FS: WW II Magnetron GL-5J29 marked Classified, NOS

[Michael A. Terrell]

"Rich, Under the Affluence" wrote:

There's something I've wanted to ask since the microwave portion
of USAF tech school. It didn't come up, because my specialty was
ECM (Electronic CounterMeasures), and all of the transmitters in
that field are intentionally as noisy as possible, since their
purpose in life is to jam.

But for, for example, radar, does a magnetron normally put out
a relatively "clean" sine wave? One of our jamming transmitters
was series-modulated with a 4-400A. (I once checked a brand-new,
in-the-box 4-400A out of Bench Stock and gave it to a buddy
who built a 20M linear with it. Being a tech in the USAF was
kewl. ;-) )

Anyway, I know they're typically pulsed for radar, and a
microwave oven doesn't care about the waveform; in fact, probably
the raggedier/noisier the better for something like that, but
during a radar pulse, is it putting out a clean signal?

Thanks,
Rich

Think about it. If it isn't clean, the echo won't be.

--
?

Michael A. Terrell
Central Florida

 

[Jim Adney]

On Thu, 22 Sep 2005 03:10:37 GMT Robert Baer
<robertbaer@earthlink.net> wrote:

Have listed at Ebay, number: 7352596690
WW II Magnetron GL-5J29 marked Classified, NOS
A genuine collector's item.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7352596690

There are a couple of these in a cabinet in the back of my office. I
checked today and one is a 5J29, like the one in this auction, and the
other one is a 5J33, which is almost the same, except that there is an
extra copper slab that sticks down from the center of the U.

As others have stated, these are all split anode magnetrons dating
from just before WWII. The U-loop is the inductance, and the
capacitance is between the blocks (there are 2 halves, each attached
to one side of the U.) Together this L & C determine the output
frequency.

There is a cylindrical cavity milled in the space between the 2 blocks
and a filament runs thru that cavity. Electrons are accelerated as in
a cyclotron and generate microwaves in the U-loop. The U-loop is
extended outside the vacuum by straight pipes which are shorted
together at an appropriate distance to tune the magnetron. Microwaves
are coupled out of the system by a loop which is coupled to this
external line.

There is a good explanaion of this at a British site. Google on
"virtual Valve Museum" for more info.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Robert Baer]

Rich Grise wrote:

On Thu, 22 Sep 2005 03:10:37 +0000, Robert Baer wrote:


Have listed at Ebay, number: 7352596690
WW II Magnetron GL-5J29 marked Classified, NOS
A genuine collector's item.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7352596690


Well, I don't know what it is, but it ain't a magnetron!

It looks like nothing but a big filament. Maybe it slid into
a 2" diameter cathode in a really really big magnetron, (magnetron
heater?) but what's in that picture is NOT a magnetron!

Good Luck!
Rich


The "U" you see is part of the resonant cavity; obviously the

resonant frequency is lower than nominal X-band maggies that you may be
familiar with,

 

[Robert Baer]

Rich Grise wrote:

On Thu, 22 Sep 2005 20:58:58 +0000, Genome wrote:

"Don Bowey" <dbowey@comcast.net> wrote in message

"Rich Grise" <rich@example.net> wrote:
On Thu, 22 Sep 2005 03:10:37 +0000, Robert Baer wrote:

Have listed at Ebay, number: 7352596690
WW II Magnetron GL-5J29 marked Classified, NOS
A genuine collector's item.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7352596690

Well, I don't know what it is, but it ain't a magnetron!

It looks like nothing but a big filament. Maybe it slid into
a 2" diameter cathode in a really really big magnetron, (magnetron
heater?) but what's in that picture is NOT a magnetron!

As I recall the eBay listing, it was stated that the magnet was not
included. Of course that means the cavities are also missing. You are
correct that what is left isn't a magnetron.

What's the point of having cavities in your magnetron if the glass gets in
the way of the electerons?


I'm surmising that this goes into a BMF magnetron, where that the
cathode is a cylinder 2" ID, that that globe slides into and heats by
IR. Once the back-bombardment starts, you don't need much heater power
to a maggie at all. I worked on a couple of maggie xmtrs in the USAF,
and one of our favorite circuits was the filament control loop -
it sensed the filament resistance (ergo temperature), and adjusted
the filament drive to maintain the right temp.

