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CX2SA > SATDIG 11.05.19 18:30l 997 Lines 42849 Bytes #999 (0) @ WW
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To : SATDIG@WW
Today's Topics:
1. Re: suitable omni antenna for FM sats? (Jeff Moore)
2. Re: What influences LEO propagation? (Hans BX2ABT)
3. Re: suitable omni antenna for FM sats? (Joe)
4. Re: non-doppler correction on linear sats (Hans BX2ABT)
5. Re: suitable omni antenna for FM sats? (Ron VE8RT)
6. Re: suitable omni antenna for FM sats? (Joe)
7. JAMSAT report, language support for GRC, Phase 4 Ground
update+strategy+test plan, GNU Radio Conference (Michelle Thompson)
----------------------------------------------------------------------
Message: 1
Date: Fri, 10 May 2019 22:34:41 -0700
From: Jeff Moore <tnetcenter@?????.???>
To: Amsat BB <amsat-bb@?????.???>
Subject: Re: [amsat-bb] suitable omni antenna for FM sats?
Message-ID:
<CALx_moSasBYuaoZZCyr_uDiyr=kxhek9dwVz-KbHZLmmkH-c5g@????.?????.???>
Content-Type: text/plain; charset="UTF-8"
As was stated multiple times in a very recent thread - omnis for sat work
are a poor compromise!! Even a small beam at a 15-degree angle will
generally blow most omnis off the roof! Even better would be a pair of
beams (one for uplink, one for downlink) on an azimuth/elevation rotor!
But handheld can work almost as good!!
7 3
Jeff Moore --- KE7ACY
CN94
On Fri, May 10, 2019 at 10:08 PM Ron VE8RT via AMSAT-BB <amsat-bb@?????.???>
wrote:
> We have a newly licenced amateur in DP79. Because they fell a few
> points of getting their Basic with Honours they do not have HF
> privileges, their only way to communicate with the outside world is via
> satellite. Anticipating this possible outcome, that they may not get
> access to the HF bands, I sent them a hard copy, (no home internet, and
> its slow and expensive there if you do have it), of the current copy of
> "Getting Started with Amateur Satellites". As we're heading into the
> time of year to do any outside work, the most pressing question is what
> is the best compromise antenna for a base station. Keeping in mind
> their location, in order to work anyone they'll have to get into the
> satellites while the satellite is close to their horizon, otherwise the
> satellite footprint will not cover areas with any satellite operators.
>
> Ron VE8RT in DP22
>
> --
> Ron VE8RT <ve8rt@?????.??>
> _______________________________________________
> Sent via AMSAT-BB@?????.???. 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
>
------------------------------
Message: 2
Date: Sat, 11 May 2019 21:11:45 +0800
From: Hans BX2ABT <hans.bx2abt@???.?????.???>
To: Chris Thompson <chrisethompson@?????.???>
Cc: AMSAT <AMSAT-BB@?????.???>
Subject: Re: [amsat-bb] What influences LEO propagation?
Message-ID: <656edf6f-36cb-3391-e3aa-cf48f36e6b9e@???.?????.???>
Content-Type: text/plain; charset=utf-8; format=flowed
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@?????.??? <mailto:amsat-bb@?????.???>> 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@?????.??? <mailto:amsat-bb@?????.???>>
> > 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@?????.??? <mailto:amsat-bb@?????.???>> 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@?????.??? <mailto:AMSAT-BB@?????.???>.
> <mailto:AMSAT-BB@?????.??? <mailto:AMSAT-BB@?????.???>.> 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@?????.??? <mailto:AMSAT-BB@?????.???>.
> 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@?????.??? <mailto:AMSAT-BB@?????.???>.
> 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@?????.??? <mailto:AMSAT-BB@?????.???>. 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
>
------------------------------
Message: 3
Date: Sat, 11 May 2019 08:19:57 -0500
From: Joe <nss@???.???>
To: Jeff Moore <tnetcenter@?????.???>, Amsat BB <amsat-bb@?????.???>
Subject: Re: [amsat-bb] suitable omni antenna for FM sats?
