xponder problems

Wxman2000

Wxman2000

New Member
OK, so I've been having a few problems with the xponder in my plane and was wondering if anyone might have a few ideas what the problem may be with it.

Sometimes, it works great, no problems through the flight. Other times, ATC is unable to pick up anything from it, though I'm still getting a reply light in the plane. And even other times, it seems to be hit and miss through the flight with ATC seeing it, sometimes not at all, sometimes what they describe as "very weak". All the while in all these cases, I'm continuously getting a reply light on the unit itself.

Any ideas what may be the problem? I was wondering if maybe it was the antenna or something since it seems to be working fine by how it acts in the plane. Any help would be much appreciated. Thanks.
 
It could be the antenna, I remember hearing that one of our training aircraft was having a similar problem last summer and it was just that. Have you have anyone look at it?
 
As some of the others said earlier check your transponder antenna and the connections to it. If that does not solve it then you might have something internal with the the transponder like a power problem that is intermittent which can cause the same thing.
 
Ditto checking the connections, but if you don't see anything obvious immediately take it to a shop with the proper test equipment.

While I don't wrench in the general aviation world, I can't tell you how many times and thousands of dollars in parts that I've seen wasted in the commercial environment (control heads, lru's, antennas) when the problem was the cable.

Very common problem on aircraft coming out of overhaul. Especially the Guadalajara specials.
 
Its either the encoder or the transponder itself. Go to a local avionics shop and have them test it on the ground with their computers. Best bet is to convince them to give you a loaner transponder to see if that fixes the problem. Most can be swapped out in less than 5 minutes. If it doesn't its probably the encoder (or antennas/connections). I call this guy that works out of a van. Usually if its working part time he will pull it apart and fix it. I would not pay more than $450 to get this fixed.

I have played with his handheld tester that gives an incredible amount of information. Something about the wavelengths being set properly could lead to a weak signal. If it is working part time you probably don't need to buy a new $1300 transponder.

This is all from my transponder problems with my plane, I don't really have a great grasp on any of it, just throwing out some ideas.

-Jason
 
Wxman2000 said:
OK, so I've been having a few problems with the xponder in my plane and was wondering if anyone might have a few ideas what the problem may be with it.

Sometimes, it works great, no problems through the flight. Other times, ATC is unable to pick up anything from it, though I'm still getting a reply light in the plane. And even other times, it seems to be hit and miss through the flight with ATC seeing it, sometimes not at all, sometimes what they describe as "very weak". All the while in all these cases, I'm continuously getting a reply light on the unit itself.

Any ideas what may be the problem? I was wondering if maybe it was the antenna or something since it seems to be working fine by how it acts in the plane. Any help would be much appreciated. Thanks.
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How old is the avionics in your airplane? Older resistors, transistors, capacitors and the like can degrade over time. They are susceptible to heat and vibration. In this day and age of disposable electronics (not necessarily avionics) people don't tend to repair electronics anymore. How many television repair places do you see anymore? However, with the cost of avionics, people rightly so continue to use older equipment. However, older avionics are, as I mentioned, susceptible to degradation.
 
Well, I've ordered a new antenna and connections to see if any of that might fix the problem. At best, it may turn out to be the cheapest thing that is wrong, so I'll go that route first.

The equipment isn't very old, the encoder was installed in 2004, and the transponder (narco at-150) was installed in either the late 90's or early 00's, can't remember right off hand.
 
Good old avionics problems. Theyre a bitch to troubleshoot sometimes, especially if the problem is "intemitant"
 
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