Author Topic: 35GHz Magnetron...  (Read 19385 times)

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Offline tron9000Topic starter

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35GHz Magnetron...
« on: June 04, 2015, 03:46:47 pm »
SO clearing out the "shed" at work and my boss hands me a lump of metal and says: "want a 35GHz magnetron?"

:wtf:

He said he bought it second hand from a US navy surplus to build a radar project commission by someone in the department: £5000-each!! this was 20 years ago. (I'll post a pic up soon)

It needs 7000V to run apparently. I read the warnings on the side, this thing is potentially lethal!

....he then hands me another.... :wtf: :wtf:

What the hell do I do with them? I know its a long shot, but: Dave, do/would you want/like one?
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Offline KJDS

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Re: 35GHz Magnetron...
« Reply #1 on: June 04, 2015, 04:03:23 pm »
It would make a fine base for a moonbounce project.

Offline SeanB

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Re: 35GHz Magnetron...
« Reply #2 on: June 04, 2015, 06:22:45 pm »
7kV pulses, not recommended for CW use. You typically run those at a 1% or less duty cycle, discharging a pulse from either a length of coax cable ( for a better rise and fall time) or a capacitor, using something like a thyratron, ignitron or other pulse capable vacuum tube ( low power you can use regular transmitter valves by grossly overrunning them just short of space charge limiting and cathode emission and relying on the low avewrage power to handle the heat) and use another vacuum tube ( with a heater winding isolated to 7kV) to limit the charging current into the pulse network.

You can get pulse outputs that are in the MW range, though the average power will be very low, using simple circuits. You might be able to run it using regular silicon devices, though you probably will have to make a cascode of 10 1kV power devices ( and some scary drive to turn them all on and off simultaneously) to do the pulse drive. At least charging the pulse network can be easy using a SMPS to generate the charge voltage and use HV rectifier diodes to get DC, just turn off the charge circuit before firing.
 

Offline N2IXK

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Re: 35GHz Magnetron...
« Reply #3 on: June 04, 2015, 06:41:16 pm »
Could always mount it behind the grille of your car and do a "drive by" past the cop with a radar gun.  See how the front end of the gun handles a megawatt input pulse.... :-DD
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Offline daqq

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Re: 35GHz Magnetron...
« Reply #4 on: June 04, 2015, 06:46:39 pm »
Quote
Could always mount it behind the grille of your car and do a "drive by" past the cop with a radar gun.  See how the front end of the gun handles a megawatt input pulse.... :-DD
Playing the 'Mine's BIGGER!' game with cops is not a smart game to play... though I'd love to see the results of such a device fired at some consumer tech...

Anyway, great gift!
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Offline SeanB

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Re: 35GHz Magnetron...
« Reply #5 on: June 04, 2015, 07:12:10 pm »
There were some fighter pilots who got into hot water for doing that, reacting to the speed gun triggering the missile warning system, and using the main weapons radar to paint the area. Mostly they got into trouble for going over the speed trap at treetop height, full military power and scaring the kak out of the police hiding in the bushes. More the speed gun being knocked over by jet wash ( low level means you fly under the tree line) or the cop knocking it over waking up from his nap than damage from the RADAR pulse.

I liked that one vehicle with the little square plate front and rear that said, in 2 languages, that the vehicle was authorised to exceed the speed limit.
 

Offline T3sl4co1l

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Re: 35GHz Magnetron...
« Reply #6 on: June 04, 2015, 07:27:08 pm »
Think I'd be surprised if it would be good for moonbounce, moisture in the atmosphere would cut into it pretty well.
http://www.rfcafe.com/references/electrical/images/atm_absorption.gif
Although, even if that's >100km of atmosphere (there and back), it's only 10dB, which is downright reasonable.  No idea if the water concentration is typical under any particular conditions, of course.

Not that you want any dB after a trip like that, but if you're timing moonbounce and nothing else, you don't need any bandwidth.

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Offline Alexei.Polkhanov

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Re: 35GHz Magnetron...
« Reply #7 on: June 04, 2015, 08:49:14 pm »
I wonder if it is designed for a Radar of some sort like a weather radar because 35GHz is very good for detecting clouds, rain etc.. To use it you'll need a pulse generator, not really trivial thing to build. You should put it for sale Ebay - at least collectors maybe interested.
There are "police" speed radars and red light cameras that use 34.200–35.200 GHz range but they are very uncommon. I have not seen police in North America using RF radars - they almost all use LIDAR these days.
 

Offline T3sl4co1l

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Re: 35GHz Magnetron...
« Reply #8 on: June 04, 2015, 08:59:37 pm »
I wonder if your boss has any of the hardware that went with them (PFNs, modulator tubes or hydrogen thyratrons, etc.), too.

Modulator tubes are fairly impressive beats.  For 50W of heater power, and all of of 100W plate dissipation, you get a plate voltage rating of 20kV and a peak current of 10A+ (with a saturation voltage in the <2kV range, so the efficiency can still be good).  Sadly, they're really just not good for much besides radar. ;D

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Offline BennVenn

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Re: 35GHz Magnetron...
« Reply #9 on: June 04, 2015, 10:36:34 pm »
RADAR magnetrons are commonly driven with solid state pulse forming networks. Vacuum tubes and high voltage SCR's aren't requried (for small magnetrons in your output range).

