Royal Navy Dido class Light Crusiers

[Guest]

In fact, if you use a receiver on the aircraft to detect the frequency being used by the shell, you can predict what interference ocsillation frequency the shell will be looking for, and just blast the air with your own transmission with the appropriate frequency to set up that oscillation, and you can detonate a whole slew of VT shells prematurely in a large region around the transmitter.

Wonder why no one did it during WWII. Must have been because they didn't know how VT shells worked.

[Guest]

But wouldn't the PEcell be in the shell's shadow at some point before the it hits near the plane, as the shell is spinning?

No, you can use a light diffuser at the nose of the shell to average the amount of light reaching the shell from all directions.

BTW, what's to keep the airplane from disguising its shadow by putting lights on its underside?

In fact this very thing was done when the British put lights on the leading edge of their ASW aircrafts so that the luminance of the plane matches the luminance of the background sky. This had a dramatic effect on the ability of German submarine lookouts to pick out an approaching aircraft against background sky.

[Werner]

The owner of the VT shells was necessarily closer to the place they fell than the German or Japanese plane....

[bengtsson]

That's interesting Werner. That system makes perfect sense. Especially the use of the shell body. That explanation is how I was led to believe it worked. Although I sure would like to see how the transmitter worked.
I was amazed when I read the photo-electric cell explaination. Although it would work. So do you think Mr. Stern got into some bad information i.e. a system that was tired but never worked out and he took it at face value as the system used in the end?

Bob B.

[Guest]

This also suggest the claim heard once before in this forum that the Japanese also had perfected a VT shell before the end of the war is not true, if the supposed Japanese VT worked on the same principle.

If the Japanese actually knew this principle (somewhat mandatory if they were to use it), then it would be easier and faster for them to outfit a some aircraft with the necessary transmitters to jam VT shells than it would be for them actually mass produce and deploy their own VT shells. The fact that their Kamakazi attacks were not accompanied by jamming aircraft that would have greatly increased the effect of the attack suggests they were not on the path to their own VT shells.

[Tiornu]

There were a number of ideas examined for use in proximity fuzes. Photo-electric has been mentioned. There was a sonic type, too. The only type ever ruggedized was the radio fuze. The British and Japanese both deployed PE fuzes. The British tried them in AA rockets, which didn' require ruggedized components. The Japanese used one solitary PE fuze during the war; it triggered a bomb dropped on a Saipan airfield. Worked great, caused a lot of damage.
The Americans were aware of the vulnerability of the VT to jamming, and it caused many sleepless nights.
The best reference for the development of the radio fuze is Baldwin's The Deadly Fuze.

[RNfanDan]

I wonder how they solved for the problems of protecting the vacuum tube (or valve, to you homelanders) amplifier and oscillator from the crushing acceleration of firing? Also, how did they arrange a voltage source for the filament and plate, again avoiding the hammerblow of firing?

I can only imagine these were encased in a resin of some sort, that was less brittle than bakelite...

Interesting thread!

Dan

[Guest]

I wonder how they solved for the problems of protecting the vacuum tube (or valve, to you homelanders) amplifier and oscillator from the crushing acceleration of firing? Also, how did they arrange a voltage source for the filament and plate, again avoiding the hammerblow of firing?

I can only imagine these were encased in a resin of some sort, that was less brittle than bakelite...

Interesting thread!

Dan

This is where printed circuits come in.

[bengtsson]

I wonder how they solved for the problems of protecting the vacuum tube (or valve, to you homelanders) amplifier and oscillator from the crushing acceleration of firing? Also, how did they arrange a voltage source for the filament and plate, again avoiding the hammerblow of firing?

I can only imagine these were encased in a resin of some sort, that was less brittle than bakelite...

Interesting thread!

