The Cavety Magnetron

[Kyle Holgate]

"the most valuable cargo ever brought to our shores". Was it? How might WW2 have progressed if this device either wasn't invented at all or the US didn't have it. Worse yet, what if the Germans invented it instead of the British.

[old_pop2000]

"the most valuable cargo ever brought to our shores". Was it? How might WW2 have progressed if this device either wasn't invented at all or the US didn't have it. Worse yet, what if the Germans invented it instead of the British.

The theory of the resonant cavity magnetron actually dates back to theoretical work done by a German physicist named Habann who developed a split tube magnetron in 1921 that worked on 3cm. The patents were filed in the US. Dr. H.E. Hollmann filed a patent for a multicavity magnetron far ahead of the English Randall and Boots.

Now as far as the detection of moving objects, Huelsmeyer of Germany developed and patented a Xmitter-Rcvr for detecting metallic objects at a distance in 1904. It was more of an anti-collision device. Many of the early attempts at using Radio waves to detect objects did not use a magnetron.

However, in point of fact, the first real practical apparatus for the purpose of detection of objects was based on the use of a high frequency oscillator using principle of the cavity resonator or magnetron.

Without this relatively small and light weight unit (not if you have ever had to lift it out of the cabinet;)), airborne radar probably would not have been a possibility. There were other ways to develop high frequency oscillations and amplifying them for transmission through an antenna array, but there were not compact all in one designs.

:D

[Kyle Holgate]

The theory of the resonant cavity magnetron actually dates back to theoretical work done by a German physicist named Habann who developed a split tube magnetron in 1921 that worked on 3cm. The patents were filed in the US. Dr. H.E. Hollmann filed a patent for a multicavity magnetron far ahead of the English Randall and Boots.

Now as far as the detection of moving objects, Huelsmeyer of Germany developed and patented a Xmitter-Rcvr for detecting metallic objects at a distance in 1904. It was more of an anti-collision device. Many of the early attempts at using Radio waves to detect objects did not use a magnetron.

However, in point of fact, the first real practical apparatus for the purpose of detection of objects was based on the use of a high frequency oscillator using principle of the cavity resonator or magnetron.

Without this relatively small and light weight unit (not if you have ever had to lift it out of the cabinet;)), airborne radar probably would not have been a possibility. There were other ways to develop high frequency oscillations and amplifying them for transmission through an antenna array, but there were not compact all in one designs.

:D

The Germans had airborn radar without the cavity magnetron. They were limited to lower frequency and/or lower power output across the board - as were the Japanese.
I wasn't really trying to get into the history of Radar here, but what the heck :p

[old_pop2000]

The Germans had airborn radar without the cavity magnetron. They were limited to lower frequency and/or lower power output across the board - as were the Japanese.
I wasn't really trying to get into the history of Radar here, but what the heck :p

This is true, the Lichtenstein FuG 202 radar used two RS394 triodes with the anodes modulated as a push-pull oscillator. The cathode, anode and grids were tuned. PRF was 2700 hz with a PK power of 450 watts.

The Allied radars that used the Maggie, had a much higher frequency, better range and better range resolution than the Lichtenstein, but you could have still had airborne radar, that is true. The Germans did have the maggie. Specifically the RD2Md split-anode magnetron. They also developed a copy of the British CV64 and gave the LMS10 designation.

[Mike Malanaphy]

"the most valuable cargo ever brought to our shores". Was it? How might WW2 have progressed if this device either wasn't invented at all or the US didn't have it. Worse yet, what if the Germans invented it instead of the British.

Hi Kyle,

I would agree. Two war winners - centimetric radar and proximity fuses. Centimetric radar on escorts and aircraft defeated the U boats. The Battle of the Atlantic could have been won without Ultra, but not without centimetric radar. In the Pacific, SJ radar made US submarines the master of the Japanese merchant marine allowing Lockwood to due what Doenitz could only dream of, winning the tonnage war. Proximity AA fuses improved the effectiveness of heavy AA fire by magnitudes and allowed almost impeneterable umbrella of steel over US Navy task forces.

[john964]

Hi Kyle,

I would agree. Two war winners - centimetric radar and proximity fuses. Centimetric radar on escorts and aircraft defeated the U boats. The Battle of the Atlantic could have been won without Ultra, but not without centimetric radar. In the Pacific, SJ radar made US submarines the master of the Japanese merchant marine allowing Lockwood to due what Doenitz could only dream of, winning the tonnage war. Proximity AA fuses improved the effectiveness of heavy AA fire by magnitudes and allowed almost impenetrable umbrella of steel over US Navy task forces.From post war testing of proximity fuses, it improved the lethality by 3 and 5 times. Three times early war mechanical timed fuses and five times contact fuses.

[old_pop2000]

From post war testing of proximity fuses, it improved the lethality by 3 and 5 times. Three times early war mechanical timed fuses and five times contact fuses.

