Marco Leon wrote:
Ray Andraka wrote:

Yes, the older encoders are designed that way. They use a heater to get
the temperature to a known value to stabilize the pressure reading.
Mine is a Trans-Cal encoder, and it takes about 8 minutes on a 60 degree
day. Takes longer on a cold day. The transponder (a Narco AT165) has
an altitude readout, which shows 0 until the encoder comes alive.


This process starts when the electrical/avionics are turned on correct?
I was thinking about putting the transponder (in my case a King KT76A)
in "ALT" instead of "STANDBY" at startup to help speed up the process
but now I'm thinking that it wouldn't make a difference.

Over the last 4-5 flights, New York TRACON has been complaining that
they only get a primary target during the early parts of my flight and
thus have refused radar service. Of course, on my way back to the
airport, it would start working. Given that the transoponder was given
a clean bill of health from a bench check, the encoder seems to be the
next logical troubleshooting step. Replacing my pole antenna with a
blade-type (at the recommendation of the shop) does not seem like it
would be the solution to the problem given the symptoms.

Marco


Um, if it were the encoder, the transponder should still reply to
mode3/A interrogations unless the encoder ready is wired to the suppress
reply pin on the transponder. If that pin is not wired to the encoder
then you've got something else going on (I believe that pin is there to
allow a DME to suppress replies while the DME is expecting a response
from the ground station).

Also, I wasn't clear about the display on the Narco with the encoder not
ready. I think it displays dashes when the encoder is not ready..
Whatever it is, it is plainly not a valid altitude.