[amsat-bb] What influences LEO propagation?

[Hans BX2ABT]

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 at 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 at 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 at amsat.org. <mailto:AMSAT-BB at 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 at 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 at 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
>
>
>