What influences LEO propagation?
The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is almost impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also ionospheric or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT)
Hans, What I believe you are really asking is what effects VHF/UHF propagation. Lighting up a bird is a line of sight connection, not propagation in the classic sense of bouncing off the ionosphere and ground like in HF comms. But, there are atmospheric phenoms that can effect VHF/UHF comms. Tropo ducting, but that is normally for terrestrial comms. Same for sporadic E, which is bouncing signals off of ionized clouds similar to the ionosphere propagation..Think horizontal. Then there is weather. Whether or not you have nice weather. Rain, snow, clouds and dust are a few of the things that can effect sat comms. --- Ciao baby, catch you on the flip side. GEO
Time flies like an arrow, fruit flies like a banana.
On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is almost impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also ionospheric or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT) _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
How do rain, snow, clouds, and dust affect satellite communications? I know rain and snow scatter do occur, but that occurs at frequencies higher than what we are using for the says.73 John AF5CC Sent from my U.S. Cellular® Smartphone -------- Original message --------From: GEO Badger via AMSAT-BB amsat-bb@amsat.org Date: 5/8/19 4:53 PM (GMT-06:00) To: amsat-bb@amsat.org, Hans BX2ABT hans.bx2abt@msa.hinet.net Subject: Re: [amsat-bb] What influences LEO propagation? Hans,What I believe you are really asking is what effects VHF/UHF propagation. Lighting up a bird is a line of sight connection, not propagation in the classic sense of bouncing off the ionosphere and ground like in HF comms. But, there are atmospheric phenoms that can effect VHF/UHF comms. Tropo ducting, but that is normally for terrestrial comms. Same for sporadic E, which is bouncing signals off of ionized clouds similar to the ionosphere propagation..Think horizontal. Then there is weather. Whether or not you have nice weather. Rain, snow, clouds and dust are a few of the things that can effect sat comms.--- Ciao baby, catch you on the flip side. GEO http://www.w3ab.orgTime flies like an arrow, fruit flies like a banana. On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote: The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is almost impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also ionospheric or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT)_______________________________________________Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum availableto all interested persons worldwide without requiring membership. Opinions expressedare solely those of the author, and do not reflect the official views of AMSAT-NA.Not an AMSAT-NA member? Join now to support the amateur satellite program!Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb%C2%A0 _______________________________________________Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum availableto all interested persons worldwide without requiring membership. Opinions expressedare solely those of the author, and do not reflect the official views of AMSAT-NA.Not an AMSAT-NA member? Join now to support the amateur satellite program!Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Well, I know VHF/UHF propagation and I know satellites are line-of-sight, but how about signals from outer space trying to traverse the ionosphere and atmosphere? Es makes terrestrial signals bounce back, but does it also make space signals bounce back into space? Or at least degrade them? You say "think horizontal" but space communications are also partly horizontal if you take low elevation into consideration. I feel there is more to this, but so far haven't found any info on this.
73 de Hans
BX2ABT
On 05/09/2019 05:53 AM, GEO Badger wrote:
Hans,
What I believe you are really asking is what effects VHF/UHF propagation. Lighting up a bird is a line of sight connection, not propagation in the classic sense of bouncing off the ionosphere and ground like in HF comms. But, there are atmospheric phenoms that can effect VHF/UHF comms. Tropo ducting, but that is normally for terrestrial comms. Same for sporadic E, which is bouncing signals off of ionized clouds similar to the ionosphere propagation..Think horizontal.
Then there is weather. Whether or not you have nice weather. Rain, snow, clouds and dust are a few of the things that can effect sat comms.
Ciao baby, catch you on the flip side. GEO
Time flies like an arrow, fruit flies like a banana.
