Anybody using the Monroy ATD-300 "TCAS" ?

[peterh337]

It looks impressive (http://www.monroyaero.com/ATD300Manual.pdf), much more so at the price. The single external antenna (info (http://www.monroyaero.com/ATD300Webpage8.pdf)) gives you azimuth info on Mode C/S targets.

User reports on google are not 100% consistent however...

There was an Aviation Consumer review Feb 2011 but I don't have access to it.

[jxc]

It would be really handy if it could transfer the info to a GPS screen or glass cockpit

[peterh337]

If you google around you can find various discussions on this. One link suggests that such data was promised but not delivered. I suspect Mr Monroy could not get hold of the document specs from Avidyne and did not want to put in the (significant) effort to reverse engineer the symbol definition and placement data stream :)

What puzzles me is how they can get 1090MHz azimuth data using the single external antenna shown on page 4 here (http://www.monroyaero.com/ATD300Webpage8.pdf), which has only a single BNC connector.

They claim to display only quadrants but even so I can't see how it can work.

[englishal]

The problem for me is that there is no data output port and so traffic can't be displayed on a GPS screen (for example). I think that whoever comes up with a cheap, directional, hardwired PCAS system with hull mounted antenna and data output port will have a great product.

The cheapest active traffic system that I have come across is the Garmin GTS-800 which cost around £6000 plus fitting when I was investigating it....I see Gulf Coast Avionics have them for $13,995 installed.

[achimha]

I seriously doubt they can detect the azimuth. How should that work with just one antenna? Even with two, it would have to be a very controlled environment (antenna position, distance, etc.).

I've been using PowerFLARM (http://www.powerflarm.aero/) for some time with good results. Obviously, it's most useful in areas where gliders are equipped with FLARM (right below clouds, white against white, often not detected by radar). PowerFLARM cannot detect Mode C but they have promised this feature even though I've heard from several experts that it is barely feasible due to the way radar stations query transponders and the inherent ambiguity of assigning Mode C responses to the originating stations. However, Mode C is technically illegal in Europe (where transponders are required). The next firmware version (currently in beta) adds TIS output for showing traffic on e.g. Garmins.

I've also heard good things about the Funkwerk product (http://www.funkwerk-avionics.com/cms/upload/Downloads/Flyer-TM250-V1.7-web.pdf).

When EASA plan to come out with the next expensive, mandatory equipment change, they should require extended squitter. All Mode S capable transponders have to support this feature (part of the certification) and once transponders always send out the aircraft's GPS position, traffic monitors become a lot more useful. Today, all aircraft > 5.7t are required to do the extended squitter and they show up nicely on the PowerFLARM.

[peterh337]

Someone very kindly sent me some reviews on the Monroy :ok:

The reports are patchy to say the least. If they are representative, I don't know how they can sell these products.

[SDB73]

This looks really interesting. Good find!

It might be multiple antennae inside the enclosure, and the signals multiplexed on the single connector / loom. Either that or (not sure why this would be the case, but I can't think of any other ideas) there's some processing going on inside the antenna enclosure and a logical signal is being sent along the cable to the device.

[Rod1]

“When EASA plan to come out with the next expensive, mandatory equipment change, they should require extended squitter. All Mode S capable transponders have to support this feature (part of the certification)”

This is not the case. The Garmin 328, the most popular mode s unit in Europe, cannot support ES at all and the Garmin 330 requires an expensive upgrade to the ES version. I am working to make it less complicated and costly to enable ADSB out using ES in the UK, but this will take time.

Rod1

[SDB73]

I may get shot here... but...

I am working to make it less complicated and costly to enable ADSB out using ES in the UK, but this will take time.

Will this stand in the way of progress? My *personal* view (and I totally accept that this isn't everyone's view, which is what makes all of this so difficult) is that if legislation which makes us all safer could be brought in faster but at a higher expense, then - within reason - I would MUCH rather just get on with it.

It's all very well championing cost-savings in terms of red tape, certain proceedures, license structures, etc within the bounds of safety, but when cost is put ahead of actual genuine flight safety, I start to question it.

By arguing this point, we run the risk of delaying safety measures.

I'm sure you do an amazing and thankless (at times) job, Rod, but we've all complained that too much politics gets in the way of progress, let's make sure we're not the cause of just that.

[achimha]

This is not the case. The Garmin 328, the most popular mode s unit in Europe, cannot support ES at all and the Garmin 330 requires an expensive upgrade to the ES version. I am working to make it less complicated and costly to enable ADSB out using ES in the UK, but this will take time.

