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

Re: Galileo interference on L band
by Tom Clark, K3IO 25 Sep '06

25 Sep '06

Sorry -- I've been away from home on business while the latest flack occurred under the general topic heading "Galileo interference on L band". First off, just so everyone can read the presentation materials that we used during the San Diego meeting, please take a look at the EaglePedia web site at http://www.amsat.org/amsat-new/eagle/EaglePedia/index.php/San_Diego_Digital…. Then take a look at my presentation "Frequency Considerations for Eagle" at http://www.amsat.org/amsat-new/eagle/EaglePedia/uploads/1/19/Microwave_Freq…. You will see (my slide 6) that I present the arguments pro/con about why (IMHO) L-band is at jeopardy as a long-term uplink band. Let me add a few comments about why I'm so concerned. The reason that the Galileo E6 (functionally the same as GPS L2, and overlaying the amateur 1260-70 MHz uplink allocation) is important for some uses is that it, when used in combination with the primary 1.57± GHz "L1" frequency (which is what all your cheap hand-held GPS receivers use), can be used to correct the ionospheric errors; the ionosphere adds upwards of 10 meters to the pseudo-range for each GPS satellite. Because of geometric factors (expressed quantitatively in VDOP), this can in turn yield errors in height of up to about 30 meters. [The WAAS and EGNOS signals provide some correction for these biases to the few meter level, but cannot be relied on during severe ionospheric storms.] There is a lot of factual evidence that when dual-frequency geodetic GPS receivers (costing ~$25,000 -- hardly cheap!) have been used in proximity to terrestrial amateur L-band stations, the GPS performance is seriously degraded. I direct your attention to several reports on the topic: * Must reading -- GPS/GLONASS vs L-band digipeaters (Also see GPS World, Oct.2002) (warning contains numbers and equations, as well as uncomplimentary comments about digipeaters) http://elib.uni-stuttgart.de/opus/volltexte/1999/278/pdf/278.pdf#search=%22… * Amateur and Radar QRM reported at a 1999 technical meeting: http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/33rdmeeting/Presentat… * A tutorial that shows how interfering signals can affect a spread spectrum GPS rcvr (caution -- contains more numbers): http://www.rin.org.uk/SITE/UPLOAD/DOCUMENT/Vuln-Owen.pdf#search=%22gps%20am… Even though US amateurs may feel that Galileo is a "European only" problem, read carefully Rick's (W2GPS) comments -- in his real life for many years he was a VP with ARINC (the people who worry about standards in the airline industry) and was on many FAA and ICAO committees that decide on airline safety. Also realize that the Europeans are absolutely determined to develop their own GNSS (Global Navigation Satellite System) call Galileo -- in part because they don't really trust a system that depends on the US Military, and in part because they see a giga-Euro business opportunity for the EC. Who knows how long it will survive, but the Russians have their competing GLONASS system. And both the Chinese and Japanese see that they need to enter into the GNSS race is they are to be world-class technical competitors. We, the Eagle technical team, have never said that L-band won't work NOW or 5 years from now. But our vision for Eagle is that when the first one flies 4-5 years from now, we want it to be a useful resource for at least a 10 year lifetime. We are very concerned about making a several million dollar (after you count the volunteer builder's blood, sweat & tears) investment only to have it blown away right after launch by the GNSS cartels just because we picked L-band to be anything like a "primary" uplink. 73, Tom

14 27

Fuel on the emergency communications(satellite)fire
by Dave Guimont 25 Sep '06

25 Sep '06

It is quite apparent that some on here have never been on either end of a need for communications, either in the form of a drill for training, or more importantly on the receiving end in an ACTUAL emergency... Some of us have been on both ends. And, PARTCULARLY, when you need an assist, ANY method of communications, no matter how brief, may be the one you need... Jungle drums, smoke signals, a five minute satellite pass, cell phone, indian code talkers, I'll take anything I can get!! 73, Dave wb6llo(a)amsat.org Disagree: I learn.... Pulling for P3E... -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.1.405 / Virus Database: 268.12.8/455 - Release Date: 9/22/2006

5 4

AO-51 38k4 report
by Douglas Quagliana 25 Sep '06

25 Sep '06

Hi, No 38k4 packets received here on the first pass, but I think I found one of the problems. Still six more days to get all the pieces working together at the same time... Douglas KA2UPW/5