On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is almost impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also ionospheric or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT) _______________________________________________ Sent via AMSAT-BB@amsat.org. mailto:AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Taiwan lies within the northern edge of the Equatorial Scintillation Zone which is an area near the magnetic equator that suffers significant signal attenuation even at VHF (and more so at UHF an up). It is more pronounced during periods of high solar activity. In the past couple of weeks we have been having some mild geomagnetic disturbances caused by coronal holes, and more recently an earth-effective sunspot. Normally we think in terms of HF impacts, but it will have big impact on space communication if you are on one side of that scintillation zone and the satellite is on the other -- forcing the signal to cross through that area. Best I've read indicates you can anticipate another 20 dB of signal loss on 70 cm. That might be the difference between a signal that sounds great and one that is below the noise level.
As many others have stated you also have weather influences, especially on the 70 cm band, that will happen due to what is going on in the Troposphere.
73, Bob, WB4SON
On Thu, May 9, 2019 at 4:03 AM Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
Well, I know VHF/UHF propagation and I know satellites are line-of-sight, but how about signals from outer space trying to traverse the ionosphere and atmosphere? Es makes terrestrial signals bounce back, but does it also make space signals bounce back into space? Or at least degrade them? You say "think horizontal" but space communications are also partly horizontal if you take low elevation into consideration. I feel there is more to this, but so far haven't found any info on this.
73 de Hans
BX2ABT
On 05/09/2019 05:53 AM, GEO Badger wrote:
Hans,
What I believe you are really asking is what effects VHF/UHF propagation. Lighting up a bird is a line of sight connection, not propagation in the classic sense of bouncing off the ionosphere and ground like in HF comms. But, there are atmospheric phenoms that can effect VHF/UHF comms. Tropo ducting, but that is normally for terrestrial comms. Same for sporadic E, which is bouncing signals off of ionized clouds similar to the ionosphere propagation..Think horizontal.
Then there is weather. Whether or not you have nice weather. Rain, snow, clouds and dust are a few of the things that can effect sat comms.
Ciao baby, catch you on the flip side. GEO
Time flies like an arrow, fruit flies like a banana.
On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is almost impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also ionospheric or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT) _______________________________________________ Sent via AMSAT-BB@amsat.org. mailto:AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Bob, Thanks for bringing that up. I had forgotten about that effect, mostly because I don't do radio near the equator. =!8^} Here is a pdf discussing VHF/UHF atmospheric losses due to weather. Lots of math.https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.370-7-199510-W!!PDF-E.pdf
--- Ciao baby, catch you on the flip side. GEO
Time flies like an arrow, fruit flies like a banana.
On Thursday, May 9, 2019, 10:14:13 AM PDT, Bob via AMSAT-BB amsat-bb@amsat.org wrote:
Taiwan lies within the northern edge of the Equatorial Scintillation Zone which is an area near the magnetic equator that suffers significant signal attenuation even at VHF (and more so at UHF an up). It is more pronounced during periods of high solar activity. In the past couple of weeks we have been having some mild geomagnetic disturbances caused by coronal holes, and more recently an earth-effective sunspot. Normally we think in terms of HF impacts, but it will have big impact on space communication if you are on one side of that scintillation zone and the satellite is on the other -- forcing the signal to cross through that area. Best I've read indicates you can anticipate another 20 dB of signal loss on 70 cm. That might be the difference between a signal that sounds great and one that is below the noise level.
As many others have stated you also have weather influences, especially on the 70 cm band, that will happen due to what is going on in the Troposphere.
73, Bob, WB4SON
On Thu, May 9, 2019 at 4:03 AM Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
Well, I know VHF/UHF propagation and I know satellites are line-of-sight, but how about signals from outer space trying to traverse the ionosphere and atmosphere? Es makes terrestrial signals bounce back, but does it also make space signals bounce back into space? Or at least degrade them? You say "think horizontal" but space communications are also partly horizontal if you take low elevation into consideration. I feel there is more to this, but so far haven't found any info on this.
