Thanks for sharing this Simon. I have a couple of Meshtastic units in the 868MHz ISM band and I see the Meshtastic emissions, even with an attenuator on. I don’t see the other pulsed, 4-5 burst signals where I am in Manchester but I’ll keep an eye out. What might be useful for you, is if you used a tool such as URH (Universal Radio Hacker) to view and attempt decoding of the signal. Also, maybe post your samples to sigid wiki, particularly if you do manage to find out what the signal is.
Thank you for these intereseting suggestions. I couldn't find it on sigid wiki so perhaps I should upload a sample there. URH is unknown to me so I will have fun looking into that !
My guess is Pilot Aware ATOM Grid. Their P3i frequency is 869.525 MHz. I have just emailed Pilot Aware's MD about this issue - on the basis of the the issues we've been seeing in Shoreham (near Shoreham Airport - where a PAW ATOM Grid TX is). I believe there is another ATOM base station at Deanland airfield near Lewes, and possibly Ringmer Gliding Club too. Admittedly, your video seems to show the signal you're receiving a little lower in the band though. So this may not be the same thing as we're seeing in Shoreham.
Thank you for your detailed reply, Simon. It is great that you have contacted Pilot Aware. I am surprised that such a "mission critical" system uses a relatively unregulated part of the spectrum which is a free for all for an unlimited number of users. In the end, who has usage priority ? I suspect it won't be Meshtastic. Did the frequency planners even foresee the Meshtastic system and make provisions for its rapid expansion ? I doubt it...
@@fotografm- Reality is that any system that is “mission critical” is really not suitable for unregulated bands. Those folks need to purchase their own bit of regulated spectrum.
Yes. PAW is not mission critical as such. It started as a homebrew, Raspberry Pi based, electronic conspicuity project. Until very recently all of the hardware (the PilotAware Rosetta and its predecessor), contains a Raspberry Pi, a cheap SDR dongle (for receiving ADS-b on 1090 MHz), a cheap GPS and external antenna (£3 from AliExpress), and an 868 MHz Tx, bundled together in a fairly basic case. I have one of these in my aircraft, as do a lot of pilots. Very recently PAW has released a new model with custom hardware. It has become very popular and, to make sense of the various different airborne systems (I.e. ADS-b, mode-S transponders, FLARM for gliders, FANET for paragliders, etc they implemented ground stations which receive all of those signals, triangulate them using MLAT, and then retransmit them (on 869.525 MHz). Along with weather station information. Aircraft will also now relay traffic information to other aircraft if they're out of range of the ATOM station, e.g. in a valley. This has all grown organically, and works. It's cheap and cheerful stuff for pilots to avoid hitting one another. It uses the ISM band for cost and speed reasons. Getting the regulators to define such a system, getting all the equipment certified, frequencies allocated, would take years and certified aviation equipment costs thousands...and will be old hat by the time its completed the certification process.
Hi Simon I can't help identify your mystery signal, not heard in Caterham I have been looking for a more serious source of continuous interference which is using 869.525 which others have reported and I find I can see traces of it almost everywhere. This is particularly annoying as it raises my noise floor on Meshtastic at home to around -115 rssi so I see nothing reported below that level. When walking around I have seen that narrower band continuous signal on your display which is within the bandwidth occupied by Meshtastic just a bit lower than 525.I do't kow what that is either hihi. It seems Meshtastic is doomed to failure in this country with such high levels of use of 525. Thanks for your interesting videos keep up the good work
Nothing like that using my RSPdx. I do see other 'shapes' of interference around 869.4MHZ-869.5MHz, but nothing that extends as far high as 869.525MHz. Incidentally, I had a much lower noise floor than you - mine was ~-130dBm. Is your RF gain turned right down increasing the quantisation noise?
Thank you for your comment, Mike. I had the RF gain set to around 22dB I expect. Above 23, the noise rises to swamp the signals and below 23, the signals sink down below the noise. I live in a very noisy building. I never really understood how the RSPDX is calibrated. According to SDRPlay, it can make absolute power measurements in dBm but I have not yet had the time to look into how to do this. Have you worked this out ?
@@fotografm I use either SDRuno or SDR Connect depending on whether I can be bothered opening the Parallels desktop on my MacBook. My approach with the RF gain is to increase it as much as possible until I get an overload warning, and then back it off until the overload report disappears. By doing this, the ADC quantisation noise relative to the input is minimised since the noise is divided by the front-end RF gain to give an input referred noise. My understanding that has been confirmed by people at SDRplay is that the absolute power measurements are calculated by relying on the calibration of the ADC against its reference, and then backing out the RF gain at the front-end against a calibration table of gain vs setting for the RF amplifier. One area of confusion is that the spectra show a different dBm value on their vertical scale when compared to the input power figure. This is because the spectra plots are derived from calculations of the power into the resolution bandwidth, whereas the power measurement assumes the power into the bandwidth of the filter (6kHz or 8kHz or whatever is chosen).
They seem to be on the increase these days. IOT is exploding in usage. Soon fridges will be holding conversations with doorbells and passing drones :-)
@@fotografm And because they're internet enabled, they have access to your wi-fi. ALL devices on your network. Is that truly what people want? Well spotted.
