ads-b out and Transponder ??

Indiana_Pilot

Indiana_Pilot

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I have been looking at the Skyguardtwx portable ads-b out transmitter. I am only wanting to do this so I can obtain all the traffic data using GDL-39 and Garmin Pilot.

My question is that I am able set a squawk code for it along with the ICAO and N Number.

Does this mean if I am on flight following I will need to change both the squawk on this ads-b out and the transponder too? Will they see 2 targets on their screen ?
 
Garmin Pilot is not listed on their compatibility list. I think they are mainly a WingX and iFly shop.
 
Hmm......good question. I'd call them directly and ask. You may or may not get an accurate answer here since basically no one has upgraded yet.
 
My Google-foo is strong today....... Cut from Garmin:



How does my transponder interact with the GDL 88?

ADS-B requires that both your Mode-C or Mode-S transponder and your GDL 88 output the same Mode 3/A “squawk” code and SPI (ident) code. With certain installations, this could mean that you have to enter the squawk code in two different places. Garmin mitigates the need for this using several methods. First, if the transponder has a compatible interface, the GDL 88 will retrieve the correct squawk code from the transponder. If the transponder doesn’t have a compatible interface our patent-pending technology allows the GDL 88 to automatically detect and synchronize with the transponder’s Mode 3/A “squawk” code and SPI. In most cases you’ll be able to retain an older transponder that may not have any wired interfaces at all.


Although this is a Garmin install, the same theory applies.
 
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Thanks for the info.. I just talked to Don the Owner of Skyguard TWX and he was very helpful. It seems that I would need to enter the squawk code in both places but more than likely the ATC is not even using the "correct view" to be able to see the data fromt he ADS-B only. It combines the data from the transponder and ads-b out..

I just ordered and it should be here next week.. If it allows me to see all the mode c traffic almost all the time I will be happy ! Should be a good test on the way to Tennennesse next weekend.
 
Still a cheap way to get ads-b out (although not certified yet)

I just want it to trigger the ground stations so I see the traffic !
 
You know whats funny....


I was on FF with APRCH and asked, " can you tell me if all required peramters are functioning correctly on ADSB? This is a new installation and want to confirm accurate reporting to ATC."


About 5 minutes later, I asked, " APRCH, and word back on those ADSB readings?" I got back, "Sorry, we had to go to another room to see. Everything looks good as far as we can tell."

Seems to me even ATC is not compliant yet.
 
Has Skyguard obtained FAA approval for their portable unit to meet the 91.225 requirement for ADS-B-out? I didn't think the FAA was going along with that.
 
Ron Levy said:
Has Skyguard obtained FAA approval for their portable unit to meet the 91.225 requirement for ADS-B-out? I didn't think the FAA was going along with that.
Click to expand...

I spoke with an FAA rep.....portables will not get the stamp of approval. Would have saved me thousands, literally. :no:
 
Ron Levy said:
Has Skyguard obtained FAA approval for their portable unit to meet the 91.225 requirement for ADS-B-out? I didn't think the FAA was going along with that.
Click to expand...

There is no need for FAA approval at this time. After 2020 the FAA says such units will be prohibited from airspace where ADS-B is required.
 
Unit74 said:
You know whats funny....


I was on FF with APRCH and asked, " can you tell me if all required peramters are functioning correctly on ADSB? This is a new installation and want to confirm accurate reporting to ATC."


About 5 minutes later, I asked, " APRCH, and word back on those ADSB readings?" I got back, "Sorry, we had to go to another room to see. Everything looks good as far as we can tell."

Seems to me even ATC is not compliant yet.
Click to expand...

Very, very true.

The fact that you found an ATC facility that has that capability is something close to a miracle. Flight Service (remember them?) has been given responsibility for ADS-B stuff, so ATC usually just answers "Huh?" when you ask them anything about it.

And just try asking someone at Flight Service about it. You'll get another "Huh?". It's almost funny.

There seems to be, like, two guys in the FAA who know butkiss about ADS-B, and I've worked with both of them. Good guys, but they're going to need to ramp up quickly to meet the 2020 deadline.
 
Ron Levy said:
Has Skyguard obtained FAA approval for their portable unit to meet the 91.225 requirement for ADS-B-out? I didn't think the FAA was going along with that.
Click to expand...

