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CX2SA > SATDIG 28.10.09 21:04l 358 Lines 12065 Bytes #999 (0) @ WW
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Subj: AMSAT-BB-digest V4 576
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Sent: 091028/1903Z @:CX2SA.LAV.URY.SA #:13141 [Minas] FBB7.00e $:AMSATBB4576
From: CX2SA@CX2SA.LAV.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: requesting help on a RF link solution (imaginary
ka-bandlink!) (i8cvs)
2. Cute competition winners (John Heath)
3. Re: Portable satellite terminals for disaster relief (Jim Wright)
4. AO-51 S band will be off 2235-2250 10/28 (Andrew Glasbrenner)
----------------------------------------------------------------------
Message: 1
Date: Wed, 28 Oct 2009 18:13:43 +0100
From: "i8cvs" <domenico.i8cvs@xxx.xx>
Subject: [amsat-bb] Re: requesting help on a RF link solution
(imaginary ka-bandlink!)
To: "AMSAT-BB" <amsat-bb@xxxxx.xxx>, <w7lrd@xxxxxxx.xxx>
Message-ID: <004501ca57f2$00a81cc0$0201a8c0@xxx.xx>
Content-Type: text/plain; charset="utf-8"
Hi Bob, W7LRD
I need to answere your question as well via AMSAT-BB because my emails
sent to w7lrd@xxxxxxx.xxx are alwais rejected to me by your provider.
From the point of view of Amateur Radio the best I can suggest to you is
the book " The Satellite Experimenters Handbook " by Martin Davidoff K2UBC
2nd Edition ARRL Order No 3185 ISBN 0-87259-318-5 and also the ARRL " UHF
MICROWAVE Experimenters's Manual" ARRL Order No 3126 ISBN 0-87259-312-6
Those books are full of easy calculations and you can follow it using a
small scientific hand held calculator but very important every chapter of
the UHF MICROWAVE Experimenter's Manual is full of "References and
Bibliography " that you can find and read/study to go deeply into details
on the above matter covering circuits and antennas which are described here
in hardware but also with related easy to follow calculations.
At the beginning you must go slowly with the above two books but after a
few months you will improve and the above matter will come very familiar to
you provided that you implement your knoledge following the recommended
References and Bibliography.
In AMSAT-BB I follow your experimental activity particularly into the S
band.............congrats !
Best 73" de
i8CVS Domenico
----- Original Message -----
From: Bob- W7LRD
To: i8cvs
Sent: Wednesday, October 28, 2009 3:23 AM
Subject: Re: [amsat-bb] Re: requesting help on a RF link solution
(imaginary ka-bandlink!)
Hello Domenico
I enjoy your posts, even though many are "out of my pay grade". Would you
aim me towards a good tutorial place you may know of where I could learn
some of the basics. I would like to gain a better understanding of this
concept.
Thanks & 73
Bob W7LRD
----- Original Message -----
From: "i8cvs" <domenico.i8cvs@xxx.xx>
To: "Samudra Haque" <samudra.haque@xxxxx.xxx>, "Amsat-bb"
<amsat-bb@xxxxx.xxx>
Sent: Tuesday, October 27, 2009 5:44:14 PM GMT -08:00 US/Canada Pacific
Subject: [amsat-bb] Re: requesting help on a RF link solution (imaginary
ka-bandlink!)
----- Original Message -----
From: "Samudra Haque" <samudra.haque@xxxxx.xxx>
To: "Amsat-bb" <amsat-bb@xxxxx.xxx>
Sent: Tuesday, October 27, 2009 11:03 AM
Subject: [amsat-bb] requesting help on a RF link solution (imaginary
ka-bandlink!)
> Hi, amsat-bb
>
> CQ any satellite link budget expert !
