On 6 Sep 2003 17:54:31 -0700, (Bob Kuykendall)
wrote:

:Earlier, Scott wrote:
:
: I haven't looked inside the new "digital" transponders, but I assume
: they still have a tube in them...
:
:I believe that that's not correct. According to the sales literature,
:current-generation transponders like the last Terras, the Microair,
:and the Garmin GTX series are completely solid state. No cavity tube.

The Terras were solid state from first, even with the damned
pushbutton face. Also, the UPS (now GarminAT) transponder has no
cavity tube. The microair is all solid state. I don't know about the
new Narco, they are claiming all digital, but so do the newer Kings
and they do have a tube.

If you can get a used TXP with a known service history, where you know
that it has, say, 500 hours on it, it can be a real bargain. But if
you don't know how many hours it has, it's unknown. You know that at
the moment it got it's yellow tag it was working. And you know that
at some point in the future, the cavity's going to burn out and it
will cost more than the txp is worth to replace it. So, get a new
one.