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"Do It Yourself" airborne proximity warning device



 
 
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  #51  
Old October 10th 18, 03:17 AM posted to rec.aviation.soaring
2G
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Default "Do It Yourself" airborne proximity warning device

On Friday, October 5, 2018 at 1:41:30 PM UTC-7, Andy Blackburn wrote:
On Friday, October 5, 2018 at 9:06:01 AM UTC-5, Dave Nadler wrote:

PS: Paper above doesn't mention REQUIRED FCC certification (and analogous
foreign certifications) - expensive, and REQUIRED.


Not to be the turd in the swimming pool, but I have some concerns about this.

Having worked on a consumer product that used the LoRa physical layer operating in the ISM band (Flarm is an ISM band device), I can attest to what Dave says and why it's important. Without specific rules regarding power, duration and frequency hopping, for example, it is easy to end up with devices that create so much congestion that they make the band useless for everyone else. Think of this as a glider with a perpetually stuck mike on their radio. This device doesn't appear to do this in isolation, but networks rarely get congested with small numbers of devices connected, even if they are poorly behaved.

It's my understanding that the over-the-air Flarm protocol has specific (and secure) methods for congestion control through timing broadcasts versus the GPS clock and this is how it is able to accommodate reasonable numbers of aircraft in proximity without too many transmissions colliding (pun intended) and blocking each other out. It is not at all clear to me whether this device has implemented the Flarm protocol or if it simply broadcasts without any congestion control under the presumption that not too many gliders will be flying at the same time. It seems from reading the GitHub documentation like maybe it is using a hack to get around this restriction which could create congestion problems - particularly in larger numbers.

Moreover, it doesn't appear that the Chinese manufacturer of these boards has pursued any FCC licensing (I doubt it) and even if they had part of the FCC licensing requires the complete device in its physical enclosure to ensure that RF pollution doesn't flood out of the device in unpredictable ways.

Mostly I have questions and suppositions as I don't know exactly what work has been done and I'm not an RF or networking engineer, but I'd be a bit concerned if one of these devices showed up at a big OLC camp. Also, beware of ramp checks if you have unlicensed (I guess technically that means illegal) devices operating on the same frequency as licensed safety devices. The Feds might frown on that. If I showed up at the airport with home-brew ADS-B Out kit in my glider I bet I'd get at least a sternly-worded letter from the FAA.

I have a lot of respect for this effort, but there is a potential need for significant caution. Many of our fellow pilots rely on this technology to keep them safe. If that technology were inadvertently being jammed, they'd have no way to know.

There are other issues with how the data port spec is or isn't implemented, but that's a whole other kettle of fish. If you are going to bet your life on a technology it's probably good for it to work as close to 100% of the time as you can manage.

Respectfully,

Andy Blackburn
9B


The FAA doesn't regulate the RF (electromagnetic) spectrum; that is the job of the FCC. It is HIGHLY unlikely that the FCC will show up at your local ramp with spectrum analyzers - they respond to serious complaints, and, then, with much plodding. Your fellow pilots, however, might get on your case if they figure out your equipment is interfering with theirs. The ISM band is pretty much the Wild West of the RF spectrum, and the FCC doesn't get involved.

https://en.wikipedia.org/wiki/ISM_band

Tom
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  #52  
Old October 10th 18, 03:53 AM posted to rec.aviation.soaring
Mike C
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Default "Do It Yourself" airborne proximity warning device

On Tuesday, October 9, 2018 at 5:52:57 PM UTC-6, Wyll Surf Air wrote:
So does this system work with Power Flarm? Mark said it does but in the documentation it does not seem to mention anything about Power Flarm, just Flarm V6 which I'm am not sure if refers to power flarm or the old Legacy flarm that is not allowed in the US. I'm wondering because if it does work with Power Flarm then I will get one for me and my partners glider since we don't have funds for a power flarm, but would like to have some sort of collision avoidance system.


I can see PowerFlarm equipped sailplanes. Pretty sure the author of the documentation is using a Flarm, and not a PowerFlarm, thus his reference to "Flarm". If you decide to buy the LoRa/Flarm device, be sure to order the 915 MHz unit and an additional antenna (also 915 MHz). The antenna that comes standard has a fairly limited range. So far there have been no interference problems with PowerFlarm units that I am aware of, this includes ground tests where the LoRa unit and a portable PowerFlarm were very close to each other.

Keep looking outside.

Mike

  #53  
Old October 11th 18, 04:40 PM posted to rec.aviation.soaring
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Default "Do It Yourself" airborne proximity warning device

Alas the 915 MHz band and other ISM bands are already congested with many other uses, and (from the wikipedia page) "communications equipment operating in these bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation." These bands were not intended for reliable communications use. It is a shame that we are forced into those marginal wastelands in the spectrum to do these things, while there are many hundreds of, e.g., aviation band comm frequencies available, now that they've been divided into 25 KHz channels (and 8.33 KHz in Europe and perhaps someday in the USA too). Of which gliders are officially allowed to use, what, 2 channels (dating to the 100 KHz spacing days), for air-to-air coordination?
  #54  
Old October 11th 18, 10:45 PM posted to rec.aviation.soaring
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Default "Do It Yourself" airborne proximity warning device

On Friday, October 5, 2018 at 5:27:25 PM UTC+2, Tom BravoMike wrote:
On Friday, October 5, 2018 at 9:06:01 AM UTC-5, Dave Nadler wrote:
On Thursday, October 4, 2018 at 11:38:15 AM UTC-4, Mark Hawkins wrote:
... "Flarm is a closed system". And why is that?


