Forum: Midget Submarines - General
Topic: Midget submarine radio transmissions
started by: Ken Hackler

Posted by Ken Hackler on Mar. 17 2004,10:28
February 21, 2004



(1)  National Archives II (NARA), College Park, MD, RG38 CNSG Active Stations Box 10 Station H Operator’s Reports 3200/6 2 of 7.

(2)  National Archives II (NARA), College Park, MD, RG38 CNSG Library Box 159 Station H Supervisor’s Reports 5830/33 2 of 7.

The past few days I have been looking at the STATION H Supervisor’s Report for the DAY WATCH on 8 and 10 December 1941 (kindly provided by Phil Jacobsen). I have also been looking at twenty-three pages of the actual radio operator’s rough logs from STATION H that the Supervisor’s Report was taken from (also provided by Phil).

My reasoning is that the I-16 midget (Midget E) was able to send two messages on the night of December 7 / 8, and maybe Midget D (found in 1960) sent a message or two at some point. Just maybe we’d get lucky and STATION H picked something up.

The Operator’s Logs (December 6 – 9) amount to 23 pages, with over 200 Japanese call signs recorded. They are mostly coded, and most do not contain a text message, but rather, a reference to an actual message someplace else. Some are simple administrative housekeeping messages, such as “How strong or clear can you hear me?” which shows on the logs as “KA N ?” The response is normally KA N followed by a number from 0 to 5 indicating the strength of the signal. So the typical response might be “KA N 3.”

Another example is “I do not have messages for you” which appears as “MU FU,” or “I have messages for you” which appears as “YU FU.”  There are a lot of those. Other very common messages / phrases are “SA RA” which means “Repeat,” and “KU RE” which means “Go Ahead.”

An example of a radio intercept as listed in the operator’s logs is this one on 6 DEC 41 (Tokyo date and time):

Note - - I added headings in bold and underlined for clarity. There are no such headings on the original documents. Ken.

To                            From
HA FU 6        DE         A NE 3

KA N ?  N M

Time               Frequency
1602                      8040M

This is from A NE 3 to HA FU 6 asking how they hear him (“KA N ?”) at 1602 Tokyo time on frequency 8040M. According to the handwritten notes on the logs, HA FU 6 is the Tokyo Fleet Broadcast call sign. I do not know who A NE 3 might be, but since they are talking to Tokyo I would assume it is a major command or ship rather than an airplane or submarine. Based on the Tokyo time of 1602 on 6 December, this was sent at 8:32 PM (2032) on 5 December 1941 Honolulu time. Remember, Tokyo was a day ahead and 4 ½ hours behind Honolulu.

There are no bearings given on the logs for these (and most) entries. A few have bearings, but remember the difficulties Station H experienced that day with bi-lateral fixes from Heeia. The Navy did have a radio station on Oahu that would give uni-lateral readings, but it was not in communication with Station H most of the morning.

I first reviewed the logs to see if there were any radio intercepts for December 7 at 10:41 PM (2241) [Honolulu date and time]. The reason is that Midget E sent her first message to the I-16 on December 8 at 1811 Tokyo date and time.   However, there is no recorded intercept at 1811.

There was a Tokyo Fleet Broadcast at 1814 (from HA FU 6) to no one in particular, and another intercept at 1815 on frequency 6420A from SU TI 5 to I RE 4 asking how he received ( KA N ? ).

It was too late at night to be an airplane, so I think SU TI 5 was probably a ship in the carrier force because there was a lot of radio traffic between the Commander Carriers (RU SI 8) and SU TI 2.

Also, SU TI 5 received a message from Tokyo (HA FU 6) that said “RECD 1   KI  U  PL” which means “Received 1 message TOP PRECEDENCE.” This was at 2030 on 8 December (Tokyo), which was 0100 on 8 December Honolulu, on frequency 4255A. I would not think a submarine or small command would send and receive messages to Tokyo, but a large command would.

Anyway, there was nothing to indicate that Station H had received Midget E’s first message. But what about her second message? I have seen a number of different times given for that second message, notably by Prange (and Burlingame since Burlingame used Prange extensively). They say the second message was at 0111 on 8 December Honolulu time, which would have been 8:41 PM (2041) in Tokyo, also on 8 December.

I did find an intercept at 2041 Tokyo time in the logs. It was a short administrative message acknowledging receipt of two messages from O SI 0 (O SI Zero) to HO MI 3 on frequency 6346M. The message simply said “RECD 2.”

I do not think this is a midget submarine message because O SI 0 was earlier speaking with Tokyo on 10380A, something a midget submarine could never have done with their short -range radio (est. 50 miles). The other, HO MI 3, exchanged messages with half a dozen stations (call signs) on at least five different frequencies, something else a midget submarine could never have done because they carried crystals for only two frequencies.

The SUBRON 4 Salvage and Inspection Report on the HA-19 (Midget C) said that the radio was removed for separate inspection by the CINCPAC Communications Officer. However, the CINCPAC Communications Officer’s report on Midget C’s radio was never attached to the SUBRON 4 report so we have no idea what frequencies the midget submarines used.

Basically I drew a blank on any Midget E radio transmissions having been intercepted by Station H. I was not too disappointed though, because there was always Midget D to look for someplace in the logs.

Gordon Prange said that Midget E’s radio was the only one that worked because none of the other midget submarines were ever heard from again, but I disagree with Prange because there is no such proof. Three of the other midget submarines would never have had a chance or a reason to transmit.  Consider this:

Midget A was sunk by USS Ward far before she would have considered using her radio.

Midget B was sunk in the harbor by USS Monaghan early on, and she too would not have tried using her radio.

Midget C had no end of problems that day, and Kazuo Sakamaki never tried using his radio by his own admission.

