JFK's greatest achievements/Apollo (Was: Deep Apologies to everyone....)

Jeffrey Hamilton wrote:
This is to both posters, I never actually realized _our_ radar had developed
that fast ! From those very large early sites used during the Battle of
Britain, to the relatively smaller naval sets being used to destroy the
Japanese shipping is a pretty steep learning curve.


What made it all possible was the British invention of the Cavity
Magnetron Tube, which made it possible to build radars that used very
short wavelengths, and therefore had far better resolution than the ones
that came before.
A cavity magnetron tube still forms the heart of all microwave ovens:
http://www.gallawa.com/microtech/magnetron.html
....and when Britain thought it was in danger of invasion early in WW II
they sent one to the US...sealed in a mysterious black box...that's
where the term "Black Box" first came from.


Pat

On Wed, 11 Feb 2009 17:46:18 +1300, Kerryn Offord
wrote:

Mark Borgerson wrote:
In article ,
says...
On Tue, 10 Feb 2009 08:35:24 -0700, Fred J. McCall
wrote:

"Jeffrey Hamilton" wrote:
:
:One more question if you have a bit of time, what does the 45 or 50 figure
:mean in these instances 16"/50 or 16"/45. I do see that it refers to a
:50-caliber barrel, but a 45 or 50 caliber is usually refering to a small
:arms or a machine gun etc. I've never understood what that signifies.
:

'Caliber' as used for artillery specifies how many barrel diameters
LONG the barrel is. Thus a 16"/50 would have barrels that were 16x50
inches long.

Caliber for small arms is a measure of bore diameter.
Caliber is the diameter, period. Artilerists say something like
6" 45 caliber as shorthand for 6" 45 calibers long.


So what are the units of 'caliber'? Inches?

Are 50 calibre rounds 0.50 inches in diameter?


Does 6" 45 caliber naval gun have a bore diameter
of 45 inches?

I think that there may be different usages when describing
naval guns and small arms.


Caliber is simply a technical term for the diameter of the bore of a
weapon.. Thus it can take any unit (of distance)..
mm, cm, inch tend to be the main three
mm or inch for small arms
mm, cm, inch for artillery

In Artillery the caliber unit is specified.. like 127mm/50 or 5"/50

The 50 cal MG is well.. change of convention due to common usage..
Technically it's a '.50"' caliber. People just drop the "." and the "inch"

Small arms are usually identified by the caliber and length of the case
(7.62x39 (Soviet) vs 7.62x51 (NATO) of the ammo they take)

Sometimes the small arms ammo has a label.. Like .45 ACP, which is
different to .45 Long Colt

Or different names for teh same caliber identifying different
ammunitions (length of case , bottle neck, etc etc..

e.g., the following are IIRC the same caliber, but different case
designs and sizes
9mm Parabellum
.38
.380
.357
(.xyz assumes inch)

There are any number of exceptions to anything that tries to look like
a rule. Many thirty cal are so called. They are actually .308 and at
least one is called a .308. There are many cartridges that are non
factory, called wildcats, and are made from something else by necking
up or down or shortening and so on. The headstamp is, of course, a
lie. Some of the wildcats get adopted by a ammo company and then get a
correct label.

Casady

On Tue, 10 Feb 2009 22:50:12 -0600, Pat Flannery
wrote:

A cavity magnetron tube still forms the heart of all microwave ovens:
http://www.gallawa.com/microtech/magnetron.html
...and when Britain thought it was in danger of invasion early in WW II
they sent one to the US...sealed in a mysterious black box...that's
where the term "Black Box" first came from.

In those days all radio gear had black paint that was covered with
wrinkles. If it had no controls or dials it was a black box, and often
so called.

Casady

Derek Lyons wrote:
"Jeffrey Hamilton" wrote:

Well that's a fascinating little tidbit, so they had been
minaturized from those great big rigs in Britain, to a smaller yet
more powerful unit for Naval battleships and yet still smaller to
accomodate a PT boat. That is a quite remarkable degree of
minaturization.

Not all of it is minaturiztion per se. Reducing the power and the
wavelength they operated at contributed just as much, if not more, to
the sets getting smaller. You can also give up features as well.

D.

Hi Derek, after I posted I googled and found some info about the various
systems used during WW2. I did gather that, by using the different settings,
just as you've stated above. Interesting stuff. I used this site they have
several pages devoted to Radar.

http://www.century-of-flight.net/index.htm

cheers....Jeff

Pat Flannery wrote:
Jeffrey Hamilton wrote:
This is to both posters, I never actually realized _our_ radar had
developed that fast ! From those very large early sites used during
the Battle of Britain, to the relatively smaller naval sets being
used to destroy the Japanese shipping is a pretty steep learning
curve.

