How to move heavy air raid siren?

Get three or four lineman from the local high school football team and offer them a pizza each to help load it. You might want to use a couple of 2 x 6's under the rim to make it easier to lift.

You can use an engine hoist, known commonly as a cherry picker.  You can rent it from a rental place. 

You'll need to use some 3/4" plywood under the hoist wheels if you intend to move it around on that unpaved ground, otherwise put the picker on the far side of it and lift it high enough to back your pickup under it.  Then set it on your pickup bed. 

That's how I move heavy things like car engines. 

Make sure you fasten the device securely with 4 ratchet straps so it can't move or tip over during your road trip. 

It would be better if you layed it on its side than stood it up like it is in the photo.

So you stole it?  And now you want to take it to the scraper for money?

Make a wood A-Frame about 5 feet tall.  On the cross piece tie a rope.  Tilt the A frame, a slight angle off vertical and tie the other end of the rope to the siren.   Quickly  push the A-frame to vertical and it will lift the siren slightly off the ground, and you can swing it, like a pendulum in your direction of travel as you continue to push the A frame Past the vertical.  all in one motion.  Reset the A frame on the ground a short distance away and repeat the process-----This will let you "Hop" or "Walk" the heavy machine, anywhere you want to go, with little effort.

I moved a solid concrete step in that manner.  Had to have been over 500 lbs.---I think the Egyptians use a variant to build the pyramids.

take/need 3ft long 2inch dia pipe - 3 nos
tilt the unit upside down on 2 pipe third one for changing
roll the unit on the pipes.
couple of crow bars needed for/while  negotiating.
100 meters in 1 hour

See if anyone you know has a portable hydraulic engine hoist.  You would probably need to lay down some boards to build up a place to set it and spread out the loads on the soil.  The hoist it up, and back the truck bed underneath it.  Some of the cheaper, lighter weight hoists can be bought for $200 or less, so if you have any friends who work on cars they may already have one.

Since it looks like you intend to scrap it, take it apart.  The individual pieces will be easier to hoist.

i would pay someone to help you do it