Message-ID: <b8f2e632-d1e9-b739-abea-aa38cc32b583@???.???>
Content-Type: text/plain; charset=windows-1252; format=flowed
And if he is only needing to work Birds close to the horizon, I would
not even bother with the elevation rotor. or even tilt the beam up any.
From what it sounds like the beam is not going to be very gigh at all,
so just from? ground reflections the main lobe will already be elevated.
so shoot for the horizion with any beam you can muster.
Maybe make up a pair of the "Cheap Yagis"
My wonder is without internet, how is he going to keep up with the ever
changing Keps?
Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 5/11/2019 12:34 AM, Jeff Moore via AMSAT-BB wrote:
> As was stated multiple times in a very recent thread - omnis for sat work
> are a poor compromise!! Even a small beam at a 15-degree angle will
> generally blow most omnis off the roof! Even better would be a pair of
> beams (one for uplink, one for downlink) on an azimuth/elevation rotor!
> But handheld can work almost as good!!
>
> 7 3
> Jeff Moore --- KE7ACY
> CN94
>
>
> On Fri, May 10, 2019 at 10:08 PM Ron VE8RT via AMSAT-BB <amsat-bb@?????.???>
> wrote:
>
>> We have a newly licenced amateur in DP79. Because they fell a few
>> points of getting their Basic with Honours they do not have HF
>> privileges, their only way to communicate with the outside world is via
>> satellite. Anticipating this possible outcome, that they may not get
>> access to the HF bands, I sent them a hard copy, (no home internet, and
>> its slow and expensive there if you do have it), of the current copy of
>> "Getting Started with Amateur Satellites". As we're heading into the
>> time of year to do any outside work, the most pressing question is what
>> is the best compromise antenna for a base station. Keeping in mind
>> their location, in order to work anyone they'll have to get into the
>> satellites while the satellite is close to their horizon, otherwise the
>> satellite footprint will not cover areas with any satellite operators.
>>
>> Ron VE8RT in DP22
>>
>> --
>> Ron VE8RT <ve8rt@?????.??>
>> _______________________________________________
>> Sent via AMSAT-BB@?????.???. 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-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
>
>
------------------------------
Message: 4
Date: Sat, 11 May 2019 21:20:12 +0800
From: Hans BX2ABT <hans.bx2abt@???.?????.???>
To: "k6vug@?????????.???? <k6vug@?????????.???>, amsat-bb@?????.???
Subject: Re: [amsat-bb] non-doppler correction on linear sats
Message-ID: <79a6750a-5921-fc34-d972-8e0b257bc769@???.?????.???>
Content-Type: text/plain; charset=utf-8; format=flowed
Hello Umesh,
I tried it the other day, but you need to constantly re-tune the
receiving signal, while handling your key and the rotator at the same
time. During low elevations the drift is minor, but high elevations and
you find yourself very busy. It's doable, but it begs for automation of
some parts of the system.
The last couple of days not many passes I could be active. Hopefully
next week is going to be better for more tries. Cheers for the advice.
Hans
BX2ABT
On 05/10/2019 02:50 AM, k6vug@?????????.??? wrote:
> Hans,
>
> The funny thing is that if both stations don't auto-correct for
> doppler they can stay in QSO for much longer since both will "walk"
> the satellite's pass band.? I guess this is how it worked in the good
> old days.
>
> So, when I faced this situation, I would tune to the calling station
> then turn OFF my auto-correction and adjust only the uplink slightly
> to hear myself when transmitting. It worked in most cases.? If the
> calling station puts out a very short CQ, like in FM sats, just TX and
> ask them to do a longer call.
>
>
> GL es 73!
> Umesh, k6vug
>
>
> On Thursday, May 9, 2019, 1:08:16 AM PDT, Hans BX2ABT via AMSAT-BB
> <amsat-bb@?????.???> wrote:
>
>
> How to deal with signals (CW/SSB) where the other party doesn't seem to
> do doppler correction? I use an Airspy/IC820H combo to receive (2m) and
> transmit (70cm) and both are controlled by Gpredict so that uplink and
> downlink on linear sats stay in tune. However, I hear many stations that
> apparently don't do this and their signals "walk" up very fast, right
> out of my passband. Difficult to get their call, let alone have a QSO.