1 0

Why do the amsats get more and more complex?
by Jason White 24 Sep '06

24 Sep '06

This is intended to be an honest question that I've wanted to ask, but I don't want to spark controversy or long threads that monopolize the reflector. I have a feeling this could go either way, so I'm just asking politely that the thread not go that way! It's not my intent. Anyway, I'm just curious why it seems that every new satellite project proposed seems to be bigger and more complex than the last? I keep hearing about exotic modes and uplink/downlink bands for P3E.. software defined transceivers, etc. etc. and what it looks like to me are more and more failure points. I understand the need to push the limits of technology as a justification for our very existence, but personally I feel like the designs are overly complicated and highly priced. I'm not ready to switch my earth station to SDRs, for instance.. I'm dubious about putting one into orbit.. then again, I'm not skilled enough to make those sorts of decisions. What I'm getting at is that Oscar 7 proved how reliable older technology can be.. For the price of one of the phase 3 birds it seems like several Mode B linear transponder sats could be put up, or a few more FM sats. I personally would much rather see a modest mode B sat in AO-40s intended orbital pattern than to try to wrangle parts for microwave. Did it get too easy for people or something? Wouldn't it be better to separate out some of the more experimental stuff from the old standbys? That way a failure of one whole sat would still leave something usable for the same money spent. My vote would be to piggyback a completely independent analog satellite onto P3E "just in case". Like I said, please, I'm looking for a real, thought out response.. I didn't write the above to be a critque or to troll or anything like that, I am just curious because it seems to me, as an outside observer, that after the failure of AO-40 the direction was to go bigger and even more complicated, which left me cold considering what I had done at my station to work AO-40. Even when AO-40 was up I felt it was very odd that time and money were spent on components and systems that were never used (did the solar panels ever deploy?) Yes, I know the sat was damaged, and that explains a good bit of it, but it still felt like some things were wasted. Emphasis on "felt".. I couldn't know the real process that resulted in the decisions made. If someone could help me understand why the direction is the way it is maybe I could get excited about the bigger sats, but I think you get more "bang for the buck" with the smaller less complicated birds. My favorite so far is PCSat I. Mostly off the shelf hardware and I had a very easy time digipeating APRS through it. One of those in an elliptical orbit would be a hoot! 73s, Jason - N1XBP P.S. - One last plea, this isn't a troll! I'm worried people will think it is.

10 12

38k4 Report
by Bruce 24 Sep '06

24 Sep '06

BB Received solid DCD indicator for both TNC31S & Spirit-2 TNC's I have. Tlmecho main downlink view showed tlm data faster then 96k. Switched to Wisp & received some d/l data. Tried to upload a file but could not get logged in, try again next pass. 73 Bruce KG4YEV

1 0

Is anyone going to record the Symposium presentations?
by Douglas Quagliana 24 Sep '06

24 Sep '06

Hi, It looks like I will not be able to attend the Symposium this year (unless a ride to the Symposium magically appears). In previous years there was (sometimes) a plan to record the presentations and then make the recordings available to those who could not attend. Is there a plan this year to make recordings? Douglas "Will record for transportation" :-)

1 0

HITSAT 23:19UTC
by Bruce Hopkins - KL7H 24 Sep '06

24 Sep '06

2330 UTC 24-Sept-06 Still no CW on this orbit at my location in NW Georgia (EM74EX)... 81 degree pass S to N... Copied strong CW call sign, first orbit after launch... 73 - Bruce - KL7H / 4 AMSAT #4679

1 0

Eagle Frequencies
by Bill Bruno 24 Sep '06

24 Sep '06

I'm trying to design, on paper, my Eagle station. Looking at the Eagle page I see proposed U,L and C band recievers, and V and C transmitters ( I assume from all the noise that S tx is not going to be used) What will the pairs be, U/V, C/C, and L/? ? Has that been proposed yet? Bill KB2RC, AMSAT 6986

2 1

help with satpc32
by Nick Pugh 24 Sep '06

24 Sep '06

I rinning xp pro and satpc32 I get an error e/a fehler 105 help thanks nick

2 1

SO-50
by DOBarrows＠aol.com 24 Sep '06

24 Sep '06

I enabled SO-50 at about 0215 on 24 Sep 2006. I tried to raise a contact but only heard one other station. Couldn't make him out because the elevation was getting too low for my Arrow antenna and it is hard to optimize the signal that is only there when someone keys up on the input. You would think there would be more activity on a weekend. Hope to hear more of you on SO-50. 73, Dave W8IJ

1 0