That leaves Midget D, the midget submarine found in 1960. No Japanese ship or submarine reported receiving a message from her, but that doesn't mean she did not try to send a message. Who says her crew didn’t make the attempt before leaving the boat, and no one in the IJN heard them?

I began looking at the radio operator's logs again with nothing in particular in mind other than ignoring the frequencies and call signs that had been identified already as being someone else or somewhere else.

There are few that stand out. Most intercepts are still meaningless to me without knowing what the midget submarine call signs were or what frequencies they used.

One example of an interesting call sign is MU” HE , which appears on the Supervisor’s Report for 8 December (Tokyo date) but not on the actual operator’s logs. The Supervisor’s Report gives the following:

Call Sign     Bearing        Frequency            GCT
MU” HE         186                  4780M               2130
MU” HE         181                  4580M

The time is given as Greenwich Civil Time (GCT), one of the few listed that way. The U.S. Navy used GCT (ZULU time for those who watch JAG). GCT was 10 ½ hours ahead of Honolulu, so the first one listed was logged at 11:00 AM (1100) on the morning of December 7 in Honolulu. There is no time listed for the second.

The bearings pose the same problem as most that day. Since it was from Heeia, was it a good bearing (i.e., uni-lateral) or was it a bi-lateral bearing? If it was bi-lateral, the bearing could have been 186 (almost due south) or it could have been 006 (almost due north).

Also, these two frequencies are not shown in the logs anywhere else, nor is the call sign MU” HE. That tells me this may not have been a common frequency, or else it was not monitored much during the day by Station Hypo. Since the call sign doesn’t appear anywhere else, I make the assumption (again) that maybe Station H simply didn’t catch it transmitting since we know there were hundreds of messages sent by the IJN that day that simply were not intercepted. It may also mean that MU” HE did not transmit much.

Let’s make a few assumptions (humor me).

First, that it was a submarine frequency as suspected by Station H and noted in the Attack Hearings. Next, assume it was a good bearing south of Oahu rather than north.

Where does that leave us?

A few things come to mind. USS Breese and several other DD’s were chasing a submarine periscope about 8 miles south of Oahu that had been sighted by a PT boat at about that time and bearing. Seems interesting to contemplate.

Also, Midget D was found fairly close to the shore at about that bearing from Heeia. Again, interesting to contemplate.

However, in the end there is no way to know since we don't know calls signs or frequencies for the submarines.

Midget D’s radio was presumably recovered when the boat was raised in 1960, but I have never seen a salvage report from the U.S. Navy or JMSDF. Perhaps there is still a way to check the crystals from her radio to see what frequencies they used.

One other item that I find interesting is that the Supervisor’s Report for 10 December has this entry:

Following reported by phone:-

HOKO     -     6510M     -     1837 GCT     -     BEARS 135
TAKA     -         “         -     1937   “       -         “    125
KOU1     -     9320E     -      2035   “       -         “    310

The reason I find these interesting is that they were phoned in. My first question is phoned in from where? Lualualei? If so then that may mean these are good bearings (i.e., uni-lateral), and that is exciting.

IF these are good bearings, HO KO and TA KA have bearings that put them in a direct line from Oahu to a postion just slightly west of Lanai Island, which is exactly where the mother submarines were waiting for three days for the midgets to appear. The times of these two also put them in the right place and time (early morning Honolulu time) on the third day of their wait.

The frequency of 6510 does not appear anywhere else on the operator’s logs, but the call sign HO KO does. On December 7 (Honolulu), this call sign transmitted five messages (no frequency given). The messages were short, and appeared to be a bearing and time at two- or three-minute intervals. The messages are:

WA RI     HO KO     000.0638.HA                      0640  (1110)
HO KO                  000.0641.HA (KA N 2-3        0642   (1112)
HO KO                  004.0643.HA (KA N 2-3)       0644   (1114)
HO KO                  003.0645.HA VE AH R WA RE. N 000 SO2 KO HE HE HE HE HE
HO KO                  355.0647.HA                      0649   (1119)

Note that the fourth message does not list a time.

The times that are shown are Tokyo time, which I have converted to Honolulu time in italics. There are no bearings noted for these intercepted transmissions. To me, they seem to be providing some type of homing signal for an aircraft, given the very short period of time between each transmission and the amount of travel (as indicated in degrees). A ship could not move from 000 degrees to 355 degrees in just a few minutes, but a plane could.

Was this a ship providing a homing service to returning aircrews? The Honolulu time works out for that to be, and the bearings make a lot of sense if a ship was talking a plane back home.

For example, if I were on a ship listening to a plane (and checking its bearing in relation to me by the plane’s radio transmissions since they had no radar) I would be telling the pilot to fly towards me. In this case, the bearings are telling the pilot to fly almost due north. That makes perfect sense because the Japanese planes were returning to carriers north of Oahu at about that time of the morning.

I think this places HO KO north of Oahu on the morning of December 7, 1941, at mid-morning when the planes were returning to their carriers. The radio intercept on December 10 is less exciting in light of that, because the bearings were very likely bi-lateral in that case, and HO KO was more probably northwest of Oahu returning to Japan with the KIDO BUTAI.

That doesn’t help much where TA KA is concerned. If I had to guess I would say that TA KA and HO KO were probably operating close to each other since the frequencies were the same, and the bearings and times were very close. As promising as it appeared at first glance, HO KO and TA KA were probably not submarines, and probably nowhere near Lanai Island.

None of this helps me a lot, but it does open the door to more research. I would really like to know if someone in Japan can check into Midget D’s radio to see if it is still possible to determine what crystals were installed. That may well help identify her.

Posted by Tracy White on Mar. 17 2004,11:59
Excellent work Ken!
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