> So what should be my strategy to deal with this?
>
> 73 de Hans
>
> BX2ABT
>
>
------------------------------
Message: 5
Date: Sat, 11 May 2019 07:46:28 -0600
From: Ron VE8RT <ve8rt@?????.??>
To: Joe <nss@???.???>
Cc: Joe via AMSAT-BB <amsat-bb@?????.???>
Subject: Re: [amsat-bb] suitable omni antenna for FM sats?
Message-ID: <20190511074628.f1979d2af14c077fac5066bf@?????.??>
Content-Type: text/plain; charset=ISO-8859-1
Thanks for the comments,
not without internet entirely, it is available in town but not at
home. So keps could be updated.
A beam and rotator might be possible, they may be challenged by the
set-up both with the hardware and software (if it is computer
tracking), and alignment.
Myself, I found the previous discussion very helpful, and here I was
worried when I lost a bird within 2 degrees of the horizon (8 element
quad on 2M, helix on 70 cm, but manual rotator control and fixed
elevation).
So I appreciate your experience, if you were in their position what
would you if you didn't have the time (summer is short), and you were
going to do this on a reasonable budget without it being too complex.
This new amateur does not have a technical background, they're a city
administrator in Cambridge Bay, NU.
Whatever I can get into Yellowknife I should be able to get onto a
company aircraft to Cambridge Bay. I'll be going over radio options
too, from time to time they pass through Yellowknife and we can get
some time for training. Last month their job took them to Colorado and
then Alaska, but they didn't have their call sign yet, it might help
and be encouraging if on a future trip they could meet up with a local
club and experienced operators.
Ron VE8RT
On Sat, 11 May 2019 08:19:57 -0500
Joe via AMSAT-BB <amsat-bb@?????.???> wrote:
> And if he is only needing to work Birds close to the horizon, I would
> not even bother with the elevation rotor. or even tilt the beam up any.
>
> From what it sounds like the beam is not going to be very gigh at all,
> so just from? ground reflections the main lobe will already be elevated.
>
> so shoot for the horizion with any beam you can muster.
>
> Maybe make up a pair of the "Cheap Yagis"
>
> My wonder is without internet, how is he going to keep up with the ever
> changing Keps?
>
> Joe WB9SBD
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 5/11/2019 12:34 AM, Jeff Moore via AMSAT-BB wrote:
> > As was stated multiple times in a very recent thread - omnis for sat work
> > are a poor compromise!! Even a small beam at a 15-degree angle will
> > generally blow most omnis off the roof! Even better would be a pair of
> > beams (one for uplink, one for downlink) on an azimuth/elevation rotor!
> > But handheld can work almost as good!!
> >
> > 7 3
> > Jeff Moore --- KE7ACY
> > CN94
> >
> >
> > On Fri, May 10, 2019 at 10:08 PM Ron VE8RT via AMSAT-BB
<amsat-bb@?????.???>
> > wrote:
> >
> >> We have a newly licenced amateur in DP79. Because they fell a few
> >> points of getting their Basic with Honours they do not have HF
> >> privileges, their only way to communicate with the outside world is via
> >> satellite. Anticipating this possible outcome, that they may not get
> >> access to the HF bands, I sent them a hard copy, (no home internet, and
> >> its slow and expensive there if you do have it), of the current copy of
> >> "Getting Started with Amateur Satellites". As we're heading into the
> >> time of year to do any outside work, the most pressing question is what
> >> is the best compromise antenna for a base station. Keeping in mind
> >> their location, in order to work anyone they'll have to get into the
> >> satellites while the satellite is close to their horizon, otherwise the
> >> satellite footprint will not cover areas with any satellite operators.
