U-boat/BdU communications

[dfscott]

Since we're attending to simulate communications with BdU as much as possible, I was curious about the logistics around how BdU and U-boats actually communicated. For example,

1) We always know exactly how much tonnage we've sunk since SH3 tells us. However, did real u-boat captains actually calculate this and include tonnage totals in their reports, or did they just report "two large merchants sunk" or something equally vague?

2) If a u-boat's enigma machine was damaged/destroyed, did they continue their patrol under their last known orders or was that cause for them to return to base?

3) Since we're posting in a forum, we can send/receive messages whether we're submerged or not. However, I imagine that a boat at 100m wouldn't be able to send or receive, correct? I know that at some point, submarines were equipped with VLF antennas that allowed them to receive brief messages at depth, usually just to tell them to surface and get the "real" message. However, did BDU just broadcast messages to subs constantly since there was no way to tell if they were listening (i.e., surfaced)?

[smilinicon]

I've been spending some time reading through this site:

http://www.uboatarchive.net/BDUKTB.htm

I saw some interesting items in prisoner interrogations about communications... I'll try to find them again for the discussion. I have not yet gone through the page I linked to, but hopefully something there will provide answers.

While simming, I always send a message when surfaced and this early in the war, I should probably be surfaced to simulate receiving from BdU too. I have noted in my reading that ship tonnages were estimated. I try to report them as such also, rounding up or down. I started using Sh3 tonnages later on and in the future I'll stick to estimates for immersion and exact tonnage for final reporting.

[smilinicon]

http://www.uboatarchive.net/U-570INT.htm

there are some items about communications in this article. Scroll down to page 25.

[smilinicon]

found a reference to a 'Sinking Signal' given by U-118.

"KR KR" - emergency signal code.

(position)

"X X X" - 'boat is sinking'

(codename of boat)

it said boat codename was given verbally before the patrol.

let's hope we don't need this one :)

[dfscott]

http://www.uboatarchive.net/U-570INT.htm

there are some items about communications in this article. Scroll down to page 25.

Interesting stuff. I also found this article on uboat.net:
http://www.uboat.net/articles/35.html

Particularly interesting is this bit:
After the WW1 scientists continued researching of underwater radio communication. They made possible "one way" underwater communication between land radio station and submerged submarine, if antenna of the submarine was deep up to 10 to 20 metres from sea surface. The "one way" communication means that the land station could transmit messages to the submarine, and the submarine was able just to receive the messages. The submarine was not able to transmit messages to the land station. Two main reasons for "one way" communication were if you communicate on frequencies of Very Low Frequency band (VLF) you need very long wire antenna and transmitter able to generate strong powered radio wave. Submarines had not enough length for the VLF antenna. Also, the submarines had not enough strong power supply for VLF transmitters.

During the WW2 underwater radio communication was very useful. Submarines were able to receive messages from their commands without surfacing, i.e. the submarines could been submerged. The submarines could not be detected by radar, and the Allies' direction finders could not detect submarines' positions because the submarines were not using their radio transmitters, just receivers. But because of the "one way" communication, it was specific organized traffic, by previously determined scheme.

Messages were marked by serial numbers, each serial number for the each submarine. The messages were transmitted without confirmation of reception, mostly by night, sometimes from the few transmitters simultaneously. Submarine knew time of transmitting, when the time was coming, the submarine was on right depth, and radio operators were monitoring the radio transmitter with best power of radio signal. Efficiency of reception was 90%. It means that 90% of all messages were received successfully. It was very good, indeed.

[Laufen zum Ziel]

Good information.

Ken

[smilinicon]

another idea if OK.. it comes from reading the real BdU and U boat messages.


BdU workload could be lightened a bit by simulating BdU messages to all (or certain) boats that were broadcast at certain hours, instead of replys to indivdual messages. Several messages could be logged (the decoded enigma thread will do this), and then one messages could send orders to each individual, several or all boats.*

Enigma messages marked SDD (urgent) would be another matter.

I note the real messages used captain's names and not Uboat numbers and a codename was given to certain groups of boats. I mention this as food for thought and do not imply changes are needed.

I also note that a secret codname was used in emergency messages to hide info from the enemy. Could be a nice addition to the excellent orders provided.


* see U-505 messages thread for examples.

[dfscott]

another idea if OK.. it comes from reading the real BdU and U boat messages.


BdU workload could be lightened a bit by simulating BdU messages to all (or certain) boats that were broadcast at certain hours, instead of replys to indivdual messages. Several messages could be logged (the decoded enigma thread will do this), and then one messages could send orders to each individual, several or all boats.

I thought the exact same thing when I was reading the 505 transcripts...