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'[EE] Homemade GPS'
2011\10\04@095946 by M.L.

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Link from a friend:
http://www.holmea.demon.co.uk/GPS/Main.htm

Homemade GPS receiver. Haven't had time to read it yet but looks very
interesting.

-- Martin K

2011\10\04@102727 by RussellMc

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Highly recommended. Look at it. Marvel.

  > http://www.holmea.demon.co.uk/GPS/Main.htm

I saw one "homemade" GPS receiver design in the early days of GPS.
The author was subsequently employed by (AFAIR) Trimble :-).

I went to look at this one not believing it would be a low level
creation and feeling it was a waste of time regardless.

While from almost any practical point of view it IS a waste of time
and of vast amounts of effort, it is utterly utterly superb. The
lengths he had to go to, the effort expended, the things he had to get
right to make it work at all and more are staggering. A relatively
simple circuit overall. More or less understandable. Even his overall
descriptions are understandable if you don't think too too hard as you
skim through them. An utter joy to see somebody doing something like
this in this day and age. Somewhat akin to climbing Everest in a small
party with a minimum of Sherpas :-) (Maybe not quite up to climbing K2
standard).



          Russell








On 5 October 2011 02:59, M.L. <spam_OUTmTakeThisOuTspamlkeng.net> wrote:
> Link from a friend:
> http://www.holmea.demon.co.uk/GPS/Main.htm
>
> Homemade GPS receiver. Haven't had time to read it yet but looks very
> interesting.
>
> --
> Martin K.
>

2011\10\04@110857 by Michael Watterson

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On 04/10/2011 15:26, RussellMc wrote:
> I went to look at this one not believing it would be a low level
> creation and feeling it was a waste of time regardless.
>
> While from almost any practical point of view it IS a waste of time
> and of vast amounts of effort, it is utterly utterly superb. The
> lengths he had to go to, the effort expended, the things he had to get
> right to make it work at all and more are staggering. A relatively
> simple circuit overall. More or less understandable. Even his overall
> descriptions are understandable if you don't think too too hard as you
> skim through them. An utter joy to see somebody doing something like
> this in this day and age. Somewhat akin to climbing Everest in a small
> party with a minimum of Sherpas:-)  (Maybe not quite up to climbing K2
> standard).
>
>
>
>             Russell
>

Yes, nice

though he is using off the shelf coils and also an FPGA.

Why I wonder?

Because he can, like the guy making logic circuits and flip flops out out 11mA filament Russian valves (tubes).

2011\10\04@144841 by Derward Myrick

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Michael,  I hope he and many others will build a lot more
projects using off the shelf coils and other parts.

I have reached the ripe old age of 80 and am starting to slowdown
and I am soon puting a site up with that type of parts. I have over
1,500,000 new Resistors, caps, Inductors and semiconductors
of all types. At this time most are not smd.  Will sell them later. So you see why I said keep buying.  Plus Tubes (valves) and
things like that.

Derward Myrick  KD5WWI   PE




{Original Message removed}

2011\10\04@151743 by RussellMc

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> I have reached the ripe old age of 80

Congratulations !!!
Good to see people keeping on keeping on and not just vegetating.


       Russel

2011\10\04@151909 by Michael Watterson

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Derward Myrick wrote:
> Michael,  I hope he and many others will build a lot more
> projects using off the shelf coils and other parts.
>
>   I was attempting to be light hearted. It's great to see people really making stuff, not just playing lego.

> I have reached the ripe old age of 80 and am starting to slowdown
> and I am soon puting a site up with that type of parts. I have over
> 1,500,000 new Resistors, caps, Inductors and semiconductors
> of all types. At this time most are not smd.  Will sell them later.
> So you see why I said keep buying.  Plus Tubes (valves) and
> things like that.
>
> Derward Myrick  KD5WWI   PE
>
>
>   I look forward to perusing your wares :-)

2011\10\04@165331 by John Ferrell

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"Why I wonder?
 Because he can, like the guy making logic circuits and flip flops out out 11mA filament Russian valves (tubes)."

There are a lot of us with that "Because I can" quirk.

That describes most of my endeavors now days.  Derward has me beat on age, I am only 71. Many of my projects see little to no use after I am satisfied with the project. For guys (& Gals!) like me, it is not the destination that I enjoy, it is the trip!


-- John Ferrell W8CCW

2011\10\04@202058 by Chris Roper

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Well put John,

My first CPU was made out of 7400 chips till one of my professors gave
me a 6800 board that he had received and couldn't or wouldn't take the
time to understand.
After 30 years in the PC industry I find myself back in electronics
faced with CPU's like the 32MX series and a bunch of wiz kids that
know C but not the slightest thing about how a CPU works let alone a
transistor. I make a living out of taming hot heads and guiding
technicians in the hope that between the two we get a working product.
But for fun and to keep myself up to date I prototype and build
devices that would cost me a dollar or so to buy from China.

We have become too specialized,  working with the current generation
chips I can see that that is important, but I still think there is
room to expand your knowledge by experimentation even if it is a waste
of time output wise. And for people who have retired (I don't think
there is such an option theses days financially) there is nothing
wrong with a hobby that keeps your mind active and answers the "How
did they work that Magic" question.

