Primarily for general aviation discussion, but other aviation topics are also welcome.
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#1803751
gaznav wrote:
PaulisHome wrote:...
It's a fairly complicated problem. It's not as simple as less power = less range. At these frequencies, range can be up to line of sight (we know we can pick up Flarm signals from gliders > 100km away with a suitable antenna, and Flarm is the lowest power of the systems we're discussing). Often the driver of whether you can see a signal at a receiver in a congested network, is the signal to noise - and the noise is the contribution from everything that's emitting in line of sight).
...
So I think we need to be quite specific about the question we're trying to answer, and look closely at the modelling which is used to answer it. Do we have these?

Paul


Paul

...
Finally, power is most definitely linked to range in the most simplest of equations - free space path loss. Yes, antennae design can also assist with this so-called problem (which can also be fed into the free space path loss equation if required). Further, receiver design can also improve things. Technology shifts on this all of the time (normally incremental gains) and certainly filters for noise on 1090Mhz have come a long with digital processing. So it may be that in the 6-8 years that this study was completed that matters have improved over what the study reported. Further, the removal of more of the non-selective Mode A transponders since will most certainly have cleaned up 1090Mhz.

...


Thanks. I understand that. What I said was "It's not as simple as less power = less range." Although that's broadly true, there are other things you need to consider. [There's a big difference between a congested and an uncongested network - an analogy might be how far away you can hear someone talking in a field when it's just you and them, compared with when there's a crowd, also talking].

I understand one of the three reports that you mention is in CAP1391 (referenced by @rjc101 earlier). Do you have links to the other two?

Paul
Last edited by PaulisHome on Sun Oct 18, 2020 9:46 am, edited 1 time in total.
gaznav liked this
By Duncan M
#1803753
Flyin'Dutch' wrote:
TheFarmer wrote:
I’m actually totally confused by so much in this discussion.


Don't be.

There are people on here who think that having Xray vision goggles alone is great for seeing everyone; they omit to mention that if nobody turns on their headlights it will still be like riding bumper cars.

ADSB is the standard; see and be seen.


The problem is that the CAA have not been specific in promoting ADSB as their preferred option. The rebate covers other types of EC equipment and therein lies the problem that many pilots have in making their purchase decision.
If the CAA had given some notice of this rebate and stated any EC device must have ASDB in/out to qualify then there would be some point to it.
I find myself in exactly the situation of The Farmer and am thinking of cancelling my Echo 2 order, merely because there isn't a sensible solution for all aircraft.
#1803755
@TheFarmer

It’s not always about you.

If you spent £250 to transmit ADSB out, then every EC device on the market could see you.

I’ll say that again EVERY EC DEVICE WILL SEE YOU

You’d be conspicuous.

Then we can at least avoid you whilst you prefer not to “only see some traffic” and sit on the fence.

You’ll be part of the solution.

(of course, you could also see me, but you’d prefer not to look)
Nick, Hollman, gaznav and 1 others liked this
By patowalker
#1803757
I thought pilots were the sort of people who preferred not to be told what to do. It turns out they are given a choice, with all the information needed to make it, plus a £250 incentive, but some still can't make up their mind. :(
By Nick
#1803758
TheFarmer wrote:I agree FD, but I’ve decided to wait until there’s a standardised system where the hardware works reliably, and the traffic info is not just a random and minimal selection.


If you just output ADS-B you will be visible to most receivers. The one that spots your transmission may be the one about to hit you.
If you have a device that recieves ADS-B you may also see that aircraft and you can both take evasive action.
It's simple really.

Nick
#1803763
@TheFarmer if I were you flying with the volumes of traffic I'm lead to belive exist in your parts I'd have the insurance policy in place. Even if disgarded after 5yrs the annual 'premium' is still less than many pay for monthly hangarage.

I would suggest that rather than the confusion resulting in you not fitting either option, fitting both would be the wiser choice. :D
gaznav, exfirepro, Nick liked this
User avatar
By ls8pilot
#1803767
Duncan M wrote:.....
I find myself in exactly the situation of The Farmer and am thinking of cancelling my Echo 2 order, merely because there isn't a sensible solution for all aircraft.


As a plea from some-one who flies an aircraft type that is difficult to see can I say to @Duncan M and all others thinking like this

"please do not"

I realise there is no one perfect solution, but doing nothing is like saying "I won't have a flu jab because it does'nt protect me from mumps"

Please get something. If you get an SE+SD you can see all the other ADSB emitters and all the Flarm emitters directly and lots of people will see you including all the PAW users. If you get a PAW you will see more (transponder only emitters), but will only receive Flarm traffic where there is ground network coverage and fewer people will see you. Take your pick, neither is the "right" or "wrong" choice - it may come down to which fits in the cockpit better.

Do one or the other, or both (it's not that costly with the £250 rebate), but please do something. I know there have been relatively few MAC's, but I know 3 people killed and 4 more who survived. If we are all honest every year we have a few "close calls", and if you occasionally see a plane and think "crikey, he did'nt see me" it probably means you are doing the same to others as well. Controlled airspace is pushing us all closer together - please dont wait for the perfect solution, you may be waiting a very long time.
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By gaznav
#1803770
@PaulisHome

Thanks. I don’t believe there is a version of the QinetiQ 2012 and 2014 studies on the internet. However, Appendix B of the following by NATS details some of those references. https://www.nats.aero/wp-content/upload ... _issue.pdf

As for the 2015 study, then QineitiQ’s report is replicated in CAP1391. However, this one was more to do with studying the effect of LPAT on ACAS/TCAS being able to receive 1090Mhz replies. Again, they reported that there was nothing to worry about at such low power levels.