What made it all possible was the British invention of the Cavity
Magnetron Tube, which made it possible to build radars that used very
short wavelengths, and therefore had far better resolution than the
ones that came before.
A cavity magnetron tube still forms the heart of all microwave ovens:
http://www.gallawa.com/microtech/magnetron.html
...and when Britain thought it was in danger of invasion early in WW
II they sent one to the US...sealed in a mysterious black box...that's
where the term "Black Box" first came from.


Pat

Yes thanks Pat, as I stated in my reply to Derek, I did google and found :

http://www.century-of-flight.net/index.htm

It went into some detail and spoke of the "Cavity
Magnetron Tube" etc. I'm no expert now but I have a slightly better idea
asto how they developed the various systems for their particular needs.
Pretty fascinating stuff.

cheers....Jeff

Richard Casady wrote:
In those days all radio gear had black paint that was covered with
wrinkles. If it had no controls or dials it was a black box, and often
so called.


In this case it showed up in a black metal deed box with no writing on
it at all and not a clue about what was inside:
http://news.bbc.co.uk/1/hi/sci/tech/6331897.stm
US customs demanded the box be opened for examination before being
allowed to enter the country, but a phone call from way up in the FDR
administration told them to let it in unopened and shut the hell up
about it.
By then of course so much attention had been drawn to it that everyone
was wondering what was in the "Black Box", in best mystery movie tradition.
Little did they know that the case also contained a jeweled solid gold
statue of a falcon, a magnificent gift from the Knights Templar to the
Spanish king Charles V who was their benefactor in granting them the
isle of Malta.
I would write more, but it's time to take a little trip to Egypt where
rumor has it a dealer in antiquities has come into possession of a most
singular item.
Yes sir, a most singular item indeed....

Pat

Jeffrey Hamilton wrote:
It went into some detail and spoke of the "Cavity
Magnetron Tube" etc. I'm no expert now but I have a slightly better idea
asto how they developed the various systems for their particular needs.
Pretty fascinating stuff.


I had a microwave oven that broke, so I salvaged the Magnetron Tube out
of it and have it on the shelf.
The magnets are quite powerful, but if you want to run into some really
powerful magnets tear a hard drive apart and get out the ones that move
the write-read stylus over the surface of the disc; those things are
absolute terrors.

Pat

On Feb 11, 2:35*pm, Pat Flannery wrote:
Jeffrey Hamilton wrote:
It went into some detail and spoke of the "Cavity
Magnetron Tube" etc. I'm no expert now but I have a slightly better idea
asto how they developed the various systems for their particular needs.
Pretty fascinating stuff.

I had a microwave oven that broke, so I salvaged the Magnetron Tube out
of it and have it on the shelf.
The magnets are quite powerful, but if you want to run into some really
powerful magnets tear a hard drive apart and get out the ones that move
the write-read stylus over the surface of the disc; those things are
absolute terrors.

Pat

I have a friend who worked for Raytheon in the Bay Area for a while.
He used to collect the failure microwave tubes and show them around
his house as objects d'art. He had a guy over who was part of one of
the museums in San Francisco. The museum guy was curious about the
tubes and asked what it would cost to buy one. This one cost $25,000
(in 1965), this one $19,000 to the point that he had about half mil in
tubes.

On Wed, 11 Feb 2009 00:56:51 GMT, (Derek Lyons)
wrote:

"Jeffrey Hamilton" wrote:

Well that's a fascinating little tidbit, so they had been minaturized from
those great big rigs in Britain, to a smaller yet more powerful unit for
Naval battleships and yet still smaller to accomodate a PT boat. That is a
quite remarkable degree of minaturization.

Not all of it is minaturiztion per se. Reducing the power and the
wavelength they operated at contributed just as much, if not more, to
the sets getting smaller. You can also give up features as well.

D.

Toward the end of WW II we also developed a radar guided missile, the
Lark, to counter komikazee attacks. It worked well enough in the lab,
but in the vibration environment of the missile in flight the radar
guidance range was reduced too much to be effective. And of course
the procimity fuse was a major advance.

Alan

Pat Flannery wrote:
Jeffrey Hamilton wrote:
It went into some detail and spoke of the "Cavity
Magnetron Tube" etc. I'm no expert now but I have a slightly better
idea asto how they developed the various systems for their
particular needs. Pretty fascinating stuff.


I had a microwave oven that broke, so I salvaged the Magnetron Tube
out of it and have it on the shelf.
The magnets are quite powerful, but if you want to run into some
really powerful magnets tear a hard drive apart and get out the ones
that move the write-read stylus over the surface of the disc; those
things are absolute terrors.

Pat

Lol, I'll remember that for future reference. Every boy needs at least one
good magnet and I do have an old HD with a few bad sectors, Ill trash it and
give the magnets to my grandson, when he is a litle older.
What's a Magnetron Tube good for ? If I save one for my grandson, is he
likely to nuke the house ? g

cheers....Jeff