's of meters.
My decametric wavelength requirement was because of the fact that
high schools and universities have programs for detecting radio
emissions from Jupiter at these wavelengths:

NASA's Radio JOVE Project.
http://radiojove.gsfc.nasa.gov/

The Discovery of Jupiter's Radio Emissions. How a chance discovery
opened up the field of Jovian radio studies. by Dr. Leonard N. Garcia
http://radiojove.gsfc.nasa.gov/libra...discovery.html

These school and university receiving antennas on Earth consist of
dozens to hundreds of vertical dipoles of lengths at the meters scale to
correspond to the radio wavelengths. Some questions I had: how intense
would the pulse have to be on the Moon to be detectable from the Moon
above background noise for a detector on Earth of say a few dozen
dipoles? Could this be done for the transmitter of power of say a few
hundred watts for a low cost, low weight lander mission? Could the
transmitter antenna on the moon be only a few meters size for the low
weight requirement?
A secondary purpose I had in mind was a pet project of mine involving
linking these many school receivers to form a global telescope at
decametric wavelengths:

From: (Robert Clark) Date: 23 May 2001 11:15:06
-0700
Subject: Will amateur radio astronomers be the first to directly detect
extrasolar planets?
Newsgroups: rec.radio.amateur.space, rec.radio.amateur.antenna,
sci.astro, sci.astro.seti, sci.space.policy
http://groups.google.com/group/sci.a...se_frm/thread/
c0018b68662c14e9

The long wavelengths should make the requirements for accurate
distance information and timing synchrony between the separate detectors
easy to manage even for amateur systems. Using this method might make
the detection achievable even if the power or transmitting antenna size
requirements are not practical for a low cost, low weight lander on the
Moon for an individual detector on Earth.
The recent achievement of real-time very long baseline interferometry
should make it possible to integrate these separate detector signals in
real-time as well:

Astronomers Demonstrate a Global Internet Telescope. Date Released:
Friday, October 08, 2004 Source: Jodrell Bank Observatory
http://www.spaceref.com/news/viewpr.html?pid=15251


You will never get uncompressed HD video transmitted from the lunar
surface. And really, there is no need for it if the compression is
handled right. Only a few people I know can do that part.

Since the image is mostly repetitive, a low bitrate can be achieved which
should allow for a very good signal level path budget. this would make
for a higher energy per bit and a more reasonable earth station within
the budget of amateurs. (if thats the goal) To achieve a very low
bitrate, such things as Pre/post-distortion to utilize less bits, (black
gamas) using extremely long GOP structures and since the action of the
video is extremely slow and repetitive, a slow frame rate such as 1fps.
These can be counteracted at the receive station with software without
effecting the total image resolution.

The image resolution is where the wow factor is anyway! :-)

My *guess* is that whomever would put a spacecraft on the lunar surface
would only have one high speed datapath back. The HD transport stream
would be muxed in with the other data elements of the spacecraft on a
transmission system without consideration for amateur reception. Perhaps
encrypted if a commercial entity is paying for the broadcast rights.

Yes. *OP said "near real time," which I take to mean "OK to drop some
frames," like the satellite video phones the reporters use from the
boondocks. *Thus, high-def can be confined to a lot lower bandwidth if you
don't mind seeing compression artifacts as each frame is being built on the
screen.

I have a contemporary example: *KABC-DT, Channel 7 Los Angeles is high-def
on 7-1 AND high-def on 7-2, with a service called Living Well. *Seehttp://livingwell.tv/Welcome.html.

Living Well is apparently getting a skimpy bitshare, as compression
artifacts are obvious, especially on scene changes and motion, whereas ABC
programming on 7-1 is just beautiful. *Living Well is very good, sharp HD,
but you can see details being "painted in" for a quarter-second after a
scene change.


There's a fairly complex trade. For a lunar mission, the scene is
going to be pretty static, just shifted. (not like there's a baskeball
team doing a fast break in the field of view), so it should compress
well, given a suitable algorithm.

The challenge is that compression (especially good compression) takes
computational power. So you have a tradeoff: do you spend you joules
on compressing the images and radiate less RF energy, or do you
compress less, and use a bigger power amp. There's also a mass
tradeoff.. big amp or big antenna. The big antenna needs more
accurate pointing, which increases complexity. Or the trade of
frequency selection, higher frequency means more antenna gain, but
usually lower efficiency in the PA and higher NF in the receiver end,
as well as higher probabiliity of weather related fading.

And even there, because Moore's law means that semiconductor
technology is always advancing, the tradespace is shifting towards
more processing (because it gets cheaper in size, weight, power, while
power amps are pretty much at the physics limits)

This is, of course, "rocket science".. or more properly, spacecraft
system engineering. It's straightforward, for the most part, but non-
trivial. Pick your requirements, define the tradespace(s), try
configurations and see what happens.

Jim Lux wrote:
Yes. OP said "near real time," which I take to mean "OK to drop some
frames," like the satellite video phones the reporters use from the
boondocks. Thus, high-def can be confined to a lot lower bandwidth if you
don't mind seeing compression artifacts as each frame is being built on the
screen.



