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  Overall Spec?
Posted by: ozindfw - 01-26-2020, 08:51 PM - Forum: Technical - Replies (3)

So far all I can see is framing information.  Where is the PHY described?  Are variable coding schemes supported?  Interleaving? Is it C4FM or some other modulation scheme?

Oz, N1OZ

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  Access control mechanism for repeaters
Posted by: md - 01-03-2020, 02:24 AM - Forum: Technical - Replies (1)

We have discussed it in the irc a bit but, it is nice to have it here. Open for everybody's comments.
-First, repeaters must have their own private key. Which is only known by repeater owner, maybe even less.(just repeater itself, if we find a secure way to distribute personal keys)
-Repeater owner or repeater itself should generate personal keys for each callsign using a hash function. ie. sha(callsign+repeater_key)
-Radio's should include this personal keys in their air data packets using another hash function. sha(data_itself+personal_key+session_id/date/time etc.)

Pros:
-Repaters do not have to keep userid/key pair. Just a banned list is enough.
-Users can be added without programming repeater.
-Callsign theft is prevented.
-When session id in the hash function is used, injection attacks are prevented.
-When time/date used, replay attacks are prevented.
-Further, repeater sourced session id will solve both problems.

Cons:
-Real time hash calculation for each packet is required.
-If some of users share their own key accidentally and insist on using exactly same callsign, repeater key must be changed. So, all users have to update their keys.

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  New Site!
Posted by: KC1AWV_smf2_import36 - 12-26-2019, 11:46 PM - Forum: General discussion - Replies (2)

Please, everyone check out the new site! [url="https://m17project.org"]https://m17project.org[/url]

The forums have also been migrated. [url="https://m17project.org/forum/"]https://m17project.org/forum/[/url]

Please update your links accordingly!

Steve KC1AWV

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  [PL] M17 projekt opensource DV
Posted by: SP2ONG - 12-22-2019, 11:23 AM - Forum: General discussion - Replies (2)

Witam,

Wojetk zalozylem watek z znacznikiem [PL] ze jest on w jezyku polskim w odroznieniu od pozostalych na forum gdzie koledzy dyskutuja w jezyku angielskim. Mysle ze ten watek bylby dla kolegow z SP ktorzy chcielby by podzielic sie swoim uwagami, pomyslami itp.

Bardzo ciekawy jestem jak pobiegna losy tego calego projektu i trzymam kciuki  Smile

Mam troche pytan na ktore nie znalazlem odpowiedzi w FAQ projektu ale napisze o tym w nastepnym poscie pozniej

Pozdrawiam

Waldek SP2ONG

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  Ethernet Framing
Posted by: SmittyHalibut - 12-13-2019, 04:54 AM - Forum: Technical - Replies (4)

@pe1rxq  Please tell me more about how you take advantage of Ethernet framing with DML.

My initial thought was that you could use kernel bridging/switching, or even an actual network switch, to automatically pass packets between multiple radios.  This would work for person-to-person stream, but I suspect the vast majority of streams will be person-to-group.  Ethernet doesn't support that very well, unless you start tapping into Multicast on Ethernet.  But even then it only supports 23 bits of multicast addressing (https://networklessons.com/multicast/mul...ss-mapping) AND your endpoints would have to handle the multicast subscriptions, etc.

It's also only good for a single local broadcast domain, which doesn't lend itself well for large scale, distributed networks.  It's a layer 2 protocol, not a layer 3 protocol.  So you couldn't use the native Ethernet packet switching to, say, link your repeater, my repeater, and 75 other repeaters together without first encapsulating the Ethernet frame in an IP, and probably TCP, and probably another application on top of that, packet.

I like Ethernet as a starting point because it's pretty close to what we're doing anyway, and I'm all about borrowing from successful systems where it makes sense to.  But I'd like to understand your reasoning for sticking strictly to Ethernet frames.

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  New version of M17_ANL !
Posted by: so3alg - 12-10-2019, 11:07 PM - Forum: Technical - Replies (10)

I plan to design a new version of M17_ANL.
Just because we are planning to support also analog FM capatibilites in our devices,
I want to use ADF7012 instead of Si4463(thank You Wojtek).
I'm thinking about using an STM32F103C8T6 microcontroller.
It has built-in USB-CDC converter, which I think is important, to make USB dongle smaller.
To make debugging easier, I want to place diodes - 4 (PWR, SYS, TX, RX) connected directly
by a resistor network to an STM32, and 2 connected to TX/RX switch.
What do You Think about it, do You have any ideas?
I will be grateful for the comments.

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  TR-9 - RF power amplifier
Posted by: SP5WWP - 12-09-2019, 06:38 PM - Forum: Technical - Replies (4)

The RF part of TR-9 uses an Si4463 chip (+20dBm output) along with a power amplifier based on AFT05MS004NT1 MOSFET (about 20dB of gain). When we are going to use the ADF7021 instead, the output level of it (+13dBm) won't be enough to drive the PA. What I suggest is to use a MMIC like this one before the output stage:
https://uk.farnell.com/nxp/bga6589-135/m...dp/2400497

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  TR-9 - display
Posted by: Eliot - 12-08-2019, 05:05 PM - Forum: Technical - Replies (4)

Here we have some RGB OLED displays. I think, that TR-9 display working temperature should be -20 degrees Celsius at least. I will be grateful for the comments.

1. https://uk.farnell.com/midas/mcot160128b...dp/2342694
2. https://uk.farnell.com/densitron/dd-1281...dp/1829707
3. https://uk.farnell.com/midas/mcot128128a...dp/2342693
4. https://uk.farnell.com/densitron/dd-160128fc-1a/display-oled-rgb-160x128/dp/1498857
5. https://uk.farnell.com/densitron/dd-1601...dp/1498858

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  Si4463 RX problem
Posted by: SP5WWP - 12-06-2019, 07:28 PM - Forum: Technical - Replies (3)

I've configured one Si4463 to transmit v3 packets and it works well, the first packet is 85ms and all other 80ms long. But when I try to detect them (with another Si4463), it only detects the first one (probably because it contains a preamble). Does anyone have any experience with Si446x chips or can buy like 2 and test them? Modules are like $3.5/each.

PS Yes, I have disabled the preamble detection (I think).

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  TR-9 analog mode?
Posted by: SP5WWP - 12-05-2019, 10:32 AM - Forum: Technical - Replies (6)

I have just came up with an interesting idea. If we can use ADF7021 instead of Si4463, we could possibly implement analog FM too.
Transmitting could be done by modulating the VCO externally (via the "VCO IN" pin) and sending the same symbol constantly (to get the carrier).
Receiving: enable internal AFC (to track the FM carrier) and take voltage input of the VCO (again - the "VCO IN" pin).

What do you think? Si4463 can only allow analog TX, because there's no VCO control voltage anywhere, but you can still modulate the VCTCXO.

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