>
> I'm trying to do a calculation on my own based upon published specs
> for the NASA MRO Ka-band experiment, but am getting some unexpected
> results for a Ka-band simplex link with Temp=3000K (hypothetical),
> operating with a Signal to Noise ratio (unitless) figure of 1.171
> (representing 4.5 dB eb/no with a data rate of 1 Gbps and a bandwidth
> of 2.4x10^9 Hz)
>
> Question : is 1 gbps not 1x10^9 bps ?
>
> Question : if both antennas are 3m parabolic (both are the same type)
> with 56.4 dBi boresight gain, what would you think the furthest
> distance the link can perform with SNR of 1.171. I have actually used
> a padding of 3 dB Eb/No in my link budget, so am not worried about any
> further signal loss at first (ok, I should be ..) For the exercise, I
> am choosing a 10 Watt estimated output on an arbitrary basis.
>
> So:
>
> P_t = 10W
>
> G_t = 56.4 dBi = G_r , can we assume the same gain for TX and RX on a
> parabolic dish ?
>
> T = 3000K at receiver
>
> SNR = 1.171 required
>
> f=32.2 GHz
>
> B = 2.4E9 Hz, (bpsk, ldpc code 0.5)
>
> DR = 1E9 bps
>
> So, I am puzzled why this link budget says the range with these
> parameters is equal to 4.644 x 10^9 Km -- that seems to be a long
> distance ! What am I not able to conceptualize.
>
> BTW, I know if I send this out, the answer will come to me soon
> thereafter, but for education, I would like to know where the problem
> in my understanding lies !
>
> Samudra N3RDX
Hi Samudra, N3RDX
If I well understand your question is to know what is the maximum
free space distance at which you can get a S/N ratio of 4.5 dB using
two identical transmitting and receiving systems having the following
characteristics:
1) Antenna gain for TX and RX = 56.4 dBi at 32.2 GHz
2) Frequency = 32.2 GHz
3) Overall receiving system noise temperature: T = 3000 kelvin
4) Bandwidth of receiving system = 2.4 x 10^9 Hz
5) TX power 10 W
6) Required Signal to Noise ratio S/N at the unknown distance = 4.5 dB
With the above data we first calculate the receiver noise floor Pn = KTB
where:
K = Boltzmann constant = 1.38 x 10^ -23 (Joule/kelvin)
T = Overall System Noise Temperature = 3000 kelvin
B = Bandwidth of receiving system = 2.4 x 10^9 Hz
Working out the numbers we get the following RX noise floor
Pn = (1.38 x 10^ -23) x (3000) x (2.4 x 10^9) = 1 x 10^-10 watt
and 10 x [ log (1 x 10^-10)] = - 100 dBW or - 70 dBm
10
Link budged calculation
TX power = 10 W =..................+ 40 dBm
TX antenna gain ........................+ 56.4 dBi
------------
Transmitted EIRP......................+ 96.4 dBm
Free space attenuation for
61.000 km at 32.2 GHz............- 218.3 dB
------------
Received power over isotropic
ant. at 61.000 km distance........- 121.9 dBm
RX antenna gain.......................+56.4 dB
-------------
Received power at RX input... - 65.5 dBm
Receiver noise floor.................- 70.0 dBm
--------------
Received S/N Ratio................. + 4.5 dB
Conclusion:
Using two boresight identical parabolic dishes having each a gain of
56.4 dBi at 32.2 GHz one transmitting with 10 watt and the other one
receiving with a receiving system having a noise temperature of 3000 kelvin
into a bandwidth = 2.4 x 10^9 Hz the free space distance at which the
signal is received with a S/N ratio = + 4.5 dB is only 61.000 km so that
your hypothetical system is not suitable for the NASA MRO Ka-band
experiment because the distance Earth to Mars is about 1 AU i.e.
1 Astronomical Unit corresponding to 149 Million/ km
73" de
i8CVS Domenico
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
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------------------------------
Message: 2
Date: Wed, 28 Oct 2009 17:31:01 +0000 (GMT)
From: John Heath <g7hia@xxxxxxxxxx.xxx>
Subject: [amsat-bb] Cute competition winners
To: Amsat <amsat-bb@xxxxx.xxx>
Message-ID: <294400.39880.qm@xxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=iso-8859-1
Cute Re-entry Competition
?
