[sci.electronics] GPS system receiver

lharris@ersys.edmonton.ab.ca (Leonard Harris) (05/16/91)

Hi.  Does anyone know what would be involved in building your
own global positioning satellite receiver?.  i know the frequencies 
they transmit on, but what data does it send.  Also more than one 
satellite has to be interrogated to calculate position.
Any ideas?
thanks /len

Leonard Harris              lharris@ersys.edmonton.ab.ca
Edmonton Remote Systems:  Serving Northern Alberta since 1982

jeff@hpuplca.nsr.hp.com ( Jeff Gruszynski ) (05/18/91)

> / hpuplca:sci.electronics / lharris@ersys.edmonton.ab.ca (Leonard Harris) /  8:17 pm  May 15, 1991 /
> Hi.  Does anyone know what would be involved in building your
> own global positioning satellite receiver?.  i know the frequencies 
> they transmit on, but what data does it send.  Also more than one 
> satellite has to be interrogated to calculate position.
> Any ideas?
> thanks /len
> 
> Leonard Harris              lharris@ersys.edmonton.ab.ca
> Edmonton Remote Systems:  Serving Northern Alberta since 1982
> ----------

	In my previous life I worked with military satellites including
	GPS.  I once considered building my own receiver, so I called up
	the GPS program office and asked for some unclassified technical
	data on the system.  Several boxes of stuff later I concluded
	it would be of the order of building a satellite TV receiver *and*
	descrambler from scratch.  You need to sync on to a spread spectrum
	signal and do a fair amount of post-processing.  Without good
	microwave and digital CAD tools it would be painful.  
	
	On the other hand I've heard a division of Rockwell Int'l is planning
	to come out with a ~$250 personal GPS receiver.

Jeff Gruszynski
T&M STE SE
Santa Clara NSR
Hewlett Packard
-----------

rusty@steelmill.cs.umd.edu (Rusty Haddock) (05/18/91)

In article <12780006@hpuplca.nsr.hp.com> jeff@hpuplca.nsr.hp.com (   Jeff Gruszynski  ) writes:
   >> / hpuplca:sci.electronics / lharris@ersys.edmonton.ab.ca (Leonard Harris) /  8:17 pm  May 15, 1991 /
   >> Hi.  Does anyone know what would be involved in building your
   >> own global positioning satellite receiver?.  i know the frequencies 
   >> they transmit on, but what data does it send.  Also more than one 
   >> satellite has to be interrogated to calculate position.
   >> Any ideas?
   >> thanks /len
   >> 
   >> Leonard Harris              lharris@ersys.edmonton.ab.ca
   >> Edmonton Remote Systems:  Serving Northern Alberta since 1982
   >> ----------
   >
   >	In my previous life I worked with military satellites including
   >	GPS.  I once considered building my own receiver, so I called up

In one of my previous lives I worked on Texas Instruments' TI-4100.  This
was a heavy box with somewhere around a dozen 4"x5"(?) PCBs in it with 2
CPU's handling receive and navigation/user interface functions.  There
was at least one other CPU for the tape deck too.  Still, that box was
designed at least 10-years ago and was meant to go almost anywhere from
the tropics to the polar regions and out to sea on an oil rig.

   >	On the other hand I've heard a division of Rockwell Int'l is planning
   >	to come out with a ~$250 personal GPS receiver.

It's about time.  I believe this is a single card that fits into a
IBM/clone-PC.  I don't know if this includes the antenna and if it's C/A
only or if it can do P-code as well.  I think it'll only track 4
satellites too but that's all you need for lat, long, alt, and speed.

	-Rusty-
--
Rusty Haddock / Computer Science Dept	DOMAIN:	rusty@mimsy.cs.umd.edu
University of Maryland			PATH:	{uunet,rutgers}!mimsy!rusty
    If someone points a quad-vectored, hyper-thermic, cosmo blaster
       at you it's a safe bet that you're about to become toast.

agodwin@acorn.co.uk (Adrian Godwin) (05/20/91)

In article <0iP121w164w@ersys.edmonton.ab.ca> lharris@ersys.edmonton.ab.ca (Leonard Harris) writes:
>Hi.  Does anyone know what would be involved in building your
>own global positioning satellite receiver?.  i know the frequencies 
>they transmit on, but what data does it send.  Also more than one 
>satellite has to be interrogated to calculate position.
>Any ideas?
>thanks /len
>
>Leonard Harris              lharris@ersys.edmonton.ab.ca
>Edmonton Remote Systems:  Serving Northern Alberta since 1982


Last years' Computer Networking Conference included a presentation on building
a GPS receiver. It included system diagrams and some details of the maths required
(though no actual listings - the radio side is covered more completely than
the processor side).

Copies of the CNC proceedings can be obtained from the American Radio Relay
League, in Newington, Connecticut. 1990 was the 9th CNC.

