On Mon, 24 Nov 2003 20:30:38 GMT, Bruce in Alaska
wrote (with possible editing):

In article ,
"Jeff Morris" wrote:

I often keep it in standby to save power and
magnetron time (they do wear out)

Just a point of note here. Leaving the radar in standby on most
civilian consumer radars does not save anything on Magnitron
Time. What wears out is the Filiment (heater) and that is
always ON whenever the Powersupply is on, even in Standby Mode.
To convise yourself of this, do this simple test. When you first
"Fire up" your radar, there is a timer that allows the Magnitron
to "Heat up and Stabalize", usually for three (3) minutes or so.
After that initial "Warm up Period", when going from "Standby"
to "Operate" does your radar require another "Warm up Period"?
If so, then you are correct on your Magnitron time statement.(Not very
likely to be this way) If not, then then "Standby" only save you
Transmit Power, and that's not really very much in most cases.
Most modern Magnitrons have between 2000 and 4000 hours of Service
Life and that is Filiment Life, really.

Bruce in alaska

No flame, Bruce, but what normally wears out a magnetron is depletion
of the cathode. The cathode is heated by the filament so that it will
emit electrons. As the tube ages, its ability to emit them decreases.
As radar operates in pulsed service, the tubes should last a good deal
longer. Often, a magnetron which is substantially dead, will still
"light up" just like the final output tubes in transmitters.
--

Larry
Email to rapp at lmr dot com