> >>
> >> Ron VE8RT in DP22
> >>
> >> --
> >> Ron VE8RT <ve8rt@?????.??>
> >> _______________________________________________
> >> Sent via AMSAT-BB@?????.???. 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-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-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
--
Ron VE8RT <ve8rt@?????.??>
------------------------------
Message: 6
Date: Sat, 11 May 2019 09:03:37 -0500
From: Joe <nss@???.???>
To: Ron VE8RT <ve8rt@?????.??>
Cc: Joe via AMSAT-BB <amsat-bb@?????.???>
Subject: Re: [amsat-bb] suitable omni antenna for FM sats?
Message-ID: <fb94d0c1-0db5-e1fc-a399-57adce6538b0@???.???>
Content-Type: text/plain; charset=windows-1252; format=flowed
I just do not want him to looose interest.
If all I had was like an eggbeater for the Birds i'd try for a few weeks
then quit out of frustration.
Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 5/11/2019 8:46 AM, Ron VE8RT wrote:
> Thanks for the comments,
>
> not without internet entirely, it is available in town but not at
> home. So keps could be updated.
>
> A beam and rotator might be possible, they may be challenged by the
> set-up both with the hardware and software (if it is computer
> tracking), and alignment.
>
> Myself, I found the previous discussion very helpful, and here I was
> worried when I lost a bird within 2 degrees of the horizon (8 element
> quad on 2M, helix on 70 cm, but manual rotator control and fixed
> elevation).
>
> So I appreciate your experience, if you were in their position what
> would you if you didn't have the time (summer is short), and you were
> going to do this on a reasonable budget without it being too complex.
> This new amateur does not have a technical background, they're a city
> administrator in Cambridge Bay, NU.
>
> Whatever I can get into Yellowknife I should be able to get onto a
> company aircraft to Cambridge Bay. I'll be going over radio options
> too, from time to time they pass through Yellowknife and we can get
> some time for training. Last month their job took them to Colorado and
> then Alaska, but they didn't have their call sign yet, it might help
> and be encouraging if on a future trip they could meet up with a local
> club and experienced operators.
>
> Ron VE8RT
>
> On Sat, 11 May 2019 08:19:57 -0500
> Joe via AMSAT-BB <amsat-bb@?????.???> wrote:
>
>> And if he is only needing to work Birds close to the horizon, I would
>> not even bother with the elevation rotor. or even tilt the beam up any.
>>
>> From what it sounds like the beam is not going to be very gigh at all,
>> so just from? ground reflections the main lobe will already be elevated.
>>
>> so shoot for the horizion with any beam you can muster.
>>
>> Maybe make up a pair of the "Cheap Yagis"
>>
>> My wonder is without internet, how is he going to keep up with the ever
>> changing Keps?
>>
>> Joe WB9SBD
>> Sig
>> The Original Rolling Ball Clock
>> Idle Tyme
>> Idle-Tyme.com
>> http://www.idle-tyme.com
>> On 5/11/2019 12:34 AM, Jeff Moore via AMSAT-BB wrote:
>>> As was stated multiple times in a very recent thread - omnis for sat work
>>> are a poor compromise!! Even a small beam at a 15-degree angle will
>>> generally blow most omnis off the roof! Even better would be a pair of
>>> beams (one for uplink, one for downlink) on an azimuth/elevation rotor!
>>> But handheld can work almost as good!!
>>>
>>> 7 3
>>> Jeff Moore --- KE7ACY
>>> CN94
>>>
>>>
>>> On Fri, May 10, 2019 at 10:08 PM Ron VE8RT via AMSAT-BB
<amsat-bb@?????.???>
>>> wrote:
>>>
>>>> We have a newly licenced amateur in DP79. Because they fell a few
>>>> points of getting their Basic with Honours they do not have HF
>>>> privileges, their only way to communicate with the outside world is via
>>>> satellite. Anticipating this possible outcome, that they may not get
>>>> access to the HF bands, I sent them a hard copy, (no home internet, and
>>>> its slow and expensive there if you do have it), of the current copy of
>>>> "Getting Started with Amateur Satellites". As we're heading into the
>>>> time of year to do any outside work, the most pressing question is what
>>>> is the best compromise antenna for a base station. Keeping in mind
>>>> their location, in order to work anyone they'll have to get into the
>>>> satellites while the satellite is close to their horizon, otherwise the
>>>> satellite footprint will not cover areas with any satellite operators.
