[amsat-bb] LONG and long overdue report

[Robert McGwier <rwmcgwier@xxxxxxxxxxx>]

Apologies to my colleagues and expect to see much more from all the 
participants in upcoming journals and meetings.
*

There has been work going on that has not been adequately described 
anywhere and I take the blame for that.   I have been spending 
engineering money on your behalf.  Let me summarize it for you and 
apologize for the length of this note.  If I include technical details 
here, it would be much too long and articles for the journal will follow 
this short report. Frank Brickle, AB2KT, and I have been involved with 
Flex Radio doing the digital signal processing code for the SDR-1000 for 
almost 2 years.  Frank and I are doing this as volunteers for Flex and I 
am doing it professionally for my employer who has myriad uses for this 
technology and software.  Frank and I  have no formal relationship with 
Flex and our work has been entirely voluntary.  We have insisted that 
all work proceed under the GPL,  but we did not have to work hard at 
this insistence since Gerald, K5SDR,  is a clear believer.  Please visit

http://www.flex-radio.com

and

http://dttsp.sourceforge.net

for full details and the code.

When asked to join the Eagle design conference, I attended with the idea 
that I would give a few ideas, listen to a few ideas, get some ideas, 
and then go home and go back to sleep.   I should know myself better by 
now.   It became clear that the same old arguments would be presented 
stating we simply cannot live without Mode B.   It was clear that we 
would have to give up significant territory in the spacecraft and power 
budget for anything that would interest me personally.   I wanted to 
jump all over CC Rider, which is a 5650 MHz uplink and 5850 MHz downlink 
transponder.  This was another terrific Tom Clark (W3IWI) idea and it 
captured my interest.

ftp://ftp.cnssys.com/pub/amsat/cc_amsat.pdf

and

ftp://ftp.cnssys.com/pub/amsat/cc-revisited.pdf

It would give us our first satellite presence in these two bands and 
would provide us with some interesting technology and engineering and 
theoretical development issues to resolve.   It would be a new 
educational prod to our users to learn and do something new.  So I 
opened my mouth and said that I would be more than happy to "write" a 
software defined transponder for all of the normal "narrow band" 
transponders if and only if,  CC Rider would be given 100% access to the 
power budget and always operational when it could be aimed at the 
earth.  I would never consider supporting a RUDAK type mission where 
lots of work would be done and almost nothing ever done to use it.  In 
fact, I claimed that all transponders could be, and likely should be, 
software defined radios.  The spacecraft mechanical design and analysis 
shone at this meeting gave sufficient power budget to meet the design 
goal of 100% Mode B or Mode LS and 100% CC Rider simultaneously.  We 
would have to constrain the CC Rider bandwidth to do all we wanted to do 
and allow small antennas on the ground but it would still be very 
interesting indeed.

That landed me in hot water.  The group put me in charge of the 
transponders period.  This has begun to bear fruit.  Frank and I have 
been building a working 48 Khz transponder for Mode  B and Mode A.   It 
is done using SDR-1000's and transverters and a Mini-ITX computer.  THIS 
IS A PROTOTYPE.   However, what can be done is pretty spectacular.   
Swapping between Mode's A and B is quite easy with this equipment.  That 
said,  this is not your father's Mode B and Mode A. We can have a three 
FM receivers and transmitters on one side of the beacon (which is in the 
center) and fully linear above the beacon.   We implement Leila in DSP 
and even loud AMSAT lovers from southern Europe could not be louder than 
the beacon by more than 3 dB no matter how many megawatts EIRP they 
transmit.   Even better, pileup participants will be shoved down to the 
noise floor where none of the emitters would be audible and good 
behavior would be strictly enforced since the sum of the people on the 
same frequency will be limited to 3 dB above the beacon!

