You have to set the Rnode with the parameters you want to sniff. So I had to set the baud rate, bandwidth and CR to match the other tracker.
A lot of gadgets that are doing off the grid chat are using the Lora chips. I’ve been watching these guys. https://www.sonnetlabs.com They say their code is open source.. On Sun, Aug 1, 2021 at 12:08 PM Kristoff <[email protected]> wrote: > Hi Steve, > > > I must really look into the Rnode. > If you say that you put the rnode into sniffer mode so you could > determine the spreading-factor, does this mean that the Rnode can do > that automatically, or that you just tried all of different spreading > factors and found that SF12 worked? > > > Yes, SF12 packets are long, but that is exactly one of the features of > digital communication: the possibility to 'tune' the transmission. The > parameters are bandwidth, bitrate (speed), transmission-power and range. > It's like WSPR or QRSS. The transmissions are very long, but you can > decode signals that are 20 to 30 db below the noise-floor. > > > If you look at page 20 of the sx1276 datasheet (*), there are some > examples of the RF sensitivity with different SF values. > It's not linear, but roughly speaking, going down 1 step in the SF > scale, you lose about 2 to 3 db of sensitivity. > > So if you go down 2 steps in the SF scale, your bitrate will be 4 times > faster, but you will loose some 40 to 50 % of range. > > > > In the context of APRS, I think aprs-over-lora has a place for (say) > portable or bicycle-mobile applications next to regular 1200 baud AFSK > on VHF or UHF for (car) mobile use. > So I do not think that the lower bitrate of LoRa is that necessarily > much of an issue. > > I hope that aprs-over-lora will make applications like chat more popular > as that is a feature of APRS that has deserves much more attention then > what it gets. > > > > Note. > I had a chat in the matrix-room of the GNU Radio community on Hamming > FEC on the Coding-Rates. > The conclusion at this time is that -indeed- there is no reason to use > Coding Rates 6 or 8. In both cases, they just add error-detection > capability to CR5 or CR7; but as aprs-over-LoRa has CRC error-detection > anyway, this does not add any value. > > So the choice is this: > CR5: no error-correction, for radio-channels with little RF interference, > CR7: error-correction enabled, for radio-channels with more RF > interference. > > > Keep in mind that a CR7 packet is 7/5 times the size of a CR5 packet. > > > > 73 > > kristoff - on1arf > > > (*) > > https://www.semtech.com/products/wireless-rf/lora-core/sx1276#download-resources > > > On 01.08.21 18:36, Steve wrote: > > Interesting that you mentioned coding rates. > > I was sniffing OE5BPA’s Lora transmitter because Xastir is not > decoding > > it. I have a feeling his packets are not quite right over the air. You > can > > put Rnode into a packet sniffer mode, which makes it easy to see things. > > OE5BPA’s config file has a default CR of 12… it is very long on its > > transmission. I changed it to CR of 5. > > > > Just a FYI… I’m just a person who has fun using this stuff, not a > developer > > with coding experience .. > > > > Steve N0FPF > > > > On Sun, Aug 1, 2021 at 5:27 AM Kristoff <[email protected]> wrote: > > > >> Hi Steve, > >> > >> > >> Interesting code. I'll look into it. Perhaps it is a better option then > >> me building something (non-standard) myself. > >> > >> > >> Concerning modifying the Coding-Rate, I think one should look at this > >> per application. > >> APRS is mostly a 'broadcast' service the most logical thing to do is to > >> use one single 'standard' modulation-scheme for everything. > >> > >> However for a service like 'aprs-messages', although the traffic is > >> transmitted inside a 'broadcast' packet, it is still directed at one > >> specific destination. > >> In that case, the igate or digipeater can operate on that. If it keeps > >> track