A homemade receiver for GPS and GLONASS satellites | Hacker News Reader

A homemade receiver for GPS and GLONASS satellites

lea.hamradio.si

This is the internet I know and love. Pure content created by someone loving what they are doing. No bullshit blingbling, no ads, no tracking, just sharing experiences and knowledge. Wonderful and inspiring!

Well, to be fair, this article is from the 90s. It's probably just a reflection of the times it was made in.

Also a possible reflection on this fact; the site may not have been designed to handle the influx of traffic we just sent it from HN as it's now unreachable. Here is the archive.org mirror:

https://web-beta.archive.org/web/20161109161053/http://lea.h...

There's no Under Construction gif, definitely not a reflection of the times.

http://www.netanimations.net/fire-under-construction-animati...

The websites of ham radio operators often are like this. It seems to be a common thread, for whatever reason. It's nice.

If you want to view a site over an amateur radio link it can't include advertisements, and the link will be slow compared to any of the 802.11 modes. Plus lots of hams learned web design in the 90's.

edit: not an hour later I land on this site http://www.phonestack.com/farhan/bitx.html

That helical antenna is gorgeous.

There's a similar project that used an FPGA here: http://www.aholme.co.uk/GPS/Main.htm

That must be one of the most professional looking electronics DIY project I've seen for a while.

That article is where I found the link to this one, actually. The FPGA one is more sophisticated for sure but the article doesn't explain how the GPS signals work quite as well, while the older one does a good job of putting GPS into context.

I think my favorite part of GPS is that it uses CDMA to set all of the transmissions on top of each other on the same frequency channel. It's incredible that this technique can recover signals under the termal noise floor.

Archive link: http://archive.is/AMNvJ

FYI, The technology detailed on that page is governed by ITAR for US citizens. You can end up facing some serious penalties if you are a US citizen and build a GPS receiver (capable of operating > 10,000 feet) for someone in another country.

They relaxed the ITAR restrictions on GPS quite a bit a few years ago. The new rules only involve decryption of the precise positioning signals, steerable antennas designed to avoid jamming, and GPS designed as missile guidance technology (ability to deliver 500kg payload at least 300km).

http://www.insidegnss.com/node/4051

Additionally, the previous restrictions specified they were to be inoperable when BOTH above 18,000m altitude (not 10,000 ft) AND 515 m/s velocity.

Many manufacturers accomplished this by restricting operation when either condition was sensed, but you could find some that could be used in applications that only violated one condition, like high-altitude balloons.

So does that mean my phone's GPS won't work in flight on a commercial jetliner? (never tried it).

Commercial jetliners never fly at 18,000 m (nor at 515 m/s). Max is about 11,000 m or so, and about 250 m/s. It would be interesting to know if consumer GPS ever worked aboard the Concorde.

If you're going to use the Concorde for a speed test then you might as well also test the SR-71. For..er... science!

The story: http://oppositelock.kinja.com/favorite-sr-71-story-107912704...

Merry Christmas to everyone who hasn't read it yet.

This one is my favorite story from the same Blackbird pilot (Brian Shul): https://www.reddit.com/r/todayilearned/comments/2q2ctc/til_t...

Bonus story, also from Brian Shul: https://www.reddit.com/r/MilitaryPorn/comments/1mimvu/80000_...

A couple of years back my kid got the GPS working on his Windows phone, using some 3rd party app that cut through all of the other location detection crap. We were able to track our speed and location in a passenger jet flying out of Maui.

You can use offline GPS navigation software on a plane. I did it several times, just as my friends. I use LG G3 and OsmAnd app.

LG G3 has very poor GPS antenna so you have to press the phone against the plane window and wait for 4-5 minutes before it finds sufficient number of sattelites.

If you take pictures from the air with an iPhone, they will be geotagged. When you land and you get internet back, they will be labeled correctly in Photos.app.

Other phones had trouble finding GPS signal in airplanes, but I never had a problem with my iPhone 6s or iPhone 7.

> The new rules only involve decryption of the precise positioning signals, steerable antennas designed to avoid jamming, and GPS designed as missile guidance technology (ability to deliver 500kg payload at least 300km).

Now I want to publish all of that info in a book and distribute it world wide, a la PGP Philip Zimmerman style. ITAR...Pssssha!

