Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Well, it's finally happened. We've come full circle. They've reinvented Echo-1. http://en.wikipedia.org/wiki/Project_Echo
Of course, that one was 10x larger. What makes this a 10m (band) operation? I expect it would work on the higher bands too, especially with the smaller size. What band did they use ~50-ish years ago?
Greg KO6TH
From: [email protected] To: [email protected]
Cancel
Date: Mon, 28 Jun 2010 13:44:45 -0400 Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
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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Looks like freqs used were right around 2 gig and just above 2 meters too. according to this book http://books.google.com/books?id=_azf94TByF8C&pg=PA4&lpg=PA4&dq=...
Joe WB9SBD Near Space Sciences
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/29/2010 12:03 AM, Greg D. wrote:
Well, it's finally happened. We've come full circle. They've reinvented Echo-1. http://en.wikipedia.org/wiki/Project_Echo
Of course, that one was 10x larger. What makes this a 10m (band) operation? I expect it would work on the higher bands too, especially with the smaller size. What band did they use ~50-ish years ago?
Greg KO6TH
From: [email protected] To: [email protected]
CancelDate: Mon, 28 Jun 2010 13:44:45 -0400 Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
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Hmmm, S-band is probably too noisy for the really weak return signal. It might be physically too small for L-band, though that's a pretty quiet place. Maybe something on C-band? C-C Rider on Balloon Bounce?
If this thing works, I wonder how big a balloon we can stuff into a Cubesat?
Greg KO6TH
Date: Tue, 29 Jun 2010 00:24:29 -0500 From: [email protected] To: [email protected] Subject: [amsat-bb] Re: HF Satellite Relay
Looks like freqs used were right around 2 gig and just above 2 meters too. according to this book http://books.google.com/books?id=_azf94TByF8C&pg=PA4&lpg=PA4&dq=...
Joe WB9SBD Near Space Sciences
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/29/2010 12:03 AM, Greg D. wrote:
Well, it's finally happened. We've come full circle. They've reinvented Echo-1. http://en.wikipedia.org/wiki/Project_Echo
Of course, that one was 10x larger. What makes this a 10m (band) operation? I expect it would work on the higher bands too, especially with the smaller size. What band did they use ~50-ish years ago?
Greg KO6TH
From: [email protected] To: [email protected]
CancelDate: Mon, 28 Jun 2010 13:44:45 -0400 Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
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 New Busy is not the old busy. Search, chat and e-mail from your inbox. http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:W... _______________________________________________ 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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Hi Greg, KO6TH
Echo-1 A was a passive communication satellite launched on 12 august 1960 in a circular orbit at 1519 - 1687 km and it was a balloon 30.5 meters in diameter made of 0.0127 mm thick metallized mylar polyester film to reflects signals transmitted from the earth at 960 MHz and 2390 MHz
Echo-1 A was also carrying two VHF TLM beacons at 108.000 and 108.03 MHz with a power of 45 mW and I was receiving both of them for several days using a homebrewed downconverter with two low noise triodes 6AN4 in a cascode input stage and a simple three elements yagi.
At that epoch time the 108 MHz band was used only for aeronautical and space communications but not for FM broadcasting as novadays so that it was free of interfering signals and man made noise and the only existing noise was the galactic noise.
By the way in the early 1960 it was my first received satellite signal and it was very exiting to receive the 45 mW beacons using only a three elements yagi and a downconverter with a noise figure at best of 6 dB while to see the balloon as a bright star by naked eye flying in the night.
For more technical informations on ECHO-1 ,ECHO-1A and ECHO-2 look at the following web page:
http://msl.jpl.nasa.gov/QuickLooks/echoQL.html
73" de
i8CVS Domenico
----- Original Message ----- From: "Greg D." [email protected] To: [email protected]; [email protected] Sent: Tuesday, June 29, 2010 7:03 AM Subject: [amsat-bb] Re: HF Satellite Relay
Well, it's finally happened. We've come full circle. They've reinvented
Echo-1.
http://en.wikipedia.org/wiki/Project_Echo
Of course, that one was 10x larger. What makes this a 10m (band)
operation? I expect it would work on the higher bands too, especially with the smaller size. What band did they use ~50-ish years ago?
Greg KO6TH
From: [email protected] To: [email protected]
CancelDate: Mon, 28 Jun 2010 13:44:45 -0400 Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
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 New Busy is not the old busy. Search, chat and e-mail from your inbox.
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They've reinvented Echo-1. http://en.wikipedia.org/wiki/Project_Echo
Of course, that one was 10x larger.
What makes this a 10m (band) operation? I expect it would work on the higher bands ...