Operational analysis did prove that the VT fuze was three times more effective than the timed fuze. One analysis showed that a twin engined bomber presented a lethal area of 90 square feet to a 40 mm but to a Mark 53 VT fuse it presented 3900 square feet. This was based on a reliability of 65% in the VT fuse. The cruiser Helena achieved the first confirmed kill on 5 January 1943.

[Mike Malanaphy]

Operational analysis did prove that the VT fuze was three times more effective than the timed fuze. One analysis showed that a twin engined bomber presented a lethal area of 90 square feet to a 40 mm but to a Mark 53 VT fuse it presented 3900 square feet. This was based on a reliability of 65% in the VT fuse. The cruiser Helena achieved the first confirmed kill on 5 January 1943.

Hi Dennis,

The USN also enjoyed the advantage of the superb Mk 37 fire control system. Plotting a continuous fire control solution pretty much allowed the 5" gun to fire effectively at near it's maximum rate.

[Kyle Holgate]

So... Allies without the magnetron? You could still detect U-boats but the prosecution of them is much more difficult. AA still works, but presumably far more Kamikaze get through the flak. Can the USN subs have radar at all without it?

2nd scenario - the Germans and/or Japanese have the device instead of the allies. A war winner? (I don't think so, but bringing up the question for discussion).

[old_pop2000]

So... Allies without the magnetron? You could still detect U-boats but the prosecution of them is much more difficult. AA still works, but presumably far more Kamikaze get through the flak. Can the USN subs have radar at all without it?

2nd scenario - the Germans and/or Japanese have the device instead of the allies. A war winner? (I don't think so, but bringing up the question for discussion).

Many historians have indicated that the invention and application of the resonant cavity magnetron was the most important technical innovation of the war even greater than the A bomb. The maggie provided more power, higher frequency for greater range and range resolution and was far more rugged. It was also heavier(Trust me on that point). We used the Raytheon QK-338 magnetron which developed about 5 MW of power at around 2900 MHZ. One point about the maggies is that they did not have the ability to change frequency like the TWT and Klystron combination. This eliminated some of the better ways of developing ECCM by the use frequency agility.

We know that the Germans and Japanese had developed or were working on the magnetron, so it is possible that your 2nd scenario could have occurred. The Japanese magnetron research commenced in 1932 at the Tokyo Shibaura Electric Co. A two split maggie was developed. Output was 200 watts at 20cm. Later versions exceeded 500 watts. Osaka Electric did extensive research and development in the area of Maggies.

[Kyle Holgate]

Many historians have indicated that the invention and application of the resonant cavity magnetron was the most important technical innovation of the war even greater than the A bomb. The maggie provided more power, higher frequency for greater range and range resolution and was far more rugged. It was also heavier(Trust me on that point). We used the Raytheon QK-338 magnetron which developed about 5 MW of power at around 2900 MHZ. One point about the maggies is that they did not have the ability to change frequency like the TWT and Klystron combination. This eliminated some of the better ways of developing ECCM by the use frequency agility.

We know that the Germans and Japanese had developed or were working on the magnetron, so it is possible that your 2nd scenario could have occurred. The Japanese magnetron research commenced in 1932 at the Tokyo Shibaura Electric Co. A two split maggie was developed. Output was 200 watts at 20cm. Later versions exceeded 500 watts. Osaka Electric did extensive research and development in the area of Maggies.

The Submarine battle of the Pacific would have been considerably different. I wonder how the US would have reacted had Japanese radar made the US subs as vulnerable as their atlantic U-boat counterparts. I'm sure the US would have managed to field radar detectors (ESM) sooner but if Japanese patrols can keep the subs down - they're much less effective. Would we have seen a USN elektroboot?

[old_pop2000]

The Submarine battle of the Pacific would have been considerably different. I wonder how the US would have reacted had Japanese radar made the US subs as vulnerable as their atlantic U-boat counterparts. I'm sure the US would have managed to field radar detectors (ESM) sooner but if Japanese patrols can keep the subs down - they're much less effective. Would we have seen a USN elektroboot?

The Japanese did research on a radar for patrol planes with a wave length of 2 meters. It was given the H-6 designation. They also researched and had developed the FK-3 for 2/3 seater aircraft. Neither was in service at the end of the war. Most of the production electronic units were radar detectors and indicators for said equipment, direction finders and one radar, the type 22-C.

They had three airborne sets; the type 51 10cm pathfinder, the FD-2 night fighter set at 500 MC and Gyuku-2 night fighter set at 150 MC. None were in production and the standard set was the Type 3, Air Mark 6, Model 4 or H-6 on 150 Mc. They also had an iff set in development, with about 600 units built.

Had they really gotten started prior to the war commencing, it would be interesting to see how this might transpire. Possibly this is something that could be added to SAS or NAW as a possiblity. Adding fighter direction radar or airborne search to the Mavis or Emily flying boats might make for some interesting changes in the Coral Sea and other areas, especially Guadalcanal.