Somehow the potential repercussions for this feel worse - your information could be used to guide actual missiles against people. I know you can make similar arguments with encryption but at least that can't deliver explosive payloads by itself

I doubt that's going to be a vector compared to driving a truck into a Christmas market.

Encryption is far more dangerous than precision positioning, but it should still be freely available.

Do these ITAR restrictions only apply to GPS, or also GLONASS / Galileo etc.?

The ITAR regulations apply to any type of satellite navigation. The speed and altitude restrictions were removed in 2014.

https://www.regulations.gov/document?D=DOS_FRDOC_0001-3863

https://www.regulations.gov/document?D=DOS-2014-0017-0001

Is there any case law on this subject?

Instructions for building a GPS receiver (which is what source code is) seems like a logical extension of Bernstein v. US.

Modern day technique with SDR. https://www.youtube.com/watch?v=uf2vatqek_o

Does anyone have a mirror including http://lea.hamradio.si/~s53mv/navsats/software.zip ?

https://web-beta.archive.org/web/20160322050334/http://lea.h...

For affordable and small high precision (centimeter level) GNSS, I really like this https://emlid.com/reach/

Can anyone suggest a good textbook for Radio, Antenna theory, Ham radio in general?

I'm quite interested in learning these but most books I've come across either seem too basic, or too advanced. I am a math major so mathematics isn't a problem for me if it is supported with enough text. Thanks!

Those are pretty wildly different topics

For "radio" I'd recommend reading on Analog and Digital Signal Processing. Antenna theory is an entirely separate field which you'd want to reference specifically. Ham is more of of the culture/context surrounding ham radio, and for that I'd recommend one of the ARRL exam study books from http://www.arrl.org/shop/What-s-New though for the easier tests these are pretty light on technicals and are more about policy and good radio operator behavior

Ah, you're right -- I meant that if there's some reference covering the relevant topics that'd be great.

Thanks for the clarification! The ARRL study books look good too.

The Radar Handbook by Merrill Skolnik often comes up as a basic reference covering some of these topics, radar and radio being intimately related. Plus the pdf is usually around: http://airspot.ru/book/file/961/radar_handbook.pdf

That looks great! Thank you.

> Plus the pdf is usually around

It's a bonus that you don't have to compensate the creator of a useful product?

Freedom does not imply free beer and vice versa.

What are you talking about? I think you might have replied to the wrong comment. The suggested book is not under a libre license.

Yes, it is a bonus. Having the pdf online also prevents me from needing to walk 500 yards to the library where I can also find it for no cost.

But seriously, I think it's safe to assume that Mr Skolnik [1] is doing just fine. Given that his publisher is likely taking the lion's share of the proceeds, and that generally speaking, writing books for academia is not a profitable enterprise, I have no problem using a found pdf or finding the book in the library. I know personally several academics who have written books and they do it to solidify their expertise and/or obtain tenure, not to make money directly from sales. Hence the movement to give books away for free [2].

[1] https://en.wikipedia.org/wiki/Merrill_Skolnik [2] https://open.umn.edu/opentextbooks/About.aspx

For antennas, you could do worse than picking up a copy of John Kraus' "Antennas" - he starts off with the basic principles and builds on them as he introduces new concepts. Uses enough math to let you understand what is going on without getting carried away with too many nasty integrals. His writeup on an idea for a gravitational transmitter/receiver system towards the end of the book is worth the money alone. :-)

For a cookbook showing you a lot of how without bothering too much about the why, Karl Rothammel's Antennenbuch (in German) can't be beat, IMHO.

Thanks! Kraus' looks like the most complete overview. Looking forward to read it through over the holidays. :)

(Edit) Just found Kraus' recorded lecture on youtube. Very interesting! https://www.youtube.com/watch?v=4nKRp7TzgBI

The ARRL Handbook [1] covers all of those topics pretty comprehensively and provides a digital edition with a large collection of supplemental content. They also publish a separate antenna book, but the Handbook does a fine job of covering antenna basics. I recommend the hardcover; this is a large book and it benefits from strong covers.

[1] https://www.arrl.org/shop/ARRL-Handbook-2017-Hardcover-Editi...

https://www.reddit.com/r/amateurradio/wiki/index is a pretty good place to start. The ARRL has manuals that walk through the theory behind the exams for the US licences. The extra class book explains the theory of building a modern transceiver, starting with doping silicon to make semiconductors.

Pft, no Galileo support? Just pathethic...

(Kidding of course. Awesome write-up.)

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