Mode C and S

[the_top_pilot]

Lee,

Over the last 3 days I have flown 13hrs 45mins in some of our PA31's. I have been using my old engineering version of PAW which detected both Mode C and S and gives coloured aircraft warnings (I do have 2 new PAW's a Classic and a bridge, but for the time being they will stay in the office as the mode C is so good on the old version we don't want to fly without it).
The PAW has been flying in parallel with our £2000 Portable Power flarm our belief is the PAW performs as well if not better than the Flarm.
My plea then is for Mode C to be introduced into the New PAW the green amber and red warnings be reintroduced for the mode C and Mode S warnings.

Many Thanks

Steve

p.s. Great work.

[Admin]

Hi Steve

Thanks for the posting.

I am still investigating this, but have somehow introduced a stability issue, this needs to be fully determined before a Mode-C release.

I presume you are using SkyDemon when you refer to the colors ?

Thx
Lee

[exfirepro]

Hi Lee,

Didn't we go round this particular loop a few weeks ago:

http://forum.pilotaware.com/index.php/topic,474.0.html  ...and I still agree with Steve re the nice colour changing Mode S alert aircraft. 


Peter

p.s. are you still away? Need advice re problems with the test software 

[the_top_pilot]

Lee,

Yes I am using Sky Demon.

We just love the PAW.

Mode C and S

Steve

[EricC]

I have just been looking at the signal strength and colour of mode
C and S warnings.
Backed up by visual contact they seem to work very well.
l am suprised by the attenuation of the signal as the range increases over a couple of miles.

[Admin]

I have just been looking at the signal strength and colour of mode
C and S warnings.
Backed up by visual contact they seem to work very well.
l am suprised by the attenuation of the signal as the range increases over a couple of miles.

Just for clarification, what you are currently able to see here are Mode-S, ADS-B and P3I only.
Mode-C is still being investigated regarding its viability

Thx
Lee

[EricC]

Thanks for the clarification.... fly both these and they are mode S equipped.

Is the sig from mode S only?

[JCurtis]

l am suprised by the attenuation of the signal as the range increases over a couple of miles.

That is quite common, for RF (and lots of other things) the signal strength is based on the Inverse Square law, so if you double the distance the signal strength goes down by 1/4.  Three times the distance and your down to 1/9th etc.  Not much you can do about that.

[EricC]

Thanks for the info, I guess you have a set value of (SIG) that changes the colour of the (SIG) box.
Will a none mode S transponder signal work just as well for range finding?

[exfirepro]

Thanks for the info, I guess you have a set value of (SIG) that changes the colour of the (SIG) box.
Will a none mode S transponder signal work just as well for range finding?

Hi Eric,

A bit of confusion appearing here. If a traffic entry has a HEX, SQuawk, ALTitude and a SIGnal strength, such as G-BRBW and G-BUCT in your tables, it is Mode S. These signals have no indicated DISTance as this cannot be accurately calculated from a raw transponder signal!

We actually have 4 practical 'sets' of 'trigger values' for mode-S alerts to cater for operation in different flying environments, plus a very wide open set (labelled 'Testing' in the (Configure) screen). These trigger levels are not based on physical distance because whilst as Jeremy says, signal strength in free space nominally increases and reduces as the square of distance, each transponder installation transmits a different strength of signal even from other examples of the same aircraft and transponder.

When we take into account that the transmitted strength of a mode S signal can vary from as little as 70 Watts at the antenna of a typical light aircraft, to as much as 500 Watts for a typical CAT, calculation of distance based on strength of signal is at best an approximation and at worst an educated guess - a route which we decided early in the development of mode-S detection not to go down.

The trigger levels were instead determined by testing and judgement to establish alerts at practical distances for the type of flying users are likely to be undertaking.

In the case of ADSB and P3i on the other hand, exact GPS based positional information is contained in the transmitted signal. This is compared to the GPS position of your own aircraft (or ground station) and a distance calculated and displayed. Alerts for both these systems are directly based on distance and relative altitude NOT signal strength.

Further information is available in the PilotAware Operation Manual available at

www.pilotawarehardware.com/dl/PAWOperationManual.pdf

Rather than using a ground station to test alert trigger distances, a more practical use is to use them to establish the distance over which the aircraft in flight first 'sees' the ground station appear on screen, which will be derived solely by GPS comparison from the ground stations P3i transmitter and displayed on both the aircraft and ground station traffic screens.

Hope this helps clarify the position

Best Regards and keep up the good work

Peter

Edit: for clarification, the first two entries on the top table in your post, which have the full range of HEX, REG, SQ, DIST, ALT and SIG are ADSB.