[Mike Malanaphy]

So... Allies without the magnetron? You could still detect U-boats but the prosecution of them is much more difficult. AA still works, but presumably far more Kamikaze get through the flak. Can the USN subs have radar at all without it?

2nd scenario - the Germans and/or Japanese have the device instead of the allies. A war winner? (I don't think so, but bringing up the question for discussion).

Hi Kyls,

All other things being equal, the Allies still win. There were effective 50 cm radar sets for surface search and fire control and meter length radars were used well after the war in RN and USN ships for long range air search. The imponderable here is who is quicker on the draw in terms of counter measures. The larger American scientific/production base put us well ahead of our opponents in either case.

The magnetron would be of more value to the Germans than the Japanese I believe for AI radar, flak, and a set small enough to be useful on U Boats. The Japanese had developed a centimetric length radar, but were unable to develop a way of transmitting enough power to make it useful. The Germans believed that the magnetron was not a useful avenue of research and were suprised when they found one in a crashed British bomber in February, 1943. Despite a comprehensive suite of radar detectors, it seems to have little helped Scharnhorst avoid her pursuers.

I'll have to check when I get home, but I thought that the Japanese had been able to field a small amount of radar equipped search planes by war's end. Even had they, there weren't enough aircraft and crews to provide adequate coverage. Oddly enough, US submarines went to war with the SD omni directional AW radar that many skippers felt the Japanese could home in on and were reluctant to use it. In 1944, the USS Batfish sank several Japanese submarines based upon Ultra information, but she located them at night by cruising at radar depth by picking up their radar pulses. The use of radar was definitely a double edged sword if your enemy was canny to it's characteristics.

[Kyle Holgate]

Hi Kyls,

All other things being equal, the Allies still win. There were effective 50 cm radar sets for surface search and fire control and meter length radars were used well after the war in RN and USN ships for long range air search. The imponderable here is who is quicker on the draw in terms of counter measures. The larger American scientific/production base put us well ahead of our opponents in either case.

The magnetron would be of more value to the Germans than the Japanese I believe for AI radar, flak, and a set small enough to be useful on U Boats. The Japanese had developed a centimetric length radar, but were unable to develop a way of transmitting enough power to make it useful. The Germans believed that the magnetron was not a useful avenue of research and were suprised when they found one in a crashed British bomber in February, 1943. Despite a comprehensive suite of radar detectors, it seems to have little helped Scharnhorst avoid her pursuers.

I'll have to check when I get home, but I thought that the Japanese had been able to field a small amount of radar equipped search planes by war's end. Even had they, there weren't enough aircraft and crews to provide adequate coverage. Oddly enough, US submarines went to war with the SD omni directional AW radar that many skippers felt the Japanese could home in on and were reluctant to use it. In 1944, the USS Batfish sank several Japanese submarines based upon Ultra information, but she located them at night by cruising at radar depth by picking up their radar pulses. The use of radar was definitely a double edged sword if your enemy was canny to it's characteristics.

As a former Electronics Warfare tech - I often wonder why the Japanese and Germans didn't spend more effort with EW. With the Allies radar blasting away one could take considerable advantage of intercepting the radar. In modern day when all sides have it as well as radar detecting and analyzing equipment - it's common for ships and planes to leave the radar off. Much like a sub pinging with active sonar, radar can be intercepted by a contact well outside the range at which it would detect it. With a bit of work (and math) one can even get a fairly good course and speed of the radar emitter.

[old_pop2000]

Hi Kyls,


I'll have to check when I get home, but I thought that the Japanese had been able to field a small amount of radar equipped search planes by war's end. Even had they, there weren't enough aircraft and crews to provide adequate coverage. Oddly enough, US submarines went to war with the SD omni directional AW radar that many skippers felt the Japanese could home in on and were reluctant to use it. In 1944, the USS Batfish sank several Japanese submarines based upon Ultra information, but she located them at night by cruising at radar depth by picking up their radar pulses. The use of radar was definitely a double edged sword if your enemy was canny to it's characteristics.

The Japanese did field the MK VI Model III and Model IV. It was an airborne ASV, AI radar first used in a Betty bomber but later installed in the H8K2 Emily flying boats. It could detect land at 90 miles, BB @ 50, DD @30, A/C @ 30 miles. Pk power was 5KW. Weighed in excess of 220 lbs. Two stages of RF and four IF with 11 tubes. BW of 300 KC.

They did have an extensive array of radar detectors and an analysis of previous battles shows they were aware of our extensive use by DDs and issue instructions on how to counter in battle.

Pardon my Intrusion

[Kyle Holgate]

I have read war reports from USN subs talking about using radar intercept (ESM) gear and "seeing" Japanese aircraft searching with radar.