This one is not a full surface sphere, but a bucky-ball wire frame with about 4 foot thin sides to each polygon making a 10 meter diameter very open structure. SO anything higher in freq just goes right through.
Bob, WB4APR
I remember Echo very well. As Domenico stated it was very visible. I remember my father taking my siblings and I outside to view. He certainly had my attention then.
73, Bill NJ1H
On 6/29/2010 2:05 PM, i8cvs wrote:
Hi Greg, KO6TH
Echo-1 A was a passive communication satellite launched on 12 august 1960 in a circular orbit at 1519 - 1687 km and it was a balloon 30.5 meters in diameter made of 0.0127 mm thick metallized mylar polyester film to reflects signals transmitted from the earth at 960 MHz and 2390 MHz
Echo-1 A was also carrying two VHF TLM beacons at 108.000 and 108.03 MHz with a power of 45 mW and I was receiving both of them for several days using a homebrewed downconverter with two low noise triodes 6AN4 in a cascode input stage and a simple three elements yagi.
At that epoch time the 108 MHz band was used only for aeronautical and space communications but not for FM broadcasting as novadays so that it was free of interfering signals and man made noise and the only existing noise was the galactic noise.
By the way in the early 1960 it was my first received satellite signal and it was very exiting to receive the 45 mW beacons using only a three elements yagi and a downconverter with a noise figure at best of 6 dB while to see the balloon as a bright star by naked eye flying in the night.
For more technical informations on ECHO-1 ,ECHO-1A and ECHO-2 look at the following web page:
http://msl.jpl.nasa.gov/QuickLooks/echoQL.html
73" de
i8CVS Domenico
----- Original Message ----- From: "Greg D."[email protected] To:[email protected];[email protected] Sent: Tuesday, June 29, 2010 7:03 AM Subject: [amsat-bb] Re: HF Satellite Relay
----- Original Message ----- From: "Robert Bruninga" [email protected] To: [email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x Sigma Pr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 1500^3 i.e the distance from the Passive HF relay satellite and the earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the Passive HF relay satellite as seen as a radar target disc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71 Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14
Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2 Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1 Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^ -25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB into a bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = - 151dBW or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi ----------- Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB ----------- Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW ----------- Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 73" de
i8CVS Domenico
You gotta love this guy! It takes me days to figure it out, but I always learn something!
73 Bob W7LRD
----- Original Message ----- From: "i8cvs" [email protected] To: "Bob Bruninga" [email protected], "AMSAT-BB" [email protected] Sent: Tuesday, June 29, 2010 6:52:57 PM Subject: [amsat-bb] Re: HF Satellite Relay
----- Original Message ----- From: "Robert Bruninga" [email protected] To: [email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x Sigma Pr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 1500^3 i.e the distance from the Passive HF relay satellite and the earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the Passive HF relay satellite as seen as a radar target disc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71 Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14
Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2 Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1 Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^ -25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB into a bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = - 151dBW or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi ----------- Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB ----------- Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW ----------- Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 73" de
i8CVS Domenico
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Dominico,
Your path loss calculations were very interesting. At first glance, I assumed it would be possible to hear 28MHz echoes off of the 10M sphere since smaller targets such as the ionized head of a meteor can reflect such signals with enough signal power to be heard.
But, I think this is one of those apples to oranges comparisons since: a. the ionization around the front of the meteor head is responsible for signal reflection, not the rock itself. And b. the diameter of the ionized atmosphere in front of the meteor may be a lot larger than one would imagine.
The 10M sphere brought another question to mind -- Mike Wantanabe, JH1KRC, managed to hear his own EME echoes on the 21MHz using a KW and a 6 element Yagi. Details and recordings are on his website (see below). I was wondering how the path loss calculations compare with his EME results.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
Thanks Dominico...
Tony -K2MO
On 6/29/2010 9:52 PM, i8cvs wrote:
----- Original Message ----- From: "Robert Bruninga"[email protected] To:[email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x SigmaPr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 1500^3 i.e the distance from the Passive HF relay satellite and the earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the Passive HF relay satellite as seen as a radar target disc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14
Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^ -25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB into a bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = - 151dBW or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi ----------- Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB ----------- Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW ----------- Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 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
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Domenico,
Thanks for the calculations. You confirmed it will not work for Hams.
That is about what I was getting and I wanted to make sure before I scratched the idea off the list of possibilities. I just wanted to check-it-out since the purpose of the large buckyball in space was for "HF REFLECTION", I wanted to see if it had any possibilities for amateurs.