And I've seen several different types of magnetrons, and I've _never_
seen one with the cavities integral to the magnet. Usually the anode
is a solid block of copper with the cavities milled out of it.

Cheers!
Rich

"*Usually* the anode is a solid block of copper with the cavities

milled out of it" (emphasis aded).
You are thinking of more modern maggies; radar was fairly new, and
used lower frequencies during the war with Germany.

 

[Robert Baer]

Jim Adney wrote:

On Thu, 22 Sep 2005 03:10:37 GMT Robert Baer
robertbaer@earthlink.net> wrote:


Have listed at Ebay, number: 7352596690
WW II Magnetron GL-5J29 marked Classified, NOS
A genuine collector's item.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7352596690


I've got 2 tubes that look just like this sitting in a cabinet in my
office. They were there when I moved in, so I'll have to ask someone
what they are. I'll have more info tomorrow.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------
I would appreciate that.

 

[Robert Baer]

John Fields wrote:

On Thu, 22 Sep 2005 22:15:49 GMT, Rich Grise <rich@example.net
wrote:


On Thu, 22 Sep 2005 20:58:58 +0000, Genome wrote:

"Don Bowey" <dbowey@comcast.net> wrote in message

"Rich Grise" <rich@example.net> wrote:
On Thu, 22 Sep 2005 03:10:37 +0000, Robert Baer wrote:

Have listed at Ebay, number: 7352596690
WW II Magnetron GL-5J29 marked Classified, NOS
A genuine collector's item.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7352596690

Well, I don't know what it is, but it ain't a magnetron!

It looks like nothing but a big filament. Maybe it slid into
a 2" diameter cathode in a really really big magnetron, (magnetron
heater?) but what's in that picture is NOT a magnetron!

As I recall the eBay listing, it was stated that the magnet was not
included. Of course that means the cavities are also missing. You are
correct that what is left isn't a magnetron.

What's the point of having cavities in your magnetron if the glass gets in
the way of the electerons?

I'm surmising that this goes into a BMF magnetron, where that the
cathode is a cylinder 2" ID, that that globe slides into and heats by
IR. Once the back-bombardment starts, you don't need much heater power
to a maggie at all. I worked on a couple of maggie xmtrs in the USAF,
and one of our favorite circuits was the filament control loop -
it sensed the filament resistance (ergo temperature), and adjusted
the filament drive to maintain the right temp.

And I've seen several different types of magnetrons, and I've _never_
seen one with the cavities integral to the magnet. Usually the anode
is a solid block of copper with the cavities milled out of it.


---
http://www.r-type.org/exhib/aac0088.htm
Thanks for the confirmation that 1) it *is* a magnetron, and 2) it is

a two-anode maggie.

 

[Robert Baer]

Pooh Bear wrote:

Rich Grise wrote:


On Thu, 22 Sep 2005 20:58:58 +0000, Genome wrote:

"Don Bowey" <dbowey@comcast.net> wrote in message

"Rich Grise" <rich@example.net> wrote:
On Thu, 22 Sep 2005 03:10:37 +0000, Robert Baer wrote:

Have listed at Ebay, number: 7352596690
WW II Magnetron GL-5J29 marked Classified, NOS
A genuine collector's item.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7352596690

Well, I don't know what it is, but it ain't a magnetron!

It looks like nothing but a big filament. Maybe it slid into
a 2" diameter cathode in a really really big magnetron, (magnetron
heater?) but what's in that picture is NOT a magnetron!

As I recall the eBay listing, it was stated that the magnet was not
included. Of course that means the cavities are also missing. You are
correct that what is left isn't a magnetron.

What's the point of having cavities in your magnetron if the glass gets in
the way of the electerons?

I'm surmising that this goes into a BMF magnetron, where that the
cathode is a cylinder 2" ID, that that globe slides into and heats by
IR. Once the back-bombardment starts, you don't need much heater power
to a maggie at all. I worked on a couple of maggie xmtrs in the USAF,
and one of our favorite circuits was the filament control loop -
it sensed the filament resistance (ergo temperature), and adjusted
the filament drive to maintain the right temp.

And I've seen several different types of magnetrons, and I've _never_
seen one with the cavities integral to the magnet. Usually the anode
is a solid block of copper with the cavities milled out of it.


And the qaulityof the copper is imporant too.

