"Chip Jones" wrote in message
nk.net...
[...]
I thought I understood the basics of some of the new in-cockpit weather
tools for GA aircraft. I figured he was getting the latest Nexrad picture
from some online resource. What I don't understand is why he needed to
turn
his transponder off to do so. Any help appreciated.

First I ever heard of something like that, but I've never used these
inflight weather download services, so it's not like I'd know.

The most likely explanation I can think of is that the transponder might
operate on a frequency that interferes with the download, either making it
incredibly slow and/or unreliable, or even impossible to download weather
while the transponder is operating.

However, I would have thought that the people who have developed these
inflight weather download equipment would have considered that, and run into
it during product testing. It seems hard to believe that one could get TSO
approval for a device that only works if you turn off your transponder, but
I guess since any TSO would be more about not interfering with other
equipment than whether it's interfered with, it's certainly possible AFAIK.

Other thoughts assume an even more hacked-together system: not enough power
from the electrical system to power the transponder at the same time as the
weather download receiver; a shared antenna that has to be manually switched
from the transponder and the download receiver.

I sure hope someone else has an actual explanation, though I wouldn't bet on
it.

I can't imagine that this is something that applies to every inflight
weather download installation though.

Pete