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Radio Direction finding by Naval Units in World War II


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During World War II what capability did Naval ships have as far as radio detection ? 

Would maneuvering units have been able to use their low powered radios to communicate without detection by enemy units.

I would think capabilities would vary by time period and navy. 

It would also vary based on if units were using shorter range weaker radios or longer range radios. Modern day it is common to have shorter range,  high frequencies for ship to ship use. And longer range low frequencies more powerful radios to use to contact more distance units. 

If I recall correctly "The" Royal Naval had some success mid to late war locating German U-Boats using radio direction finding. During the period when the German Naval command was setting up wolf packs. 

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DK Brown did a very good book on Royal Navy escorts, which included details of the Sonar and HF/DF fit. Its recently be turned into a Kindle book, so its easy to find now.

https://www.amazon.co.uk/Atlantic-Escorts-Ships-Weapons-Tactics-ebook/dp/B00K5B2W4Q/ref=sr_1_12?qid=1638777586&refinements=p_27%3ADavid+K+Brown&s=digital-text&sr=1-12&text=David+K+Brown

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16 hours ago, sunday said:

The USN used during WWII what they called TBS (talk between ships) radio, using VHF that only went line-of-sight, and HF for longer distances.

When I read "Neptune's Inferno" there was reference to the "talk between ships" being used as the USN moved into contact with the IJN. I wondered if the IJN was able to locate USN ships because of this.

In addition to my original question on ability to direction find RF I also ask about radar system detection. I would think radar would be even easier to locate since transmissions are continuous and stronger.  

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If they only used TBS when in contact, it's not going to compromise location as it would already be known.  There would be other intelligence disadvantages, but the better comms were probably worth it.

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The USN was using the TBS while moving INTO contact trying to set up a surprise attack. They were also using radar which would be more detectable if the IJN had radio detection equipment.

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Would maneuvering units have been able to use their low powered radios to communicate without detection by enemy units.

Not many navies used low powered radio in major warships (light/coastal forces are another matter), the USN's TBS being the exception, that spread across the allied fleets during the course of the war. Being VHF and so basically line of sight, any enemy close enough to DF VHF signals to any real advantage would be within within kissing distance anyway. 
 

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I would think capabilities would vary by time period and navy. 

Well yes, in that I don't think any navies were doing VHF DF against surface targets at sea in WWII. I know the RN/RAF were doing it against KM coastal traffic in the Channel/North Sea, but that was from shore bases. Pure speculation on my part, and can't recall seeing evidence for it, but I would not be surprised if they were doing it in the Med too.  Then if the British were doing it, one has to assume the Germans and Italians were too, but again I can't recall coming across any direct mention of it. 

 

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It would also vary based on if units were using shorter range weaker radios or longer range radios. Modern day it is common to have shorter range,  high frequencies for ship to ship use. And longer range low frequencies more powerful radios to use to contact more distance units. 


Same then, only as I say most navies didn't use the low power VHF/UHF stuff much for comms between major warships. HF morse was the standard for all BVR comms, with flags and lights for WVR comms, and it worked fine for the most part. Flags and lights were no real disadvantage so tactically it didn't make much difference most of the time. Jellicoe might have struggled with them at Jutland, but when you weren't trying to waltz with the largest fleet to ever play close formation drill in the North Sea mostly power by coal, visual comms were a lot more reliable. Coastal Forces were an exception to this, as was of course the TBS system. But AFAIK beyond those exceptions where major warships were fitted with VHF/UHF radio it was mostly for talking to aircraft. 

 

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If I recall correctly "The" Royal Naval had some success mid to late war locating German U-Boats using radio direction finding. During the period when the German Naval command was setting up wolf packs. 