73 de Hans
BX2ABT
On 05/09/2019 05:53 AM, GEO Badger wrote:
Hans,
What I believe you are really asking is what effects VHF/UHF propagation. Lighting up a bird is a line of sight connection, not propagation in the classic sense of bouncing off the ionosphere and ground like in HF comms. But, there are atmospheric phenoms that can effect VHF/UHF comms. Tropo ducting, but that is normally for terrestrial comms. Same for sporadic E, which is bouncing signals off of ionized clouds similar to the ionosphere propagation..Think horizontal.
Then there is weather. Whether or not you have nice weather. Rain, snow, clouds and dust are a few of the things that can effect sat comms.
Ciao baby, catch you on the flip side. GEO
Time flies like an arrow, fruit flies like a banana.
On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is almost impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also ionospheric or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT) _______________________________________________ Sent via AMSAT-BB@amsat.org. mailto:AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
_______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Wow, first time I've heard about this and it explains very well what I've been seeing lately. Especially the deep, fast fading on many of the AO-91/92/95 passes. I found this page that explains the basics of equatorial scintillation: https://www.sws.bom.gov.au/Satellite/6/3. Fascinating stuff, but on the other hand it makes my ham life in Taiwan a bit more complicated. Also found this white paper, but I haven't read it yet: http://web.stanford.edu/group/scpnt/gpslab/website_files/sbas-ion_wg/sbas_io.... What I do get is that a lot of it is about scintillation on GPS frequencies and the L-band. The bands we use are a lot lower, but still suffer some influence.
Thank you Bob, lots to read this weekend.
Hans
BX2ABT
On 05/10/2019 01:11 AM, Bob via AMSAT-BB wrote:
Taiwan lies within the northern edge of the Equatorial Scintillation Zone which is an area near the magnetic equator that suffers significant signal attenuation even at VHF (and more so at UHF an up). It is more pronounced during periods of high solar activity. In the past couple of weeks we have been having some mild geomagnetic disturbances caused by coronal holes, and more recently an earth-effective sunspot. Normally we think in terms of HF impacts, but it will have big impact on space communication if you are on one side of that scintillation zone and the satellite is on the other -- forcing the signal to cross through that area. Best I've read indicates you can anticipate another 20 dB of signal loss on 70 cm. That might be the difference between a signal that sounds great and one that is below the noise level.
As many others have stated you also have weather influences, especially on the 70 cm band, that will happen due to what is going on in the Troposphere.
73, Bob, WB4SON
On Thu, May 9, 2019 at 4:03 AM Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
Well, I know VHF/UHF propagation and I know satellites are line-of-sight, but how about signals from outer space trying to traverse the ionosphere and atmosphere? Es makes terrestrial signals bounce back, but does it also make space signals bounce back into space? Or at least degrade them? You say "think horizontal" but space communications are also partly horizontal if you take low elevation into consideration. I feel there is more to this, but so far haven't found any info on this.
73 de Hans
BX2ABT
On 05/09/2019 05:53 AM, GEO Badger wrote:
Hans,
What I believe you are really asking is what effects VHF/UHF propagation. Lighting up a bird is a line of sight connection, not propagation in the classic sense of bouncing off the ionosphere and ground like in HF comms. But, there are atmospheric phenoms that can effect VHF/UHF comms. Tropo ducting, but that is normally for terrestrial comms. Same for sporadic E, which is bouncing signals off of ionized clouds similar to the ionosphere propagation..Think horizontal.
Then there is weather. Whether or not you have nice weather. Rain, snow, clouds and dust are a few of the things that can effect sat comms.
Ciao baby, catch you on the flip side. GEO
Time flies like an arrow, fruit flies like a banana.
On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is almost impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also ionospheric or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT) _______________________________________________ Sent via AMSAT-BB@amsat.org. mailto:AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Hans,
We get two different effects from the tumbling. First the polarization changes as the antennae rotate because they have linear polarization. You can minimize that impact if you have circular polarization on the ground. Second the antenna pattern is rotating and it has nulls which may pass over your station. Depending on the speed of rotation they might prevent you opening the transponder. They definitely impact telemetry reception.
