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Hood
Post subject: Re: My AU German navyPosted: February 5th, 2019, 12:26 pm
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Sonar and radar are fundamentally different.
Sonar uses sound propagation, sound is a vibration that propagates as an audible wave of pressure, through a transmission medium, in this case water. Note, these are not electromagnetic waves.
Radar uses radio waves through air.

The design of their transmitting and receiving apparatus is entirely different. Sonars then used piezoelectric materials, typically crystals like ammonium dihydrogen phosphate or quartz.
Radar was essentially radio transmitter technology, but transformed by the cavity magnetron high-powered vacuum tube which enabled smaller wavelength radio waves to be produced.
Superficially the concept is similar but the technology is completely different.

Sure you could fix an Asdic or early sonar in the bows but you would have no bearing information and the noise of the flow over the bows would mask a lot of the returning echo signal. So the information would not be very useful. Also, the reflected signal is vastly weaker than the emitted signal, so would would need a powerful emitter and the ability to detect very small and precise reflected echoes. It just simply wasn't possible with 1940s technology.
It wasn't until the 1950s that development using barium titanate and lead zirconate titanate (LZT) piezoelectric systems improved performance, LZT wasn't developed until 1952. The big improvements came with Magnetostrictive transducers and even then they did not supersede the LTZ systems until the 1970s when high tensile alloys like Terfenol-D and Galfenol were developed.

Sonars were located further aft so they could give directional coverage all-round the ship and were located as far noisy sources as possible (as far as is practical on a ship emitting internal and external noise. Sound acoustics in water is a complicated business, perhaps far more so than radar and its electromagnetic waves.

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Cargil48
Post subject: Re: My AU German navyPosted: February 5th, 2019, 12:35 pm
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Wow, I'm apalled, Hood! Many thanks for your invaluable contribution! That is really what I expect here in this forum, people like you, with the interest to go deep into the subjects. Good man!


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acelanceloet
Post subject: Re: My AU German navyPosted: February 5th, 2019, 2:50 pm
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As for the radar dish on the bow, this is not done because of a few things.
- Radar horizon. The higher the antenna is, the further it can see, due to the curvature of the earth. This is why you often see surface search radars higher in the mast then the other radar systems.
- Field of vision. Due to the high speed of aircraft, forward is where you will be very soon, so most likely where your target is. Especially on early radars, an larger field of vision required a larger weight of the system, so they made the radars longer ranged but focussed on a small field, looking forward instead of around. On a ship, the interesting area might be anywhere and you have a lot more weight and power to distribute, so the antenna's were mounted to look around an not just forwards.
- Spray. Water is not only harmfull for electronics, it also blocks radio waves, so the spray of the waves and your ship moving trough them would hinder your radars effectiveness and also possibly damage it.
- Systems. A ships bow is fairly empty a part of the ship, filled mostly by things like ballast tanks, paint lockers and a bit further aft often things like crew spaces. This is quite something different then electronics, waveguides, cooling systems etc a radar requires. For high effectiveness, you also want your radar displays in your command center, which is done easiest by having all the electronics and systems for them near your command spaces.

So, in essence, and especially on early radars, this requires you to have your radar antenna high up, amidships and with a clear field of vision all around. More setups became possible since then, for example radars on gun mountings, but the general rules are still basically the same.

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Cargil48
Post subject: Re: My AU German navyPosted: February 5th, 2019, 3:01 pm
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Also to you, acelanceloet, many thanks for your highly valuable contribution here! I think many of us learnt in these two last posts, yours and Hood's, a lot about radar and sonars! Especially in the beginning stages of these two technologies. I really am grateful to both of you. Cheers!

PS: The second line of your signature says it all!...
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I ask of you to prove me wrong. Not to say I am wrong but prove it, because then I will have learned something new.


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Cargil48
Post subject: Re: My AU German navyPosted: February 5th, 2019, 3:57 pm
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Last edited by Cargil48 on February 22nd, 2019, 8:25 pm, edited 1 time in total.

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Cargil48
Post subject: Re: My AU German navyPosted: February 5th, 2019, 11:05 pm
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Last edited by Cargil48 on February 22nd, 2019, 8:26 pm, edited 9 times in total.

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Cargil48
Post subject: Re: My AU German navyPosted: February 6th, 2019, 11:49 pm
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Last edited by Cargil48 on February 22nd, 2019, 8:26 pm, edited 1 time in total.

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Cargil48
Post subject: Re: My AU German navyPosted: February 9th, 2019, 7:54 pm
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Last edited by Cargil48 on February 22nd, 2019, 8:27 pm, edited 7 times in total.

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Cargil48
Post subject: Re: My AU German navyPosted: February 9th, 2019, 11:02 pm
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Last edited by Cargil48 on February 22nd, 2019, 8:27 pm, edited 1 time in total.

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emperor_andreas
Post subject: Re: My AU German navyPosted: February 10th, 2019, 2:54 am
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Very nice work!

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