September 2006 - AMSAT-BB - mailman.amsat.org

[Fwd: S-band on Eagle]
by Jim Sanford 09 Sep '06

09 Sep '06

-------- Original Message -------- Subject: S-band on Eagle Date: Thu, 07 Sep 2006 21:40:37 -0400 From: Jim Sanford <wb4gcs(a)amsat.org> To: amsat-bb(a)amsat.org Ladies and gentlemen: I have been reading the comments regarding the Eagle S-band downlink decision. I herewith respond to some. All along, the Eagle project has put a premium on hard science, rigorous peer review, and dispassionate analysis. All along we knew there might or would be some changes to what we've been planning. With several other issues on the move or decided, we took a few days in late June to hammer out, based on science, the transponder situation. We did multiple, independent link analyses, and all came to the same conclusion. We validated interference predictions with measurements that have been taken. The conclusion is that S-band is marginally useful as a downlink today (unusable in many locations), and by the time Eagle is launched, and through it's lifetime, will be unusable. Personally, I do not like this decision. I have S-band equipment that I was looking forward to using. Personally, I can live with this decision, and defend it to myself, let alone anyone else, because I am convinced that it is technically sound. As one of you commented this evening, AO-40 wasn't exactly a rock crusher on S-band. It worked, and adequately, at least on CW, but was not great. As I reflect on my personal AO-40 experiences, I now understand that there are 2 reasons for my disappointment. Local noise was one, and transponder distortion was another -- the latter will be corrected by SDX. S-band on AO-40, by necessity not choice, got many of us out of our comfort zones and convinced us that microwaves really aren't that hard. Let's enter the realm of S up and C down with that same realization. REMEMBER THAT AMSAT IS DEVELOPING THE GROUND STATION ALONG WITH THE SPACE SEGMENT. You will not be left on your own to develop ground equipment. You will not be asked to mortgage your house; affordability by the masses is a key component of the design for the entire system. Comparison with AO-51 is an "apples and oranges" thing. The path losses are much different. FM is very unlike CW/SSB or wideband digital modes. Remember that a goal of the Eagle system is that everything is on all the time. No more matrix switches, no more schedules. We need up and downlinks to be useful throughout the entire orbit. Why did we "regress" to U/V? For one reason, many of you asked for it, and some of us worked hard to somehow incorporate that capability in response to member's desires. The foot in the door was the utility of a V-band beacon in case everything else goes sour. The forcing function was as follows. A goal of Eagle has always been some kind of hand-held or jump bag portable ground station capability for entry into the emergency area while the tsunami waters are receeding and the hurricane winds are down to gale force. Many of us thought we could take advantage of the gain in small antennas to do this on the microwaves. Rigorous link analysis led us to the conclusion that the best place to do this is U/V -- both from a RF/DC power perspective, and from a link standpoint. This leads to the digital and "traditiona"l transponder package for U/V, implemented in SDX. Why not also include a (switchable) S-band downlink in parallel with the V-band? Remember, no switches. Also, we run into an antenna space problem. We've already increased the size of the spacecraft from where we started, and for many reasons, do NOT want to build something as large as AO-40. A couple of you have commented this evening that perusing EaglePedia has not revealed the details of the decisions. That is because, while Bob McGwier (N4HY) and I have been working on the report of the meeting, it is not public. We've been working hard on it since June, in and around other AMSAT, ham radio, and life events. Shortly after I push send on this message, I'll begin my final look at that document prior to public release. Before I go spend time with the spousal unit TONIGHT, I will finish it and publish it. I will send an announcement on the amsat-bb that it is public. To read the report, go to the EaglePedia main page, and select project index. From there, select Team and Meetings, and there will be several options, not all public. The San Diego meeting minutes will be obvious and public. Several of you have commented, "If S-band is unusable, why is it flying on P3E?" Fair question, but I can't answer for AMSAT-DL. I DO know that the P3E system design is considerably older and farther along than Eagle. Eagle design decisions were made based on the best information in June of 2006. Aspects of this discussion have been worthy of /dev/null. More aspects of this discussion have raised valid points and reasonable questions, deserving of response, which is why I've been composing this note for the last four hours or so. A few have raised the old allegation of the builders doing what they want, without regard to users needs. This is not true. While the desire to advance the state of the art (part of amateur radio's justification for existence and allocation of valuable spectrum) leads to enthusiasm and study of potentially useful new techniques, this desire had no impact on our analysis-based decisions. We started with requirements and services, and explored what would deliver. I thank all of you for your interest and support. Your Eagle team is working hard to develop a system that will serve our needs, as well as advance the state of the art. As promised, we are making decisions based on sound, peer-reviewed science, not anybody's opinions or desires. Please read the report, study the spreadsheets, download the excel file and play with it. If you can, make your own measurements and put those numbers into the spreadsheet. I think you'll understand how these decisions were reached. After contemplating the report, send me your questions. I'll either respond or forward to he who can best respond. Another fundamental tenet of the Eagle project is openness, so you have a right to a response to a rational question. Please recognize that we're volunteers too, and subject to the realities of day jobs, families, and a real life. Response may not be instantaneous. Thanks again and very 73, Jim James A. Sanford, PE Eagle Project Manager wb4gcs(a)amsat.org

