[amsat-bb] Re: Eagle U/V modes

Robert McGwier rwmcgwier at comcast.net
Wed Oct 11 06:56:06 PDT 2006


In Eaglepedia  there are the San Diego Meeting notes,   the excel 
spreadsheet (adapted from KA9Q by N4HY), and in the annual meeting 
procedings there is an article by Frank Brickle, AB2KT on the technical 
approach to the messaging itself but there is not yet a coherent 
presentation of the entire system.   We are making sure the receiver 
design on 70cm,  a fantastic job by KD6OZH of this thread,  has the 
correct design for the LO's.   After that design is in final revision,  
which will enable us to compute a theoretical performance,  we can sign 
antennas, transmitters, etc.

In the interim,  AB2KT and I will be attempting to get the job done on 
the design of the device up to prototype stage using HP donations in the 
form of IPAQ's,  the HPSDR Odyssey (http://hpsdr.org),  and we will be 
testing through AO-7.  

We are going to set up a jabber service on the web using AMSAT or other 
facilities so we can perfect the protocol.  The protocol doesn't care if 
the medium is the internet or the satellite!

There is a lot to do to make this work and finalize the design.  I 
SUSPECT that it will have a great deal more coding than you have 
presented here and will use residual carrier to help acquistion and 
tracking.  The plan is indeed to have the spacecraft do acquisition, 
tracking, demod/decode of the uplink and then remod on the downlink.  
This service is so fantastic in potential,  but it might require 
additional horsepower to accomplish, and this has to be weighed in the 
balance of power/complexity . . .


Douglas Quagliana wrote:
> At 9:08 PM -0700 10/10/06, Greg D. wrote:
>>> 1.  I was also excited by what I heard about the Text Messaging 
>>> proposal.  
> Are any of the details of the Text Messaging system published
> yet? I looked on Eaglepedia, but didn't find any details.
> Will the SDK regenerate the bits at the satellite, or
> will it just send the ground station's digital signal
> back through the SDR bent pipe?
> Is this going to be a heavy coded downlink like the
> AO-40 telemetry (Reed Solomon plus Viterbi r=1/2 k=7)?
> Coding? Baud rate? Message format? Modulation scheme?
> kb5mu at amsat.org wrote:
>> This not being Star Trek, we can't improve the uplink by shunting 
>> warp power to the receivers. 
> Hmmmm... What would be the RF equivalent of a
> Heisenberg compensator? :-)
> Douglas KA2UPW/5

AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
"You see, wire telegraph is a kind of a very, very long cat.
You pull his tail in New York and his head is meowing in Los
Angeles. Do you understand this? And radio operates exactly
the same way: you send signals here, they receive them there.
The only difference is that there is no cat." - Einstein

More information about the AMSAT-BB mailing list