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ADSB

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dlm34077(at)gmail.com
Guest

Posted: Sat Oct 24, 2015 12:44 pm Post subject: ADSB

Having used ADSB in/out for the last six months, I believe there is a problem coming. At airports below radar coverage there are going to be gaps in the traffic info after 2020. My aircraft is a hybrid system which uses 1090 for broadcast and receives both 1090/30 and 987 (UAT) It is my understanding that the on board receivers receive only on about two meters and the ADSB transceivers use the same about two meter frequency.   

   

At E60 radar coverage from PHX TRACON and ABQ center extends down to about 2500MSL. The airport surface is about 1500 MSL. If an aircraft using the UAT frequency is preparing to takeoff and I am preparing to land. I don't believe he will be able to "see" me on his traffic since I will be transmitting on the 1090 channel. I will be able to "see" him on my system because I receive directly both systems. Even though we both should be able to be "listening" to an ADSB transceiver on about two meters, the rebroadcast will not show either aircraft because both are below radar coverage for PHX TRACON and ABQ center. The same sort of thing occurs at KAVQ and others. The problem is acute in areas that are sparsely populated with mountainous terrain.  

   

Any others experience with this using ADSB?    

   

      	 		 			 				 			 		 		 			

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Bob Turner

Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA

Posted: Sat Oct 24, 2015 2:00 pm Post subject: Re: ADSB

First of all, there is no '2 meter' broadcast. You listed the frequencies used - both around 1GHz or 30 cm wavelength.

Second, what matters is the location of ADSB rebroadcast stations (-C). There may be one at your airport.

But, generally speaking, you are correct. Low aircraft may be unable to receive ground station broadcasts. Of course, unless you are in class B, C, or the class B mode C veil, or above 10,000', there is no requirement for an aircraft to be ADSB equipped at all.

You still need to see and avoid.

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_________________
Bob Turner
RV-10 QB

jack(at)bedfordlandings.c
Guest

Posted: Sat Oct 24, 2015 3:06 pm Post subject: ADSB

Oh my God!  You mean we’ll actually have to look out our windshields, instead of watching cockpit TV?

 

Don’t get too reliant on ADSB.  At those same airports with poor ADSB coverage, there are still plenty of NORDO airplanes flying that ADSB will NEVER see.  While flying my Pietenpol Air Camper, I was almost run over by a Diamond DA-40 whose driver (I won’t call him a pilot) was too busy playing with his glass cockpit to look out the window for traffic.  See and Be Seen is still the law of the land.

 

Jack Phillips

#40610 Fuselage

Smith Mountain Lake, Virginia

 

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of DLM

Sent: Saturday, October 24, 2015 4:41 PM

To: rv10-list(at)matronics.com

Subject: ADSB

 

Having used ADSB in/out for the last six months, I believe there is a problem coming. At airports below radar coverage there are going to be gaps in the traffic info after 2020. My aircraft is a hybrid system which uses 1090 for broadcast and receives both 1090/30 and 987 (UAT) It is my understanding that the on board receivers receive only on about two meters and the ADSB transceivers use the same about two meter frequency. 

 

At E60 radar coverage from PHX TRACON and ABQ center extends down to about 2500MSL. The airport surface is about 1500 MSL. If an aircraft using the UAT frequency is preparing to takeoff and I am preparing to land. I don't believe he will be able to "see" me on his traffic since I will be transmitting on the 1090 channel. I will be able to "see" him on my system because I receive directly both systems. Even though we both should be able to be "listening" to an ADSB transceiver on about two meters, the rebroadcast will not show either aircraft because both are below radar coverage for PHX TRACON and ABQ center. The same sort of thing occurs at KAVQ and others. The problem is acute in areas that are sparsely populated with mountainous terrain.

 

Any others experience with this using ADSB?  

 

 





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Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sat Oct 24, 2015 4:44 pm Post subject: ADSB

Correct. Radar is mostly irrelevant, and many terminal radar sites will 

be shut down after 2020.

The ground stations are only designed to provide coverage to aircraft at 

or above 1500 AGL, so there is no coverage for traffic taking off or 

landing unless there happens to be a ground station very nearby. At FFZ 

you are fortunate to have a ground station right there. It is too bad 

there won't be all that much coverage at CGZ with all the instrument 

training and practice that happens there.



On 10/24/2015 3:00 PM, Bob Turner wrote:

 	  Quote: 	
		   



 First of all, there is no '2 meter' broadcast. You listed the frequencies used - both around 1GHz or 30 cm wavelength.

 Second, what matters is the location of ADSB rebroadcast stations (-C). There may be one at your airport.

 But, generally speaking, you are correct. Low aircraft may be unable to receive ground station broadcasts. Of course, unless you are in class B, C, or the class B mode C veil, or above 10,000', there is no requirement for an aircraft to be ADSB equipped at all.

 You still need to see and avoid.



 --------

 Bob Turner

 RV-10 QB





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=448251#448251

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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

deej(at)deej.net
Guest

Posted: Sat Oct 24, 2015 4:49 pm Post subject: ADSB

On 10/24/2015 4:40 PM, DLM wrote:

 	  Quote: 	
		   The airport surface is about 1500 MSL. If an aircraft using the UAT

 frequency is preparing to takeoff and I am preparing to land. I don't

 believe he will be able to "see" me on his traffic since I will be

 transmitting on the 1090 channel. I will be able to "see" him on my

 system because I receive directly both systems. Even though we both

 should be able to be "listening" to an ADSB transceiver on about two

 meters, the rebroadcast will not show either aircraft because both are

 below radar coverage for PHX TRACON and ABQ center. The same sort of

 thing occurs at KAVQ and others. The problem is acute in areas that are

 sparsely populated with mountainous terrain.


	




What frequency do you believe is being used near two meters?  My 

understanding is that UATs are using 987 Mhz and ES transponders are 

using 1090 Mhz, and those are the only two frequencies being used for 

ADS-B.  The ground station rebroadcasters are listening/transmitting 

between these two frequencies.



I believe you are correct in terms of the aircraft only receiving on 987 

Mhz not being able to see you transmitting on 1090 Mhz because there 

will be no rebroadcast ground station in range.  It is for that reason 

that I believe most people are equipping with receivers that cover both 

frequencies.



-Dj



-- 

Dj Merrill - N1JOV - EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

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