Fw: Re: NASA's American Student Moon Orbiter...
----- Original Message ----- From: [email protected] To: [email protected] Cc: [email protected] ; [email protected] Sent: Saturday, July 05, 2008 1:21 AM Subject: Re: [amsat-bb] Re: NASA's American Student Moon Orbiter...
Hi Joe.
Looking at 70cm up and 2m down, Dom has shown the 2m path can be achieved with a 13dB gain antenna on the ground and 10 Watts on the satellite. That's a very small bandwidth transponder
For the uplink, it's not quite as easy. I've just run a link budget calculator and it looks like you need about 80 Watts and 20dB of antenna gain on 70cm. That produces around 5000 Watts ERP (allowing for losses)
As Dom pointed out, you dont just need a signal thats just above the noise level at the satellite. Up there you need enough of a signal at the receiver so that the satellites transmitter can generate a decent amount of power on 2m.
The 5kW ERP generates a signal around 16dB above noise at the satellite. With luck, that will be sufficient to produce enough power on the 2m downlink.
Of course there are a lot of variables and 'detail' . but 5kW ERP up and a 13dB gain antenna on the downlink are 'In the ballpark' for a minimal working U/V system.
Thanks
David
Hi David, G0MRF
Looking at the specifications of AO40 I found that at 435 MHz the equivalent noise temperature of the RX is TN (k) = 500 kelvin The Prx (23) i.e. the power needed by the receiver to develope a signal of 23 dB over the noise is -145 dBW The 435 MHz satellite antenna gain is 14 dBi It is not specified the transponder output power with a S/N=23 dB because it depends on what transponder is intended to be used for the downlink. Probably -145 dBW at the RX input is the power needed to get a S/N = 23 dB at the IF input before to be switched by the matrix to different transponders.
By the way the attenuation earth to moon at 435 MHz for 400.000 km is 197 dB and going back to calculations we get :
TX power at 435 MHz on earth........................ + 20 dBW (100 W) 435 MHz antenna gain on earth ....................... + 18 dB ----------------- EIRP of the ground station................................ + 38 dBW ( 6.3 kW)
Attenuation 435 MHz for 400.000 km .............. -197 dB ------------------ Power received on a 435 MHz isotropic........... - 159 dBW antenna at a distance of 400.000 km Satellite antenna gain ......................................... + 14 dBi ------------------ Received power at RX input for S/N=23 dB.... - 145 dBW
It seems that both calculations match and 5 kW to 6 kW EIRP up on 70 cm and 13 dBi antenna gain on the 2 meters downlink are a minimum necessary provided that the satellite antennas orbiting around the moon are constantly directed toward the earth but this is a very difficult task.
73" de
i8CVS Domenico
UV is a problem as hams in much of the U.S. are limited to 1 kW EIRP on 70 cm. The military is the primary user of the band. Recently, some repeaters near PAVE PAWS sites have had to reduce power to 5 W due to interference with the return signal from the 4 GW EIRP RADAR.
73,
John KD6OZH
----- Original Message ----- From: "i8cvs" [email protected] To: "AMSAT-BB" [email protected]; [email protected]; "Joe" [email protected]; "G0MRF David Bowman" [email protected] Sent: Sunday, July 06, 2008 08:53 UTC Subject: [amsat-bb] Fw: Re: NASA's American Student Moon Orbiter...
----- Original Message ----- From: [email protected] To: [email protected] Cc: [email protected] ; [email protected] Sent: Saturday, July 05, 2008 1:21 AM Subject: Re: [amsat-bb] Re: NASA's American Student Moon Orbiter...
Hi Joe.
Looking at 70cm up and 2m down, Dom has shown the 2m path can be achieved with a 13dB gain antenna on the ground and 10 Watts on the satellite. That's a very small bandwidth transponder
For the uplink, it's not quite as easy. I've just run a link budget calculator and it looks like you need about 80 Watts and 20dB of antenna gain on 70cm. That produces around 5000 Watts ERP (allowing for losses)
As Dom pointed out, you dont just need a signal thats just above the noise level at the satellite. Up there you need enough of a signal at the receiver so that the satellites transmitter can generate a decent amount of power on 2m.
