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Old transponder interface details

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etienne.phillips(at)gmail
Guest

Posted: Wed Feb 04, 2009 1:39 pm Post subject: Old transponder interface details

Hi All



I'm building a converter from the serial protocol used by Garmin to  

the old Gilham encoding used by the older transponders. I'm lacking  

detail on the voltages used to send a transponder the encoded  

altitude. I'm using a old Narco AT 150 TSO... The binary values for  

each pin is pretty much done, so I'm looking for the electrical  

details now.



Can anyone help me out?



Thanks

Etienne

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jdubner(at)yahoo.com
Guest

Posted: Mon Feb 16, 2009 12:35 pm Post subject: Old transponder interface details

Etienne,



The transponder inputs are TTL logic levels with inverted polarity 

(active low).  The converter should use open collector outputs as all 

encoders do AFAIK but I don't see any problem using active outputs 

unless you intend to parallel additional encoders.



I built a similar converter some years ago and you may find something it 

it that is helpful.

http://www.mail2600.com/EncoderConverter/EncoderConverter.html



Best,

Joe

Independence, OR

Aircraft Position:   http://www.mail2600.com/position

Aircraft Last Track: http://www.mail2600.com/track

Etienne Phillips wrote:

 	  Quote: 	
		   

 <etienne.phillips(at)gmail.com>

 

 Hi All

 

 I'm building a converter from the serial protocol used by Garmin to the 

 old Gilham encoding used by the older transponders. I'm lacking detail 

 on the voltages used to send a transponder the encoded altitude. I'm 

 using a old Narco AT 150 TSO... The binary values for each pin is pretty 

 much done, so I'm looking for the electrical details now.

 

 Can anyone help me out?

 

 Thanks

 Etienne

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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etienne.phillips(at)gmail
Guest

Posted: Mon Feb 16, 2009 10:18 pm Post subject: Old transponder interface details

That is most useful. Thanks very much! 

  

  

 2009/2/16 Joe Dubner <jdubner(at)yahoo.com (jdubner(at)yahoo.com)>

 [quote]--> AeroElectric-List message posted by: Joe Dubner <jdubner(at)yahoo.com (jdubner(at)yahoo.com)>

 

Etienne,



The transponder inputs are TTL logic levels with inverted polarity (active low).  The converter should use open collector outputs as all encoders do AFAIK but I don't see any problem using active outputs unless you intend to parallel additional encoders.

 

I built a similar converter some years ago and you may find something it it that is helpful.

http://www.mail2600.com/EncoderConverter/EncoderConverter.html

 

Best,

Joe

Independence, OR

Aircraft Position:   http://www.mail2600.com/position

Aircraft Last Track: http://www.mail2600.com/track

 



Etienne Phillips wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Etienne Phillips <etienne.phillips(at)gmail.com (etienne.phillips(at)gmail.com)>

 

Hi All



I'm building a converter from the serial protocol used by Garmin to the old Gilham encoding used by the older transponders. I'm lacking detail on the voltages used to send a transponder the encoded altitude. I'm using a old Narco AT 150 TSO... The binary values for each pin is pretty much done, so I'm looking for the electrical details now.

 

Can anyone help me out?



Thanks

Etienne

	


http://www.matronics.com/Navigator?AeroElectric-List

 ref="http://forums.matronics.com/" target="_blank">http://forums.matronics.com

 p;                  -Matt Dralle, List Admin.

 =====



[b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

etienne.phillips(at)gmail
Guest

Posted: Wed Feb 18, 2009 3:56 am Post subject: Old transponder interface details

Hi Joe

  

 I noticed that the encoding is somewhat different to Gray coding, despite the terms Gilham and Gray being used interchangably in all the aviation documentation.

  

 As far as I know, Gray code is constructed by applying the -1200 offset, taking the binary value, and XOR-ing it with the same binary right-shifted by one position. All is well for the first few values, but after the 5th value (-800 odd), the two codes diverge, with Gray being 000000111, and Gilham being 000000100...

   

 Do you by any chance have the method for generating Gilham code? I've spent days looking for it on the web, but without any success! I've also tried to distill the solution looking a the table on your website, also without any joy.

   

 Thanks

 Etienne

 2009/2/17 Etienne Phillips <etienne.phillips(at)gmail.com (etienne.phillips(at)gmail.com)>

 [quote] That is most useful. Thanks very much! 

  

  

 2009/2/16 Joe Dubner <jdubner(at)yahoo.com (jdubner(at)yahoo.com)>   

 

  	  Quote: 	
		  --> AeroElectric-List message posted by: Joe Dubner <jdubner(at)yahoo.com (jdubner(at)yahoo.com)>

 

Etienne,



The transponder inputs are TTL logic levels with inverted polarity (active low).  The converter should use open collector outputs as all encoders do AFAIK but I don't see any problem using active outputs unless you intend to parallel additional encoders.

 

I built a similar converter some years ago and you may find something it it that is helpful.

http://www.mail2600.com/EncoderConverter/EncoderConverter.html

 

Best,

Joe

Independence, OR

Aircraft Position:   http://www.mail2600.com/position

Aircraft Last Track: http://www.mail2600.com/track

 



Etienne Phillips wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Etienne Phillips <etienne.phillips(at)gmail.com (etienne.phillips(at)gmail.com)>

 

Hi All



I'm building a converter from the serial protocol used by Garmin to the old Gilham encoding used by the older transponders. I'm lacking detail on the voltages used to send a transponder the encoded altitude. I'm using a old Narco AT 150 TSO... The binary values for each pin is pretty much done, so I'm looking for the electrical details now.

 

Can anyone help me out?



Thanks

Etienne

	


http://www.matronics.com/Navigator?AeroElectric-List

 ref="http://forums.matronics.com/" target="_blank">http://forums.matronics.com

 p;                  -Matt Dralle, List Admin.

 =====



	




 



[b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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