Graham

Paraphrase of Jimmy Cagney: "You dirty Copper!".

 

[Robert Baer]

Pooh Bear wrote:

Rich Grise wrote:


On Thu, 22 Sep 2005 03:10:37 +0000, Robert Baer wrote:


Have listed at Ebay, number: 7352596690
WW II Magnetron GL-5J29 marked Classified, NOS
A genuine collector's item.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7352596690

Well, I don't know what it is, but it ain't a magnetron!

It looks like nothing but a big filament. Maybe it slid into
a 2" diameter cathode in a really really big magnetron, (magnetron
heater?) but what's in that picture is NOT a magnetron!

Good Luck!
Rich


This is better.

http://www.tubecollector.org/5j29.htm

Certainly not a *resonant cavity magnetron*.

Graham


Thanks for the reference.

 

[John Woodgate]

I read in sci.electronics.design that Jim Adney <jadney@vwtype3.org>
wrote (in <nmd9j1d8mjnks2ljfa2pvjfddv9047rstb@4ax.com&gt about 'FS: WW II
Magnetron GL-5J29 marked Classified, NOS', on Fri, 23 Sep 2005:

There is a cylindrical cavity milled in the space between the 2 blocks

That's a neat trick! What type of cutter do you use to make a cavity in
a vacuum?(;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Reg Edwards]

According to Fourier, there is an inevitable extremely wide spectrum
associated with a continuous pure sine wave amplitude modulated by a
sharp low-repetition-rate pulse.

The receiver can't work properly unless it has a very wide bandwith to
accommodate a large proportion of it. Otherwise radar echos from
different distances become blurred and merge with each other on the
screen.

Its just hard luck if the transmitted spectrum interferes with
not-so-adjacent frequencies.

Micowave oven magnetrons are not modulated but are are contiuous wave
devices. The frequency may drift very slightly as the temperature and
magnetron dimensions change. But your rice pudding couldn't care two
hoots.
----
Reg.

 

[John Woodgate]

I read in sci.electronics.design that Reg Edwards
<g4fgq.regp@ZZZbtinternet.com> wrote (in
<dh3476$qv2$1@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com&gt about 'FS: WW II
Magnetron GL-5J29 marked Classified, NOS', on Sat, 24 Sep 2005:

But your rice pudding couldn't care two
hoots.

Please use only SI units. The SI unit of concern is the angst. One hoot
is equal to 0.5 femtoangst.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Robert Baer]

John Woodgate wrote:

I read in sci.electronics.design that Jim Adney <jadney@vwtype3.org
wrote (in <nmd9j1d8mjnks2ljfa2pvjfddv9047rstb@4ax.com&gt about 'FS: WW II
Magnetron GL-5J29 marked Classified, NOS', on Fri, 23 Sep 2005:

There is a cylindrical cavity milled in the space between the 2 blocks


That's a neat trick! What type of cutter do you use to make a cavity in
a vacuum?(;-)
One could be flip and say that a vacuum is the absence of matter, or

a cavity in the matter...

 

[Jim Adney]

On Sat, 24 Sep 2005 02:20:03 GMT "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

"Rich, Under the Affluence" wrote:

Anyway, I know they're typically pulsed for radar, and a
microwave oven doesn't care about the waveform; in fact, probably
the raggedier/noisier the better for something like that, but
during a radar pulse, is it putting out a clean signal?

Think about it. If it isn't clean, the echo won't be.

Maybe I'm missing something, but it seems to me that the only thing
we're interested in here is the time between the outgoing pulse and
the echo. This time delay will be the same for all frequencies, since
there is virtually no dispersion (variation in velocity as a function
of frequency) for microwaves in air or vacuum.

Since all frequencies would arrive back together, it really wouldn't
matter whether the transmitted or returning signal was clean or
"dirty." However, to avoid clutter from other signals, it would be
best if the receiver was narrow-band.

OTOH, making the transmitted signal also narrow band would also make
it harder for someone at the other end to detect and would keep the
transmitted signal from interfering with other communications.