One of the RADAR's I maintain at work operates at similar powers around 1/4 the frequency. Basicly, a HV power supply generates approx 300vdc and will charge an array of capacitors (selected via a series of relays according to the pulse duration you select - and therefore range). This 300vdc is dumped via a SCR into a L-R pulse forming network, then into a pulse transformer (toroid) where it is boosted to a few KV to drive the magnetron.

The whole circuit is made of discrete components and would fit in a shoe box with room to spare.

Coupling the RF away from you would be the biggest challenge IMO, waveguide, circulators, TR cell's etc...
 

Offline Melt-O-Tronic

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Re: 35GHz Magnetron...
« Reply #10 on: June 07, 2015, 12:58:46 am »
Think I'd be surprised if it would be good for moonbounce, moisture in the atmosphere would cut into it pretty well.
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You could think of it more as a lunar cheese melter.  Then the return signal wouldn't even matter.   :)
 

Offline Alexei.Polkhanov

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Re: 35GHz Magnetron...
« Reply #11 on: June 07, 2015, 02:44:12 am »
"Soviets, apparently just for practice, have set the radar to track the moon for as much as half an hour. This makes the intercept job much easier, as we then see the signal continuously rather than in short bursts as the beam swings by the moon....". Full story is here: https://www.cia.gov/library/center-for-the-study-of-intelligence/kent-csi/vol11no2/html/v11i2a05p_0001.htm

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Offline boz

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Re: 35GHz Magnetron...
« Reply #12 on: June 07, 2015, 03:17:12 am »
Fearless diver and computer genius
 

Offline amyk

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Re: 35GHz Magnetron...
« Reply #13 on: June 07, 2015, 03:11:18 pm »
How about a microwave oven...
 

Offline Refrigerator

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Re: 35GHz Magnetron...
« Reply #14 on: June 07, 2015, 04:03:35 pm »
How about a microwave oven...
Could roast a whole pig in one second.
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Offline NiHaoMike

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Re: 35GHz Magnetron...
« Reply #15 on: June 08, 2015, 05:11:52 am »
Probably way too complicated, but what about a microwave ignition gasoline engine? I actually remember reading about it in an effort to boost gasoline engine efficiency.
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Offline tron9000Topic starter

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Re: 35GHz Magnetron...
« Reply #16 on: June 08, 2015, 08:09:56 am »
lol! these are all really good suggestions, I like the idea of firing it at consumer products, a sort of will til blend? but with a microwave transmitter: Will it fry?
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Offline poida_pie

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Re: 35GHz Magnetron...
« Reply #17 on: June 08, 2015, 08:33:02 am »
microwave oven fuckery:

 

Offline TerraHertz

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Re: 35GHz Magnetron...
« Reply #18 on: June 08, 2015, 01:06:37 pm »
SO clearing out the "shed" at work and my boss hands me a lump of metal and says: "want a 35GHz magnetron?"

It needs 7000V to run apparently. I read the warnings on the side, this thing is potentially lethal!

....he then hands me another.... :wtf: :wtf:

What the hell do I do with them? I know its a long shot, but: Dave, do/would you want/like one?

Step 1: Take photos.
Step 2: Post photos here.
Step 3: ? ? ?
Step 4: Profit!!!
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Offline TiN

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Re: 35GHz Magnetron...
« Reply #19 on: June 08, 2015, 02:34:08 pm »
Could at least take some nice pron photos for us :D O0
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Offline tron9000Topic starter

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Re: 35GHz Magnetron...
« Reply #20 on: June 09, 2015, 08:13:43 am »
yes sorry, been busy doing daddy duties, photo's will be up after today.
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Offline McBryce

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Re: 35GHz Magnetron...
« Reply #21 on: June 09, 2015, 08:52:14 am »
How about a microwave oven...
Could roast a whole pig in one second.

Not to mention the fact that the pig was in the Scottish highlands at the time :D

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Offline tron9000Topic starter

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Re: 35GHz Magnetron...
« Reply #22 on: June 12, 2015, 07:56:01 am »
sorry guys! Been a bit delayed, I promise to put some photo's up by the end of today.
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Offline Zero999

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Re: 35GHz Magnetron...
« Reply #23 on: June 12, 2015, 08:47:06 am »
How about a microwave oven...
It wouldn't cook food in the same manner as a conventional microwave oven. The higher frequency radiation would be absorbed nearer to the surface of the food so it would be across between a grill and a microwave.
 

Offline Refrigerator

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Re: 35GHz Magnetron...
« Reply #24 on: June 12, 2015, 11:56:01 am »
How about a microwave oven...
It wouldn't cook food in the same manner as a conventional microwave oven. The higher frequency radiation would be absorbed nearer to the surface of the food so it would be across between a grill and a microwave.
Now let's start a KS campaign for this and let's call the product " the grillwave ".
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