>>>>
>>>> Ron VE8RT in DP22
>>>>
>>>> --
>>>> Ron VE8RT <ve8rt@?????.??>
>>>> _______________________________________________
>>>> Sent via AMSAT-BB@?????.???. 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-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-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
>
------------------------------
Message: 7
Date: Sat, 11 May 2019 09:15:17 -0700
From: Michelle Thompson <mountain.michelle@?????.???>
To: AMSAT BB <amsat-bb@?????.???>
Subject: [amsat-bb] JAMSAT report, language support for GRC, Phase 4
Ground update+strategy+test plan, GNU Radio Conference
Message-ID:
<CACvjz2W7jf40v+x1fMmWtMg_GT+xv2oHH6yMU_zge7CfjzThzw@????.?????.???>
Content-Type: text/plain; charset="UTF-8"
My daughter Geneva and I had a wonderful time at JAMSAT Symposium in March
2019! There was a wide variety of talks about so many different payloads, a
very special banquet dinner, adventures in Kyoto and Osaka, visits to ham
radio stores, getting to see a new ICOM radio up close, lots of Pokemon, a
Fire Festival, and making so many new friends. We were welcomed and will
never forget the hospitality.
A big part of Symposium was the GNU Radio Workshop by Imamura-san. It was
an honor to share how we on Phase 4 Ground use GNU Radio in our
presentation on Sunday morning.
GNU Radio is a digital signal processing framework for software-defined
radio. It?s the software that tells the hardware in your radio what to do.
We need to be able to quickly and easily set up a software-defined radio to
do whatever modulation and coding we want during development of new
payloads and new ground stations. In many cases, GNU Radio is the exact
right tool for this job.
GNU Radio Companion is a Graphical User Interface that allows us to drag
and drop functions onto a canvas. We click block outputs to connect to
block inputs. When we do this, it creates a directed graph that implements
radio functions. The signals flow from beginning to end. Each block
modifies the signal, as if it was part of a circuit. The flow graph looks
something like a block diagram combined with a software flowchart. GNU
Radio has software variables. It can adapt to signal conditions and user
input.
The workshop at JAMSAT was held after the last talk on Sunday. It was
several hours of hands-on training. Participants brought their own
computers, installed GNU Radio, and created useful radio flow graphs that
worked with real hardware. Several experiments were done in order.
Imamura-san kept everything organized through a set of projected slides
that had clear instructions. Optimizations and customizations were made so
that participants could see how they can use GNU Radio to achieve their
goals. The hardware included RTL-SDRs and Plutos. Imamura-san also
demonstrated a live video transmission from the podium.
Something that I noticed in the workshop was how much easier it would be if
this community could use the software if it was in Japanese. I decided to
see what was required. After some homework and reading, I got a very simple
example working and understood the basic workflow. I asked JAMSAT if they
were interested in a localized version of GNU Radio Companion. JAMSAT
responded positively and work began in earnest! It started to become clear
that after this initial groundwork, that additional languages would be much
easier. I reached out to AMSAT-DL next, and got an enthusiastic response
there too. As of today, both German and Japanese are in progress! I
received an inquiry about Portuguese following the initial announcement
that the main menus had successful translations in testing. It's now on the
list after we fully test localization for German and Japanese.
While at JAMSAT, I was able to give a status update for Phase 4 Ground.
Phase 4 Ground is a broadband digital microwave system for both terrestrial
and space use. It complies with both ITAR and EAR open source and public
domain carve-outs, so it?s open to participation worldwide. All engineering
is published as it?s created. All are welcome to participate.