Also, as others have mentioned, while a CW signal can be narrow band,
once you modulate/pulse it, you've introuduced sidebands that I don't
think you can get rid of. These are not likely to be much of a
problem, however, because they'll be at frequencies very close to the
carrier since they are at the carrier freq +/- the pulse freq.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Jim Adney]

On Sat, 24 Sep 2005 08:53:58 +0000 (UTC) "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

According to Fourier, there is an inevitable extremely wide spectrum
associated with a continuous pure sine wave amplitude modulated by a
sharp low-repetition-rate pulse.

I understand this, and I agree.

The receiver can't work properly unless it has a very wide bandwith to
accommodate a large proportion of it. Otherwise radar echos from
different distances become blurred and merge with each other on the
screen.

Am I missing something here? I don't see why a narrow band echo
wouldn't give a nice time delay signiture. Is this a Heisenberg
uncertainty principle thing, with f & t the variables?

(delta f) times (delta t) < h/2pi

Is this what we're up against here? I haven't tried to work out the
numbers, but HU doesn't usually come into play until we get to really
tiny quantities.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[me]

Jim Adney <jadney@vwtype3.org> wrote in
news:00hdj1levdbu8cnb2j4cqhnvu25s7cott8@4ax.com:

On Sat, 24 Sep 2005 08:53:58 +0000 (UTC) "Reg Edwards"
g4fgq.regp@ZZZbtinternet.com> wrote:

According to Fourier, there is an inevitable extremely wide spectrum
associated with a continuous pure sine wave amplitude modulated by a
sharp low-repetition-rate pulse.

I understand this, and I agree.

It is not modulated, just a pulse of rf.

The receiver can't work properly unless it has a very wide bandwith to
accommodate a large proportion of it. Otherwise radar echos from
different distances become blurred and merge with each other on the
screen.

The reciever has a narrow bandwidth.

Am I missing something here? I don't see why a narrow band echo
wouldn't give a nice time delay signiture. Is this a Heisenberg
uncertainty principle thing, with f & t the variables?

(delta f) times (delta t) < h/2pi

Is this what we're up against here? I haven't tried to work out the
numbers, but HU doesn't usually come into play until we get to really
tiny quantities.

umm, no....

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

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[Robert Baer]

me wrote:

Jim Adney <jadney@vwtype3.org> wrote in
news:00hdj1levdbu8cnb2j4cqhnvu25s7cott8@4ax.com:


On Sat, 24 Sep 2005 08:53:58 +0000 (UTC) "Reg Edwards"
g4fgq.regp@ZZZbtinternet.com> wrote:


According to Fourier, there is an inevitable extremely wide spectrum
associated with a continuous pure sine wave amplitude modulated by a
sharp low-repetition-rate pulse.

I understand this, and I agree.


It is not modulated, just a pulse of rf.


The receiver can't work properly unless it has a very wide bandwith to
accommodate a large proportion of it. Otherwise radar echos from
different distances become blurred and merge with each other on the
screen.


The reciever has a narrow bandwidth.


Am I missing something here? I don't see why a narrow band echo
wouldn't give a nice time delay signiture. Is this a Heisenberg
uncertainty principle thing, with f & t the variables?

(delta f) times (delta t) < h/2pi

Is this what we're up against here? I haven't tried to work out the
numbers, but HU doesn't usually come into play until we get to really
tiny quantities.



umm, no....


-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------




----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Ahem, "it is not modulated, just a pulse of rf" is incorrect.
Even *one* pulse of RF -->IS<-- modulation.

 

[Tony Williams]

In article <00hdj1levdbu8cnb2j4cqhnvu25s7cott8@4ax.com>,
Jim Adney <jadney@vwtype3.org> wrote:

On Sat, 24 Sep 2005 08:53:58 +0000 (UTC) "Reg Edwards"
g4fgq.regp@ZZZbtinternet.com> wrote:

The receiver can't work properly unless it has a very wide
bandwith to accommodate a large proportion of it. Otherwise
radar echos from different distances become blurred and merge
with each other on the screen.

Am I missing something here? I don't see why a narrow band echo
wouldn't give a nice time delay signiture. Is this a Heisenberg
uncertainty principle thing, with f & t the variables?

(delta f) times (delta t) < h/2pi

<http://www.doramusic.com/patents/579154.htm> might be
an interesting read. Patent first applied for in 1940.

--
Tony Williams.

