KT78A transponder
Thread Starter
KT78A transponder
My secondhand plane had a transponder installed, and how impressive I found that! It is labelled KT78A, I take that to indicate (Bendix-)King.
Now that the time has come to actually fly, I am looking into this transponder, and have some questions. And of course there is no manual, though there was one for the altitude encoder.
-) no amount of websearching found me a manual, I only came up with a 2-page pdf describing installation and cabling. But perhaps there is not much to say, beyond that?
-) apparently, there are 3 similar models: 76A, 76C, 78A - what are the differences?
-) when I switch the transponder on, in its normal "alt" mode, the orange indicator flickers busily, even on the ground. I suppose every flicker indicates an interrogation, but are these really so frequent? Even on the ground, outside most radar station's range?
Now that the time has come to actually fly, I am looking into this transponder, and have some questions. And of course there is no manual, though there was one for the altitude encoder.
-) no amount of websearching found me a manual, I only came up with a 2-page pdf describing installation and cabling. But perhaps there is not much to say, beyond that?
-) apparently, there are 3 similar models: 76A, 76C, 78A - what are the differences?
-) when I switch the transponder on, in its normal "alt" mode, the orange indicator flickers busily, even on the ground. I suppose every flicker indicates an interrogation, but are these really so frequent? Even on the ground, outside most radar station's range?
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Basically it's a lower specification KT76 A with lower power output and it is unable to code mode C above 15000ft.
I would guess that it was built as a low cost unit to use parts that work but don't meet the spec for being fitted to a KT76A, King also did this with the KN62 DME, when unit failed meet the KN62 power out put they badged it as a KN64.
If you got lucky your KN64 had only missed the spec by a few watts and you had very good DME in terms of output for a budget price.
I would guess that it was built as a low cost unit to use parts that work but don't meet the spec for being fitted to a KT76A, King also did this with the KN62 DME, when unit failed meet the KN62 power out put they badged it as a KN64.
If you got lucky your KN64 had only missed the spec by a few watts and you had very good DME in terms of output for a budget price.
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76C is digital (buttons and a display) - the other two have mechanical selectors.
78A is less powerful (100 ish watts instead of 200 watts) and is limited to a certain height. It's effectively the 'VFR' model.
It's quite normal for the light to flash almost constantly on the ground - just depends where you are in relation to the radar stations.
78A is less powerful (100 ish watts instead of 200 watts) and is limited to a certain height. It's effectively the 'VFR' model.
It's quite normal for the light to flash almost constantly on the ground - just depends where you are in relation to the radar stations.
Don't TCAS equipped commercial aircraft also interrogate transponders? Your transponder will flash when responding to TCAS equipped aircraft in the vicinity - even when out or range of a ground based secondary radar system.