Hello. Could an electronic warfare device operating in standby mode be the source of the mysterious signal? From the comments I understand that there is an airport near you. Electronic warfare equipment may clog the channel with interference after detecting your packet.
@@fotografm My dad recently set up a weather station in his garden. The manual says "433MHz/868MHz/915MHz". It's difficult to say if this is exact frequencies. Perhaps I need to invest in one of those SDRs and sort of reverse direction find it to see what signals are coming from it.
Feasible. FLARM uses 868.6 MHz. I suspect not though, because this is a constant/ regularly repeating signal day and night, rather than a transitory glider. (Which would be daylight only). I suspect it's a Pilot Aware ATOM grid station which receives FLARM (868.6 MHz), and ADS-b (1090 MHz) and Mode-S transponders (1090 MHz), uses MLAT to locate Mode-S only aircraft, then retransmits the locations of all of these aircraft (plus weather station information) on the P3i frequency (869.525 MHz) every 1.5 seconds. Aircraft within range then pick this up with their Pilot Aware Rosetta devices, which shows the traffic, and weather, on their chosen EFB - e.g. Sky Demon - on an iPad/Android Tablet.
Thank you, Simon. That is a lot of new acronyms for me ! Do you have any such devices ? It would be interesting to see them working and?or to monitor the corresponding signals.
Could be. I need to look into how that system works. I noticed all the hype a couple of years ago and assume that it had fizzled out. Perhaps it has just been swamped with the hype about Meshtastic :-)
@@fotografm It did fizzle out, miners went from $500 to under $100, there is still some attention and if you check their map there is an absolute ton of miners everywhere, still. My area is entirely flooded. I'm surprised we can do LoRA at all given all the noise.
Excellent as always Simon .
Many thanks, Julian !
Thanks for sharing this Simon. I have a couple of Meshtastic units in the 868MHz ISM band and I see the Meshtastic emissions, even with an attenuator on. I don’t see the other pulsed, 4-5 burst signals where I am in Manchester but I’ll keep an eye out.
What might be useful for you, is if you used a tool such as URH (Universal Radio Hacker) to view and attempt decoding of the signal.
Also, maybe post your samples to sigid wiki, particularly if you do manage to find out what the signal is.
Thank you for these intereseting suggestions. I couldn't find it on sigid wiki so perhaps I should upload a sample there. URH is unknown to me so I will have fun looking into that !
@@fotografm - URH is pretty cool, worth a go.
Apparently the ‘PilotAware’ system at Shoreham airport uses 869.525MHz. I can’t post the link here….
I tried to post a link it deleted my comment
Facebook messenger deleted my private chat and threatened to ban me because I typed in a frequency to my chat partner !
My guess is Pilot Aware ATOM Grid. Their P3i frequency is 869.525 MHz.
I have just emailed Pilot Aware's MD about this issue - on the basis of the the issues we've been seeing in Shoreham (near Shoreham Airport - where a PAW ATOM Grid TX is). I believe there is another ATOM base station at Deanland airfield near Lewes, and possibly Ringmer Gliding Club too.
Admittedly, your video seems to show the signal you're receiving a little lower in the band though. So this may not be the same thing as we're seeing in Shoreham.
Thank you for your detailed reply, Simon. It is great that you have contacted Pilot Aware. I am surprised that such a "mission critical" system uses a relatively unregulated part of the spectrum which is a free for all for an unlimited number of users. In the end, who has usage priority ? I suspect it won't be Meshtastic. Did the frequency planners even foresee the Meshtastic system and make provisions for its rapid expansion ? I doubt it...
@@fotografm- Reality is that any system that is “mission critical” is really not suitable for unregulated bands. Those folks need to purchase their own bit of regulated spectrum.
Yes. PAW is not mission critical as such. It started as a homebrew, Raspberry Pi based, electronic conspicuity project. Until very recently all of the hardware (the PilotAware Rosetta and its predecessor), contains a Raspberry Pi, a cheap SDR dongle (for receiving ADS-b on 1090 MHz), a cheap GPS and external antenna (£3 from AliExpress), and an 868 MHz Tx, bundled together in a fairly basic case. I have one of these in my aircraft, as do a lot of pilots.
Very recently PAW has released a new model with custom hardware.
It has become very popular and, to make sense of the various different airborne systems (I.e. ADS-b, mode-S transponders, FLARM for gliders, FANET for paragliders, etc they implemented ground stations which receive all of those signals, triangulate them using MLAT, and then retransmit them (on 869.525 MHz). Along with weather station information.
Aircraft will also now relay traffic information to other aircraft if they're out of range of the ATOM station, e.g. in a valley.
This has all grown organically, and works.
It's cheap and cheerful stuff for pilots to avoid hitting one another.
It uses the ISM band for cost and speed reasons.
Getting the regulators to define such a system, getting all the equipment certified, frequencies allocated, would take years and certified aviation equipment costs thousands...and will be old hat by the time its completed the certification process.
@@simondale9641 - I’m not knocking the concept, it’s just a shame that it’s causing issues with your Meshtastic setup.