 

[Gary Schafer]

On Sun, 25 Sep 2005 21:45:50 -0500, Jim Adney <jadney@vwtype3.org>
wrote:

On Sat, 24 Sep 2005 08:53:58 +0000 (UTC) "Reg Edwards"
g4fgq.regp@ZZZbtinternet.com> wrote:

According to Fourier, there is an inevitable extremely wide spectrum
associated with a continuous pure sine wave amplitude modulated by a
sharp low-repetition-rate pulse.

I understand this, and I agree.

The receiver can't work properly unless it has a very wide bandwith to
accommodate a large proportion of it. Otherwise radar echos from
different distances become blurred and merge with each other on the
screen.

Am I missing something here? I don't see why a narrow band echo
wouldn't give a nice time delay signiture. Is this a Heisenberg
uncertainty principle thing, with f & t the variables?

(delta f) times (delta t) < h/2pi

Is this what we're up against here? I haven't tried to work out the
numbers, but HU doesn't usually come into play until we get to really
tiny quantities.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
----A clean signal is important. Too much side band energy and more power falls outside of the receiver pass band which gives a weaker return.

The ideal radar pulse, as far as resolution goes, would be a near
perfect square wave which would give excellent range resolution. The
sharper the pulse the more distinct the leading edge is on the return.
However, the problem with a very fast rise time on the pulse is that
it creates many side bands which makes for a wide signal. With a very
wide signal it requires a very wide receiver pass band to reproduce
it.
A wide receiver pass band lowers the receiver usable sensitivity.

So a compromise is done to specifically shape the rise and fall time
of the transmitter pulse that gives sufficient resolution yet reduces
or limits the amount of side band energy. Then a narrower bandwidth
receiver can be used and can accommodate all of the useful energy of
the received pulse. The narrower bandwidth allows for a more sensitive
receiver which equates to more useful range.

If the receiver pass band is too narrow it will not capture all the
necessary side band energy and will "round" off the pulse and range
resolution will be lost.

Regards
Gary K4FMX-------------------------------------------

 

[Hal Murray]

Am I missing something here? I don't see why a narrow band echo
wouldn't give a nice time delay signiture. Is this a Heisenberg
uncertainty principle thing, with f & t the variables?

(delta f) times (delta t) < h/2pi

Is this what we're up against here? I haven't tried to work out the
numbers, but HU doesn't usually come into play until we get to really
tiny quantities.

Yes, there is a fundamental range/velocity ambiguity, and the numbers
are interesting. I'm not smart enough to explain it, at least not
without a lot of work to refresh my memory.

Consider the extreme cases:
1) sharp pulse. You get back a pulse. You can clearly measure
the time delay. But what is the dopler shift?
2) a continous tone. You get back a shifted tone so you can
easily measure the dopler shift. But what is the time delay?

I remember something like the integral of probability of the
target being at some range/velocity is 1 (after normalization).
You can push it around by changing the pulse shape/pattern, but
you can't make it go away. If you push the ambigiuity to someplace
where you are sure the target isn't then you don't have to worry
about it.

Where do the radar geeks hang out?

--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.

 

[Robert Baer]

Hal Murray wrote:

Am I missing something here? I don't see why a narrow band echo
wouldn't give a nice time delay signiture. Is this a Heisenberg
uncertainty principle thing, with f & t the variables?

(delta f) times (delta t) < h/2pi

Is this what we're up against here? I haven't tried to work out the
numbers, but HU doesn't usually come into play until we get to really
tiny quantities.


Yes, there is a fundamental range/velocity ambiguity, and the numbers
are interesting. I'm not smart enough to explain it, at least not
without a lot of work to refresh my memory.

Consider the extreme cases:
1) sharp pulse. You get back a pulse. You can clearly measure
the time delay. But what is the dopler shift?
2) a continous tone. You get back a shifted tone so you can
easily measure the dopler shift. But what is the time delay?

I remember something like the integral of probability of the
target being at some range/velocity is 1 (after normalization).
You can push it around by changing the pulse shape/pattern, but
you can't make it go away. If you push the ambigiuity to someplace
where you are sure the target isn't then you don't have to worry
about it.

Where do the radar geeks hang out?

If one was *really* concerned aboout a "target" that was relatively

fixed, one could use a pulse relatively sharp to determine range fairly
accurately, and then use CW doppler shift to refine the distance within
1/4 wavelength.
The scheme can be repeated as desired, which would resolve
"reasonable" movement of the "target".