Huff Duff 
I still think Terrain's 'Business in Great Waters' is about as good a single volume to cover all this. But here's my 10 cent precis. Radio was the principal ASW tool in WWII, from the Admiralty's perspective. I make that distinction because other people at other times have a different ideas about what ASW means, but for the RN it boiled down to the safe and timely arrival of merchant shipping - sinking submarines was just a bonus. So from that basis the first line of defence was just trying to insure submarines and shipping didn't cross paths, to that end the Admiralty had a dedicated plot that just tacked U-boats, every U-Boat, all the time. The Submarine Tracking Room was a remarkable operation run by a single bloke for most of the war and they got good.
Anyway, the two principal inputs into the Submarine Plot were both derived from Radio, obliviously Enigma was important, but the real key was RF direction finding. Britain had that global network of bases, which give it a global mesh of RF DF stations, and they also controlled the undersea telegraph network, so they had a quick and secure means of collecting all the DF data.  The net result being a strategic level picture of where U-Boats were transmitting from. If they could then decrypt the signals so much the merrier, but just on the basis of transmission datums supported by other intel, they could usually put a U-number to a transmission and so derive its probable intentions.  This was great for vectoring convoys around U-Boats, but it didn't always work and in any case it was a strategic, or at best operational, level picture. It couldn't generate fixes fast enough or tight enough to be that useful tactically. As in they could tell a Convoy that a U-Boat had broadcast from within 100 mile circle of X coords at Y time, but the time and resolution wasn't there give a better picture - entre Huff Duff.

The RN had been doing DF at sea in a serious was since WWI, and by WWII has pretty good handle on it, but conventional DF with loop antenna from a single station against short form U-Boat signals was not going to pin point submarines either. HF/DF as developed by Watson-Watt to track lighting strikes, used a fixed aerial array and a long glowing phosphor CRT display to give an almost instantaneous bearing on any blip of a transmission though 360 degrees, in a package that could go to sea and survive on an escort. This in turn allowed the convoy commander to know when a U-boat was transmitting around them and go hunting contact boats and the like. Huff Duff was big bad medicine, essentially adding on OTH layer to the escort sensor suite, Huff Duff, then Radar, then ASDIC/SONAR. 
This was most useful of course in situations that saw a U-Boat transmitting in close proximity to a convoy, and it just so happened that Donitz's methods, Wolf Pack in its variations, had one pretty standard element, where ever possible the U-Boat that found a convoy would act as the contact boat. Trailing the convoy, regularly broadcasting its position to call the Wold Pack in - with Huff Duff that become a little.... problematic. On a good day the Escort Commander would just send a destroyer back to sit on the U-Boat for a few hours, keeping it down while the convoy broke contact, before the Destroyer sprinted off to catch up and leave the U-Boat to try and regain contract - on a bad day it was a Hunter Killer Group. 

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Kretchmer apparently read about Admiralty success in the Great War breaking German codes, so resolved that, against orders, he would attack first, then call in convoy sighting reports secondly. I believe it was suggested that this may have been part of the reason for his success, nobody knew he was there because they were not picking him up on HF/DF. Its telling that it was a combination of Radar and Sonar that did for him in the end.

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  • 4 weeks later...

The USN had a sophisticated landbased HF/DF system in the Pacific for WWII, taking advantage of the geographic arc of the west coast from the Aleutians to So. California, plus Hawaii and Samoa. They would take advantage of an operator's "hand" to monitor location and movement of IJN warships to the extent that a failure to receive traffic of major interest, i.e. carriers and battleships, for a certain number of days, an alert would be sounded to all major commands. For years postwar, one could see the towers and buildings of a USN HF/DF station at Ft Ward on Bainbridge Island WA, not removed until the Fort was turned over to the local government  c.1994, leading me to wonder how long it had continued to operate. One answer (1959) is here:  https://stationhypo.com/2016/03/15/nsga-bainbridge-island-wa-disestablished/

Tactically, ASW hunter-killer groups later in the war in both Pacific and Atlantic Fleets were capable of using HF/DF to the extent that they could reroute convoys and/or vector aircraft and DEs from the flagship CVE to 'run down' contacts. Airships such as blimps were also in use through 1962, bringing aerial radars in support of surface HK task forces, which also used their TBF torpedo bombers equipped with radar for ASW work.

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Adm Fluckey writes in his recollections of the USS Barb's 12th war patrol near the sea of Ochotsk that he sent his reports by radio only if he had been spotted already and the Japanese knew that he was in the area. That indicates that all all major powers in WW2 had the capability to triangulate even relatively short radio transmissions.