Not possible to be certified. Plus it is invisible to certified receivers such as the GDL88.
 
Ron Levy said:
Has Skyguard obtained FAA approval for their portable unit to meet the 91.225 requirement for ADS-B-out? I didn't think the FAA was going along with that.
Click to expand...
No, the Skyguard has not received approval. The owner of Skyguard is seeking approval for his system as a permanently mounted system and is in his second round of testing with the FAA.If he gains approval it will be the existing units with an add on kit to make it a permanent mount. If approved he will sell this kit with permanent antennas, ship power, and mounting. I have doubts the GPS Puck will be approved as a WAAS position source but according to others that have spoken with him recently he has a plan B for that.
 
Firefighter_324 said:
Still a cheap way to get ads-b out (although not certified yet)

I just want it to trigger the ground stations so I see the traffic !
Click to expand...

AFAIU though it will trigger the ground stations (at least until 2020), it may not depict you as traffic to others, including ATC.
So ironically, if this interim solution takes off, it might not show you some important "low end" GA traffic, which use the same (or similar) uncertified OUT units to trigger the ground stations.

In any case, please share your experiences with the unit when you get it.
 
I know ADS-B has lots of quirks that not everyone knows. But it would be nice if Don made it clear that using his unit hides you from being visible on certified ADS-B equipped aircraft.
 
Pedals2Paddles said:
I know ADS-B has lots of quirks that not everyone knows. But it would be nice if Don made it clear that using his unit hides you from being visible on certified ADS-B equipped aircraft.
Click to expand...

I think "hides" is a touch too strong, since if your mode C (or even primary?) is seen by ATC, the certified bunch will still see you, just like when you have no ADS-B at all. But if ATC does not see you, and all you have is an uncertified ADS-B OUT (which does reach a ground station), you might see the others, but they won't see you (unless they have TCAS or PCAS).
I am no expert, so I stand to be corrected.
 
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Pedals2Paddles said:
I know ADS-B has lots of quirks that not everyone knows. But it would be nice if Don made it clear that using his unit hides you from being visible on certified ADS-B equipped aircraft.
Click to expand...

I discussed this with Exelis. They are aware of the situation and will be addressing it with a future upgrade to the GBT software. I understand they will take into account the SIL and SDA values in determining if a TISB is generated for a unit that reports these as zero. It is not clear if this will also eliminate responding to one of these units. Certainly after 2020, they will be ignored.
 
tmyers said:
it shows up on TIS-B receivers!!!!
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No it does not!!!!

The GBT currently treats it as a client and not as a mode C target, so a TISB is not generated for it. Since a certified unit is required to discard it due to a zero SIL or SDA, it is not displayed as either an ADS-B target or as a TISB target, therefore it is invisible.
 
John, How does it know to not show the Mode-C target in circumstances where it can't positively match the Mode-C target with the ADS-B client? For example, if you're just sqwaking 1200, it has no way to know that your 1200 Mode-C target is the same as your ADS-B Client target. I would think in such a case, it would not show your ADS-B client, but it would show the random 1200 Mode-C target, which happens to be you.
 
Pedals2Paddles said:
I know ADS-B has lots of quirks that not everyone knows. But it would be nice if Don made it clear that using his unit hides you from being visible on certified ADS-B equipped aircraft.
Click to expand...
In my experience flying with a friend who could see my tail number from his aircraft it is not hiding
 
John Collins said:
No it does not!!!!

The GBT currently treats it as a client and not as a mode C target, so a TISB is not generated for it. Since a certified unit is required to discard it due to a zero SIL or SDA, it is not displayed as either an ADS-B target or as a TISB target, therefore it is invisible.
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But it did!!!!
 
Pedals2Paddles said:
John, How does it know to not show the Mode-C target in circumstances where it can't positively match the Mode-C target with the ADS-B client? For example, if you're just sqwaking 1200, it has no way to know that your 1200 Mode-C target is the same as your ADS-B Client target. I would think in such a case, it would not show your ADS-B client, but it would show the random 1200 Mode-C target, which happens to be you.
Click to expand...