Yes, I also use a similar way to explain as your field analogy. I tend to use a sports stadium with 20,000 people in it. If everyone is talking then everyone can hear each other locally (say within 10 people of each other) - that is what Low Power ADS-B at 20Wis trying to do. But then if the stadium owners need everyone to know what is going on from one end of the stadium to the other, then they use the PA - that is your Class 1 500W Mode S ES transponder on an airliner is doing where its signal is critical to provide safe separation in IFR Controlled Airspace (however, the very few LPATs that are really close to each other may still be able to ‘hear’ themselves talk as well) :thumright:
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User avatar
By gaznav
#1803776
TheFarmer wrote:
Surely, if no-one can see your SkyEcho then you don’t need to worry about “draconian implications these days for busts”? :cyclopsani:

That seems to contradict itself, a wee bit?


So, are you now saying my Mode S Funke doesn’t do anything at all? Ok, I’ll keep that turned off too.

I’m actually totally confused by so much in this discussion.


Ok, so your Funke Mode S transponder is the most likely thing to get you noticed should you be unfortunate to have an airspace ‘bust’. By getting a SE2 then this will make you the most conspicuous - and most importantly with an accurate position from a GPS - to other GA aircraft in your vicinity. You will also be able to see their ADS-B and also FLARM if they are carrying it and you pay the £30 FLARM licence fee.

So what is not to like - see and be seen amongst your GA buddies - and for now few ATCRUs can see you from that device?
By Crash one
#1803785
The Farmer’s decision not to go for SE2 was based on people having problems with it, not with what it is supposed to do.
Correct me if I’m wrong.
#1803786
gaznav wrote:Yes, I also use a similar way to explain as your field analogy. I tend to use a sports stadium with 20,000 people in it. If everyone is talking then everyone can hear each other locally (say within 10 people of each other) - that is what Low Power ADS-B at 20Wis trying to do.

I am sorry Gaz but I am not sure you have an understanding of what is happening here
1090mhz does not emit a modulated carrier, allowing corruptions due to overlaps.

PilotAware, Flarm and UAT emit a carrier modulated by frequency changes in sympathy with the information, with no gaps

Also what you fail to define, is the sensitivity of the receiver, it is irrelevant to talk of 500W, 70W, 20W - because the overall link budget is determined by transmission power, antenna location/performance and receiver sensitivity

So using your analogy, if I have a 500W emitter at 2nm, at what distance will a 20W emitter need to be, in order to be visible ?

If no 500W emitter is present, what difference does that make to the above ?
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User avatar
By leemoore1966
#1803788
gaznav wrote:Ok, so your Funke Mode S transponder is the most likely thing to get you noticed should you be unfortunate to have an airspace ‘bust’. By getting a SE2 then this will make you the most conspicuous - and most importantly with an accurate position from a GPS - to other GA aircraft in your vicinity. You will also be able to see their ADS-B and also FLARM if they are carrying it and you pay the £30 FLARM licence fee.

So what is not to like - see and be seen amongst your GA buddies - and for now few ATCRUs can see you from that device?

Is this serious or a joke ?
Is this the strategy, to disable the only existing safety technology that makes you visible to ATC ?

I hope that the other supporters of EC agree with me that this is NOT a strategy that should be condoned, and maybe the CAA should upgrade their position of ADSB through a transponder to something more than preferred
User avatar
By gaznav
#1803791
leemoore1966 wrote:
gaznav wrote:Ok, so your Funke Mode S transponder is the most likely thing to get you noticed should you be unfortunate to have an airspace ‘bust’. By getting a SE2 then this will make you the most conspicuous - and most importantly with an accurate position from a GPS - to other GA aircraft in your vicinity. You will also be able to see their ADS-B and also FLARM if they are carrying it and you pay the £30 FLARM licence fee.

So what is not to like - see and be seen amongst your GA buddies - and for now few ATCRUs can see you from that device?

Is this serious or a joke ?
Is this the strategy, to disable the only existing safety technology that makes you visible to ATC ?

I hope that the other supporters of EC agree with me that this is NOT a strategy that should be condoned, and maybe the CAA should upgrade their position of ADSB through a transponder to something more than preferred


Lee, I think you have come in mid-conversation on this one. The Farmer said originally that he didn’t want SkyEcho to see him being seen for, his term, a ‘bust’. I then said that it was very unlikely right now that many would see him anyway, so it was a contradiction. He then said he had a Funke Mode S and I said that was far more likely to be seen were he unfortunate to have a bust. Finally, I offered that if he wants his aircraft to be accurately seen by GA pilots, through a reported GPS signal, then get a SE2.

This being the original quote:
After all the negativity about SE2’s reliability, the fact that nobody seems to know what’s best to get, and the draconian implications these days for busts (not that I’ve ever had one), I’ve decided to cancel my order for an SE2 until the whole process settles down, companies stop bickering here like little kids, and the hardware works as it should.
Back to stealth mode.... :batman:


I’m unsure if his Mode S is non-ES or not, but we have heard that upgrading early Funke Mode S to ES is very expensive and so SE2 makes the cheapest way and easiest way to have ADS-B Out from such a set up.

Maybe that will calm you down a tad, now I have explained the whole conversation?

PS. As for the simple analogy, it is just that. I’m sure if I start breaking out formulae like this one, then to most it will be lost:
Image
#1803795
gaznav wrote:PS. As for the simple analogy, it is just that. I’m sure if I start breaking out formulae like this one, then to most it will be lost:
Image


That’s interesting Gaz, but unrelated
Firstly, you have omitted any reference to receiver sensitivity

Let me simplify, If two 1090/ADSB packets arrive either simultaneously, or overlapping, one arrives with -3db relative power of the other, but both exceeding the sensitivity of the receiver

What would happen ?

Thx
Lee
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