In article ,
"Steve Lusardi" wrote:

Sorry Marc, you are not correct, power is not reduced at lower range
selections. The transmitter tube is a magnetron, which effectively is a
resonant cavity within a permanent magnet. It is excited by driving the
cathode severely negative with a high voltage pulse. There are no other
controls. The cavity will resonate only as long as the cathode sees the high
energy.

Yes, I know that as an MSEE and anyone can verify it watching their
microwave oven that operates on the same principle. I did not want to
make the discussion more technical than necessary. I was referring to
average power to be precise.

Perhaps you are referring to average power as opposed to peak power.
In which case you would be partially correct, but this is a function of
pulse length and pulse recurrent frequency (range selection). Normally, as
the pulse length decreases, the PRF increases proportionally, so even the
average power doesn't change too much.

Actually average power is reduced usually because the pulse length
decreases more than the pulse repetition frequency:

Data from Swissradar JFS364C that I currently have at hand:

Range 2 km 8 km 64 km
Pulse repetition frequency 3000 Hz 2000 Hz 1000 Hz
Pulse length 50ns 150 ns 600 ns
Average emitted power 0.6 W 1.2 W 2.4 W

So for a close range the average power is reduced to one quarter of the
power at long range.

Anyway most people would not care about power, and they do not have to
because the available units take care of that design decision.

Marc

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