-adrian


-- 
--------------------------------------------------------------------------
Adrian Godwin                                        (agodwin@acorn.co.uk)

Norbert.Zacharias@arbi.informatik.uni-oldenburg.de (Norbert Zacharias) (05/21/91)

agodwin@acorn.co.uk (Adrian Godwin) writes:

>Copies of the CNC proceedings can be obtained from the American Radio Relay
>League, in Newington, Connecticut. 1990 was the 9th CNC.

>-adrian
How can i reach they via e-mail???
Norbert
-- 
=============================================================================
Norbert Zacharias          Norbert.Zacharias@arbi.informatik.uni-oldenburg.de
FB Physik                                               148964@DOLUNI1.bitnet
Carl-von-Ossietzky-Universitaet
Tel. 0049-441-7983527
 Was Du nicht willst das man Dir tu, das will auch nicht was willst denn Du?
							   Heinz Erhard
=============================================================================

ken@hertz.njit.edu (ken ng cccc) (05/22/91)

In article <12780006@hpuplca.nsr.hp.com> jeff@hpuplca.nsr.hp.com (   Jeff Gruszynski  ) writes:
:	In my previous life I worked with military satellites including
:	GPS.  I once considered building my own receiver, so I called up
:	the GPS program office and asked for some unclassified technical
:	data on the system.  Several boxes of stuff later I concluded
:	it would be of the order of building a satellite TV receiver *and*

What government agency did you go to and what did you ask for?  From the
Air Force I got a copy of the SV interface specification and an introduction
to GPS.  Combined its about 2 inches thick.  From the Institute of Navigation
I got the reprints on the design and experiments with GPS, that's 3 half
height books about 3 inches thick.  Assorted magazine article xeroxes comes
to about an inch thick.  But still, unless you've got some pretty small
boxes, I'm curious as to what you have.  I'm also willing to trade where
I got my stuff if anyone is interested.

:	descrambler from scratch.  You need to sync on to a spread spectrum
:	signal and do a fair amount of post-processing.  Without good
:	microwave and digital CAD tools it would be painful.  

Yup, its by no means trivial.

:	On the other hand I've heard a division of Rockwell Int'l is planning
:	to come out with a ~$250 personal GPS receiver.

I'm dying to find out where I can get one of these beasts.  I've heard that
its a 5 chanel unit which makes it REAL NICE :-).

Kenneth Ng
"No problem, this is how you make it" -- R. Barclay, ST: TNG

cjp@megatek.UUCP (Christopher J. Pikus) (05/22/91)

> > / hpuplca:sci.electronics / lharris@ersys.edmonton.ab.ca (Leonard Harris) /  8:17 pm  May 15, 1991 /
> > Hi.  Does anyone know what would be involved in building your
> > own global positioning satellite receiver?.  i know the frequencies 
> > they transmit on, but what data does it send.  Also more than one 
> > satellite has to be interrogated to calculate position.
> > Any ideas?
> > thanks /len
> > 
> > Leonard Harris              lharris@ersys.edmonton.ab.ca
> > Edmonton Remote Systems:  Serving Northern Alberta since 1982
> > ----------
> 
> 	On the other hand I've heard a division of Rockwell Int'l is planning
> 	to come out with a ~$250 personal GPS receiver.
> 
> Jeff Gruszynski
> T&M STE SE
> Santa Clara NSR
> Hewlett Packard
> -----------

	There is an article about the Rockwell GPS chip set in the April 8, 
1991 issue of EE Times. I have the article in front of me since I wanted to 
build one of these myself.

	The development kit is a 2.5"x4.0" board that has all the electronics
on it. All you add is a power supply, antenna, and display. They expect the
kit to be about $500.

	It is most cool...


-- 
... And I mean it!!!
Christopher J. Pikus,               Megatek Corp.
INTERNET:     cjp@megatek.uucp      San Diego, CA
UUCP:         uunet!megatek!cjp or ucsd!megatek!cjp

maverick@vaxkab.lne.kth.se (05/22/91)

Hi !
You say you know the frequencies of the GPS. If you could post them in a
mail in this group I would be very grateful. A GPS is really a neat
thing to work with ! 
Thanks in advance !
Fred

ken@sugra.uucp (Kenneth Ng) (05/27/91)

In article <1991May22.130035.3708@kth.se>, maverick@vaxkab.lne.kth.se writes:
: You say you know the frequencies of the GPS. If you could post them in a
: mail in this group I would be very grateful. A GPS is really a neat
: thing to work with ! 

I hope none of this is classified, I don't know how it could be:

L1 = 1575.42 Mhz
L2 = 1227.6 Mhz

Those are the base frequencies, but due to the spread spectrum nature, they
broadcast kinda all over.

-- 
Kenneth Ng
Please reply to ken@hertz.njit.edu until this machine properly recieves mail.
"No problem, here's how you build it" -- R. Barclay, ST: TNG