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Transponder troubles

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Kellym

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

Posted: Sat Sep 10, 2011 5:55 am Post subject: Transponder troubles

Had strange occurrence with Salt Lake Approach yesterday. Initially,

when they said they couldn't see my transponder, I had a reply light.

Then they said they could see a 1200 code from it, not the 0363

assigned that I had dialed in. A bit later they saw the correct code,

and it continued to be okay until out of their airspace. Now I

departed the Phoenix area the day before, communicating with 2 radar

equipped towers that had no complaints on my transponder and were

giving me radar traffic callouts, so I know it was working. Not sure

how a transponder could possibly put out a 1200 code when set to

something else, and then revert to sending the selected code. I could

see one or two digits being wrong, but the whole code? I could only

think they had a weak signal, but checked after I landed and antenna

was clean. I guess I can check the coax connection, and reseat the

unit in its tray, but would rather not have to spend for an

unnecessary bench check. It is an old model with cavity tube, but has

been rock solid since it was aligned 8 yrs ago, passing every biennial

check. Any other thoughts?

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

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Sep 10, 2011 6:38 am Post subject: Transponder troubles

At 09:52 AM 9/10/2011, you wrote:




Had strange occurrence with Salt Lake Approach yesterday. Initially,

when they said they couldn't see my transponder, I had a reply light.

Then they said they could see a 1200 code from it, not the 0363

assigned that I had dialed in. A bit later they saw the correct code,

and it continued to be okay until out of their airspace. Now I

departed the Phoenix area the day before, communicating with 2 radar

equipped towers that had no complaints on my transponder and were

giving me radar traffic callouts, so I know it was working. Not sure

how a transponder could possibly put out a 1200 code when set to

something else, and then revert to sending the selected code. I could

see one or two digits being wrong, but the whole code? I could only

think they had a weak signal, but checked after I landed and antenna

was clean. I guess I can check the coax connection, and reseat the

unit in its tray, but would rather not have to spend for an

unnecessary bench check. It is an old model with cavity tube, but has

been rock solid since it was aligned 8 yrs ago, passing every biennial

check. Any other thoughts?



     Don't worry about it . . . yet. Aviation electronics, transponders

     in particular are prime examples of what CAN happen when one agency

     with no particular expertise has the power to mandate behaviors

     to others without regard or responsibility for the unintended

     consequences.



     Modern transponders are descendants of the WWII IFF (identification,

     friend or foe) systems that helped avoid shooting down our own

     airplanes. The Mode A (identification only) systems of the 1960's

     were relatively simple pulse generators tide to an almost stable

     high power oscillator that would, most of the time, let the guy

     on the ground sort your primary radar return from perhaps hundreds

     of other returns.



     Then they added altitude reporting by making this little bitty

     change to the pattern of pulses . . . that were supposed to let

     the system on the ground tell the difference between two closely

     spaced string of pulses . . . first being I.D. the second being

     altitude. Of course, there were volumes of specifications written

     to which willing players complied so that they could play in the

     avionics sand-box.



     When some transponders failed to deliver a flavor of pulses

     distasteful to the ground systems, it was discovered that the

     agency in question 'made a mistake' in writing the specifications.

     The cost of a work-around nearly sank Terra. This is but one

     of many examples for how our avionics and the efficiency to which

     they perform has be regulated into inept antiquity . . .



     While the rest of the universe is communicating in digital

     spread spectrum, we still talk on radios that suck for air

     (VHF AM). This is but a hand-full of examples of system

     evolution that has been subject to administrative retardation.



     Yeah, it's getting "better" . . . but only by stacking band-aid

     on top of band-aid to a system that should have been trashed

     and replaced decades ago. You've got more capability, flexibility

     and utility in the computer upon which you're reading these words

     than the FAA has in their radar systems they depend on to tell

     other folks what to do . . . ostensibly to keep them from running

     into each other. It's sorta like sending a one armed man blind

     in one eye into a sword fight with a atomic powered table knife.

     If he's VERY talented, he'll be okay most of the time.



     So when somebody on the ground says there's something wrong

     with your radios, do your own due diligence but don't be surprised

     if the difficulty cannot be identified or repeated. His

     perceptions are altered by systematic retardation and may

     not always be accurate.



     Bob . . .



   Bob . . .

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at6c(at)bellsouth.net
Guest

Posted: Sat Sep 10, 2011 8:19 am Post subject: Transponder troubles

It's ATC problem.  I have had the same issue with ATC on a number of

occasions, if one radar site has a problem and nobody else does I wouldn't

be in a hurry to get to the repair shop.

George



--

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ainut(at)knology.net
Guest

Posted: Sat Sep 10, 2011 8:46 am Post subject: Transponder troubles

interference from something else?



Kelly McMullen wrote:

 	  Quote: 	
		   



 Had strange occurrence with Salt Lake Approach yesterday. Initially,

 when they said they couldn't see my transponder, I had a reply light.

 Then they said they could see a 1200 code from it, not the 0363

 assigned that I had dialed in. A bit later they saw the correct code,

 and it continued to be okay until out of their airspace. Now I

 departed the Phoenix area the day before, communicating with 2 radar

 equipped towers that had no complaints on my transponder and were

 giving me radar traffic callouts, so I know it was working. Not sure

 how a transponder could possibly put out a 1200 code when set to

 something else, and then revert to sending the selected code. I could

 see one or two digits being wrong, but the whole code? I could only

 think they had a weak signal, but checked after I landed and antenna

 was clean. I guess I can check the coax connection, and reseat the

 unit in its tray, but would rather not have to spend for an

 unnecessary bench check. It is an old model with cavity tube, but has

 been rock solid since it was aligned 8 yrs ago, passing every biennial

 check. Any other thoughts?



    


	


-- 

If you're an American, just say NO to the Obamanation, to socialism, and get rid of Soros.



..democracy and a republic can function only in a firm partnership with morality and religion. -- John Adams.  Indeed.  Same should be said for ANY type of gubmnt

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Speedy11(at)aol.com
Guest

Posted: Sun Sep 11, 2011 8:43 am Post subject: Transponder troubles

Bob,

 Perfectly worded.  Sounds like Congress.

 Stan Sutterfield

 Do not archive

  

  In a message dated 9/11/2011 3:01:15 A.M. Eastern Daylight Time,  aeroelectric-list(at)matronics.com writes:

  	  Quote: 	
		  prime    examples of what CAN happen when one agency

     with no    particular expertise has the power to mandate behaviors

        to others without regard or responsibility for the unintended

         consequences.



	


 [quote][b]

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