Hi Simon I can't help identify your mystery signal, not heard in Caterham I have been looking for a more serious source of continuous interference which is using 869.525 which others have reported and I find I can see traces of it almost everywhere. This is particularly annoying as it raises my noise floor on Meshtastic at home to around -115 rssi so I see nothing reported below that level. When walking around I have seen that narrower band continuous signal on your display which is within the bandwidth occupied by Meshtastic just a bit lower than 525.I do't kow what that is either hihi. It seems Meshtastic is doomed to failure in this country with such high levels of use of 525. Thanks for your interesting videos keep up the good work
Thanks for your comments Bryan. Yes the band is very crowded and that's the only portion that supports the higher power.
Smartmeter? Radiator valves...?
It seems too persistant for that but thank you for your suggestion.
Nothing like that using my RSPdx. I do see other 'shapes' of interference around 869.4MHZ-869.5MHz, but nothing that extends as far high as 869.525MHz. Incidentally, I had a much lower noise floor than you - mine was ~-130dBm. Is your RF gain turned right down increasing the quantisation noise?
Thank you for your comment, Mike. I had the RF gain set to around 22dB I expect. Above 23, the noise rises to swamp the signals and below 23, the signals sink down below the noise. I live in a very noisy building. I never really understood how the RSPDX is calibrated. According to SDRPlay, it can make absolute power measurements in dBm but I have not yet had the time to look into how to do this. Have you worked this out ?
@@fotografm I use either SDRuno or SDR Connect depending on whether I can be bothered opening the Parallels desktop on my MacBook. My approach with the RF gain is to increase it as much as possible until I get an overload warning, and then back it off until the overload report disappears. By doing this, the ADC quantisation noise relative to the input is minimised since the noise is divided by the front-end RF gain to give an input referred noise. My understanding that has been confirmed by people at SDRplay is that the absolute power measurements are calculated by relying on the calibration of the ADC against its reference, and then backing out the RF gain at the front-end against a calibration table of gain vs setting for the RF amplifier. One area of confusion is that the spectra show a different dBm value on their vertical scale when compared to the input power figure. This is because the spectra plots are derived from calculations of the power into the resolution bandwidth, whereas the power measurement assumes the power into the bandwidth of the filter (6kHz or 8kHz or whatever is chosen).
@@Mike-H_UK Thank you for your detailed reply. That makes things look a bit more complicated !
@@fotografm Sorry!! ;-)
I know that Ringway Manchester has been receiving unidentified signals .
They seem to be on the increase these days. IOT is exploding in usage. Soon fridges will be holding conversations with doorbells and passing drones :-)
@@fotografm And because they're internet enabled, they have access to your wi-fi. ALL devices on your network. Is that truly what people want? Well spotted.
Hello. Could an electronic warfare device operating in standby mode be the source of the mysterious signal? From the comments I understand that there is an airport near you. Electronic warfare equipment may clog the channel with interference after detecting your packet.
maybe but it could be anything really...
Weather station?
Could be. I am wondering what frequency all those wireless weather stations for home use are using.
@@fotografm My dad recently set up a weather station in his garden. The manual says "433MHz/868MHz/915MHz". It's difficult to say if this is exact frequencies. Perhaps I need to invest in one of those SDRs and sort of reverse direction find it to see what signals are coming from it.
@@TheIaindavidson That would be fun thing to do. Those are probably just the generic frequency bands and not the ctual frequency.
Could be FLARM signals?
Feasible. FLARM uses 868.6 MHz. I suspect not though, because this is a constant/ regularly repeating signal day and night, rather than a transitory glider. (Which would be daylight only).
I suspect it's a Pilot Aware ATOM grid station which receives FLARM (868.6 MHz), and ADS-b (1090 MHz) and Mode-S transponders (1090 MHz), uses MLAT to locate Mode-S only aircraft, then retransmits the locations of all of these aircraft (plus weather station information) on the P3i frequency (869.525 MHz) every 1.5 seconds. Aircraft within range then pick this up with their Pilot Aware Rosetta devices, which shows the traffic, and weather, on their chosen EFB - e.g. Sky Demon - on an iPad/Android Tablet.
Thank you, Simon. That is a lot of new acronyms for me ! Do you have any such devices ? It would be interesting to see them working and?or to monitor the corresponding signals.
@@simondale9641hmm, won't duty cycle limits (10%) still apply to this frequency as per ISM? (edit: fixed duty cycle %)
@@GertBurger isn't our duty cycle limit 10% ?
@@fotografmcorrect, I misread the frequency for P3i :P so that should be 10% in my previous comment.
A Helium miner perhaps?
Could be. I need to look into how that system works. I noticed all the hype a couple of years ago and assume that it had fizzled out. Perhaps it has just been swamped with the hype about Meshtastic :-)
@@fotografm It did fizzle out, miners went from $500 to under $100, there is still some attention and if you check their map there is an absolute ton of miners everywhere, still. My area is entirely flooded. I'm surprised we can do LoRA at all given all the noise.
@@luc5543 Thanks for the reply. I will go and take a look at their map !