Apparentlly it will only be good for HF megawatt radars... Thanks Bob, WB4APR
-----Original Message----- From: i8cvs [mailto:[email protected]] Sent: Tuesday, June 29, 2010 9:53 PM To: Bob Bruninga; AMSAT-BB Subject: Re: [amsat-bb] HF Satellite Relay
----- Original Message ----- From: "Robert Bruninga" [email protected] To: [email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler
of
+/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link
budget
using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical,
so
the reflection coefficient would be constant within 1 dB.
That
is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an
amateur
capability to use it. It is not designed for comms, but as a calibration sphere
for
over the horizon radars that have LOTS more power and LOTS
more
gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere
is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept
of Radar
Equation is as follows:
Pt x Gt x Ar x SigmaPr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square
meters.
R = Radius of a sphere wich distance from the earth is 1500^3
i.e
the distance from the Passive HF relay satellite andthe earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the
Passive
HF relay satellite as seen as a radar targetdisc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14
Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1
Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^
-25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the
Noise Figure
belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB
into a
bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = -
151dBW
or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi
Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB
Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB
Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW
Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 73" de
i8CVS Domenico
I agree,
It's not the meteor or even the ionized portion near the head that you bounce signals off of, it's the inonized trail that it leaves behind. and that can be many many miles long.
Now about reflecting off of odd shaped things. A buddy an myself used to in the late 70's have fun on 2 meters just playing around. we were too far apart for direct communication, I was in the northwest suburbs of Chicago, he was down in central indiana.
We would point our 4 ele beams at eachother and run like a meteor scatter transmission sequesnce. and would make a qso. it was flaky and wide variations in signal strength. But what did we use?
It was all the Jets coming in to land at Ohare! between us was the main route for all the jets to com in on. The route killed TV all the time by making signals in phase and then out then in then out, so we thought if it's strong enough reflection to cancel out a direct megawayy signal, hmmm. so we tried and it worked and worked faily well. each "Opening" lasted between 10 and 15 seconds. and would go most times from s zero to peg the meter.
was fun and thats an odd shaped reflector. that for me was ohhh 60 miles away, and for him close to 100 miles.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/30/2010 3:31 AM, Tony wrote:
Dominico,
Your path loss calculations were very interesting. At first glance, I assumed it would be possible to hear 28MHz echoes off of the 10M sphere since smaller targets such as the ionized head of a meteor can reflect such signals with enough signal power to be heard.
But, I think this is one of those apples to oranges comparisons since: a. the ionization around the front of the meteor head is responsible for signal reflection, not the rock itself. And b. the diameter of the ionized atmosphere in front of the meteor may be a lot larger than one would imagine.
The 10M sphere brought another question to mind -- Mike Wantanabe, JH1KRC, managed to hear his own EME echoes on the 21MHz using a KW and a 6 element Yagi. Details and recordings are on his website (see below). I was wondering how the path loss calculations compare with his EME results.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
Thanks Dominico...
Tony -K2MO
On 6/29/2010 9:52 PM, i8cvs wrote:
----- Original Message ----- From: "Robert Bruninga"[email protected] To:[email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x SigmaPr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 1500^3 i.e the distance from the Passive HF relay satellite and the earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the Passive HF relay satellite as seen as a radar target disc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14
Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^ -25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB into a bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = - 151dBW or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi ----------- Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB ----------- Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW ----------- Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 73" de
i8CVS Domenico
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What about the narrow band digital EME modes?
Mark N8MH
On Wed, Jun 30, 2010 at 9:45 AM, Robert Bruninga [email protected] wrote:
Domenico,
Thanks for the calculations. You confirmed it will not work for Hams.
That is about what I was getting and I wanted to make sure before I scratched the idea off the list of possibilities. I just wanted to check-it-out since the purpose of the large buckyball in space was for "HF REFLECTION", I wanted to see if it had any possibilities for amateurs.
Apparentlly it will only be good for HF megawatt radars... Thanks Bob, WB4APR
-----Original Message----- From: i8cvs [mailto:[email protected]] Sent: Tuesday, June 29, 2010 9:53 PM To: Bob Bruninga; AMSAT-BB
----- Original Message ----- From: "Joe" [email protected] To: [email protected] Sent: Wednesday, June 30, 2010 4:35 PM Subject: [amsat-bb] Re: HF Satellite Relay
I agree,
Now about reflecting off of odd shaped things. A buddy an myself used to in the late 70's have fun on 2 meters just playing around. we were too far apart for direct communication, I was in the northwest suburbs of Chicago, he was down in central indiana.
We would point our 4 ele beams at eachother and run like a meteor scatter transmission sequesnce. and would make a qso. it was flaky and wide variations in signal strength. But what did we use?