Here's a back of the envelope link budget for a 500E3 km link carrying 1
Mbps

Let's assume 2GHz for the working frequency (not necessarily a good
choice, but somewhere to start)

Free Space Path Loss from Moon to earth, between isotropic antennas =
32.44 + 20*log10(500E3) + 20*log10(2E3) = 32.44 + 114 + 66 = about 212 dB

Assume an antenna 2m in diameter at one end (moon end)
lambda for 2GHz is 15cm, so the antenna is 13 wavelengths in diameter
Beamwidth will be about 70/13 = 5 degrees.. OK, because Earth is 2
degrees wide from the moon, so you can just point at the middle of the
visible earth.

Assume an antenna 10m in diameter at the earth end. Beamwidth will be 1
degree, twice the visible lunar disc size, so you can just point at the
moon, generally.

Gains of antennas
2m @ 2GHz = 30dB
10m @ 2GHz = 44dB

Preceived at Earth = Ptransmitted +30 - 212 +44dB = Ptransmit -138dB.

Assume transmitting with 10 Watts or +40dBm..
Prec = -100dBm

Now, let's look at the receiver:
Power Spectral density of Noise is kT+NF.. kT is -174dBm/Hz and a decent
NF might be 2dB (allowing for some plumbing losses, etc.

-172 dBm/Hz

Eb (energy/Bit) = -100dBm -60dB (1Mbps) = -160dBmJ

So, Eb/No is about +12dB... If you allow 2dB for implementation loss,
that gets you to 10dB, which will get you a BER of 1E-6, which isn't
terrible. Coding will improve it, etc.

Take home message:

10W at 2Ghz with reasonably sized antennas at moon and earth can carry 1
Mbps.

Scales linearly with data rate.. You want 10Mbps, you need 100W. Or
bigger antennas.

On Jun 17, 11:32*am, Jim Lux wrote:
Jim Lux wrote:
Yes. *OP said "near real time," which I take to mean "OK to drop some
frames," like the satellite video phones the reporters use from the
boondocks. *Thus, high-def can be confined to a lot lower bandwidth if you
don't mind seeing compression artifacts as each frame is being built on the
screen.

Here's a back of the envelope link budget for a 500E3 km link carrying 1
Mbps

Let's assume 2GHz for the working frequency (not necessarily a good
choice, but somewhere to start)

Free Space Path Loss from Moon to earth, between isotropic antennas =
32.44 + 20*log10(500E3) + 20*log10(2E3) = 32.44 + 114 + 66 = about 212 dB

Assume an antenna 2m in diameter at one end (moon end)
lambda for 2GHz is 15cm, so the antenna is 13 wavelengths in diameter
Beamwidth will be about 70/13 = 5 degrees.. OK, because Earth is 2
degrees wide from the moon, so you can just point at the middle of the
visible earth.

Assume an antenna 10m in diameter at the earth end. *Beamwidth will be 1
degree, twice the visible lunar disc size, so you can just point at the
moon, generally.

Gains of antennas
2m @ 2GHz = 30dB
10m @ 2GHz = 44dB

Preceived at Earth = Ptransmitted +30 - 212 +44dB = Ptransmit -138dB.

Assume transmitting with 10 Watts or +40dBm..
Prec = -100dBm

Now, let's look at the receiver:
Power Spectral density of Noise is kT+NF.. kT is -174dBm/Hz and a decent
NF might be 2dB (allowing for some plumbing losses, etc.

-172 dBm/Hz

Eb (energy/Bit) = -100dBm -60dB (1Mbps) = -160dBmJ

So, Eb/No is about +12dB... *If you allow 2dB for implementation loss,
that gets you to 10dB, which will get you a BER of 1E-6, which isn't
terrible. *Coding will improve it, etc.

Take home message:

10W at 2Ghz with reasonably sized antennas at moon and earth can carry 1
Mbps.

Scales linearly with data rate.. You want 10Mbps, you need 100W. *Or
bigger antennas.

Thanks for the info. This at least should be doable with receiving
antennas operated by universities.


Bob Clark

On Jun 16, 6:57 pm, Robert Clark wrote:
On another forum there was debate about whether the requirement of
"near real time" high definition video transmissions was achievable
for a such a low-cost mission.
It would certainly be doable if the receiving antennas on Earth were
the large radio antennas used for space communications with
interplanetary probes or those radio antennas used for radio
astronomy. This is evidenced by the fact that the Kaguya(Selene) lunar
orbiter mission was able to send high definition video to a large
receiving dish radio antenna. And also by the fact that DirecTV sends
high definition video to only 2 foot size antennas from geosynchronous
orbit; so 10 times larger antennas would be able to receive such
signals from a 10 times larger distance at the Moon.
However, I was wondering if it would be possible to detect this using
amateur sized equipment at such a large distance. Usually for
receiving high data rates you used transmissions at very high
frequencies, as higher frequencies can carry more data. For instance
both Kaguya and DirecTV transmit the high def video at gigahertz
frequencies.
However, for the system I'm imaging I'm thinking of using much lower
frequencies, and necessarily longer wavelengths. What I wanted to do
is transmit at decametric wavelengths. High data transmissions rates
would be achieved by making it be pulsed in an on-off fashion at high
intensity but at a rapid rate.
On that other forum the data rate required for high def TV was given
as 256,000 bits per second. So I wanted to make these transmissions be
pulsed at this rapid rate at wavelengths of a few tens's of meters.
My decametric wavelength requirement was because of the fact that
high schools and universities have programs for detecting radio
emissions from Jupiter at these wavelengths:

