In article , Glenfiddich
wrote:

On 21 May 2004 19:14:11 GMT, (B2431) wrote:

I have seen phased array aircraft radars that look as if they still
mechanically sweep the dish. I thought the entire reason for phased
arrays was
so they wouldn't need to mechanically move. I know how phased arrays work in
principle, but that's as far as I go. What am I missing here?

A flat phased array antenna can instantly swing its beam
electronically to point *anywhere* ahead but can NOT look
'behind' the plane of the antenna array. And its efficiency
falls off as it squints to extreme port or starboard...

Therefore, to get 'all-round' coverage you either add more arrays
(facing left, right and rear, as you see on the bridge structure of
many modern ships) - or physically swing the one antenna you already
have.

Adding a turntable to a single antenna sounds like an engineer's
answer to the design problem.
A simple, robust rotator, being very 'old-tech', is probably a lot
cheaper and more reliable than 3 more arrays...

OK for big platforms like AWACS or E-2C, but problematic for fast-movers.
From an engineering standpoint...

--
Harry Andreas
Engineering raconteur