Dan

I agree, I'de sure like to see an actual photo of the physical circuit and components. Any tube would have a heck of a ride going out of that gun barrel Also, what kind of maintenance would the fuses need. They'de have to be fully charged and ready to go when needed. The oscillator and band pass filter are all very basic and rugged stuff if incased in something with a little cushioning effect. It is the power source and tube types that I wonder about. Printed circuits are not always as rugged as the old wire and solder. I worked on alot of electronics of the late 50s through early 70s and the old stuff was tough as heck!
However you look at it, the VT fuse was a major triumph for electrical engineers of that time. The theory is very, very basic. But putting it into a shell fuse? Now that was something!

Bob B.

[Foeth]

If you use the tube as an amplifier, you'd better replace it with solid state amplifiers. They are better in all regards. Audiphiles still use the vacuum tubes because they are morons.

[Werner]

Remember, the transistor was developed by William Shockley of Bell Labs in 1947. Nothing could be "solid state" before that.

[Foeth]

Yes, that does help. But, after that period one could apply the solid state amplifier (and I guess they did?).

[Tiornu]

I agree, I'de sure like to see an actual photo of the physical circuit and components.

I believe you can see at least a drawing of the circuit in Louis Brown's A Radar History of World War II.

[RNfanDan]

I wonder how they solved for the problems of protecting the vacuum tube (or valve, to you homelanders) amplifier and oscillator from the crushing acceleration of firing? Also, how did they arrange a voltage source for the filament and plate, again avoiding the hammerblow of firing?

Dan

This is where printed circuits come in.

Printed circuits dealt with the interconnections between devices, not the devices themselves. The transistor was still to be invented, and RF oscillators and amplifiers were vacuum-tube based. It was obviously done, I'm just interested in the circuitechture and topology.

I believe you can see at least a drawing of the circuit in Louis Brown's A Radar History of World War II.

Would this happen to have any information on the component arrangements?

[Tiornu]

I can only suggst you find the two books I mentioned. I think you'll be pleased with both; they are excellent sources.

[RNfanDan]

If you use the tube as an amplifier, you'd better replace it with solid state amplifiers. They are better in all regards. Audiphiles still use the vacuum tubes because they are morons.

The vacuum tube remains champion in S+N/N ratio, with a noise floor comparable to an electronic Marianas Trench. Even today, it remains the best choice for virtually noise-free audio amplifiication.

[Foeth]

The vacuum tube remains champion in S+N/N ratio, with a noise floor comparable to an electronic Marianas Trench. Even today, it remains the best choice for virtually noise-free audio amplifiication.

`

For audio amplification modern solid-state amplifiers reach S/N ratios of 150 db and that's far far far far better than tubes could ever match. The harmonic distortion of a well-designed tube amplifier is also always worse that a well-designed solid state amplifier. Plus, their characteristics degrade over time. Damping factor is usually low, so for audio that means interaction with the loudspeaker can occur. There is absolutely NOTHING a tube does better than solid state for audio amplification, they are obsolete and they are bought by audiophiles who are either shockingly undereducated in how electronics actually work or are ripped off by clever sales men who convinced them that that $15,000 30W amplifier has such a unique sound. "Don't you just love the sound of that warm tube amplifier?". I do like the looks of these outrageous amplifiers and I think it must be a great hobby to build and design them, but in my house I look for a low distortion and efficient amplifier. Nearly all amplifiers do that and ALL sound the same. If not, it should be trashed as a bad design. The only advantage of a tube amplifier is that its characteristics are more favourable when you are demanding more that its design load. But what idiot is going to overload an amplifier and claim superior sound? Buy a amplifier with 40 watts or more...

The ten biggest lies in audio

[Werner]

As an aside, when I was young, there were great wars over these things, and endless debates about the superiority of vinyl to CDs. Now, it appears at this remove that these debates are over and audiophiles are even willing to tolerate the lossy sound of mpegs, if they can get their hands on a rare recording.

What happened?