Phase 4 Ground is best suited for GEO and HEO satellite missions. The
uplink is frequency division multiple access. We use a 5GHz uplink. The
regenerative repeater payload receives the uplink signals, digitizes them,
multiplexes them, and processes them into DVB-S2 and DVB-S2X frames. The
downlink is 10GHz. DVB-S2 is Digital Video Broadcasting Satellite 2nd
edition. The X stands for extensions down in to Very Low SNR modulation and
codings. Very Low SNR is of interest to hams, so we include the extension
to the main standard DVB-S2.
We use both pilots and short frame lengths in order to make the receiver
implementation as easy as possible. Pilot tones are optional, and there are
medium and long frames available in the standard.
There is a recommended order to receive DVB-S2/X frames. The first stage of
the demodulator is symbol timing recovery. We have to figure out the best
possible time to measure, or take a snapshot, of the received signal. The
receiver does not know the phase of the transmitter clock. We will not be
automatically coordinated with it. It's not just a problem with phase,
either. The receiver and transmitter may disagree in terms of the period of
the clocks, or we might have jitter, or we might have drift. We have to
analyze the received waveform and synchronize our receiver clock to the
transmitter clock that is ?hidden? in the received signal. Then, once we
are synchronized, we sample that symbol and report the results.
Doing this gives us a reliable value for the received symbol. Now that we
have a series of received symbols, we have to figure out the start of the
frame. This is done in DVB-S2 (and many other protocols) by sending a fixed
pattern at the start of every frame. For DVB-S2, this is called a Physical
Layer Start of Frame sequence. It?s 26 symbols long. This is what we look
for. Once we see it, we know where the start of the frame is!
Frame synchronization can be done in several ways. There are two different
methods described in the implementation guidelines for DVB-S2/X. One is
relatively simple, using shift registers. The other is bit more complex,
using state machines. There are advantages to using the state machine
method, but it?s more complicated and expensive. The shift registers is
simple and cheap, but gives up a bit of performance. This is the constant
balance in digital communications. Performance comes at a cost!
Right after frame synchronization, we correct for carrier frequency error.
First we do a coarse correction. This can be done with a delay-and-multiply
frequency error detector. Then we do a fine correction. This can be done
with something like a feed-forward estimation algorithm. Coarse correction
is in the MHz, and fine correction is the hundreds of kHz.
Next, we do phase recovery. This is to fix any residual frequency offset
from the coarse and fine frequency offsets. Phase 4 Ground will support all
the modulation and codings of DVB-S2/X, but we expect lower order
modulations to be more heavily used. This means that a pilot-assisted
maximum-likelihood (ML) feed-forward estimator will be the most useful. If
you compute the average phase of each pilot field, then you can subtract
this out and improve the signal. Higher-order modulations will need another
feedback loop.
Automatic gain control is next. AGC can be done in many ways. One way to do
it depends on the pilot symbols in DVB-S2/X standard. These symbols are
sent at regular intervals to provide a known easy-to-receive signal. We use
these known pilot symbols in order to determine the amplitude
multiplication factor for the rest of the signal. Pilot symbols are
optional in the DVB standard, but Phase 4 Ground requires them. When the
pilot symbols are on, the AGC is listening. When the pilot symbols are off,
the AGC turns off, and the information from the AGC is used.
After AGC, the constellation is decoded. DVB-S2 has a lot of them! There
are many techniques to get the bits from the constellations. GNU Radio has
a very versatile and powerful constellation block.
Instead of the usual MPEG transport stream (DVB-S2 is for satellite TV, so
the content is usually broadcast television signals), we use the more
flexible Generic Stream Encapsulation standard from DVB.org. This means we
have less overhead and complexity, and can handle any digital traffic that
the amateur operator wants to transmit. It?s just a digital pipe.
Phase 4 Ground uses GNU Radio extensively in research and development as
well as for archiving and publishing our work. GNU Radio is not just a tool
to figure things out, but is also a way to define a reference design for
the radio.
Because Phase 4 Ground is not a bent pipe, the payload is more complex.
This complexity needs to be fully tested on the ground before risking large
digital circuits in space.