of the coding-rate of the last packet it received from that > >> station, it can use that information in its transmissions towards that > >> station. > >> (you can find the coding-rate of the last packet received in register > >> 0x18 of the chip). > >> > >> Concerning the coding-rate, yesterday I found this video from ccc 33c3 > >> (2016), where Matt Knight explained how he reverse-engineered most of > >> the LoRa PHY (*) > >> > >> There is also this document from him. (**) > >> > >> > >> It had an interesting part in it where he explains the 4 transformations > >> done on the LoRa datastream, one of them is Hamming-coding Forward Error > >> correction. > >> His document has this on it: > >> --- cut here --- cut here --- > >> > >> A larger codeword size improves the robustness of the FEC: Hamming(5,4) > >> and (6,4) provide error detection as a parity bit would, whereas (7,4) > >> and (8,4) provide single bit correction with (8,4) additionally > >> providing dual error detection. > >> --- cut here --- cut here --- > >> > >> > >> > >> As I see it, going from FEC 4/5 to 4/7 is interesting as it adds the > >> possibility to do error-correction of a single bit. > >> Going from 4/7 to 4/8 does add the ability to detect more errors, but it > >> cannot correct it. > >> > >> Now, as APRS is a datacommunication-protocol (i.e. the content of the > >> data is unknown, so the whole packet must be correct or it will not be > >> processed) and the LoRa frame also has a CRC field, I do not see the > >> additional advantage of that 8th bit (i.e. 4/8 vs. 4/7). It may provide > >> more error-detection, but CRC does that anyway. > >> > >> So, as I see it, it looks that if you are in a area of bad coverage, it > >> is useful to use the 4/7 coding-rate instead of the standard 4/5, but > >> not 4/8 (as I previously mentioned). In fact, using 4/8 creates larger > >> packets then when using 4/7, which -I think- might be a disadvantage as > >> a bigger packets simply has more bits that can get corrupted. > >> > >> > >> But, as I not an expert on hammings FEC, I might be wrong. > >> > >> If somebody knows more about this, feel free to reply. > >> > >> > >> > >> > >> (*) https://media.ccc.de/v/33c3-7945-decoding_the_lora_phy#t=2382 > >> (**) https://pubs.gnuradio.org/index.php/grcon/article/view/8 > >> > >> > >> 73 > >> kristoff - on1arf > >> > >> > >> On 31.07.21 22:38, Steve wrote: > >>> I’ve noticed that the KISS implementation on a lot of these devices is > a > >>> forked over version of the Rnode. He used the Sx 1276 chip as well > >> because > >>> it has really good RX sensitivity at the lower rates. He also has a > newer > >>> and easier form of KiSSattach. > >>> https://github.com/markqvist/tncattach > >>> > >>> > >>> > >>> I like your thoughts about changing modulation on the fly. I’ve seen it > >>> done with higher level stuff , Ubiquiti and others. Just wonder how > much > >>> it would slow things down. Cause I think you would do that per packet. > >>> Maybe per connection. > >>> > >>> Right now I’m just interested in tying a few of the different versions > >> and > >>> seeing what works. No real goals in mind, just checking it out and > >>> experimenting. > >>> > >>> I’ve thought about a repeater, but that would kill the great RX > >> sensitivity > >>> , but a digi would be good. A old style repeater separated by distance > >> and > >>> a link would work. > >>> > >>> > >>> Might even try Winlink on it and see what what happens when I stir that > >> pot! > >>> So many ideas. > >>> > >>> Steve N0FPF > >>> > >>> On Sat, Jul 31, 2021 at 12:58 PM Kristoff <[email protected]> wrote: > >>> > >>>> Steve, > >>>> > >>>> > >>>> I also have this model: > >>>> > >>>> > >> > https://www.amazon.nl/DollaTek-LoRa32-SD-kaart-draadloze-module/dp/B07RXSKPBX/ > >>>> The disadvantage is that it lacks the 8 Mbit PSRAM chip (which is on > the > >>>> T-beam) so the ESP32 is a bit short on memory for