Winners Declared
?
It seems that when a satellites,? reache an altitude as low as about 170km
they will be down very quickly. According to Space Track elements, and
InstanTrak tracking software Cute was still orbiting when the perigee was
below 150 Km.
?
My theory?is that cubesats stay in orbit longer because they have a large
mass relative to their very small cross section and so experience far drag
than bulkier objects.
?
Using that idea I ran the last element set for several orbits and made an
arbitrary decision that re-entry probably took place at a perigee of 130Km
or so thus putting re-entry pretty much dead centre between two competition
entries.
?
I therefore declare Ib OZ1MY and David G0MRF as joint winners !!!
?
On receipt of current postal addresses I will mail out a patch kit to each
of the lucky winners.
?
Thanks to Ib, David and everyone else who took part, it was fun to plot the
curves and I learned a bit about atmospheric density and solar flux.
?
73 John G7HIA
?
PS
IPS Radio and Space Services, have a useful paper on satellite orbital decay
calculations.
Thanks to Ken GW1FKY for sending me a copy.
------------------------------
Message: 3
Date: Wed, 28 Oct 2009 14:36:20 -0400
From: Jim Wright <wa4ivm@xxxxx.xxx>
Subject: [amsat-bb] Re: Portable satellite terminals for disaster
relief
To: Daniel Schultz <n8fgv@xxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Message-ID: <4AE88F24.3010603@xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
In the proverbial "pinch", emergency that is unexpected, we can still
deploy our I-gate feed over there $$Expensive$$ satellite feed and keep
on truckin' with our APRS system as it evolves, probably faster than the
"government appropriations" for those big guys that can do all, see all,
but not plan for everything.
My two cents,
Jim
Daniel Schultz wrote:
> JoAnne Maenpaa, K9JKM, wrote:
>
>
>> I guess you're observing that AMSAT's GEO proposal has to fit into the GEO
>>
> satellite commodity market.
>
> Should Amsat be working with NetHope to design a better terminal? How do we
> work with these guys to convince them that they should be using a ham
> satellite instead of a commercial service? One big advantage of the
commercial
> service is that it exists now. How do we get the money from funding
agencies,
> either government, corporate, or non-profit? Where does Amsat fit in to this
> world? Have they even heard of us, our history and our capabilities?
>
>
>> I've maintained that a GEO satellite is best suited to link widely deployed
>>
> sectors of the Incident Command System.
>
> I think most government-based emergency authorities are not going to be
> interested in building or funding a system that they do not design and
> control. They consider amateur radio to be a last-ditch thing that they
would
> rather not count on, they would rather have an in-house system that fits
in to
> their chain of command and shows their funding authorities that they are
fully
> on top of emergency communications and don't need to rely on amateur
> volunteers coming forward in time of need. A non-governmental organization
> like NetHope might be more receptive to our proposals. We need to think hard
> and come up with new ideas.
>
> Dan Schultz N8FGV
>
>
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. 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
>
>
>
------------------------------
Message: 4
Date: Wed, 28 Oct 2009 14:53:17 -0400
From: Andrew Glasbrenner <glasbrenner@xxxxxxxxxx.xxx>
Subject: [amsat-bb] AO-51 S band will be off 2235-2250 10/28
To: Amsat-BB <amsat-bb@xxxxx.xxx>
Message-ID: <4AE8931D.3020100@xxxxxxxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
AO-51 S band will be off 2235-2250 10/28 for some telemetry collection
on 435.150.
73, Drew KO4MA
------------------------------
_______________________________________________
Sent via amsat-bb@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
http://amsat.org/mailman/listinfo/amsat-bb
End of AMSAT-BB Digest, Vol 4, Issue 576
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