[Foeth]

There is still a large group of people bent on vinyl, claiming it to be superior. You can still buy players, ranging from the cheaper USB(!) versions to the tens of thousands of euro/dollars variety. But, the CD is superior to vinyl is every way. In the early days, not all CD's were recorded properly and the signal often exceeded the CD's bandwidth (This is still the case with many recordings, especially pop. The Jass/Classical audience is somewhat more cirital). If you do take care then you have a perfect recording. That is, whatever you want to record is recorded perfectly, the sound itself can still be lousy. The multi-channel DVD-Audio and Super Audio CD offer a better bandwidth, but recent double-blind tests indicated you cannot distinguish this higher bandwidth from standard 16-bit 44.1 khz CD. These formats do offer multichannel, which can be a great addition, and are often recorded with more care so are usually a lot better. But a well-recorded CD remains an excellent CD.

The MP3 format is not lossless (MPEG is video, with MPEG2 as the current DVD standard and I think MPEG4 for the newr formats) so if you take a low bitrate it sounds absolutely awful. But I've played around with higher MP3 bandwidth and then you don't hear a thing. Of course, that doesn't stop the audiophile from buying speakers that have a linear response (or so it is claimed but I don't believe it) up to 80 kHz. A factor of 5 beyond the average adults hearing range! Totally ludicrous, but they claim they can hear it and the high-frequency interaction makes al the difference. You'd guess that wonderful interaction was already recorded as low-frequency content, but better not talk to much to these guys.

BTW, the above link leads to a great no-nonsense only-cold-hard-fact website frorm which I also took the link above. Another great site with objective (?) and informative audio and video is audioholics.

The audiophile is listening to vinyl through speakers with passive filtering using tube amplifiers. All very expensive and all with high distortion. I recently purchased plans of loudspeakers by Linkwitz. You'll like the site. Everything is explained, though it does require some scientific background. So, next to finishing HMS Hood, I hope to obtain sound Walhalla!

[RNfanDan]

The harmonic distortion of a well-designed tube amplifier is also always worse that a well-designed solid state amplifier.

NOTE: This side discussion is foreign to the thread of Dido-class cruisers. In the interest of propriety, this will by my last post on the subject under this heading. An excerpt (my own emphasis added):

A SHORT PRIMER

Younger folks reading this may not remember vacuum tube radios and televisions, and others probably still think tubes went out with eight track tape players, since over the last 25 years tubes electronics have been displaced in most applications by transistor devices. In computers, tubes were ridiculous. Early computers consumed entire rooms. Televisions also suffered size and design limitations when they used vacuum tube devices. In TVs, controls had to be adjusted frequently, since tubes change as they age. Adjustments (vertical hold, for one) had to be fiddled with regularly to get a watchable picture.

Hi-fi audio is another matter altogether. Back in the days when all stereos(monos?) were all vacuum tube, we didn't have those cute little mini stereo systems the size of a bread box that are so popular today. Still, as the average consumer has gotten access to better and better sound, there are ever-increasing numbers of people who demand better fidelity in their audio systems. The rise in popularity of tube audio has, more than anything else, to do with sound quality.

Solid state (transistor) amplifiers, at least on paper, produce less distortion of the type that is commonly measured, namely harmonic and inter modulation distortion. The problem is that those two measurements don't tell the whole story. Early transistor audio gear sounded absolutely awful. If you're skeptical, find a piece of early 1960's-vintage transistor gear and listen on modern loudspeakers for as long as you can stand it. The type of distortion they produce is different from the kind produced by tubes. Tube amplifiers produce more (total) harmonic distortion, but the type they produce is referred to as even order distortion, and is not as harsh-sounding as the odd order distortion transistors produce.

Large amounts of even-order distortion (as high as 1-2%) produces little listening fatigue, and can even be relatively pleasant. Electric guitar players favor tube amps for this very reason. On the other hand, small amounts of odd-order distortion (less than .5%) are audible, even by untrained ears, and make music harder to enjoy.