If we got tired of this configuration, we could turn it into several 
digital transponders or FILL IN THE BLANK, by simply changing the DSP 
configuration.  Frank and I have made that very easy to do in our 
system.   We will likely have to do some serious experimentation with 
processors to find the suitable one to carry the load and not need half 
the power budget but it is a great challenge and one I relish.  What was 
it Tom and I used to say? "It's only software!"  Indeed it is and the 
nicest thing is, most of the software already exists (for a change). 
This MODE B AND MODE A TRANSPONDER WILL BE DEMONSTRATED AT THE ANNUAL 
MEETING IN LOUISIANA.  Once we decide on the politics and legalities of 
where to place the transmitter and receiver bands, we will announce what 
equipment to bring.  Please bring your G3RUH PSK demodulator and decoder 
software to see the M blocks coming your way.

Recently, Frank and I joined the Gnu Radio "family" and I own (and so 
does AMSAT) the Gnu Radio project's Universal Software Radio Peripheral 
(USRP).

http://www.gnu.org/software/gnuradio/

and

http://www.ettus.com/

John Stephensen,  KD6OZH, has kindly donated two of his DCP-1's and we 
are building them up to use as well for our experiments.  With his OFDM 
modem, we can even start transmitting the digital signals of interest to 
us in this transponder or utilize that structure in a modified way for 
the ground stations.  These units

http://www.arrl.org/tis/info/pdf/020910qex041.pdf

These two units, USRP and DCP-1, are FPGA based engines.  We are 
planning on running several design experiments on these units.   Matt 
Ettus, N2JMI has given us a receiver for L band and will be doing the 
same for an S band transmitter.  We can program the unit, using the same 
prototyping system that will run the Mode B transponder prototype, to do 
a few hundred KHz wide LS transponder.  If we get the parts and can get 
some minor control going, it will be very easy to run a transponder on 
the USRP.  THIS IS A PROTOTYPING EXPERIMENT. Again, we are going to have 
to carefully size our needs to have a possible power budget for the 
processing needed to put this transponder on the air as the USRP in its 
current form, takes 10 watts to do the job. For the initial CC Rider 
concept, we have a difficult task.  We are proposing to use patch 
antennas with several small transmitters and preamps at the antenna and 
phasing these to be Nadir pointing.    The USRP is uniquely qualified to 
enable these experiments.  It has four receiver and four transmitter 
ports.  We could do our phasing experiments using these ports.  If this 
does not work out,  and it is the riskiest part of the CC Rider concept, 
we can fall back to traditional gain antennas but it will limit the 
utility of this transponder to near-apogee and when nadir pointing. Tom 
Clark found an interesting part for 5 Ghz that looks promising.  It is 
the Hittite 1 watt linear amplifier (HCM408LP3) and we have two 
evaluation modules to get a clear idea of the operational 
characteristics at differing power levels.  This would be important if 
we wish to allow for side lobe tapering by use of a scaling on some of 
the elements in the phased array.

Frank, Tom Clark, Rick Hambly, and I have been having regular meetings 
in Rick's lab.  These experiments are proceeding and with some of these 
results, we will be calling together several people to try to get them 
to participate in our ambitious projects.

Expect to hear more and see more in the journal as we continue this work 
and we pick up the pace in anticipation of the annual meeting.


A new IHU for Phase 3 E and AMSAT Eagle

Recently we have begun preparing the new integrated housekeeping unit 
for Phase 3E and AMSAT Eagle.  Lyle Johnson and Chuck Green have done a 
great job in designing and getting it getting it ready for testing and 
ready to accept IPS, the standard spacecraft operating system originated 
by Karl Meinzer, DJ4ZC.  Karl was heavily involved in the design of the 
watchdog system and the overall architecture.  He has asked that we work 
on a software defined receiver utilizing a very powerful forward error 
correcting code and that it be run on the IHU-3.  If this is successful 
and proves reliable on P3E, it will be the primary link to the ambitious 
P5A Mars mission Karl is leading.

Yesterday the test code suite came up and ran on the IHU.  Immediately 
after finalizing that and getting it to Stacey Mills, who will be doing 
radiation testing for us, we will begin putting IPS on it.  Expect to 
see the development model running this code at the annual meeting and 
expect to see an article by several folks with Lyle and Chuck taking the 
lead on that.

Thank you for reading and for your continued support of AMSAT.

73's
Bob
N4HY
*
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