One thing to note is if telemetry is being received. If you can see the RSSI and there are no other stations in the footprint then you can sometimes see the received signal strength from your station. Have FoxTelem plot the graph real time and see what effect transmitting has. If the sat is receiving you but not being opened then perhaps the tone is not being decoded correctly due to peaks and nulls from the rotation.
73 Chris
On Fri, May 10, 2019, 08:20 Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
Wow, first time I've heard about this and it explains very well what I've been seeing lately. Especially the deep, fast fading on many of the AO-91/92/95 passes. I found this page that explains the basics of equatorial scintillation: https://www.sws.bom.gov.au/Satellite/6/3. Fascinating stuff, but on the other hand it makes my ham life in Taiwan a bit more complicated. Also found this white paper, but I haven't read it yet:
http://web.stanford.edu/group/scpnt/gpslab/website_files/sbas-ion_wg/sbas_io....
What I do get is that a lot of it is about scintillation on GPS frequencies and the L-band. The bands we use are a lot lower, but still suffer some influence.
Thank you Bob, lots to read this weekend.
Hans
BX2ABT
On 05/10/2019 01:11 AM, Bob via AMSAT-BB wrote:
Taiwan lies within the northern edge of the Equatorial Scintillation Zone which is an area near the magnetic equator that suffers significant
signal
attenuation even at VHF (and more so at UHF an up). It is more
pronounced
during periods of high solar activity. In the past couple of weeks we
have
been having some mild geomagnetic disturbances caused by coronal holes,
and
more recently an earth-effective sunspot. Normally we think in terms of
HF
impacts, but it will have big impact on space communication if you are on one side of that scintillation zone and the satellite is on the other -- forcing the signal to cross through that area. Best I've read indicates you can anticipate another 20 dB of signal loss on 70 cm. That might be the difference between a signal that sounds great and one that is below
the
noise level.
As many others have stated you also have weather influences, especially
on
the 70 cm band, that will happen due to what is going on in the
Troposphere.
73, Bob, WB4SON
On Thu, May 9, 2019 at 4:03 AM Hans BX2ABT via AMSAT-BB <
amsat-bb@amsat.org>
wrote:
Well, I know VHF/UHF propagation and I know satellites are line-of-sight, but how about signals from outer space trying to traverse the ionosphere and atmosphere? Es makes terrestrial signals bounce back, but does it also make space signals bounce back into space? Or at least degrade them? You say "think horizontal" but space communications are also partly horizontal if you take low elevation into consideration. I feel there is more to this, but so far haven't found any info on this.
73 de Hans
BX2ABT
On 05/09/2019 05:53 AM, GEO Badger wrote:
Hans,
What I believe you are really asking is what effects VHF/UHF propagation. Lighting up a bird is a line of sight connection, not propagation in the classic sense of bouncing off the ionosphere and ground like in HF comms. But, there are atmospheric phenoms that can effect VHF/UHF comms. Tropo ducting, but that is normally for terrestrial comms. Same for sporadic E, which is bouncing signals off of ionized clouds similar to the ionosphere propagation..Think horizontal.
Then there is weather. Whether or not you have nice weather. Rain, snow, clouds and dust are a few of the things that can effect sat
comms.
Ciao baby, catch you on the flip side. GEO
Time flies like an arrow, fruit flies like a banana.