It was all the Jets coming in to land at Ohare! between us was the main route for all the jets to com in on. The route killed TV all the time by making signals in phase and then out then in then out, so we thought if it's strong enough reflection to cancel out a direct megawayy signal, hmmm. so we tried and it worked and worked faily well. each "Opening" lasted between 10 and 15 seconds. and would go most times from s zero to peg the meter.
was fun and thats an odd shaped reflector. that for me was ohhh 60 miles away, and for him close to 100 miles.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
Hi Joe, WB9SBD
I agree that the QSO was possible because It was the reflection of all the Jets coming in to land at Ohare! between you and your ham friend it was the main route for all the jets to com in on.
For the above reason I have sent to you a zipped file of a very interesting article on this matter titled "Aircraft Scatter" written by Kent Britain, WA5VJB.
If someone is isterested on it drop me a request off line.
Best 73" de
i8CVS Domenico
----- Original Message ----- From: "Mark L. Hammond" [email protected] To: [email protected] Cc: "i8cvs" [email protected]; "AMSAT-BB" [email protected] Sent: Wednesday, June 30, 2010 4:51 PM Subject: Re: [amsat-bb] Re: HF Satellite Relay
What about the narrow band digital EME modes?
Mark N8MH
Hi Mark, N8MH
I don't know if a narrow band digital EME mode can detect a 28 MHz signal ranging betwen -45 to -48 dB belove the noise but also the Doppler would make that difficult.
73" de
i8CVS Domenico
On 6/30/2010 10:35 AM, Joe wrote:
I agree,
It's not the meteor or even the ionized portion near the head that you bounce signals off of, it's the inonized trail that it leaves behind. and that can be many many miles long.
Joe - It would seem that the plasma cloud in front of the meteor would be moving at the same velocity as the meteor itself and would cause the fast Doppler shift we see prior to the trail formation.
Tony -K2MO
Now about reflecting off of odd shaped things. A buddy an myself used to in the late 70's have fun on 2 meters just playing around. we were too far apart for direct communication, I was in the northwest suburbs of Chicago, he was down in central indiana.
We would point our 4 ele beams at eachother and run like a meteor scatter transmission sequesnce. and would make a qso. it was flaky and wide variations in signal strength. But what did we use?
It was all the Jets coming in to land at Ohare! between us was the main route for all the jets to com in on. The route killed TV all the time by making signals in phase and then out then in then out, so we thought if it's strong enough reflection to cancel out a direct megawayy signal, hmmm. so we tried and it worked and worked faily well. each "Opening" lasted between 10 and 15 seconds. and would go most times from s zero to peg the meter.
was fun and thats an odd shaped reflector. that for me was ohhh 60 miles away, and for him close to 100 miles.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/30/2010 3:31 AM, Tony wrote:
Dominico,
Your path loss calculations were very interesting. At first glance, I assumed it would be possible to hear 28MHz echoes off of the 10M sphere since smaller targets such as the ionized head of a meteor can reflect such signals with enough signal power to be heard.
But, I think this is one of those apples to oranges comparisons since: a. the ionization around the front of the meteor head is responsible for signal reflection, not the rock itself. And b. the diameter of the ionized atmosphere in front of the meteor may be a lot larger than one would imagine.
The 10M sphere brought another question to mind -- Mike Wantanabe, JH1KRC, managed to hear his own EME echoes on the 21MHz using a KW and a 6 element Yagi. Details and recordings are on his website (see below). I was wondering how the path loss calculations compare with his EME results.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
Thanks Dominico...
Tony -K2MO
On 6/29/2010 9:52 PM, i8cvs wrote:
----- Original Message ----- From: "Robert Bruninga"[email protected] To:[email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x SigmaPr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 1500^3 i.e the distance from the Passive HF relay satellite and the earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the Passive HF relay satellite as seen as a radar target disc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71 Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^ -25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB into a bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = - 151dBW or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi ----------- Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB ----------- Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW ----------- Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 73" de
i8CVS Domenico
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But how would you detect a doppler shift of something that lasts less than a second?
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/30/2010 12:55 PM, Tony wrote:
On 6/30/2010 10:35 AM, Joe wrote:
I agree,
It's not the meteor or even the ionized portion near the head that you bounce signals off of, it's the inonized trail that it leaves behind. and that can be many many miles long.
Joe - It would seem that the plasma cloud in front of the meteor would be moving at the same velocity as the meteor itself and would cause the fast Doppler shift we see prior to the trail formation.
Tony -K2MO
Now about reflecting off of odd shaped things. A buddy an myself used to in the late 70's have fun on 2 meters just playing around. we were too far apart for direct communication, I was in the northwest suburbs of Chicago, he was down in central indiana.
