We lost 1215-1240 MHz to GPS and were required to accept interference from ISM devices on 2400-2450 MHz 25 years ago so further restrictions are possible in the future.
73,
John KD6OZH
----- Original Message ----- From: sco@sco-inc.com To: amsat-bb@amsat.org Sent: Wednesday, September 20, 2006 18:30 UTC Subject: [amsat-bb] Re: Why do the amsats get more and more complex?
Looks to me that only the commercial service will possibly interfere with the Ham L band uplink. The open service signals will not be in the L band. Even then the Commercial service will be broadcast in three bands, only one of those is in our ham band. I would therefore assume if the commercial receiver was having interference on the CS channel (our L band) that it would switch over to one of the other TWO Open channels to gets its info. See the specs below. So what is the problem. Are we afraid that we might offend the Europeans if we are on one of their three channels? Sounds to me like Europe is building this system so they will have their own GPS if they decide to go to war with us. I hope they build it such that the Islamic Fascists can't use it to deliver bombs and missiles.
Les W4SCO
At 02:05 PM 9/20/2006, John B. Stephensen wrote:
Unfortunately, the Gaileo downlink covers 1258-1299 MHz, the first satellite has been lanched and the satellites in the constellation will be on over the entire world. Our uplink antennas have sidelobes that are 10-20 dB down, so a 1 kW EIRP SSB uplink results in 10-100 W radiated towards terrestrial receivers. A 256 kbps uplink would require 16 kW EIRP and be 0.5-1 MHz wide.
P3E has a second L receiver tuned to a null in the Galileo signal (there is only one null in the 1260-1270 MHz band) but no one knows if this will help. SSB users can move to the U uplink if L is a problem. However, this only works for narrowband signals. A wideband uplink won't fit in the null and can't move down in frequency.
73,
John KD6OZH
There will be four different navigation services available: * The Open Service (OS) will be free for anyone to access. The OS signals will be broadcast in two bands, at 1164-1214 http://en.wikipedia.org/wiki/MHzMHz and at 1563-1591 MHz. Receivers will achieve an accuracy of <4 m horizontally and <8 m vertically if they use both OS bands. Receivers that use only a single band will still achieve <15 m horizontally and <35 m vertically, comparable to what the civilian GPS C/A service provides today. It is expected that most future mass market receivers, such as http://en.wikipedia.org/wiki/Automotive_navigation_systemautomotive navigation systems, will process both the GPS C/A and the Galileo OS signals, for maximum coverage. * The encrypted Commercial Service (CS) will be available for a fee and will offer an accuracy of better than 1 m. The CS can also be complemented by ground stations to bring the accuracy down to less than 10 cm. This signal will be broadcast in three frequency bands, the two used for the OS signals, as well as at 1260-1300 MHz. * The encrypted Public Regulated Service (PRS) and Safety of Life Service (SoL) will both provide an accuracy comparable to the Open Service. Their main aim is robustness against jamming and the reliable detection of problems within 10 seconds. They will be targeted at security authorities (police, military, etc.) and safety-critical transport applications (air-traffic control, automated aircraft landing, etc.), respectively.
In addition, the Galileo satellites will be able to detect and report signals from COSPAS-SARSAT search-and-rescue http://en.wikipedia.org/wiki/Emergency_Position-Indicating_Radio_Beaconbeacons in the 406.0-406.1 MHz band, which makes them a part of the http://en.wikipedia.org/wiki/Global_Maritime_Distress_Safety_SystemGlobal Maritime Distress Safety System.
----- Original Message ----- From: sco@sco-inc.com To: amsat-bb@amsat.org Sent: Wednesday, September 20, 2006 16:16 UTC Subject: [amsat-bb] Re: Why do the amsats get more and more complex?
Galileo (if it is ever built and launched and worked) would just be over Europe, right? That would leave the rest of the world the ability to use our L band uplink, right? If we hams are using a dish pointed at the sky with a narrow bandwidth how is that going to interfere with ground receivers some distance from us? We would be smart enough to not have the Eagle uplink on the same freq, right? And we would design Eagle such that we could (from ground control) move the Eagle receive freq away from any potential conflict with Galileo, right? And Eagle would be in orbit and operational long before Galileo, right? And Galileo receivers on the ground will have the ability to cut out any possible interference from us, right?
Seems to me that we are planning to give up the L band (as an uplink) based on a lot of bad assumptions.
Les W4SCO
The answer is in two parts. First, an L-band ground antenna would be too large to disguise as a TVRO dish. Second, there is fear that over the lifetime of Eagle that L-band could become unavailable, particularly in Europe, if the Galileo system is deployed. Galileo would be a primary service and Ham transmissions would likely interfere with low cost commercial receivers.
I don't wish to debate these points. I'm just telling you the reasoning that went into not choosing L-band. I assure you that every possibility was considered. Lists were created and discussed on each alternative.
Rick W2GPS AMSAT LM2232
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_______________________________________________ Sent via AMSAT-BB@amsat.org. 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