The 5kW ERP generates a signal around 16dB above noise at the satellite. With luck, that will be sufficient to produce enough power on the 2m downlink.
Of course there are a lot of variables and 'detail' . but 5kW ERP up and a 13dB gain antenna on the downlink are 'In the ballpark' for a minimal working U/V system.
Thanks
David
Hi David, G0MRF
Looking at the specifications of AO40 I found that at 435 MHz the equivalent noise temperature of the RX is TN (k) = 500 kelvin The Prx (23) i.e. the power needed by the receiver to develope a signal of 23 dB over the noise is -145 dBW The 435 MHz satellite antenna gain is 14 dBi It is not specified the transponder output power with a S/N=23 dB because it depends on what transponder is intended to be used for the downlink. Probably -145 dBW at the RX input is the power needed to get a S/N = 23 dB at the IF input before to be switched by the matrix to different transponders.
By the way the attenuation earth to moon at 435 MHz for 400.000 km is 197 dB and going back to calculations we get :
TX power at 435 MHz on earth........................ + 20 dBW (100 W) 435 MHz antenna gain on earth ....................... + 18 dB
EIRP of the ground station................................ + 38 dBW ( 6.3 kW)
Attenuation 435 MHz for 400.000 km .............. -197 dB
Power received on a 435 MHz isotropic........... - 159 dBW antenna at a distance of 400.000 km Satellite antenna gain ......................................... + 14 dBi
Received power at RX input for S/N=23 dB.... - 145 dBW
It seems that both calculations match and 5 kW to 6 kW EIRP up on 70 cm and 13 dBi antenna gain on the 2 meters downlink are a minimum necessary provided that the satellite antennas orbiting around the moon are constantly directed toward the earth but this is a very difficult task.
73" de
i8CVS Domenico
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi John, KD6OZH
There are many 432 MHz EME stations in USA and probably using big dish (33 ft) in the range of 30 dBi gain with a lobe of 5 degrees at -3 dB do not create interference to PAVE PAWS when the dish is aimed toward the moon.
73" de
i8CVS Domenico
----- Original Message ----- From: "John B. Stephensen" [email protected] To: "i8cvs" [email protected]; "AMSAT-BB" [email protected]; [email protected]; "Joe" [email protected]; "G0MRF David Bowman" [email protected] Sent: Sunday, July 06, 2008 2:24 PM Subject: Re: [amsat-bb] Fw: Re: NASA's American Student Moon Orbiter...
UV is a problem as hams in much of the U.S. are limited to 1 kW EIRP on 70 cm. The military is the primary user of the band. Recently, some repeaters near PAVE PAWS sites have had to reduce power to 5 W due to interference with the return signal from the 4 GW EIRP RADAR.
73,
John KD6OZH
----- Original Message ----- From: "i8cvs" [email protected] To: "AMSAT-BB" [email protected]; [email protected]; "Joe" [email protected]; "G0MRF David Bowman" [email protected] Sent: Sunday, July 06, 2008 08:53 UTC Subject: [amsat-bb] Fw: Re: NASA's American Student Moon Orbiter...
----- Original Message ----- From: [email protected] To: [email protected] Cc: [email protected] ; [email protected] Sent: Saturday, July 05, 2008 1:21 AM Subject: Re: [amsat-bb] Re: NASA's American Student Moon Orbiter...
Hi Joe.