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In his memoir, Submarine Commander, Paul Schratz mentioned the Japanese having radar detection capability; the first I've read about this.

Absent a system like TBS, how did ships securely communicate at night?  Light signals could be seen a long way off, so did they just carefully use low or red light and hope?

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5 hours ago, Ssnake said:

Adm Fluckey writes in his recollections of the USS Barb's 12th war patrol near the sea of Ochotsk that he sent his reports by radio only if he had been spotted already and the Japanese knew that he was in the area. That indicates that all all major powers in WW2 had the capability to triangulate even relatively short radio transmissions.

Even if it had turned out the Japanese had no similar EW capability, it would be prudent to assume they did.

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On 1/4/2022 at 12:13 PM, Ssnake said:

Adm Fluckey writes in his recollections of the USS Barb's 12th war patrol near the sea of Ochotsk that he sent his reports by radio only if he had been spotted already and the Japanese knew that he was in the area. That indicates that all all major powers in WW2 had the capability to triangulate even relatively short radio transmissions.

Even if you don't have true DF capabilities the signal strength alone will reveal that you are around "here somewhere".

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If you have a loop antenna, and transmissions are long enough, you can get two bearings 180 degrees apart.  Unless there are other circumstances or information, you can't tell which one is correct.

Edited by shep854
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Canada built HF direction finding units in Newfoundland. The stations would report the bearing they picked it up on, then a Convoy plotting room would take the bearings from a couple of stations and plot it, sending out coded signals to convoys in the area so they could alter to avoid the subs. I read a report that the smaller ships like corvettes had a hard time DFing signals as the rolled to much, creating to much uncertainty in the bearing.

If a good bearing was had on a sub nearby by a frigate or destroyer would run down that bearing to force the sub under. Corvette would do it, but struggled to catch up to the convoy that had altered course and increased speed.

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1 hour ago, shep854 said:

If you have a loop antenna, and transmissions are long enough, you can get two bearings 180 degrees apart.  Unless there are other circumstances or information, you can't tell which one is correct.

That was start of the art in the 20's, then some smart cookie got the bearing and turned the antenna 90 degrees and used the directional indicator to work out which was the correct bearing. It didn't take long after that for other smarty pants with more resources to put a second loop at 90 degrees to the first and bingo instant bearing discrimination. Took some folks a while to catch on however. 

Best I can tell by 1945 the IJN had operational radar detectors at sea, in aircraft and on land, mostly based on the E-27 receiver,  with a range of antenna  inc metox. None of which is much of a surprise, the Japanese were pretty competent at radio themselves and would have been seeing the latest German kit on U-Boats within months of it being deployed.

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32 minutes ago, Colin said:

Canada built HF direction finding units in Newfoundland. The stations would report the bearing they picked it up on, then a Convoy plotting room would take the bearings from a couple of stations and plot it, sending out coded signals to convoys in the area so they could alter to avoid the subs. I read a report that the smaller ships like corvettes had a hard time DFing signals as the rolled to much, creating to much uncertainty in the bearing.

If a good bearing was had on a sub nearby by a frigate or destroyer would run down that bearing to force the sub under. Corvette would do it, but struggled to catch up to the convoy that had altered course and increased speed.

Colin those Canadian stations were part of a worldwide RN network, so working with others in Bermuda, the UK, South Africa, Gib, Malta, Egypt, Aden, India, Aust, NZ, Fijji (IIRC) and probably others I forget - and then the US stations joined in the fun. Depending on time of day and atmospherics they could get cross bearings from almost anywhere. Accuracy varied with range of course, but they were all helpful as not every station would hear every transmission and even a fuzzy bearing from the right quadrant could tell north form South Atlantic and help narrow things down. :D

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When I was in the Civil Air Patrol, I tracked down emergency locator transmitters (ELTs) with my handheld radio, using my body as a partial block to weaken the signal when I was turned away from the source.  Crude, but workable if I were patient.  It's also possible to get bearings with comm radios in a plane; simply turn the aircraft and note when a wing blanked out the signal.

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