Cheers
Chris

p.s a few years behind John, but close enough to understan

2011\10\04@220246 by Sean Breheny

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Really, really beautiful! I most certainly do NOT think it is a waste
of time! I find that re-inventing the wheel (under the appropriate
circumstances) can be very educational and can lead to discoveries of
improvements to be made.

I have seen a "homebrew" GPS receiver before, but that was in grad
school where some fellow students were doing research on alternative
uses of GPS (like trying to get orientation information from GPS based
on Doppler effects and moving antennas).

GPS is one of those technologies which just doesn't seem like it
should really work. Theoretically possible, but it is amazing that it
is practical for consumer-grade items!

Sean


On Tue, Oct 4, 2011 at 9:59 AM, M.L. <.....mKILLspamspam@spam@lkeng.net> wrote:
> Link from a friend:
> http://www.holmea.demon.co.uk/GPS/Main.htm
>
> Homemade GPS receiver. Haven't had time to read it yet but looks very
> interesting.
>
> --
> Martin K.
>

2011\10\05@043314 by alan.b.pearce

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> Really, really beautiful! I most certainly do NOT think it is a waste
> of time! I find that re-inventing the wheel (under the appropriate
> circumstances) can be very educational and can lead to discoveries of
> improvements to be made.

I agree it is really beautiful, although I would have preferred to see the decoding part put into an FPGA instead of a program inside a PC.

But the other thing I like about a project like this is that the person makes various discoveries along the way, and often comes up with explanations about the discovery that help others who aren't ever going to duplicate their project understand the technology they can buy off the shelf for relative peanuts.
-- Scanned by iCritical.

2011\10\05@071520 by M.L.

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On Wed, Oct 5, 2011 at 4:31 AM,  <alan.b.pearcespamKILLspamstfc.ac.uk> wrote:
> I agree it is really beautiful, although I would have preferred to see the decoding part put into an FPGA instead of a program inside a PC.
>
> But the other thing I like about a project like this is that the person makes various discoveries along the way, and often comes up with explanations about the discovery that help others who aren't ever going to duplicate their project understand the technology they can buy off the shelf for relative peanuts.

I gathered, perhaps incorrectly, that the guy is extremely smart at
the GPS and RF portions, maybe not quite as much so on the FPGA side.
Or maybe he just didn't have enough time to devote to the FPGA
portion?

The other thing is that it was probably just much easier to write the
code on his PC than design the logic.

-- Martin K.

2011\10\05@075654 by Dave Tweed

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M.L. wrote:
> On Wed, Oct 5, 2011 at 4:31 AM, <.....alan.b.pearceKILLspamspam.....stfc.ac.uk> wrote:
> > I agree it is really beautiful, although I would have preferred to see
> > the decoding part put into an FPGA instead of a program inside a PC.
>
> I gathered, perhaps incorrectly, that the guy is extremely smart at the GPS
> and RF portions, maybe not quite as much so on the FPGA side. Or maybe he
> just didn't have enough time to devote to the FPGA portion?

Actually, he states explicitly that he only had room for the four correlator
channels in the FPGA. This is the same FPGA that is synthesizing the local
oscillator for the RF board. He's simply reusing hardware that he had
developed previously.

> The other thing is that it was probably just much easier to write the code
> on his PC than design the logic.

That, too. He's using some memory- and compute-intensive techniques to get
high performance, and it would be difficult to implement a processor with
equivalent power inside the FPGA.

-- Dave Twee

2011\10\05@080819 by M.L.

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On Wed, Oct 5, 2011 at 7:56 AM, Dave Tweed <EraseMEpicspam_OUTspamTakeThisOuTdtweed.com> wrote:
>> I gathered, perhaps incorrectly, that the guy is extremely smart at the GPS
>> and RF portions, maybe not quite as much so on the FPGA side. Or maybe he
>> just didn't have enough time to devote to the FPGA portion?
>
> Actually, he states explicitly that he only had room for the four correlator
> channels in the FPGA. This is the same FPGA that is synthesizing the local
> oscillator for the RF board. He's simply reusing hardware that he had
> developed previously.
>

He goes on to say that he could possibly improve it by multiplexing
channels. Either way the FPGA portion is not ideal, but defaming him
wasn't my intent. I was just saying that there's room for improvement.
(obviously, you may say.)

-- Martin K

2011\10\05@084051 by RussellMc

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> I gathered, perhaps incorrectly, that the guy is extremely smart at
> the GPS and RF portions, maybe not quite as much so on the FPGA side.
> Or maybe he just didn't have enough time to devote to the FPGA
> portion?


FPGA was almost full at 4 channels he says.

There's little doubt you/he could extend it into the FPGa but the PC
has the overwhelming advantages of flexibiity /  low cycle time.


2011\10\05@144356 by Brooke Clarke

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Hi:

The original Trimble Trimpack GPS receivers were 1-bit designs, but did not use modern logic chips, just a 68000.  See their key patent:
http://www.prc68.com/I/Trimpack.shtml#Pat

-- Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.End2PartyGovernment.com/

2011\10\07@062525 by Oli Glaser

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On 04/10/2011 14:59, M.L. wrote:
> Link from a friend:
> http://www.holmea.demon.co.uk/GPS/Main.htm
>
> Homemade GPS receiver. Haven't had time to read it yet but looks very
> interesting.
>

Wow, that's a great project - inspiring stuff.
Thanks for the link..

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