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S-Band and Eagle -- User Inputs to the Design Process
by Bruce Rahn 09 Sep '06

09 Sep '06

I've been following the thread regarding the decision to drop S-Band downlink capabilities from Eagle with great interest. As usual, the factions are clearly falling into two groups--the "techies" and the "user community". However, before getting into my discussion on these two groups, I'd like to share a little research I did on peer reviewed work which has been done regarding an S-Band spectrum survey. I ran across an interesting paper titled "Measurements of Man-Made Spectrum Noise Floor" (NASA/CR-2004-213551 November 2004) based on work sponsored by NASA and the Department of Transportation and may be found at http://strategis.ic.gc.ca/epic/internet/insmt-gst.nsf/vwapj/smse00205-novat… Of interest to AMSAT members is Section 2, "L, S, and ISM Bands Survey". This section is an expanded version of the paper titled "L and S Bands Spectrum Survey in the San Francisco Bay Area" presented at the IEEE PLANS 2004 conference and may be found at http://waas.stanford.edu/~wwu/papers/gps/PDF/DoIEEEPLANS04.pdf I encourage all interested parties to download and review these two documents! This is peer reviewed science--not casual observations or opinions. The papers support the arguments presented by the Eagle team that the S-Band noise floor is 14 to 29 dB higher than thermal noise due to all the terrestrial emitters operating in this spectrum. However, it is very noteworthy, and must be pointed out, that all of these measurements were done with antenna systems pointed at the horizon! This forced me to ask the question of what does the spectrum look like at 5, 10, 15, 30 etc. degrees above the horizon? More on this later. In a recent email, Dr. Clark encourages folks to make spectrum surveys. Conceptually, this is a wonderful idea, but I seriously doubt many of us have the resources at hand to duplicate the measurement set up described in the above references. Without some form of a standardized measurement system the results obtained by "amateur observers" really do not hold water! It's imperative to have a calibrated measurement system along with a uniform methodology of taking measurements for them to have any true meaning. Otherwise we are back to subjective interpretation of the results. In another recent email to this list, Dr. McGwier provided us an EaglePedia link to the meeting minutes of the San Diego meeting. Thanks for this information Bob...it may not be ready for prime time, but it sure was interesting! It is with concern I noted that among the list of attendees, they were all "techies". Not a single name stuck out as a representative of the "USER community". This is sad! Years ago Boeing started bringing aircraft users into the design process by having them attend and actively participate in design reviews. As a result, Boeing has produced better aircraft which have received much higher marks from the users because their concerns were addressed during the design process. Google something to the effect of 'user involvement in the design process' and you will find a wealth of information on how to accomplish this as well as how successful it has been to countless concerns in addition to Boeing. From the outcry of AMSAT satellite users on this list, one can clearly see that many feel they are being ignored. And while I haven't been active on a bird in over 10 years, I have to concur with their feelings. EaglePedia is a wonderful idea, those involved in it are to be commended, but sadly, it provides information to the users AFTER the decisions have been made. AMSAT leaders...now is the time to actively bring users into the design process. There are multiple voices out there with good input waiting to be heard! It is too late after the "techie" decisions have been made. Back to the spectrum survey and the fact data was only measured at the horizon. Wouldn't it be interesting to have data at other elevation cuts? Perhaps we would find that the noise level is acceptable 60 to 75 percent of the time (this is a pure assumption for the sake of discussion). Would the user community be happy with this vs. horizon to horizon coverage? Would it be acceptable to the user community to employ a directional antenna to achieve this coverage? Given a trade-off between a whole new microwave station vs. antenna/tracking improvements, which way would the users want to go? You have to involve the users to get the answers! And how about this...how about adaptive antennas and null steering at the ground station to deal with this noise problem? 15 plus years ago when I looked at this it was out of the question in terms of cost for the average ham to implement. But oh how technology has changed with time. Give me a seven element S-Band array with a little hardware and software and I stand a good chance of nulling out six sources of terrestrial interference. Enough? Who knows...but without an S-Band downlink few will have the inclination to explore this fascinating area of technology at the ham radio level! Are we throwing out the baby with the bath water by ruling S-Band out on Eagle? I strongly think so. We all are subjected to interference in one form or another...be it from your neighbor's cordless phone to power line interference to junk transmitters in the commercial sector. There are solutions...not always easy ones, but there are solutions. You never find them unless you try. In closing, AMSAT has made some wonderful steps forward with EaglePedia but the organization needs to take this one step further. You have to actively involve the user community in the design process by including them in design reviews in real-time, not after the fact. Officers, board of directors, and AMSAT members...ask yourself one simply question and answer it please...why does AMSAT have such a low retention rate of members? I personally believe it is because the membership in general feels they have no say in matters and their voices are not heard. You want more satellites (numbers and performance) you have to grow the membership base. A vital step is in membership RETENTION! Listen to the members...they might stick around for decades vs. a year or two. Regards -- Bruce -- Bruce Rahn Wisdom has two parts: 1. having a lot to say; and 2. not saying it!

