Mode C/S

[rogerabc]

Please don't give up the mode C detection without sufficient trialling. Although PAW may be superior we need to work with the existing environment which is still predominantly mode C I think.

I have used TCAS on the A320, MD902 helicopter & Zaon PCAS on light aircraft. Each system has it's own benefits and limitations which I'm happy to discus.

The Zaon (which measures range using signal strength) is very useable and has regularly altered me to nearby traffic which I then spotted.

Lee, you are welcome to borrow my Zaon to assist in calibration & comparison.

Roger

[scsirob]

Quite right, I think this is the whole problem with relying on signal strength, but this is what the ZAON tools were using, and people claim they were useful, I am not convinced - hence the ongoing analysis.

The XRX appears to have multiple small antenna's under its dome. This allows directional detection. I'm not sure how they determine distance.

[T67M]

[snip] but I don't see how signal strength can be reliable, as being a radio ham I know that atmospheric conditions affect radio propagation greatly, just a thought.

The advantage that the PAW has over the older Zaon products is that it can automatically calibrate the sensitivity dynamically based upon current known ADS-B target geometry. Such an auto-cal won't be perfect, and obviously won't take into account antenna shielding or transmit power variations, but it'll be a whole lot better than the nothing we currently have.

Some of the reviews of the, now defunct, ZAON units highlight the unpredictability of the results.  There must be a reason why they folded?

I suspect a large part of the commercial failure of Zaon was the very high price (around £800 IIRC) compared to the functionality. The work Lee and the team have done to bring about the PAW reverses that equation, giving us a lot of functionality for a very low price.

Another very willing Mode-C/S trialist/guinea-pig here, Lee.

[Steve6443]

Quite right, I think this is the whole problem with relying on signal strength, but this is what the ZAON tools were using, and people claim they were useful, I am not convinced - hence the ongoing analysis.

The XRX appears to have multiple small antenna's under its dome. This allows directional detection. I'm not sure how they determine distance.

As far as I am aware, on the XRX the minor variation in difference of time of signal reception gave an indication as to which sector the intruding aircraft was in as the connectors between aerial and receiver were standardised.... even with such a small distance between the antennae, the delays in signal reception was apparently sufficient to calculate where the signal was coming from. Strength only gave approximate distance.

For info, I still use my Zaon MRX on every flight, what amazes me is that even with just one antenna, somehow it can still work out whether the intruder is climbing, descending, above or below me - and for me, collision avoidance means ALTITUDE, after all, I'm only going to hit an aircraft which is at the same altitude I'm flying, and that's how to optimally use the MRX.

Look to see what height the intruder is at, is it climbing or descending. Using this info, increase the vertical separation and problem sorted. If Lee could work out how Zaon established the aircraft height and whether it was climbing / descending using just Mode C, that would be a major step forward.....

[Paul_Sengupta]

Well, that's easy, altitude is part of the Mode C transmission which can be decoded.

[ianfallon]

What's depressing is the number of people who fly Mode A when they have Mode C.
I hear some people do not understand that "Alt" = Mode C !!! 

[scsirob]

I hear some people do not understand that "Alt" = Mode C !!! 

Not too surprising, considering "alt" stands for "alternate" on just about everything else in aircraft.

[tfede]

Hi,


any news about C  mode detection ?

[exfirepro]

Hi all,

I'm new to this forum, and am playing catch-up while I wait for the bits to build a PAW - ADSB only at first, though I have ordered a 'shield' from Jeremy Curtiss to add baro input so can easily add ARF (or whatever) later. In the absence of anything better over the years, I have been using a Zaon MRX in my flex wing since 2009. Despite its limitations I can vouch for the fact that it can be a life saver as an extra pair of eyes. Ok it doesn't provide any directional info on the contact, but a contact with rapidly decreasing range or altitude separation really focuses the mind and at least in the case of altitude points to which way you need to look and whether to climb or descend to maintain separation!

