Hi,

A question : how weak is a geostationnary satellite signal at the edge ?
(case study)

Imagine a geostationnary TV satellite like AMC-6 located over NY or so (72
deg W) with a signal 50 dB in area 500 km wide, decreasing down to 30 dB a
few hundreds miles offshore and thus very weak in Europe (10 dB ?)
The satellite transmits two signals : its NTSC video (vertically polarized)
near 3.88 GHz and an audio at 6.8 MHz FM mode (monaural), standard specs
used e.g. by NASA TV.

Is there a way to capture its signals from Europe (say ON) using a 2 to 4m
wide type TVRO or Quorum dish (with preamp, NTSC/PAL converter, etc) knowing
that its beam is quite narrow and the signal very weak ?
In addition a beam cut on 6.8 MHz 'd be used to capture its FM signal on HF,
the satellite being not to high above the horizon ... (supposition)
NB. In this example the longitude difference is 50-75 degrees !!

Theoretically, is it possible to built such a system being so far from the
satellite and the satellite being so low over the horizon ?
or the beamwidth of the satellite dish does not permit receiving at such
longitude differences ?

Or say in other words, has an european ham already tried to capture US
geostat satellites successfully ? and using what kind of system (RX and
antenna diam.)
or conversely, has an US ham succeeded to capture signal from an european
geostat satellite (Meteosat...) ?

What should be the minimum antenna specs to get a "good" receive (diameter,
preamp gain, without or without downconverter and then rx qrg, longitude
difference max., signal strength at receive on 2m and 4m dish...)

I think that it is possible with a dish 2m, but I 'd like a confirmation.

Thanks in advance

Thierry, ON4SKY
http://www.astrosurf.com/lombry

"Thierry" - wrote in message ...
Hi,

A question : how weak is a geostationnary satellite signal at the edge ?
(case study)

Imagine a geostationnary TV satellite like AMC-6 located over NY or so (72
deg W) with a signal 50 dB in area 500 km wide, decreasing down to 30 dB a
few hundreds miles offshore and thus very weak in Europe (10 dB ?)
The satellite transmits two signals : its NTSC video (vertically
polarized)
near 3.88 GHz and an audio at 6.8 MHz FM mode (monaural), standard specs
used e.g. by NASA TV.

Is there a way to capture its signals from Europe (say ON) using a 2 to 4m
wide type TVRO or Quorum dish (with preamp, NTSC/PAL converter, etc)
knowing
that its beam is quite narrow and the signal very weak ?
In addition a beam cut on 6.8 MHz 'd be used to capture its FM signal on
HF,
the satellite being not to high above the horizon ... (supposition)
NB. In this example the longitude difference is 50-75 degrees !!

Theoretically, is it possible to built such a system being so far from the
satellite and the satellite being so low over the horizon ?
or the beamwidth of the satellite dish does not permit receiving at such
longitude differences ?

Or say in other words, has an european ham already tried to capture US
geostat satellites successfully ? and using what kind of system (RX and
antenna diam.)
or conversely, has an US ham succeeded to capture signal from an european
geostat satellite (Meteosat...) ?

What should be the minimum antenna specs to get a "good" receive
(diameter,
preamp gain, without or without downconverter and then rx qrg, longitude
difference max., signal strength at receive on 2m and 4m dish...)

I think that it is possible with a dish 2m, but I 'd like a confirmation.

Thanks in advance

Thierry, ON4SKY
http://www.astrosurf.com/lombry

Do the math- what is the minimum dish size required to receive the signal
in the 50dB contour? If your contour is 10dB- you are 40 dB down. Dish gain
goes up 6dB each time you double the diameter- so you need a dsih 128X the
diameter of the 50dB contour dish. to yield the same pix quality.

Dale W4OP

"Dale Parfitt" wrote in message
news:l3Sfd.5421$dW.482@trnddc08...

"Thierry" - wrote in message ...
Hi,

A question : how weak is a geostationnary satellite signal at the edge ?
..

Do the math- what is the minimum dish size required to receive the
signal
in the 50dB contour? If your contour is 10dB- you are 40 dB down. Dish
gain
goes up 6dB each time you double the diameter- so you need a dsih 128X the
diameter of the 50dB contour dish. to yield the same pix quality.