We would point our 4 ele beams at eachother and run like a meteor scatter transmission sequesnce. and would make a qso. it was flaky and wide variations in signal strength. But what did we use?
It was all the Jets coming in to land at Ohare! between us was the main route for all the jets to com in on. The route killed TV all the time by making signals in phase and then out then in then out, so we thought if it's strong enough reflection to cancel out a direct megawayy signal, hmmm. so we tried and it worked and worked faily well. each "Opening" lasted between 10 and 15 seconds. and would go most times from s zero to peg the meter.
was fun and thats an odd shaped reflector. that for me was ohhh 60 miles away, and for him close to 100 miles.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/30/2010 3:31 AM, Tony wrote:
Dominico,
Your path loss calculations were very interesting. At first glance, I assumed it would be possible to hear 28MHz echoes off of the 10M sphere since smaller targets such as the ionized head of a meteor can reflect such signals with enough signal power to be heard.
But, I think this is one of those apples to oranges comparisons since: a. the ionization around the front of the meteor head is responsible for signal reflection, not the rock itself. And b. the diameter of the ionized atmosphere in front of the meteor may be a lot larger than one would imagine.
The 10M sphere brought another question to mind -- Mike Wantanabe, JH1KRC, managed to hear his own EME echoes on the 21MHz using a KW and a 6 element Yagi. Details and recordings are on his website (see below). I was wondering how the path loss calculations compare with his EME results.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
Thanks Dominico...
Tony -K2MO
On 6/29/2010 9:52 PM, i8cvs wrote:
----- Original Message ----- From: "Robert Bruninga"[email protected] To:[email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x SigmaPr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 1500^3 i.e the distance from the Passive HF relay satellite and the earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the Passive HF relay satellite as seen as a radar target disc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71 Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^ -25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB into a bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = - 151dBW or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi ----------- Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB ----------- Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW ----------- Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 73" de
i8CVS Domenico
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----- Original Message ----- From: "Tony" [email protected] To: "AMSAT-BB" [email protected]; "i8cvs" [email protected] Sent: Wednesday, June 30, 2010 10:31 AM Subject: Re: [amsat-bb] Re: HF Satellite Relay
Dominico,
The 10M sphere brought another question to mind -- Mike Wantanabe, JH1KRC, managed to hear his own EME echoes on the 21MHz using a KW and a 6 element Yagi. Details and recordings are on his website (see below). I was wondering how the path loss calculations compare with his EME results.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
Thanks Dominico...
Tony -K2MO
Hi Tony, K2MO
I have heard the EME echoes on the 21 MHz EME test from JH1KRC and they are very strong for a 6 element yagi claiming 18 dBi at 10° elevation and 1 KW output at the antenna but the moon was only 10.8° above the horizon for JH1KRC so that he was advantaged by the gain of the ground at such low moon elevation.
By the way on day 14 jan 2006 the moon was at a distance of 400.000 km from the earth and at a range of 405.000 km from JH1KRC so that the elapsed time from TXing to the echoes must be ( 405.000 x 2 ) / 300.000 = 2.7 seconds and this by hears seems to be accordingly.
We know that the range from the Moon and JH1KRC was 405.000 km and we know that the radius of the Moon is 1735 km or 1735 x 10^3 meters Also we know that the reflectivity coefficient of the moon at 21 MHz is 7 %
The 21 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x Sigma Pr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 21 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 21 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 405 x 10^6 meters i.e the distance from the Moon and the earth expressed in meters.
Sigma = Surface of the Moon in square meters i.e. of the Moon as a radar target like a disc multiplied by the reflectivity coefficient of 7 %
Computing:
/ 2 2 /\ 14.3 Ar = ---------- = ----------- = 16.24 square meters 4 x 3,14 4 x 3,14
Sigma = (1735 x 10^3) ^2 x 3.14 x 0.07 = 6.62 x 10^11 square meters
1 x 1 x 16.24 x (6.62 x 10^11) Pr = --------------------------------------- = 2.53 x 10^-24 watt [(4 x 3.14 x ( 405 x 10^6)^2]^2
1 Round trip attenuation = 10 log ----------------- = 236 dB 2.53 x 10^-24
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations as that of JH1KRC the galactic noise is the limiting factor and at 21 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 21 MHz do not improve the S/N ratio.