Looking at 70cm up and 2m down, Dom has shown the 2m path can be
achieved
with a 13dB gain antenna on the ground and 10 Watts on the satellite. That's a very small bandwidth transponder
For the uplink, it's not quite as easy. I've just run a link budget calculator and it looks like you need about 80 Watts and 20dB of antenna gain on 70cm. That produces around 5000
Watts
ERP (allowing for losses)
As Dom pointed out, you dont just need a signal thats just above the noise level at the satellite. Up there you need enough of a signal at
the
receiver so that the satellites transmitter can generate a decent amount of power on 2m.
The 5kW ERP generates a signal around 16dB above noise at the
satellite.
With luck, that will be sufficient to produce enough power on the 2m downlink.
Of course there are a lot of variables and 'detail' . but 5kW ERP up
and
a 13dB gain antenna on the downlink are 'In the ballpark' for a minimal working U/V system.
Thanks
David
Hi David, G0MRF
Looking at the specifications of AO40 I found that at 435 MHz the equivalent noise temperature of the RX is TN (k) = 500 kelvin The Prx (23) i.e. the power needed by the receiver to develope a signal of 23 dB over the noise is -145 dBW The 435 MHz satellite antenna gain is 14 dBi It is not specified the transponder output power with a S/N=23 dB
because
it depends on what transponder is intended to be used for the downlink. Probably -145 dBW at the RX input is the power needed to get a S/N = 23 dB at the IF input before to be switched by the matrix to different transponders.
By the way the attenuation earth to moon at 435 MHz for 400.000 km is
197
dB and going back to calculations we get :
TX power at 435 MHz on earth........................ + 20 dBW (100 W) 435 MHz antenna gain on earth ....................... + 18 dB
EIRP of the ground station................................ + 38 dBW (
6.3
kW)
Attenuation 435 MHz for 400.000 km .............. -197 dB
Power received on a 435 MHz isotropic........... - 159 dBW antenna at a distance of 400.000 km Satellite antenna gain ......................................... + 14
dBi
Received power at RX input for S/N=23 dB.... - 145 dBW
It seems that both calculations match and 5 kW to 6 kW EIRP up on 70 cm and 13 dBi antenna gain on the 2 meters downlink are a minimum necessary provided that the satellite antennas orbiting around the moon are constantly directed toward the earth but this is a very difficult task.
73" de
i8CVS Domenico
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
The 420-450 MHz Military PRIMARY Allocation is an issue in a number of countries, in some of which Radio Amateurs do not have transmit access to 70cm at all.
The United Kingdom Regulator OFCOM has published on their website the following information on Fylingdales in the UK.
Interference to UHF Band 1 and GSM Radio Systems from Fylingdales Radar http://www.ofcom.org.uk/radiocomms/spectrumawards/completedawards/award_412/...
PDF Interference to UHF Band 1 and GSM Radio Systems from Fylingdales Radar http://www.ofcom.org.uk/radiocomms/spectrumawards/completedawards/award_412/...
PDF Fylingdales co-ordination tool http://www.ofcom.org.uk/radiocomms/spectrumawards/completedawards/award_412/...
Fylingdales co-ordination tool workshops http://www.ofcom.org.uk/radiocomms/spectrumawards/completedawards/award_412/...
Questions and Answers on the award of wireless telegraphy licences for use of the spectrum bands 412-414 MHz paired with 422-424 MHz http://www.ofcom.org.uk/radiocomms/spectrumawards/completedawards/award_412/...
I recall that several years ago I think Peleg 4X1GP on this list, pointed out that 70cm isn't an Amateur band (apologies Peleg if I misquote you). The Amateur Primary allocations stop at 146 MHz and then there's nothing until 24 GHz.
73 Trevor M5AKA
--- On Sun, 6/7/08, John B. Stephensen [email protected] wrote:
UV is a problem as hams in much of the U.S. are limited to 1 kW EIRP on 70 cm. The military is the primary user of the band. Recently, some repeaters near PAVE PAWS sites have had to reduce power to 5 W due to interference with the return signal from the 4 GW EIRP RADAR.