On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB amsat-bb@amsat.org wrote:
The last couple of days the Fox birds haven't been coming in as well as before. Signal strengths are down, fading has increased and it is
almost
impossible for me to open them. Now the sporadic E season also has kicked off in the last few days, with increased activity here in east Asia. Is this a coincidence or do the two have a connection? And are there other factors that influence LEO propagation? I know satellite tumbling is one factor that causes fades, but are there also
ionospheric
or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT) _______________________________________________ Sent via AMSAT-BB@amsat.org. mailto:AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
Opinions
expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
Opinions expressed
are solely those of the author, and do not reflect the official views of
AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Hello Chris,
Thanks for that explanation. There are so many factors involved in reception of satellites that it almost seem too complex. By monitoring as much as I can there are certain patterns that are emerging. I do know for example that mountains to the south-east from me block signals below 5 degrees and I do get a lot of RF reflected back to me from a metal rooftop building near-by. If you take these and other local factors into account (antenna elevation, local buildings, etc). then there are still a lot of anomalies that take place during passes that are similar in direction/elevation.
I'll check the RSSI thing, but earlier this week the problem was that I couldn't even get any telemetry in. Passes that would normally yield 40-80 DUV frames netted maybe 1 or 2. I could see signal, hear it, albeit noisy (less than 5 dB SNR), but ever so weak. The next day a similar pass with stellar signals (SNR 30+dB). Could get in, but only part of the pass. Then later a pass where I can work stations towards my south, but not my north, while my south is always more difficult to work. It's almost like shortwave propagation, where "life's like a box of chocolates." Are spin rates of birds like AO-91/92/95 known?
And...are there more parameters in FoxTelem which you can check to study variations in signal propagation? Cheers for any hints. 73
Hans
BX2ABT
P.S. Chris, did you get the zip with 1.0.6. data I sent you Monday? I sent it before, but it came back, then sent it again. Hope we don't have email troubles, again.
On 05/11/2019 12:21 AM, Chris Thompson wrote:
Hans,
We get two different effects from the tumbling. First the polarization changes as the antennae rotate because they have linear polarization. You can minimize that impact if you have circular polarization on the ground. Second the antenna pattern is rotating and it has nulls which may pass over your station. Depending on the speed of rotation they might prevent you opening the transponder. They definitely impact telemetry reception.
One thing to note is if telemetry is being received. If you can see the RSSI and there are no other stations in the footprint then you can sometimes see the received signal strength from your station. Have FoxTelem plot the graph real time and see what effect transmitting has. If the sat is receiving you but not being opened then perhaps the tone is not being decoded correctly due to peaks and nulls from the rotation.
73 Chris
On Fri, May 10, 2019, 08:20 Hans BX2ABT via AMSAT-BB <amsat-bb@amsat.org mailto:amsat-bb@amsat.org> wrote:
Wow, first time I've heard about this and it explains very well what I've been seeing lately. Especially the deep, fast fading on many of the AO-91/92/95 passes. I found this page that explains the basics of equatorial scintillation: https://www.sws.bom.gov.au/Satellite/6/3. Fascinating stuff, but on the other hand it makes my ham life in Taiwan a bit more complicated. Also found this white paper, but I haven't read it yet: http://web.stanford.edu/group/scpnt/gpslab/website_files/sbas-ion_wg/sbas_iono_scintillations_white_paper.pdf. What I do get is that a lot of it is about scintillation on GPS frequencies and the L-band. The bands we use are a lot lower, but still suffer some influence. Thank you Bob, lots to read this weekend. Hans BX2ABT On 05/10/2019 01:11 AM, Bob via AMSAT-BB wrote: > Taiwan lies within the northern edge of the Equatorial Scintillation Zone > which is an area near the magnetic equator that suffers significant signal > attenuation even at VHF (and more so at UHF an up). It is more pronounced > during periods of high solar activity. In the past couple of