NASA's Radio JOVE Project.http://radiojove.gsfc.nasa.gov/

The Discovery of Jupiter's Radio Emissions.
How a chance discovery opened up the field of Jovian radio studies.
by Dr. Leonard N. Garciahttp://radiojove.gsfc.nasa.gov/library/sci_briefs/discovery.html

These school and university receiving antennas on Earth consist of
dozens to hundreds of vertical dipoles of lengths at the meters scale
to correspond to the radio wavelengths. Some questions I had: how
intense would the pulse have to be on the Moon to be detectable from
the Moon above background noise for a detector on Earth of say a few
dozen dipoles? Could this be done for the transmitter of power of say
a few hundred watts for a low cost, low weight lander mission? Could
the transmitter antenna on the moon be only a few meters size for the
low weight requirement?
A secondary purpose I had in mind was a pet project of mine involving
linking these many school receivers to form a global telescope at
decametric wavelengths:

From: (Robert Clark)
Date: 23 May 2001 11:15:06 -0700
Subject: Will amateur radio astronomers be the first to directly
detect extrasolar planets?
Newsgroups: rec.radio.amateur.space, rec.radio.amateur.antenna,
sci.astro, sci.astro.seti, sci.space.policyhttp://groups.google.com/group/sci.astro.seti/browse_frm/thread/c0018...

The long wavelengths should make the requirements for accurate
distance information and timing synchrony between the separate
detectors easy to manage even for amateur systems. Using this method
might make the detection achievable even if the power or transmitting
antenna size requirements are not practical for a low cost, low weight
lander on the Moon for an individual detector on Earth.
The recent achievement of real-time very long baseline interferometry
should make it possible to integrate these separate detector signals
in real-time as well:

Astronomers Demonstrate a Global Internet Telescope.
Date Released: Friday, October 08, 2004
Source: Jodrell Bank Observatoryhttp://www.spaceref.com/news/viewpr.html?pid=15251


In this post I suggested using DirecTV's and other satellite TV
companies receiving dishes for SETI:

Newsgroups: sci.astro.seti, sci.astro, rec.radio.amateur.space,
sci.physics
From: (Robert Clark)
Date: 7 Feb 2005 15:07:03 -0800
Subject: Could DirecTV satellite dishes be used for the Square
Kilometer Array - and a more radical proposal[ Can DirectTV-type
satellite dishes be used for SETI?]
http://groups.google.com/group/sci.a...25e5339227855a

In the discussion in that thread there were mentioned several
problems with that proposal (possibly fixable with some expensive
retrofits) but one big problem is that satellite TV is not designed to
be two-way. Some satellite services are two-way when they are also
used for internet access, but this is a much smaller proportion of the
satellite TV subscribers.
However, instead of using the satellite TV dishes, we could use
individual dipole antennas attached to each house. You would need to
communicate high data rates for the signals detected so you would need
broadband internet access for this.
These dipole antennas as per the Radio JOVE project are just simple
vertical wires so could be attached to the house when the installer is
connecting the wiring for the broadband. Possibly you could use the
same external wiring as for the broadband but that might cause
interference with the internet signals.
As shown on the Radio JOVE page the receivers for these dipole
antennas are quite simple so would contribute minimally to the cost of
installation. You do need accurate positional determination and timing
synchrony for each receiving system to do the very long baseline
interferometry, but at these decametric wavelengths this would be easy
to do with GPS receivers carried by the installers. Over time you
could keep the systems in synchrony by timing stamps accessed over the
internet.
I suggested before using 10 million dipoles world-wide for detecting
Jovian-sized planets close in to their primaries out to perhaps 10
light-years. According to this page, over 16.6 million new broadband
internet users came online just in one quarter this year alone,
bringing the number of broadband users world-wide to 429 million:

More people worldwide are subscribing to high-speed Internet
connections.
China and other Asian countries among the growth leaders.
http://www.nationmultimedia.com/2009...y_30105358.php

New broadband subscribers would automatically get the dipole
antennas. At the rate of increase of broadband subscribers, it would
only take 3 months to reach 10 million separate dipoles. If each
installer when setting up a new system, also retrofitted an another
existing broadband system, then you could reach the full coverage of
all the broadband subscribers dipoles in 6 years.
The number of world-wide broadband subscribers will be 500 million by
2010. At current growth rates it would be 900 million within the 6
years it took to equip each broadband subscriber system with one of
the antenna dipoles. This is nearly two orders of magnitude better
sensitivity than a 10 million dipole system. You could detect out to
100 light-years, opening up many more stars to the possibility of
detection.



Bob Clark