73,
John KD6OZH
----- Original Message ----- From: "i8cvs" [email protected] To: "AMSAT-BB" [email protected]; [email protected]; "Joe" [email protected]; "G0MRF David Bowman" [email protected] Sent: Sunday, July 06, 2008 08:53 UTC Subject: [amsat-bb] Fw: Re: NASA's American Student Moon Orbiter...
----- Original Message ----- From: [email protected] To: [email protected] Cc: [email protected] ; [email protected] Sent: Saturday, July 05, 2008 1:21 AM Subject: Re: [amsat-bb] Re: NASA's American
Student Moon Orbiter...
Hi Joe.
Looking at 70cm up and 2m down, Dom has shown the 2m
path can be achieved
with a 13dB gain antenna on the ground and 10 Watts on
the satellite.
That's a very small bandwidth transponder
For the uplink, it's not quite as easy. I've just run a link budget calculator and it
looks like you need about
80 Watts and 20dB of antenna gain on 70cm. That
produces around 5000 Watts
ERP (allowing for losses)
As Dom pointed out, you dont just need a signal thats
just above the
noise level at the satellite. Up there you need enough
of a signal at the
receiver so that the satellites transmitter can
generate a decent amount
of power on 2m.
The 5kW ERP generates a signal around 16dB above
noise at the satellite.
With luck, that will be sufficient to produce enough
power on the 2m
downlink.
Of course there are a lot of variables and
'detail' . but 5kW ERP up and
a 13dB gain antenna on the downlink are 'In the
ballpark' for a minimal
working U/V system.
Thanks
David
Hi David, G0MRF
Looking at the specifications of AO40 I found that at
435 MHz the
equivalent noise temperature of the RX is TN (k) = 500 kelvin The Prx (23) i.e. the power needed by the receiver to
develope a signal
of 23 dB over the noise is -145 dBW The 435 MHz satellite antenna gain is 14 dBi It is not specified the transponder output power with
a S/N=23 dB because
it depends on what transponder is intended to be used
for the downlink.
Probably -145 dBW at the RX input is the power needed
to get a S/N = 23
dB at the IF input before to be switched by the matrix
to different
transponders.
By the way the attenuation earth to moon at 435 MHz
for 400.000 km is 197
dB and going back to calculations we get :
TX power at 435 MHz on earth........................
- 20 dBW (100 W)
435 MHz antenna gain on earth .......................
- 18 dB
EIRP of the ground
station................................ + 38 dBW ( 6.3
kW)
Attenuation 435 MHz for 400.000 km ..............
-197 dB
Power received on a 435 MHz isotropic........... -
159 dBW
antenna at a distance of 400.000 km Satellite antenna gain
......................................... + 14 dBi
Received power at RX input for S/N=23 dB.... - 145
dBW
It seems that both calculations match and 5 kW to 6
kW EIRP up on 70 cm
and 13 dBi antenna gain on the 2 meters downlink are a
minimum necessary
provided that the satellite antennas orbiting around
the moon are
constantly directed toward the earth but this is a
very difficult task.
73" de
i8CVS Domenico
Sent via [email protected]. Opinions expressed are
those of the author.
Not an AMSAT-NA member? Join now to support the
amateur satellite program!
Subscription settings:
http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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They're lucky not to live in a restricted area. I had to live with the 1 kW EIRP restriction for many years. 2 meter or 13 cm uplinks eliminate the problem.
73,
John KD6OZH
----- Original Message ----- From: "i8cvs" [email protected] To: "John B. Stephensen" [email protected]; "AMSAT-BB" [email protected]; [email protected]; "Joe" [email protected]; "G0MRF David Bowman" [email protected] Sent: Sunday, July 06, 2008 21:35 UTC Subject: Re: [amsat-bb] Fw: Re: NASA's American Student Moon Orbiter...
Hi John, KD6OZH
There are many 432 MHz EME stations in USA and probably using big dish (33 ft) in the range of 30 dBi gain with a lobe of 5 degrees at -3 dB do not create interference to PAVE PAWS when the dish is aimed toward the moon.