Yes, that's very unfortunate and rather disappointing. As long as pilots have to spend considerable funds to be visible to others without being legally required to do so, we are not going to get there.

I have the TRT800A transponder (http://www.funkwerk-avionics.com/cms/upload/Downloads/Flyer-TRT800A-V2.7-web.pdf) which is advertised as having ES and I tried to hook it up to my GNS430W but so far no success. There is very limited knowledge in the field and I have never managed to find somebody that has made this configuration work. The transponder supports a protocol called "COMM A/B" which is supposedly called "Aviation No Alt" on the GNS unit but it's not working yet. The next attempt will be to connect the transponder to a Garmin 695 unit and use the NMEA protocol which both sides support. The downside of this is an uncertified GPS position resulting in the upcoming TCAS 4 not trusting your position data.

[peterh337]

The ATD-300 antenna is just a dumb microwave antenna. They even say you can use a standard DME antenna in its place. So there is no processing done inside it.

So, no idea how they resolve azimuth.

[asyncio]

My guess is that they try and do it purely from the timing of the pulses.
Similar to the way LORAN works, you would have a hyperbola of possible locations and you could probably narrow it down by aggregating over multiple radar sweeps.

But I suspect that would become increasingly difficult as the number of targets increases, or when being interrogated by multiple radar heads.

[goldeneaglepilot]

The description "dumb Microwave Antenna" does not give too much away... What is it, a single dipole? a flat plane antenna? or even possibly an array within the housing. A picture inside the housing would help explain a lot

[peterh337]

I am certain their antenna doesn't do any "azimuth encoding". It seems to be a standard blade antenna, made by somebody like Antcom (http://www.antcom.com/).

What they probably do is make use of the variation of the antenna gain versus azimuth (i.e. the antenna won't be perfectly omnidirectional) in conjunction with the Mode C pulse shape distortion which is going to be distance related.

They do call it "directional antenna" after all.

But I still can't see how they can resolve between say 3 o'clock and 9 o'clock targets because that antenna appears to be symmetrical left-to-right.

It is possible their antenna distorts the incoming pulse according to the direction it comes in from.

There are plenty of reviews online but those I have read are too banal and devoid of detail to make much sense of.

[goldeneaglepilot]

I'm guessing but the unit will probably just sense signal strength of the transponder over a given time and calculate position and direction relative to your aircraft by some clever maths within the unit. In short if the transmitting transponder closes in on you on a reciprocal course the signal strength of the transmission received will increase at a linear rate. if its offset to one side or the other it will plot a non linear strength v time graph.

Another guess would be that the azimuth data is simply done by taking the altitude data from the recived signal and cross referencing it to the altitude encoder in the device. It talks in the instructions of leaving the device to stabalise for upto 5 minutes for altitude after powering up.

The problem I see (if thats the method used) is how to differentiate the position of several common transponders on say 7000.

To gauge distance you would need to know the gain of the aerial, which is easy with its own antenna, but using a third party DME or transponder aerial?

My thoughts are that the unit has too many varibles in terms of installation to provide meaningful warnings that could be regarded with reliability.

The old saying about if its cheap and it looks to good to be true comes to mind. I guess in real practical terms it may have the same value as a graphic equaliser display on a 1980's stereo.

[Rod1]

SDB73

Right now almost no UK SEP aircraft (G reg) are emitting ADSB out. With a small tweak in the regs this could jump to 10% in under a year with increase year on year. The same regulation currently makes it impossible to do ADSB out (legally) on my £50k aircraft. The change will also lower the cost. I am unwilling to go too deep on this as it is a live issue.

Rod1

[SDB73]

Thanks for the response Rod. As an idle outside observer, I can't comment with any authority at all.

I think I misread your post, as I thought you were saying that there are regulations being proposed which would cost GA operators a lot of money, but you were arguing against them with an alternative which would be cheaper, but that this would "take time".

From this I thought you were indicating that the incoming regs were being argued / delayed in order to try to find an alternative.

From your second reply it sounds like that isn't the case, so thanks for all you're doing.

[gyrotyro]

I have a Monroy ATD-300 in my Vans RV-6A.

[peterh337]

The reg which prevents the radiation of one's GPS position is the totally bogus and artificial piece of junk regulation from EASA whose "experts" invented the distinction between Elementary Mode S and Enhanced Mode S.

Elementary Mode S is required on 99% of GA, but also the said GA fleet is prohibited from having Enhanced Mode S.