Fine ! (a way of speaking) it's a new information for me.
OK that a 100m dish is not really realistic, at least for an amateur :-((

But the problem is also : as I am very much "out" of the main beam (say 50°
off in longitude), can I receive some signal ?
I have thought that the beam was like a cone and outside there was no
receive at all.
But you seem to say that the decreasing of signal strength is more or less
constant with distance, there is not abrupt decreasing say below 0 dB
contour or so ? right ?
Or in other words is there a maximum distance or a longitude difference over
which there is no more signal ? none ?
For short all 'd be a question of receive dish diameter... (and visibility
of the sat.) ?

Thierry, ON4SKY


Dale W4OP

"Thierry" - wrote in message ...

"Dale Parfitt" wrote in message
news:l3Sfd.5421$dW.482@trnddc08...

"Thierry" - wrote in message ...
Hi,

A question : how weak is a geostationnary satellite signal at the edge
?
..

Do the math- what is the minimum dish size required to receive the
signal
in the 50dB contour? If your contour is 10dB- you are 40 dB down. Dish
gain
goes up 6dB each time you double the diameter- so you need a dsih 128X
the
diameter of the 50dB contour dish. to yield the same pix quality.

Fine ! (a way of speaking) it's a new information for me.
OK that a 100m dish is not really realistic, at least for an amateur :-((

But the problem is also : as I am very much "out" of the main beam (say
50°
off in longitude), can I receive some signal ?
I have thought that the beam was like a cone and outside there was no
receive at all.
But you seem to say that the decreasing of signal strength is more or less
constant with distance, there is not abrupt decreasing say below 0 dB
contour or so ? right ?
Or in other words is there a maximum distance or a longitude difference
over
which there is no more signal ? none ?
For short all 'd be a question of receive dish diameter... (and visibility
of the sat.) ?

Thierry, ON4SKY


Dale W4OP

They may also reuse the frequency.

Tam

Who here remembers Bob Cooper and CATJ magazine from 25 years ago?

There was a fellow in the UK who was doing exactly what you ask, but I can't remember his name. He wrote a column in
CATJ describing his work. I don't recall what size dish he used, but I am sure it was no larger than 10 meters, as he
had limited resources and space.

On the other hand, national governments routinely do what you are describing, using 50 to 100 meter dishes, even the 200
meter one in West Virginia before it collapsed.

--
Crazy George
Remove N O and S P A M imbedded in return address
"Thierry" - wrote in message ...
Hi,

A question : how weak is a geostationnary satellite signal at the edge ?
(case study)

Imagine a geostationnary TV satellite like AMC-6 located over NY or so (72
deg W) with a signal 50 dB in area 500 km wide, decreasing down to 30 dB a
few hundreds miles offshore and thus very weak in Europe (10 dB ?)
The satellite transmits two signals : its NTSC video (vertically polarized)
near 3.88 GHz and an audio at 6.8 MHz FM mode (monaural), standard specs
used e.g. by NASA TV.

Is there a way to capture its signals from Europe (say ON) using a 2 to 4m
wide type TVRO or Quorum dish (with preamp, NTSC/PAL converter, etc) knowing
that its beam is quite narrow and the signal very weak ?
In addition a beam cut on 6.8 MHz 'd be used to capture its FM signal on HF,
the satellite being not to high above the horizon ... (supposition)
NB. In this example the longitude difference is 50-75 degrees !!

Theoretically, is it possible to built such a system being so far from the
satellite and the satellite being so low over the horizon ?
or the beamwidth of the satellite dish does not permit receiving at such
longitude differences ?

Or say in other words, has an european ham already tried to capture US
geostat satellites successfully ? and using what kind of system (RX and
antenna diam.)
or conversely, has an US ham succeeded to capture signal from an european
geostat satellite (Meteosat...) ?

What should be the minimum antenna specs to get a "good" receive (diameter,
preamp gain, without or without downconverter and then rx qrg, longitude
difference max., signal strength at receive on 2m and 4m dish...)

I think that it is possible with a dish 2m, but I 'd like a confirmation.

Thanks in advance

Thierry, ON4SKY
http://www.astrosurf.com/lombry