You will find a clear explanation of this policy he
http://flarm.com/wp-content/uploads/...patibility.pdf

As to wide adoption, most GA aircraft (including gliders) in Europe now
have FLARM; EASA now permits panel installation in certificated AC.

I'm a firm believer in open source (and funded it heavily in my former
corporate life), but I also know well how frequently it goes off the rails.
This application would suffer from anything other than top-notch,
full-time attention. Commercially-funded open source works when there are
lots of deep pockets with common interests (see GCC, newlib, RedHat, Eclipse).
Casual open-source, for small markets, without funding, not so much.

You may not agree with this, but it has been given serious consideration
but a lot of very committed and extremely sharp folks.

Respectfully, Dave

PS: Paper above doesn't mention REQUIRED FCC certification (and analogous
foreign certifications) - expensive, and REQUIRED.


Compatibility seems to be a big word in the article. Is FLARM actually compatible across the globe? I mean, if you take your glider from the US to Europe, South Africa, Australia for whatever reason: competition, job assignment, long vacation, retirement - will the PowerFlarm work there and be compatible with the locals?


PowerFLARM is not globally compatible - you need to buy a different unit for each frequency region, as I found out in both NZ and Europe. If you want to change the frequency on the unit, it's 500 Euros + VAT + shipping.
  #55  
Old October 11th 18, 10:49 PM posted to rec.aviation.soaring
[email protected]
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Posts: 47
Default "Do It Yourself" airborne proximity warning device

On Friday, October 5, 2018 at 10:41:30 PM UTC+2, Andy Blackburn wrote:
On Friday, October 5, 2018 at 9:06:01 AM UTC-5, Dave Nadler wrote:

PS: Paper above doesn't mention REQUIRED FCC certification (and analogous
foreign certifications) - expensive, and REQUIRED.


Not to be the turd in the swimming pool, but I have some concerns about this.

Having worked on a consumer product that used the LoRa physical layer operating in the ISM band (Flarm is an ISM band device), I can attest to what Dave says and why it's important. Without specific rules regarding power, duration and frequency hopping, for example, it is easy to end up with devices that create so much congestion that they make the band useless for everyone else. Think of this as a glider with a perpetually stuck mike on their radio. This device doesn't appear to do this in isolation, but networks rarely get congested with small numbers of devices connected, even if they are poorly behaved.

It's my understanding that the over-the-air Flarm protocol has specific (and secure) methods for congestion control through timing broadcasts versus the GPS clock and this is how it is able to accommodate reasonable numbers of aircraft in proximity without too many transmissions colliding (pun intended) and blocking each other out. It is not at all clear to me whether this device has implemented the Flarm protocol or if it simply broadcasts without any congestion control under the presumption that not too many gliders will be flying at the same time. It seems from reading the GitHub documentation like maybe it is using a hack to get around this restriction which could create congestion problems - particularly in larger numbers.

Moreover, it doesn't appear that the Chinese manufacturer of these boards has pursued any FCC licensing (I doubt it) and even if they had part of the FCC licensing requires the complete device in its physical enclosure to ensure that RF pollution doesn't flood out of the device in unpredictable ways.

Mostly I have questions and suppositions as I don't know exactly what work has been done and I'm not an RF or networking engineer, but I'd be a bit concerned if one of these devices showed up at a big OLC camp. Also, beware of ramp checks if you have unlicensed (I guess technically that means illegal) devices operating on the same frequency as licensed safety devices. The Feds might frown on that. If I showed up at the airport with home-brew ADS-B Out kit in my glider I bet I'd get at least a sternly-worded letter from the FAA.

I have a lot of respect for this effort, but there is a potential need for significant caution. Many of our fellow pilots rely on this technology to keep them safe. If that technology were inadvertently being jammed, they'd have no way to know.

There are other issues with how the data port spec is or isn't implemented, but that's a whole other kettle of fish. If you are going to bet your life on a technology it's probably good for it to work as close to 100% of the time as you can manage.

Respectfully,

Andy Blackburn
9B


My reading of the implementation is that it implements the (radio) traffic control inherent in the protocol exactly the same as FLARM does. Not an expert.
  #56  
Old October 12th 18, 07:36 AM posted to rec.aviation.soaring
Steve Koerner
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Posts: 384
Default "Do It Yourself" airborne proximity warning device

On Thursday, October 11, 2018 at 8:41:00 AM UTC-7, wrote:
Alas the 915 MHz band and other ISM bands are already congested with many other uses, and (from the wikipedia page) "communications equipment operating in these bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation." These bands were not intended for reliable communications use. It is a shame that we are forced into those marginal wastelands in the spectrum to do these things, while there are many hundreds of, e.g., aviation band comm frequencies available, now that they've been divided into 25 KHz channels (and 8.33 KHz in Europe and perhaps someday in the USA too). Of which gliders are officially allowed to use, what, 2 channels (dating to the 100 KHz spacing days), for air-to-air coordination?


The ISM band is congested in an urban setting but certainly not congested where gliders do their flying. The range of influence from all those many ISM devices out there is limited because their power output is limited by regulation. So the band becomes a pretty good choice actually to take advantage of the chips, antennas etc that are available at low cost.

 




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