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Remembering the days of AO-40.
by GregWycoff 08 Sep '06

08 Sep '06

Remembering the days of AO-40. AO-40 had many ups and down as we all know, but S-band dwnlink did prove to be a life jacket for AO-40, and worked out great, many hams arond the world proved that you did not need a large dish to access the satellite's dwnlink provided the squint angle was below 20 degrees. remember the S1 tx'er I only had 33 contacts on that band but man did it kick some butt, on S2 tx'er I had 568 contacts, 40+ country's worked, hours of qso's, remember the many AO-40 beacon plus 20 nets, thanks to Dave WB6LLO no problems their. if AMSAT is going to take survey's of what the membership wants then don't do something different, this is how you loose members and funding, I like many others have already sent hundreds of dollars to the project eagle based on what your "AMSAT" survey had showed thinking that was the direction it would take. tell me if I'm wrong, but did the survey not show members want HEO's over LEO's and mode's preffered most was Mode-B and mode-S if it takes longer to come up with a design that will work based on what the members want so be it, I for one don't care if we don't have coverage 24/7 but we have a at least one HEO in orbit all times. Greg N0ZHE

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FS: Gulf Alpha EasySat Dual Band Yagi
by John Zaruba Jr 08 Sep '06

08 Sep '06

I was originally going to replace my broken, aged Hy-Gain 2m/70cm twist Yagis with this antenna and put a dish on the other side of my az-el rotator. I have since decided to repair the Hy-Gains and this antenna is now excess to my needs. It is NEW, UNASSEMBLED, and in the original UNOPENED shipping container. $100 plus $15 shipping to CONUS. Please contact me off list if you are interested. 73, John AA2BN