All the uplink channels are received with a polyphase filter bank. The
current polyphase filter bank implementation in GNU Radio needs some
updates in order to achieve the speeds and performance that we want. This
is an active area of research and development. There have been three
efforts over the past three years by various groups that have attempted to
update and improve the existing working polyphase filter bank in GNU Radio.
There is some recent good news here! EJ Kreinar reported that his open
project (Theseus Cores) has an open source FPGA polyphase channelizer! This
works with RFNoC. We will experiment with this in our payload design. This
could fill in a big piece of the system that we need. Check it out here:
http://gitlab.com/theseus-cores/theseus-cores
Ron Economos and Paul Williamson successfully implemented GSE in GNU Radio
and in Wireshark. This made it possible to do transport layer testing. Ron
Economos is the lead author of the DVB blocks in GNU Radio. Improvements to
GSE continue today. The current focus is improving internetworking
functions so that large amounts of data can be more easily handled. We
intend to use multicast IP as much as possible, and making sure GSE
integrates well with multicast IP is important. The path forward with that
is in our test plan. You can find our test plan here:
https://github.com/phase4ground/documents/blob/master/Papers_Articles_Presenta
tions/Papers/P4G%20Testbed%20Proposal.md
The error correction in DVB-S2/X is state of the art. There are not many
other error correcting codes that are better than Low Density Parity Check
+ BCH. This is a concatenated digital code specified by the DVB standard
for S2 and T2 transmissions. We have two open source implementations of
LDPC decode for DVB-S2/X. The first one is for graphical processing units
and was written by Charles Brain. It was demonstrated at 2017 AMSAT-NA
Symposium and at several events following.
The second open source implementation is in C by Ahmet Inan and can be
found here: https://github.com/xdsopl/LDPC
This version has been incorporated into GNU Radio by Ron Economos. This can
be found here: https://github.com/drmpeg/gr-dvbs2rx
The next step for LDPC is to implement and publish an open source version
for FPGA.
GNU Radio is very important for our voice codec work, uplink modulation
experiments, and trying out authentication and authorization schemes. GNU
Radio allows us to use a wide variety of off the shelf hardware to achieve
things that were not possible only a few short years ago. The GNU Radio
community has been welcoming, helpful, supportive, friendly, and a source
of continually amazing software-defined radio advancements.
GNU Radio has an annual conference. In 2018, we held a week-long ?Block
Party? for DVB-S2/X. We had fun, set up multiple demos, explained DVB-S2/X,
made the case for open source LDPC, and made progress on DVB-S2 correlates
and GSE. Phase 4 Ground made significant progress due to the generous
support of the conference organizers and the community.
Learn more about the conference here:
https://www.gnuradio.org/grcon/grcon19/
Registration for 2019 is open. The conference will be held September 16-20,
2019 in Huntsville, AL, USA. There is a poster session, proceedings, talks,
workshops, contests, and social activities. The theme for 2019 is Space
Communications! There are special gifts for space themed content. If you
have a GNU Radio project that you want to share, consider making a
presentation at or sending a poster to GNU Radio Conference 2019.
The collaboration between Phase 4 Ground and JAMSAT has been absolutely
stellar and we all look forward to continued enjoyment and success. Next
generation payloads will be more complicated with multiplexing and advanced
digital techniques. We all need to be able to work together,
internationally. Open source and public domain is the best way forward.
Phase 4 Ground and Open Research Institute are entirely dedicated to making
this happen. We will be keeping the momentum and progress going. ORI is
proud to be an affiliate member of Open Source Initiative
https://opensource.org/
Join the Phase 4 Ground team! Our work benefits all AMSAT organizations.
Our mailing list can be found at our website https://openresearch.institute/
Write me at w5nyv@????.??? if you want to join our Slack account. This is
where daily engineering discussions take place.
More soon!
-W5NYV
------------------------------
Subject: Digest Footer
_______________________________________________
Sent via amsat-bb@?????.???.
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 member? Join now to support the amateur satellite program!
https://www.amsat.org/mailman/listinfo/amsat-bb
------------------------------
End of AMSAT-BB Digest, Vol 14, Issue 188
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