Replies: 5 comments 5 replies
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There's a pretty simple DIY Navtex receiver detailed here [ http://www.harpoon.si/uploads/Razvoj%20podpora/Navtex.pdf | http://www.harpoon.si/uploads/Razvoj%20podpora/Navtex.pdf ]
& one built & tested & improved here [ https://www.youtube.com/channel/UCOm-zS6cpo6cv0mkxnkiZjQ | https://www.youtube.com/channel/UCOm-zS6cpo6cv0mkxnkiZjQ ]
that could easily (using modern sm components) be made to fit in a 1" tube
An Open Source Inmarsat receiver would be a first and possible very popular as there is a lot of interest in it - there is a GnuRadio flow for it - [ https://thinair.aelogic.com/french-guiana-firing-exercise/ | https://thinair.aelogic.com/french-guiana-firing-exercise/ ]
That website is the dev of Scytale-C who is working on a standalone commandline (still using an SDR) Rpi solution
…----- On 19 Feb, 2022, at 20:34, Mikhail Grushinskiy ***@***.***> wrote:
Based on success of the design of Maiana, especially idea of putting decoder
inside antenna enclosure and using ethernet
as data and a power media as only wire going down to the cabin,
I just thought (and hoped) you could be interested in designing (following same
pattern) two other devices:
one for Inmarsat-STD-C
and another for NavTex?
there are open source de-modulators / decoders for both.
and there were successful attempts to decode those transmissions with SDR and
active antennas.
Decoders source codes:
NavTex: [ https://arachnoid.com/JNX/JNX_source.tar.gz |
https://arachnoid.com/JNX/JNX_source.tar.gz ] ( [ https://arachnoid.com/JNX/ |
https://arachnoid.com/JNX/ ] )
Inmarsat-STD-C: [ https://github.com/cropinghigh/stdcdec |
https://github.com/cropinghigh/stdcdec ] ( [
https://github.com/cropinghigh/inmarsatc |
https://github.com/cropinghigh/inmarsatc ] )
NavTex antenna design: [ http://dl1dbc.net/SAQ/miniwhip.html |
http://dl1dbc.net/SAQ/miniwhip.html ]
The PA0RDT Mini Whip
Thanks,
--MG
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A quick survey of the Navtex market shows a wide range of devices down to 180 British pounds (https://www.nasamarine.com/product/2754/). In addition, unlike with AIS, there is a large second hand market. Therefore, I will pass. |
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Inmarsat might be more interesting.
Here is how antenna looks like:
https://youtu.be/PKO8hgtJUZ0
Thanks
…Sent from my iPhone
On Feb 20, 2022, at 1:09 PM, Peter Antypas ***@***.***> wrote:
A quick survey of the Navtex market shows a wide range of devices down to 180 British pounds (https://www.nasamarine.com/product/2754/). In addition, unlike with AIS, there is a large second hand market. Therefore, I will pass.
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Yeah, I've seen those. I'm not worried about antennas - I can build a proper PIFA in a snap. I'm more worried about silicon. I can't think of a low cost L-Band receiver IC with PSK support. There are plenty of sub-GHz receivers with (G)FSK support which made AIS possible. |
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Maybe this ... https://www.maximintegrated.com/en/products/comms/wireless-rf/MAX2121.html |
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It says PSK here
https://www.xonelec.it/mpn/maxim/max2112eti
…Sent from my iPhone
On Feb 20, 2022, at 1:26 PM, Peter Antypas ***@***.***> wrote:
Maybe this ... https://www.maximintegrated.com/en/products/comms/wireless-rf/MAX2121.html
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It looks like this family of chips are generic receivers with baseband I/Q outputs. So in theory they could be used to decode any modulation scheme. That said, these devices are designed for DVB-S so they expect a dish antenna with a built-in LNA. So there is definitely a need for a very low noise front end + bandpass filter. Thankfully, most GPS LNAs will work well for this. But GPS SAW filters are out of the question. |
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I will not build legacy satellite receivers. All I can say is that I have just seen the future of satellite IoT and it's less than 2 years away. When it comes, all of these services will migrate into a dirt cheap device that every boater will be able to afford. I hope to get started on this very soon. |
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Yeah I looked around a bit and found that there is something modern missing when it comes to systems like NAVTEX, Inmarsat-STD-C and the like. |
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There's a lot happening on this front now. We'll be seeing a new generation of constellations launching over the next year that will compete directly with cellular IoT in terms of economics. I'm tapping into one of these as soon as I can get silicon. The next step is orbiting cellular towers from AST (https://ast-science.com/) and/or a satellite modem in the iPhone. That's several years away. |
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Based on success of the design of Maiana, especially idea of putting decoder inside antenna enclosure and using ethernet
as data and a power media as only wire going down to the cabin,
I just thought (and hoped) you could be interested in designing (following same pattern) two other devices:
one for Inmarsat-STD-C
and another for NavTex?
there are open source de-modulators / decoders for both.
and there were successful attempts to decode those transmissions with SDR and active antennas.
Decoders source codes:
NavTex: https://arachnoid.com/JNX/JNX_source.tar.gz (https://arachnoid.com/JNX/)
Inmarsat-STD-C: https://github.com/cropinghigh/stdcdec (https://github.com/cropinghigh/inmarsatc)
NavTex antenna design: http://dl1dbc.net/SAQ/miniwhip.html
The PA0RDT Mini Whip
Thanks,
--MG
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