In addition during the 15mEME01 QRO test on CW JH1KRC claims to have used a RX CW filter with a bandwidth of only 10 Hz as you can read in his web page.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
With the above data the noise floor of this receiver for CW into a bandwidth of 10 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 10 = - 173.7 dBW or - 142.6 dBm
Link budged calculation:
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+18 dBi ----------- Transmitted EIRP .................................+48 dBW Round trip attenuation 1500 km..........- 236 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-188 dBW RX antenna gain....................................+ 18 dB ----------- Available power at RX input............... - 170 dBW RX noise floor...................................... - 173.7 dBW ----------- Signal received with a S/N ratio.......... + 3.7 dB
So according with the above calculations the signal of JH1KRC is 3.7 dB over the noise and so it is detectable very strong as recorded in the file 15m01142006_31qro in the following web page.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
In addition since the test was made with the Moon at a very low elevation of 10.8° we must add to 3.7 dB at least 1 or 2 dB or more due to the gain of the ground.
Probably if a new test will be made at higher moon elevation the echoes of file 15m01142006_31qro would be audible but not so spectacular.
Best 73" de
i8CVS Domenico
The article by VJB makes it sound like this airplane scatter is just as weak and any other weak signal mode.
That is not what I remember for two reasons.
1- we had full scale signals on 2 meter FM simplex.
2- Imagine how strong the reflected signal has to be off the plane to totally cancel out a megawatt direct signal from a TV Transmitter? you know arrive 180 deg out of phase so it take that mega watt STRONG signal and makes it drop into the snow. That can't be no weak signal for sure!
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/30/2010 11:48 AM, i8cvs wrote:
----- Original Message ----- From: "Joe"[email protected] To:[email protected] Sent: Wednesday, June 30, 2010 4:35 PM Subject: [amsat-bb] Re: HF Satellite Relay
I agree,
Now about reflecting off of odd shaped things. A buddy an myself used to in the late 70's have fun on 2 meters just playing around. we were too far apart for direct communication, I was in the northwest suburbs of Chicago, he was down in central indiana.
We would point our 4 ele beams at eachother and run like a meteor scatter transmission sequesnce. and would make a qso. it was flaky and wide variations in signal strength. But what did we use?
It was all the Jets coming in to land at Ohare! between us was the main route for all the jets to com in on. The route killed TV all the time by making signals in phase and then out then in then out, so we thought if it's strong enough reflection to cancel out a direct megawayy signal, hmmm. so we tried and it worked and worked faily well. each "Opening" lasted between 10 and 15 seconds. and would go most times from s zero to peg the meter.
was fun and thats an odd shaped reflector. that for me was ohhh 60 miles away, and for him close to 100 miles.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
Hi Joe, WB9SBD
I agree that the QSO was possible because It was the reflection of all the Jets coming in to land at Ohare! between you and your ham friend it was the main route for all the jets to com in on.
For the above reason I have sent to you a zipped file of a very interesting article on this matter titled "Aircraft Scatter" written by Kent Britain, WA5VJB.
If someone is isterested on it drop me a request off line.
Best 73" de
i8CVS Domenico
Joe,
But how would you detect a doppler shift of something that lasts less
than a second? Joe WB9SBD
It may not last very long, but the Doppler is easily detected. It's common to see frequency shifts of 500Hz or more on VHF over a period of 1/2 second or so. The reflections from the ionized trail left behind by the meteor can last several seconds or more during a major shower.
The image found on the link below illustrates the Doppler caused by the motion of the meteor and the duration of the reflected signal (steady trace) after the trail was formed. Notice that the Doppler starts a few hundred Hertz above the steady carrier.
http://www44.zippyshare.com/v/57215533/file.html
Tony -K2MO
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/30/2010 12:55 PM, Tony wrote:
On 6/30/2010 10:35 AM, Joe wrote:
I agree,
It's not the meteor or even the ionized portion near the head that you bounce signals off of, it's the inonized trail that it leaves behind. and that can be many many miles long.
Joe - It would seem that the plasma cloud in front of the meteor would be moving at the same velocity as the meteor itself and would cause the fast Doppler shift we see prior to the trail formation.
Tony -K2MO
Now about reflecting off of odd shaped things. A buddy an myself used to in the late 70's have fun on 2 meters just playing around. we were too far apart for direct communication, I was in the northwest suburbs of Chicago, he was down in central indiana.
We would point our 4 ele beams at eachother and run like a meteor scatter transmission sequesnce. and would make a qso. it was flaky and wide variations in signal strength. But what did we use?
It was all the Jets coming in to land at Ohare! between us was the main route for all the jets to com in on. The route killed TV all the time by making signals in phase and then out then in then out, so we thought if it's strong enough reflection to cancel out a direct megawayy signal, hmmm. so we tried and it worked and worked faily well. each "Opening" lasted between 10 and 15 seconds. and would go most times from s zero to peg the meter.
was fun and thats an odd shaped reflector. that for me was ohhh 60 miles away, and for him close to 100 miles.