I certainly would appreciate the addition of any Mode C /S alerting to the PAW system even if the range is a bit 'iffy'. Let's face it the number of aircraft flying at our level with ADS-B out (which I have) is much smaller than those with Mode C/S so let's not reject any opportunity to 'see' the mode C or S aircraft that are about!

Previous comments about how the two Zaons work is pretty much spot on by the way, range is estimated from signal strength with altitude being decoded from the transponders signal.

Best Regards to all

Peter

[FERRYAIR]

Federico,

I think the PAW unit would be a superb Traffic Avoidance system for the Italian ULM users as you have to endure the crazy altitude restrictions that Air Traffic Control & AeCi put upon you.

I have never understood the reason behind the ULM Low level level restrictions?
With such a enthusiastic ULM environment in Italy  where virtually every ULM is at the same level buzzing around like firecrackers I would find the PAW extremely useful if the ULM fraternity employed this system.

On a personal note : Whilst you have Pilots like Crono campaigning for better conditions for Italian ULM users I would imagine that he will have opinions on PAW 😊
Crono is an Electronic genius who would alongside yourself make a great pair of users to test the PAW units.

Advertising the PAW unit on the VFR Forum is a great idea as I have to  admit that the enthusiasm of VFR Forum users is very positive & I think the uptake of PAW users in Italy would be far more than it is in the UK.

It sounds anyhow encouraging, if you will include the function as a "testing the beta of the beta" i will test it for sure.

Trying also to spread the infos in the Italian VFR forum, more and more people getting interested there in the wole system.

Thank you for your work !

Federico

[Admin]

I have an update regarding Mode C/S bearingless targets

http://forum.pilotaware.com/index.php/topic,304.0.html

[exfirepro]

Lee, as you know, I'm a strong believer in the significant potential benefits of incorporating Mode C/S detection into PAW in some form or other, so it's great to hear that you have made further progress on this front.

I will PM/e-mail you about possible testing of your 'prototype' against my ZAON MRX.

Regards

Peter

[Andy Fell]

Don't forget, it will not only be a function of the transponding aircraft's antenna performance, but also the performance of the PAW antenna.

There are so many variables.

[tnowak]

Regarding Mode C and bearingless targets, have you looked at the Free Path Loss equation, or FRISS Transmission formula? If you Google for FRISS you will see how it may be possible to determine the approximate range of a transmitting target. Okay, it won't be very accurate or tell you where the target is in relation to a PAW device but may be of use in filtering out Mode C at FL200?
This url has a very good simple(ish) description): http://www.antenna-theory.com/basics/friis.php
TonyN

[Admin]

Regarding Mode C and bearingless targets, have you looked at the Free Path Loss equation, or FRISS Transmission formula? If you Google for FRISS you will see how it may be possible to determine the approximate range of a transmitting target. Okay, it won't be very accurate or tell you where the target is in relation to a PAW device but may be of use in filtering out Mode C at FL200?
This url has a very good simple(ish) description): http://www.antenna-theory.com/basics/friis.php
TonyN

Hi Tony,
Actually filtering based upon altitude is not an issue, we are looking at mode C/S, so we already have the Altitude of the targets. So we can filter any signal between +/- Nft, whatever we decide N to be, lets say 1000ft for arguments sake. So now all we have to contend with, is the signal level of all Transponder returns at +/- 1000ft.
The reality is that we are not dealing with a 'perfect' environment, as mentioned in many earlier posts,
we have losses at the transmitting end(s) and losses at the receiveing end, and these losses are not uniform in all directions, or across all installations.
So +200ft from target A could give a different totally different signal strength to +200ft from target B.
That is the reality because I have analysed in detail, ADS-B signals of corresponding traffic at equivalent distance/altitude

I see this approach as complimentary to the far more accurate ADS-B/P3I transmissions, but clearly quite vague in its nature, and possibly providing only a short window of warning, in order to ignore many of the potential false positives.

Not giving up yet, and still pursuing this as an additional safety net to what we have already accomplished.

As I mentioned in another thread, I sometimes think our efforts may be better spent convincing our fellow Pilots to adopt PilotAware and/or ADS-B (out).

Thx
Lee