The mode A/C target can't always be determined to be the same target as the ADS-B Out target, in which case you see ghosting. The mode A/C target location is based on the radar calibration and resolution and especially for longer range radars, it is going to cause some ghosting. I have seen this on my GDL88/GTX330/GNS530W installation even though you would think that the mode S aircraft ID being identical to the UAT aircraft ID would eliminate the ghosting. I surmise that if the radar is not a mode S radar, this is the explanation.
 
tmyers said:
But it did!!!!
Click to expand...

A TISB target is only generated by the ground station when the target only has Mode A/C/S capability without ADS-B Out capability. It is not generated by an aircraft that is identified by the ground station to be a client or in other words has ADS-B Out capability. So if the Skyguard is treated by the ground station as an ADS-B target it considers it a client. The ground station will not generate a TISB for a client as it would be redundant and always show up as a ghost target.

Do you believe that TISB targets are generated for ADS-B Out clients? If so, this is a misunderstanding of how the system works.
 
It is a definate possibility that I don't fully understand it all. I will query my friend and let you know what he saw.
 
The logic actually makes sense to me now.

The TIS-B transmission from the ground tower in response your ADS-B out is for YOU, not everyone around you. You don't need to know about you. So of course it doesn't include you in the transmission.

AND

Other nearby aircraft can receive your ADS-B out transmission directly, air-to-air, without the ground towers. Therefore, the ground towers repeating what you've already said gains nobody anything they don't already know. It is a waste of bandwidth, so they don't do it.

BUT

Today, there are uncertified ADS-B out units in use, such as the Skyguard. The air-to-air reception as described above is blocked on certified receivers. And the TIS-B rebroadcast is blocked as described above. It's a conflicting problem for the developers to work out.
 
Also, the radar targets are fed into the system as well, ADSB or not, and broadcast on TIS.
 
John, I spoke with my friend and all he remembers is that he was seeing my tail number on his display. Since I was not on flight following am I correct in stating the tail number had to come from my ADS-B out? If I understand you correctly ATC is not seeing my ADS-B out. With that in mind is it safe to say he was receiving me air to air?
 
tmyers said:
John, I spoke with my friend and all he remembers is that he was seeing my tail number on his display. Since I was not on flight following am I correct in stating the tail number had to come from my ADS-B out? If I understand you correctly ATC is not seeing my ADS-B out. With that in mind is it safe to say he was receiving me air to air?
Click to expand...

Your friend was receiving your ADS-B Out coming from the Skyguard via air to air. My guess is that he was using a portable receiver which is not a certified receiver. A portable doesn't distinguish between a valid ADS-B Out an one that is not a certified unit, but a certified system will not display target information from a portable unit with a SIL and/or SDA of zero. To a certified system, your Skyguard is invisible.

ATC can't use your ADS-B Out, but the ground station does receive it and provides you with client services.
 
Tim, What ADS-B in device was he using? If he was using a portable unit for a tablet, then yes he would indeed receive your ADS-B signal direct air-to-air. The uncertified portable ADS-B IN receivers do not care and will show anybody regardless of certification.

If he was using a certified receiver like a GDL88 displaying traffic on his panel, that certified receiver should not have seen you for the reasons previously outlined above.
 
Hmmmm....guess I'm gonna want to keep my non-certified "in" box....so I can "see" everyone.

....even after I install an ES "out" transponder.
 
Pedals2Paddles said:
The logic actually makes sense to me now.

The TIS-B transmission from the ground tower in response your ADS-B out is for YOU, not everyone around you. You don't need to know about you. So of course it doesn't include you in the transmission.

AND

Other nearby aircraft can receive your ADS-B out transmission directly, air-to-air, without the ground towers. Therefore, the ground towers repeating what you've already said gains nobody anything they don't already know. It is a waste of bandwidth, so they don't do it.

BUT

Today, there are uncertified ADS-B out units in use, such as the Skyguard. The air-to-air reception as described above is blocked on certified receivers. And the TIS-B rebroadcast is blocked as described above. It's a conflicting problem for the developers to work out.
Click to expand...