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break from S band gnashing
by w7lrd＠comcast.net 08 Sep '06

08 Sep '06

Hi I just spent AOS to LOS on AO7 saying CQ to myself. Put the keyboard aside and talk to me. Strong downlink sigs to. 73 Bob W7LRD Seattle

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New software released
by Thierry F6BXM 08 Sep '06

08 Sep '06

Hi A friend, Gabriel F6DQM just release a new version of Sat Explorer program freeware ! http://rivat.chez-alice.fr/software.htm -- 73 de Thierry f6bxm(a)amsat.org

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Eagle modes
by McGrane 08 Sep '06

08 Sep '06

Greetings Happy to have read about the design changes for eagle. Sorry so many people are upset about S band not being there. Wont it be on Phase 3E? I was very impressed that the amsat design team wants to please a large number of users without requiring large investments in ground stations. Better to accommodate as many as possible instead of evryone subsidizing a project for a select few high tech types. I will continue to donate to eagle in the future. Thanks to the design committee, patrick N2OEQ

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Re: S band and Eagle: an appeal for more transparency (was Sband and Eagle: an appeal for a higher level discussion)
by i8cvs 08 Sep '06

08 Sep '06

----- Original Message ----- From: "Stefan Wagener" <stefan_wagener(a)hotmail.com> To: <brobertson(a)mta.ca>; <amsat-bb(a)amsat.org> Sent: Friday, September 08, 2006 1:57 AM Subject: [amsat-bb] S band and Eagle: an appeal for more transparency (was Sband and Eagle: an appeal for a higher level discussion) > The main problem with the whole discussion is that the majority of folks > have NOT seen the data. In addition, if the data are as sound as they are > portrait, why is AMSAT-DL not believing in them and is including S-band as > a downlink. How is the discussion between ANSAT-NA and AMSAT-DL > going on this? > 73, Stefan VE4NSA Hi Stefan, VE4NSA The reverse is true. If the result of the S band as a downlink on AO40 was extremely succesfull why AMSAT-NA is not believing in AMSAT-DL ? The decision of AMSAT-DL to reuse the S band for downlink of P3E is based on already experimented facts using AO40 and there is no question about that. Is someone in condition to demonstrate that the S band of AO40 was a catastrophical affair ? Don't worry about because if P3E will be succesfull in orbit at the end of 2007 than the S band as a downlink will be again the voice of truth. Best 73" de i8CVS Domenico

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BEFORE IT IS READY
by Robert McGwier 08 Sep '06

08 Sep '06

This is released before we are ready. We have much more documentation, analysis, etc. to provide. It will be forthcoming. http://www.amsat.org/amsat-new/eagle/EaglePedia/index.php?title=San_Diego_D… Bob N4HY -- AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman "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

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No Mode S on Eagle
by Jim Kelly 08 Sep '06

08 Sep '06

A concerned satellite enthusiast wrote: "it's a horrid >marketing decision. Bad mojo for a organization that lives on the donations >of it's members." I've been around hamsats long enough now (>16 years) to vividly remember how the AMSAT movers and shakers bludgeoned us over Mode B, which we operators desperately wanted as primary on AO-40, but we were told, no, we have to move higher to Mode S. Now that many of us made the investment in Mode S and learned the technology, now that also is into the trash barrell because the techies have determined that it's too noisy. Gentlemen, the point is that the designers and engineers are running the program just as they always have and us users don't count for much except our donations. I'm sorry if this comes off as sour grapes but hell, I've been there, done that. 73, Jim Kelly, KK3K Former member AMSAT #22420 Jim Kelly, ARS KK3K, TCA 99-49842 TINPLATE TIMES http://www.tinplatetimes.com STANDARD GAUGE LIST http://groups.yahoo.com/group/standg Personal Homepage: http://mysite.verizon.net/skeptic491 __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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