weeks we have > been having some mild geomagnetic disturbances caused by coronal holes, and > more recently an earth-effective sunspot. Normally we think in terms of HF > impacts, but it will have big impact on space communication if you are on > one side of that scintillation zone and the satellite is on the other -- > forcing the signal to cross through that area. Best I've read indicates > you can anticipate another 20 dB of signal loss on 70 cm. That might be > the difference between a signal that sounds great and one that is below the > noise level. > > As many others have stated you also have weather influences, especially on > the 70 cm band, that will happen due to what is going on in the Troposphere. > > 73, Bob, WB4SON > > On Thu, May 9, 2019 at 4:03 AM Hans BX2ABT via AMSAT-BB <amsat-bb@amsat.org <mailto:amsat-bb@amsat.org>> > wrote: > >> Well, I know VHF/UHF propagation and I know satellites are >> line-of-sight, but how about signals from outer space trying to traverse >> the ionosphere and atmosphere? Es makes terrestrial signals bounce back, >> but does it also make space signals bounce back into space? Or at least >> degrade them? You say "think horizontal" but space communications are >> also partly horizontal if you take low elevation into consideration. I >> feel there is more to this, but so far haven't found any info on this. >> >> 73 de Hans >> >> BX2ABT >> >> >> On 05/09/2019 05:53 AM, GEO Badger wrote: >>> Hans, >>> >>> What I believe you are really asking is what effects VHF/UHF >>> propagation. Lighting up a bird is a line of sight connection, not >>> propagation in the classic sense of bouncing off the ionosphere and >>> ground like in HF comms. But, there are atmospheric phenoms that can >>> effect VHF/UHF comms. Tropo ducting, but that is normally for >>> terrestrial comms. Same for sporadic E, which is bouncing signals off >>> of ionized clouds similar to the ionosphere propagation..Think >>> horizontal. >>> >>> Then there is weather. Whether or not you have nice weather. Rain, >>> snow, clouds and dust are a few of the things that can effect sat comms. >>> >>> --- >>> Ciao baby, catch you on the flip side. >>> GEO >>> >>> http://www.w3ab.org >>> >>> Time flies like an arrow, fruit flies like a banana. >>> >>> >>> On Wednesday, May 8, 2019, 7:12:57 AM PDT, Hans BX2ABT via AMSAT-BB >>> <amsat-bb@amsat.org <mailto:amsat-bb@amsat.org>> wrote: >>> >>> >>> The last couple of days the Fox birds haven't been coming in as well as >>> before. Signal strengths are down, fading has increased and it is almost >>> impossible for me to open them. Now the sporadic E season also has >>> kicked off in the last few days, with increased activity here in east >>> Asia. Is this a coincidence or do the two have a connection? And are >>> there other factors that influence LEO propagation? I know satellite >>> tumbling is one factor that causes fades, but are there also ionospheric >>> or atmospheric influences? Thanks for the insight. 73 de Hans (BX2ABT) >>> _______________________________________________ >>> Sent via AMSAT-BB@amsat.org <mailto:AMSAT-BB@amsat.org>. <mailto:AMSAT-BB@amsat.org <mailto:AMSAT-BB@amsat.org>.> AMSAT-NA >>> makes this open forum available >>> to all interested persons worldwide without requiring membership. >>> Opinions expressed >>> are solely those of the author, and do not reflect the official views >>> of AMSAT-NA. >>> Not an AMSAT-NA member? Join now to support the amateur satellite >> program! >>> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb >> _______________________________________________ >> Sent via AMSAT-BB@amsat.org <mailto:AMSAT-BB@amsat.org>. AMSAT-NA makes this open forum available >> to all interested persons worldwide without requiring membership. Opinions >> expressed >> are solely those of the author, and do not reflect the official views of >> AMSAT-NA. >> Not an AMSAT-NA member? Join now to support the amateur satellite program! >> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb >> > _______________________________________________ > Sent via AMSAT-BB@amsat.org <mailto:AMSAT-BB@amsat.org>. AMSAT-NA makes this open forum available > to all interested persons worldwide without requiring membership. Opinions expressed > are solely those of the author, and do not reflect the official views of AMSAT-NA. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb > > > _______________________________________________ Sent via AMSAT-BB@amsat.org <mailto:AMSAT-BB@amsat.org>. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
participants (5)
-
af5cc2 -
Bob -
Chris Thompson -
GEO Badger -
Hans BX2ABT