Following your above description, if you have an uncertified ADS-B OUT, you won't get your own aircraft back from the ground station (which as you say you don't need). Other aircraft with certified units in the area won't get your aircraft position via air-to-air (assuming they don't have TCAS), since it will be blocked (unless they have a portable IN too). BUT the other aircraft in the area should still get your aircraft location from the ground station broadcast (assuming they are in range). In fact, even if you don't have ADS-B OUT and only transmit mode A/C (and maybe only a primary return), the ground station should still tell them about you, let alone if it's also receiving an ADS-B OUT signal from you (albeit uncertified). If the ground station does not report the position of an aircraft with mode A/C and uncertified ADS-B OUT to others, that would be a serious safety deficiency (and very poor design).
 
If you have an uncertified ADS-B out, you will be invisible to certified ADS-B IN under all circumstances.

The towers will never rebroadcast anyone's ADS-B OUT location because they assume it is being received direct air-to-air. There is no need to rebroadcast something that everyone is already receiving air-to-air directly. The towers merely add Mode C traffic to the picture and cross link to 1090ES traffic. This all has nothing to do with it being certified or uncertified. I believe this behavior is the same regardless.

The problem is the certified receivers ignore uncertified transmitters. So certified receivers will never receive the direct air-to-air that the ground towers are assuming you receive. It's a design oversight, probably because the designers hadn't counted on uncertified portable out units.

A Mode-C target that matches your an ADS-B out is not transmitted through TIS-B. Because again, there is no need. It would be duplicitive of the direct air-to-air information. The only time a Mode-C target gets transmitted out on TIS-B is if there is no matching ADS-B target.

The traffic picture painted on your screen is a combination of:
- Direct air-to-air ADS-B targets
- Mode C targets that don't match the above ADS-B targets.
- Cross linked targets from 1090ES mode-s transponders on 1090Mhz.

I think I got that right...
 
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Pedals2Paddles said:
If you have an uncertified ADS-B out, you will be invisible to certified ADS-B IN under all circumstances.

The towers will never rebroadcast anyone's ADS-B OUT location because they assume it is being received direct air-to-air. There is no need to rebroadcast something that everyone is already receiving air-to-air directly. The towers merely add Mode C traffic to the picture and cross link to 1090ES traffic. This all has nothing to do with it being certified or uncertified. I believe this behavior is the same regardless.

The problem is the certified receivers ignore uncertified transmitters. So certified receivers will never receive the direct air-to-air that the ground towers are assuming you receive. It's a design oversight, probably because the designers hadn't counted on uncertified portable out units.

A Mode-C target that matches your an ADS-B out is not transmitted through TIS-B. Because again, there is no need. It would be duplicitive of the direct air-to-air information. The only time a Mode-C target gets transmitted out on TIS-B is if there is no matching ADS-B target.

The traffic picture painted on your screen is a combination of:
- Direct air-to-air ADS-B targets
- Mode C targets that don't match the above ADS-B targets.
- Cross linked targets from 1090ES mode-s transponders on 1090Mhz.

I think I got that right...
Click to expand...

It would seem to me that logically, if the ground station decides not to upload your GPS-derived position because it doesn't trust it (e.g. uncertified), then it should not assume that other traffic would know about it via air-to-air (since the certified ones would suppress it). And if so, there is no logic to NOT upload at least the mode C position in the broadcast to other aircraft.
If the above is wrong, then I would consider it a serious safety defect.
At the very least, if that software algorithm is not fixed ASAP, the uncertified OUT units should be prohibited as a safety hazard.
 
That's exactly what I meant when I said It's a design oversight, probably because the designers hadn't counted on uncertified portable out units.

According to John, they know of this conundrum and are working on a doing exactly what you describe... possibly have the ground towers rebroadcast uncertified ADS-B targets.
 
Pedals2Paddles said:
That's exactly what I meant when I said It's a design oversight, probably because the designers hadn't counted on uncertified portable out units.

According to John, they know of this conundrum and are working on a doing exactly what you describe... possibly have the ground towers rebroadcast uncertified ADS-B targets.
Click to expand...

I agree with your analysis.

What I am not sure about is when and how Excelis will resolve the issue. One option would be for them to generate a TISB for a target that has a SIL or SDA of 0. A second question is whether or not the GBT will treat an aircraft as a non client, and therefore not generate any TISB or ADSR services on its behalf. Currently it treats the portable as a client and as you described, that is why it doesn't generate a TISB for it.
 
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