Comments by "Sar Jim" (@sarjim4381) on "The Drydock - Episode 082" video.

  1. 15th! This Channel Admin section is the best ever!
    7
  2. It's not just the radar top hamper we can see that contributes to the weight devoted to radars. In those days of vacuum tubes (valves), even a surface search radar display could run to a ton. Once larger plan position indicators (those sweeping oscilloscope type screens) and associated electronics could add another 4-8 tons. In order to coordinate all those radars and fire control systems, something like the USN combat information center (CIC) was now required, with hundreds to tens of thousands of pounds of electronics, radios, phone systems, plus the people to man all of those gadgets. That meant about ten officers and NCOs and another 20 or so enlisted in a cruiser sized vessel, and about half that requirement for a destroyer. Once fighter direction was added to the CIC, another five to seven people had to be crowded into an already inadequate space. The only good thing about being crammed into a small space like a CIC is they were generally one of the first spaces to be air conditioned. Lest you think the Navy had gone soft on the crew, the a/c manual made it clear that it existed mainly to decrease the humidity in the CIC, since all that moisture caused the electronics to break down. Even the so-call plotting tables were in reality large primitive vacuum tube powered analogue computers, each weighing another 3 to 6 tons each. Space also had to be found to accomodate all these men and equipment. The next problem was all the additional bunk and messing space, plus stores for the extra crew, and that could easily add up to another several thousand tons per mission just for stores. But we're not done yet. Something had to make all those all power hungry vacuum tubes light up, and that meant larger steam and diesel generators along with things like dynamotors and sundry other things needed to keep all those screens lit and radar antennas turning, such as additional miles of very heavy electrical cabling, and coaxial cables for the radars themselves. it's hard to find estimates for all the weight added to ships for all these electronics and ancillary things like the CIC. The only seemingly accurate one I've read was in the July (or maybe August) 1945 issue of Combat Information Center magazine, a Navy publication that attempted pull together the best practices from men all over the fleet about how to makes a CIC run efficiently. That estimate included the weight all the electronics and mechanical equipment needed to run all the radars and the CIC itself, plus the CIC staff, but not including some of the engine room generators or radar antennas. That estimate was about 78 tons for a cruiser, 107 tons for a battleship, and an astounding 138 tons for an aircraft carrier, and that didn't include the weight of all the radar antennas. A cruiser size CIC required a minimum of 480 sq ft, a battleship 740, and an aircraft carrier about 950 sq ft. All of this gives some indication that radar was a lot more than slapping a radar antenna on a mast. The next time you look at a late war picture of a USN or RN vessel with those antennas everywhere, just remember that, like an iceberg, a lot of what was required to make them useful was below decks.
    7
  3. ​ @BB.61  CXAM is a good example of both the promise and limitations of radar in general, but early radars in particular. The CXAM radio frequency operated at 1.5 meters, or 200 MHz, a very high wavelength in 1938, when CXAM was being tested. The antenna resembled a very large inner spring mattress - very large. The CXAM was 15 feet wide and 16 feet tall, and just the antenna weighed 5,000 pounds. At the time, the most sensitive receiver type was a superheterodyne (superhet), but 200 MHz was such a high frequency that only a superregenerative (regen) receiver was the only type that could provide enough signal amplification to make the return signal visible on a horizontal oscilloscope. It was hard enough to tune in a regen signal sitting in the radio shack on dry land let alone doing so on a rocking, pitching ship. It also required a powerful transmitter on the order of 1,000 watts, something that just didn't exist before 1938. When the radar was on, about 10% of the 10% of the ships power had to be diverted to the CXAM to obtain full transmitting power. Mounted at the very top of a battleship mast, it had a range about 14 miles on a large ship target and 50 miles on a bomber size target. Even with these rather primitive sets, the range was well beyond human lookouts, especially in poor visibility. Luckily for the USN, Admiral Nimitz was something of an electronics tinkerer, and he put himself through a three week radar instruction course in 1938. When he became C in C, Pacific Fleet, he speeded up the number of trainees being sent through radar schools, and he ordered his captains to provide a weekly report of radar usage and issues. He knew too many of his hidebound captains didn't trust radar, and he needed to find a way to make sure it was in use at all time. After a shaky start, it didn't take long for radar to start proving itself, and British and US researchers kept turning out better sets. Radar is generally credited with being among the top three weapons of WWII in the Pacific.
    1