73" de
i8CVS Domenico
----- Original Message ----- From: "John B. Stephensen" [email protected] To: "i8cvs" [email protected]; "AMSAT-BB" [email protected]; [email protected]; "Joe" [email protected]; "G0MRF David Bowman" [email protected] Sent: Sunday, July 06, 2008 2:24 PM Subject: Re: [amsat-bb] Fw: Re: NASA's American Student Moon Orbiter...
UV is a problem as hams in much of the U.S. are limited to 1 kW EIRP on 70 cm. The military is the primary user of the band. Recently, some repeaters near PAVE PAWS sites have had to reduce power to 5 W due to interference with the return signal from the 4 GW EIRP RADAR.
73,
John KD6OZH
----- Original Message ----- From: "i8cvs" [email protected] To: "AMSAT-BB" [email protected]; [email protected]; "Joe" [email protected]; "G0MRF David Bowman" [email protected] Sent: Sunday, July 06, 2008 08:53 UTC Subject: [amsat-bb] Fw: Re: NASA's American Student Moon Orbiter...
----- Original Message ----- From: [email protected] To: [email protected] Cc: [email protected] ; [email protected] Sent: Saturday, July 05, 2008 1:21 AM Subject: Re: [amsat-bb] Re: NASA's American Student Moon Orbiter...
Hi Joe.
Looking at 70cm up and 2m down, Dom has shown the 2m path can be
achieved
with a 13dB gain antenna on the ground and 10 Watts on the satellite. That's a very small bandwidth transponder
For the uplink, it's not quite as easy. I've just run a link budget calculator and it looks like you need about 80 Watts and 20dB of antenna gain on 70cm. That produces around 5000
Watts
ERP (allowing for losses)
As Dom pointed out, you dont just need a signal thats just above the noise level at the satellite. Up there you need enough of a signal at
the
receiver so that the satellites transmitter can generate a decent amount of power on 2m.
The 5kW ERP generates a signal around 16dB above noise at the
satellite.
With luck, that will be sufficient to produce enough power on the 2m downlink.
Of course there are a lot of variables and 'detail' . but 5kW ERP up
and
a 13dB gain antenna on the downlink are 'In the ballpark' for a minimal working U/V system.
Thanks
David
Hi David, G0MRF
Looking at the specifications of AO40 I found that at 435 MHz the equivalent noise temperature of the RX is TN (k) = 500 kelvin The Prx (23) i.e. the power needed by the receiver to develope a signal of 23 dB over the noise is -145 dBW The 435 MHz satellite antenna gain is 14 dBi It is not specified the transponder output power with a S/N=23 dB
because
it depends on what transponder is intended to be used for the downlink. Probably -145 dBW at the RX input is the power needed to get a S/N = 23 dB at the IF input before to be switched by the matrix to different transponders.
By the way the attenuation earth to moon at 435 MHz for 400.000 km is
197
dB and going back to calculations we get :
TX power at 435 MHz on earth........................ + 20 dBW (100 W) 435 MHz antenna gain on earth ....................... + 18 dB
EIRP of the ground station................................ + 38 dBW (
6.3
kW)
Attenuation 435 MHz for 400.000 km .............. -197 dB
Power received on a 435 MHz isotropic........... - 159 dBW antenna at a distance of 400.000 km Satellite antenna gain ......................................... + 14
dBi
Received power at RX input for S/N=23 dB.... - 145 dBW
It seems that both calculations match and 5 kW to 6 kW EIRP up on 70 cm and 13 dBi antenna gain on the 2 meters downlink are a minimum necessary provided that the satellite antennas orbiting around the moon are constantly directed toward the earth but this is a very difficult task.
73" de
i8CVS Domenico
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (3)
-
i8cvs -
John B. Stephensen -
Trevor