MPN-1 GCA
Chugalug,
Thank you for the two links. The first (more Canadian experiences) is very interesting. It would seem that the original MPN-1 came in more than one design. There are things mentioned that are quite outside my experience. The Search PPI has a range quoted at 40 miles. I think our max was 20. Then the dual-range PAR tubes (10 and 3 miles) were certainly not in our trucks, and I know nothing about them. And the antennae servos for the PAR were operated by foot pedals ??? The mind boggles !
The precision sweep on later (CPN-4 and PAR) was electronically produced on the tube. But the MPN-1 moved the whole waveguides bodily by a sort of big Meccano. This caused a regular one-sweep a second "heart-beat"- inside it was like being in the engine room of a tramp steamer. After a while you got so used to this that you didn't hear it any more.
What you did hear was the "Fast Scan" (4 sweeps/sec) that Talkdown switched in for extra accuracy in the last mile. Then all Hell let loose; "the joint was jumpin'", and as your desk top (and everything else inside) was on a 4° slope, you had to watch that your cup/mug and everything else didn't dance off onto the floor. (It was like your car "fast wipe" in heavy rain).
You might well wonder who was daft enough to design a thing like that. The answer is interesting. It seems that originally the elevation precision antenna was fitted so that it swept down to the horizontal with the truck level on its four hydraulic jacks (reasonable, as aircraft rarely fly underground, and then not very far).
But then the radar couldn't pick up the ground markers which you must have to set-up. And now the things were coming off the production line: it would be very expensive to halt it and redesign. Bright idea: why not tilt the whole truck a few degrees down on its jacks to achieve the same result ? Done, problem solved, all happy ?
Well, no. The shaft on the PPI waveguide was now out of vertical to the same extent, PPI tube useless ! Now what ? Again the ad hoc solution, saw shaft off at roof level, cut a suitable wedge off the truck top corner, fit universal joint in shaft, restore status quo. Now they'd "hacked-it", except that when you put the truck back on its wheels (for a runway change) it looked rather funny with a rotating Leaning Tower of Pisa up top. (And was it four degrees as I was told, or two, as the Canadians say ? Dunno, really).
As to the second link: if I ever finish it I'll know far more about radar than ever I learned at Shawbury !
I have reason to suppose you have a birthday some time this month, if so Many Happy Returns ! (if not put it down to Senile Decay - mine, not yours)....D
MPN11,
I fear the MPN-1 is a lost cause in the mists of the past now, we're unlikely to turn up much else about it.....D.
Molemot,
I remember seeing one in a Mess (Linton ?). Huge thing....D
Time for bed now. Goodnight, all. Danny.