On Mon, 24 Nov 2003 16:01:11 -0500, "Jeff Morris"
wrote:

I was curious about this issue, so I sent a query to RayMarine a couple of years
ago. Here's what I asked, with reference to a SL72 radar:
//
The magnetron is being heated anytime the radar is in standby. This will not,
however, significantly impact the life of the magnetron. Actual transmit time
is what really wears out the magnetron. ///
Jim McGowan
Senior Product Support Engineer

Raymarine Inc.
http://www.raymarine.com

-jeff

In case you're wondering....
the cathode coating 'wears out' by electron emission
from the 'dull emitter' surface so that its emissivity drops.

Brian W