embedded python. > (less > >>>> then 1 MByte of RAM available). > >>>> > >>>> > >>>> Software development-wize, perhaps it makes more sense to turn the > >>>> radio-device into just a dumb 'packet-modem', connect it to a > >>>> single-board computer (say, a raspberry pi) and do all development > >>>> overthere. That way you can run higher-level code, easily interface > with > >>>> the internet, connect other devices (e.g. a VHF/UHF packet mode), etc. > >>>> > >>>> Last week, I found this python module for processing aprs message (*) > >>>> which I think would be a good basis to do some experimental > development > >>>> for aprs-code. > >>>> > >>>> > >>>> > >>>> > >>>> I do like the sx1276 chip. It has a couple of nice features. > >>>> > >>>> - as it also has a FSK modem, It might also be able to transmit POCSAG > >>>> (paging) messages. If this works, we should be able to build a > >>>> APRS-to-POCSAG gateway with just one piece of hardware: send a aprs > >>>> text-message to a certain APRS node and it transmit that message as a > >>>> POCSAG paging message. > >>>> > >>>> I once wrote some code to create pocsag-message. (**) > >>>> > >>>> > >>>> - The automatic header-detection in lora is nice, > >>>> This means that if you send a packet with (say) a coding-rate of 4/8 > to > >>>> a lora-node configured with 4/5, the chip will still receive and > decode > >> it. > >>>> So, if you know that you are in area with bad APRS-over-lora coverage, > >>>> you can switch to a coding-rate that provides better error-correction > >>>> (like 4/8). Your packets will become larger (by 37.5 % in this case) > but > >>>> your packet might still arrive, which it might not have done with a > >>>> coding-rate of 4/5. > >>>> > >>>> Note that that bandwidth and Spread-Factor do need to match. If not, > >>>> your packet will not be demodulated/decoded. > >>>> > >>>> - Another nice thing is that, although the chip does have > CRC-generation > >>>> and CRC validation in silicon, it will still pass packets to the > >>>> receiver, even if they fail the CRC check. > >>>> It will flag it as 'CRC error', but the code on application-level will > >>>> still be able to retrieve it. > >>>> Most other radio-chips I have looked at so far do have do not do this > >>>> and will silently drop that message. > >>>> > >>>> This would allow for a nice lora "DX-ing" mode by implementing > >>>> additional error-correction code on application-level. > >>>> > >>>> > >>>> > >>>> > >>>> Ah yes, there is also a GNU Radio implementation of the Lora PHY. > (***) > >>>> I haven't tried it yet, so I do not know if it works but It would be > >>>> interesting to experiment with this, e.g. tweaking the parameters even > >>>> further to do even further DX. > >>>> > >>>> > >>>> > >>>> I am not on Facebook. > >>>> > >>>> I prefer mailing-lists for in-depth discussions. To get real-time > help, > >>>> ... I am on matrix / element.io which is an open-source and > >>>> decentralized IM/voice/video service. > >>>> There are quite some open-source groups reachable via matrix, either > >>>> directly on matrix itself or via bridges to IRC or some other IM > >> protocol. > >>>> It's used the GNU Radio community. > >>>> > >>>> > >>>> (*) https://github.com/ampledata/aprs > >>>> (**) https://github.com/on1arf/pocsag > >>>> (***) https://www.epfl.ch/labs/tcl/resources-and-sw/lora-phy/ > >>>> > >>>> > >>>> 73 > >>>> kristoff - on1arf > >>>> > >>>> > >>>> On 31.07.21 20:31, Steve wrote: > >>>>> I gave two of the TTGO units including a couple of Rnodes. > >>>>> > >>>>> I’m going to try a couple of the existing firmware options out there. > >>>> Some > >>>>> are KISS based some are not. I like the possibility of using the wifi > >> or > >>>>> Bluetooth with the TTGO with some of the APRS programs fir the > phones. > >>>>> > >>>>> Seems for a mobile device, not have a extra board such as a PI might > be > >>>>> nice… we’ll see! > >>>>> > >>>>> The