This isn't a question regarding amateur satellites but it is an interesting theoretical one to pose here and the same laws of physics apply. I know that the higher the frequency that is transmitted from a satellite the larger the Doppler shift will be. The Iridium satellites transmit at around 1.5gHZ. At that frequency I know the Doppler is large. How do they manage to keep the portable handsets on the ground locked to the signal? Are the handsets frequency agile to an extent? How do they achieve frequency lock so that the digital signals are decoded?
Dave Marthouse N2AAM dmarthouse@gmail.com
On 13 Oct 2013 at 18:30, Dave Marthouse wrote:
This isn't a question regarding amateur satellites but it is an interesting theoretical one to pose here and the same laws of physics apply. I know that the higher the frequency that is transmitted from a satellite the larger the Doppler shift will be. The Iridium satellites transmit at around 1.5gHZ. At that frequency I know the Doppler is large. How do they manage to keep the portable handsets on the ground locked to the signal? Are the handsets frequency agile to an extent? How do they achieve frequency lock so that the digital signals are decoded?
Dave Marthouse N2AAM dmarthouse@gmail.com
Interesting question Dave
I suspect as the XM/SIRIUS radio a data signal is sent back to the receiver position to minimized the doppler effect and some sort of data error correction also help to counteract the doppler effect. A similar system is implemented into the wxtoimg NOAA weather satellite fax decoding software.
It is an educated guess who only need to be reeducated... Lets say my Sirius receiver in a plain flat field suffer some signal breaks that i can't explain.
Luc Leblanc VE2DWE WAC BASIC CW PHONE SATELLITE
I found this paper:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&a...
Which seems to state that the subscribers of Iridium communications (the handset) adjust for Doppler shift. Each satellite is spaced such that there is also a "guard band" so they don't interfere with each other.
Bryce
On Sun, Oct 13, 2013 at 6:55 PM, lucleblanc6@videotron.ca wrote:
On 13 Oct 2013 at 18:30, Dave Marthouse wrote:
This isn't a question regarding amateur satellites but it is an
interesting
theoretical one to pose here and the same laws of physics apply. I know that the higher the frequency that is transmitted from a satellite the larger the Doppler shift will be. The Iridium satellites transmit at
around
1.5gHZ. At that frequency I know the Doppler is large. How do they
manage
to keep the portable handsets on the ground locked to the signal? Are
the
handsets frequency agile to an extent? How do they achieve frequency
lock
so that the digital signals are decoded?
Dave Marthouse N2AAM dmarthouse@gmail.com
Interesting question Dave
I suspect as the XM/SIRIUS radio a data signal is sent back to the receiver position to minimized the doppler effect and some sort of data error correction also help to counteract the doppler effect. A similar system is implemented into the wxtoimg NOAA weather satellite fax decoding software.
It is an educated guess who only need to be reeducated... Lets say my Sirius receiver in a plain flat field suffer some signal breaks that i can't explain.
Luc Leblanc VE2DWE WAC BASIC CW PHONE SATELLITE
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participants (3)
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Bryce Salmi -
Dave Marthouse -
lucleblanc6＠videotron.ca