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 6/30/2010 3:31 AM, Tony wrote:
Dominico,
Your path loss calculations were very interesting. At first glance, I assumed it would be possible to hear 28MHz echoes off of the 10M sphere since smaller targets such as the ionized head of a meteor can reflect such signals with enough signal power to be heard.
But, I think this is one of those apples to oranges comparisons since: a. the ionization around the front of the meteor head is responsible for signal reflection, not the rock itself. And b. the diameter of the ionized atmosphere in front of the meteor may be a lot larger than one would imagine.
The 10M sphere brought another question to mind -- Mike Wantanabe, JH1KRC, managed to hear his own EME echoes on the 21MHz using a KW and a 6 element Yagi. Details and recordings are on his website (see below). I was wondering how the path loss calculations compare with his EME results.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
Thanks Dominico...
Tony -K2MO
On 6/29/2010 9:52 PM, i8cvs wrote:
----- Original Message ----- From: "Robert Bruninga"[email protected] To:[email protected] Sent: Monday, June 28, 2010 7:44 PM Subject: [amsat-bb] HF Satellite Relay
Heard today of a Passive HF relay satellite being proposed. Wondered if Hams could relay off of it.
It's a 10m diameter sphere. I assumed a 10m signal and 1000 Watts And antenna gains at both ends of 10 dB. Unless I made a dumb error, it looks impossible? I get a received signal of -170 dBm Compared to a good HF receiver of -122 dBm So its 48 dB down in the noise. Going to narrow band, could improve things, but the Doppler of +/- 600 Hz would make that difficult.
Anyway, if someone else wants to double check the link budget using the radar range equation, go for it.
The beauty of this system is that it is perfectly spherical, so the reflection coefficient would be constant within 1 dB. That is the advantage over trying to use the ISS or other large rocket body... They vary by 20 dB making communication by reflection impossible.
Oh, and it would be in space for 30 years or more. So with something that reliable, it would be worth developing an amateur capability to use it. It is not designed for comms, but as a calibration sphere for over the horizon radars that have LOTS more power and LOTS more gain than we do.
Bob, Wb4APR
Hi Bob, WB4APR
I have assumed that the altitude of the Passive HF relay satellite over the earth is 1500 km and as we know the diameter of the sphere is 10 meters. Also I assumed that the reflectivity coefficient of the sphere is 50%
The 28 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x SigmaPr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 28 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 28 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 1500^3 i.e the distance from the Passive HF relay satellite and the earth expressed in meters.
Sigma = Surface of the target in square meters i.e. of the Passive HF relay satellite as seen as a radar target disc multiplied by the reflectivity coefficient of 50%
Computing:
/ 2 2 /\ 10.71 Ar = ---------- = ----------- = 9.13 square meters 4 x 3,14 4 x 3,14Sigma = 5^2 x 3.14 x 0.5 = 39.2 square meters
1 x 1 x 9.13 x 39.2Pr = --------------------------------------- = 4.47 ^ -25 watt (4 x 3.14 x 1500000^2) ^2
1Round trip attenuation = 10 log --------------- = 243.5 dB 4.47^ -25
Link budged calculation:
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations the galactic noise is the limiting factor and at 28 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 28 MHz do not improve too much the S/N ratio.
With the above data the noise floor of this receiver for SSB into a bandwidth of 2500 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 2500 = - 151dBW or - 121 dBm
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+10 dBi ----------- Transmitted EIRP .................................+40 dBW Round trip attenuation 1500 km..........- 243.5 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-203.5 dBW RX antenna gain....................................+ 10 dB ----------- Available power at RX input............... - 193.5 dBW RX noise floor...................................... - 151 dBW ----------- Signal received with a S/N ratio.......... - 42.5 dB
So according with Bob calculations the signal is 42.5 dB under the noise and so it is not detectable.
Best 73" de
i8CVS Domenico
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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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Dominico,
Thank you very much for the calculations. It would seem that it is possible to work EME on the higher HF bands using WSJT modes under the right conditions. But, I can see that it would take an exceptional HF station to work CW on a regular basis. Of course there's the ionosphere to contend with as well.
Thanks again.