TTGO can also be used for this: > >>>>> https://tinygs.com > >>>>> > >>>>> The Rnode guy is also implementing a MESH system but is only in the > >> alpha > >>>>> stage. Beyond my ability. > >>>>> > >>>>> I’ll have to get back to you on Freq, I only got my TTGO going last > >> night > >>>>> and didn’t bother to look! > >>>>> > >>>>> There is a LORA APRS group on Facebook, grin, that is mostly from > >> Europe > >>>>> who have a lot of experience with this . > >>>>> > >>>>> Steve N0FPF > >>>>> > >>>>> > >>>>> > >>>>> On Sat, Jul 31, 2021 at 11:20 AM Kristoff <[email protected]> > wrote: > >>>>> > >>>>>> Steve, > >>>>>> > >>>>>> > >>>>>> Your project interests me too. > >>>>>> > >>>>>> We are using this hardware: > >>>>>> https://github.com/LilyGO/TTGO-T-Beam > >>>>>> > >>>>>> We are on 433.775 MHz, 150 KHz, SF12, 4/5 > >>>>>> What frequency and what mode do you use? > >>>>>> > >>>>>> > >>>>>> The software comes from this project: > >>>>>> https://github.com/lora-aprs > >>>>>> But if the code of your project is standard arduino, it shouldn't be > >> to > >>>>>> difficult to port it to ESP32. > >>>>>> > >>>>>> Apparently, there are also some high-altitude balloon projects that > >> use > >>>>>> lora for their telemetry download. > >>>>>> > >>>>>> > >>>>>> > >>>>>> My personal interest is to use this for doing some software > >>>>>> experimentation, so I use micropython on the ESP32 (fast > development) > >>>>>> and not the arduino code. > >>>>>> > >>>>>> > >>>>>> > >>>>>> 73 > >>>>>> Kristoff - on1arf > >>>>>> > >>>>>> > >>>>>> > >>>>>> > >>>>>> On 31.07.21 20:05, Steve wrote: > >>>>>>> I connected it to my 10 db Omni antenna at home right at the base > to > >>>>>>> minimize the loss. > >>>>>>> > >>>>>>> I was impressed that it was heard around some of the hills in west > >>>>>> seattle . > >>>>>>> I have plans to put a IGate at a high point around the end of the > >>>> summer. > >>>>>>> I also found a small bi- directional amp too. Boost it to a watt > or > >>>> two. > >>>>>>> Just don’t want to kill the receive sensitivity. Around $60. > >>>>>>> > >>>>>>> It’s all in the antenna. > >>>>>>> > >>>>>>> Steve N0FPF > >>>>>>> > >>>>>>> > >>>>>>> On Sat, Jul 31, 2021 at 10:59 AM Tom Russo <[email protected]> > >> wrote: > >>>>>>>> On Sat, Jul 31, 2021 at 10:35:44AM -0700, we recorded a > >>>> bogon-computron > >>>>>>>> collision of the <[email protected]> flavor, containing: > >>>>>>>>> I have interfaced the Rnode Lora device. It does Kiss and used a > PI > >>>> 3. > >>>>>>>>> Pretty straight forward. > >>>>>>>>> > >>>>>>>>> https://unsigned.io/projects/rnode/ > >>>>>>>>> > >>>>>>>>> I was able to do a client and a IGAte. > >>>>>>>> That is pretty cool! > >>>>>>>> > >>>>>>>> -- > >>>>>>>> Tom Russo KM5VY > >>>>>>>> Tijeras, NM > >>>>>>>> > >>>>>>>> echo "prpv_a'rfg_cnf_har_cvcr" | sed -e 's/_/ /g' | tr > >> [a-m][n-z] > >>>>>>>> [n-z][a-m] > >>>>>>>> > >>>>>>>> _______________________________________________ > >>>>>>>> Xastir-dev mailing list > >>>>>>>> [email protected] > >>>>>>>> http://xastir.org/mailman/listinfo/xastir-dev > >>>>>>>> > >>>>>> _______________________________________________ > >>>>>> Xastir-dev mailing list > >>>>>> [email protected] > >>>>>> http://xastir.org/mailman/listinfo/xastir-dev > >>>>>> > >>>> _______________________________________________ > >>>> Xastir-dev mailing list > >>>> [email protected] > >>>> http://xastir.org/mailman/listinfo/xastir-dev > >>>> > >> _______________________________________________ > >> Xastir-dev mailing list > >> [email protected] > >> http://xastir.org/mailman/listinfo/xastir-dev > >> > _______________________________________________ > Xastir-dev mailing list > [email protected] > http://xastir.org/mailman/listinfo/xastir-dev > -- Pardon the brevity, sent from a mobile device. So there. _______________________________________________ Xastir-dev mailing list [email protected] http://xastir.org/mailman/listinfo/xastir-dev