Yet a stock GTX330 will radiate what amounts to Enhanced Mode S, straight out of the box, simply by connecting various GPS etc signals to the back of it. An installation with those signals thus connected (which would be the installation default anywhere else in the world) is illegal in EU airspace :ugh:

What this means is that most visiting aircraft are radiating all the extra parameters anyway. It is basically just EU based avionics shops that are "not supposed" to make those extra connections :ugh:

If it wasn't for this stupid ban, a large % of GA (as they use a GTX330) would now be radiating their GPS data, which could be picked up by any suitable receiver, anytime they are pinged by ground based radar.

This is not quite ADS-B which is a continuous transmission of the stuff, but is effectively the same thing in the European context because there is virtually constant SSR coverage.

I imagine that somebody is now pressing EASA to change this ridiculous regulation which serves no apparent purpose. The GTX330 installation manual does not even contain the words Elementary or Enhanced. It is a purely EASA invention, which they did without looking at the hardware actually on the market :ugh:

[achimha]

Where did you find that EASA regulation? Neither the transponder makers nor the avionics shops I talked to mentioned any issues regarding GPS ES operation.

From what I was told, the GTX330 needs an expensive update to do GPS ES. The TRT800A installation manual (http://www.funkwerk-avionics.com/cms/upload/Downloads/Handbuecher/03.2112.010.71e_TRT800A-OLED_OI_Rev1.04_111110_WEB.pdf) documents how to enable GPS radiation (page 32).

[peterh337]

Here (http://www.peter2000.co.uk/aviation/tb20-experience/mode-s.html) is a note from 2008 - not sure how current it is.

[Rod1]

I do not know what you are talking about Peter – my concern is SIL.

Rod1

[goldeneaglepilot]

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[peterh337]

What is SIL?

[goldeneaglepilot]

Surveillance Integrity Limit (SIL) - Specifies the probability of exceeding the NIC-specified integrity containment region.

It’s part of the GPS Accuracy and Integrity limits controlling ADS-B devices, at the moment its extremely topical in relation to UAV deployment in non-military airspace and collision avoidance systems

Peter : Your thoughts about ADS-B transmission of data being continuous are wrong, the data is transmitted by way of an update every 1 second. Radar tends to interrogate a transponder about every 12 seconds, so the potential accuracy of an ADS-B system is far greater than a radar based interrogation system.

I doubt that we will see airspace that is totally dependent on ADS-B, due to the dangers presented by the potential for GPS outage or jamming.

[joris]

I understood that de developer of the ATD300 (Jose Monroy)contributed a long time ago to the development of the TCAS system.....I would like to understand also how bearing can be identified with the ANT300 antenna. I think this system works better that the zaon stuff...based on what I found out so far...
Location of the Antenna is crucial...
I use a small zaon MRX with the antenna remotely mounted with a reverse SMA jack antenna cable. The antenna is as as closely as possible mounted to the wind shield (the same one you can by for wireless LAN's). This set up works remarkably well though I miss the bearing info a lot..;-))

[peterh337]

Your thoughts about ADS-B transmission of data being continuous are wrong, the data is transmitted by way of an update every 1 second. Radar tends to interrogate a transponder about every 12 seconds, so the potential accuracy of an ADS-B system is far greater than a radar based interrogation system.
I thought I said that... somewhere...

You will however usually get transponder emissions more often, because in most cases, in Europe, one's transponder is being pinged by more than one radar at any one time.

If I look at my transponder display, it is responding to something every 1-2 seconds.

What you also get with GPS-derived lat/long/alt is a precise target trajectory, which can be similarly extrapolated with a reasonable level of confidence.

I doubt that we will see airspace that is totally dependent on ADS-B, due to the dangers presented by the potential for GPS outage or jamming.
I agree; however I went to a Eurocontrol conference c. 2008 where they said they want to shut down primary radars, because the airlines were putting pressure on them to reduce route charges :)

On the ATD-300, one thing which concerns me is user reports from the USA saying that one often has to press IDENT, to stop the unit from latching onto your own transponder. This would be totally unacceptable in Europe - ATC would go berserk. In fact I am suprised you can do it in the USA.

[goldeneaglepilot]

If it wasn't for this stupid ban, a large % of GA (as they use a GTX330) would now be radiating their GPS data, which could be picked up by any suitable receiver, anytime they are pinged by ground based radar.

This is not quite ADS-B which is a continuous transmission of the stuff, but is effectively the same thing in the European context because there is virtually constant SSR coverage.


Peter - sorry I must have misread your post :)