i worked on 270s & 271 3 yrs in ww2. they were big ground units hid where they could;nt be seen. they had a range of 200 miles.the tubes in the transmiter where so big they were water cooled.in 1942 & 1943 WE HAD A LOT OF TROUBLE WITH GAS ENGINES TILL WE SWITCHED TO DIESEL. WHEN WE PICKED UP A TARGET WE INTERSEPTED WITH P 39S & P 4OS, WE A;SO HAD B 24 & B 17S & LB 30S. I WAS IN THE 554TH SIGNAL AW BN. ATTACHES TO THE ARMYS 6TH AIR FORCE. WE WORKED IN A UNIT OF 30 MEN. I WAS IN THE ATO. I WAS A RADAR OPERATOR,A PLOTER,RECORDER& radio opt. i could call a target in to our big information center 2,000 miles. our units picked up ships, subs &planes. the wires to our antena were 3/4 of a inch big. if you know what a spark gap is ,we had big ones. our antena was 50 ft. high & looked like a big bed springs.i am 82 yrs old now & i could talk about radar the rest of my life (thank god i was only blowed up once) i like email