Tony -K2MO
On 6/30/2010 6:11 PM, i8cvs wrote:
----- Original Message ----- From: "Tony"[email protected] To: "AMSAT-BB"[email protected]; "i8cvs"[email protected] Sent: Wednesday, June 30, 2010 10:31 AM Subject: Re: [amsat-bb] Re: HF Satellite Relay
Dominico,
The 10M sphere brought another question to mind -- Mike Wantanabe, JH1KRC, managed to hear his own EME echoes on the 21MHz using a KW and a 6 element Yagi. Details and recordings are on his website (see below). I was wondering how the path loss calculations compare with his EME results.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
Thanks Dominico...
Tony -K2MO
Hi Tony, K2MO
I have heard the EME echoes on the 21 MHz EME test from JH1KRC and they are very strong for a 6 element yagi claiming 18 dBi at 10° elevation and 1 KW output at the antenna but the moon was only 10.8° above the horizon for JH1KRC so that he was advantaged by the gain of the ground at such low moon elevation.
By the way on day 14 jan 2006 the moon was at a distance of 400.000 km from the earth and at a range of 405.000 km from JH1KRC so that the elapsed time from TXing to the echoes must be ( 405.000 x 2 ) / 300.000 = 2.7 seconds and this by hears seems to be accordingly.
We know that the range from the Moon and JH1KRC was 405.000 km and we know that the radius of the Moon is 1735 km or 1735 x 10^3 meters Also we know that the reflectivity coefficient of the moon at 21 MHz is 7 %
The 21 MHz Round Trip Isotropic Attenuation using the concept of Radar Equation is as follows:
Pt x Gt x Ar x SigmaPr = ------------------------------ (4 x 3.14 x R^2)^2
where :
Pr = received power
Pt = transmitted power = 1watt
Gt = gain of a 21 MHz isotropic antenna = 1 in power ratio
Ar = Aperture of the isotropic antenna at 21 MHz in square meters.
R = Radius of a sphere wich distance from the earth is 405 x 10^6 meters i.e the distance from the Moon and the earth expressed in meters.
Sigma = Surface of the Moon in square meters i.e. of the Moon as a radar target like a disc multiplied by the reflectivity coefficient of 7 %
Computing:
/ 2 2 /\ 14.3Ar = ---------- = ----------- = 16.24 square meters 4 x 3,14 4 x 3,14
Sigma = (1735 x 10^3) ^2 x 3.14 x 0.07 = 6.62 x 10^11 square meters
1 x 1 x 16.24 x (6.62 x 10^11)Pr = --------------------------------------- = 2.53 x 10^-24 watt [(4 x 3.14 x ( 405 x 10^6)^2]^2
1Round trip attenuation = 10 log ----------------- = 236 dB 2.53 x 10^-24
Assuming that we are using a good HF receiver with a NF= 8 dB equivalent to 1539 kelvin we must consider in addition that the receiver sensitivity is limited by the external available noise power.For quiet,rural locations as that of JH1KRC the galactic noise is the limiting factor and at 21 MHz the noise temperature is around 29.000 kelvin so that reducing the Noise Figure belove 8 dB at 21 MHz do not improve the S/N ratio.
In addition during the 15mEME01 QRO test on CW JH1KRC claims to have used a RX CW filter with a bandwidth of only 10 Hz as you can read in his web page.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
With the above data the noise floor of this receiver for CW into a bandwidth of 10 Hz can be calculated as follows:
Noise Floor = KTB = 1.38 x 10^-23 ( 1539 + 29.000 ) x 10 = - 173.7 dBW or - 142.6 dBm
Link budged calculation:
TX power 1000 watt.............................+30 dBW TX Antenna gain....................................+18 dBi ----------- Transmitted EIRP .................................+48 dBW Round trip attenuation 1500 km..........- 236 dB ----------- Received power Pr on isotropic antenna on the earth ..............................-188 dBW RX antenna gain....................................+ 18 dB ----------- Available power at RX input............... - 170 dBW RX noise floor...................................... - 173.7 dBW ----------- Signal received with a S/N ratio.......... + 3.7 dB
So according with the above calculations the signal of JH1KRC is 3.7 dB over the noise and so it is detectable very strong as recorded in the file 15m01142006_31qro in the following web page.
http://eme.dokidoki.ne.jp/sound/jh1krc/index.html
In addition since the test was made with the Moon at a very low elevation of 10.8° we must add to 3.7 dB at least 1 or 2 dB or more due to the gain of the ground.
Probably if a new test will be made at higher moon elevation the echoes of file 15m01142006_31qro would be audible but not so spectacular.
Best 73" de
i8CVS Domenico
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participants (8)
-
Bill Bordy, NJ1H -
Bob- W7LRD -
Greg D. -
i8cvs -
Joe -
Mark L. Hammond -
Robert Bruninga -
Tony