DF Calibration

charles henry
24th March 2009, 14:06
Flown out to Suez waiting for a ship to arrive I was pressed into service to calibrate the DF of a vessel bround for Port Said. Did it in the "LAKES" and it was a gut churning experience but was lucky and the "curve" was PERFECT.

Anyone else out there was saddled with this job?

Personally I found the Bellini Tosi system much superior to the single loop used on the US vessels although in my opinion the "Lodestone" was a piece of pretty junk, much preferred the old TRF one with the little gonio mounted in the receiver.

de chas(Pint)

K urgess
24th March 2009, 14:14
Never had any problems with the Lodestone. In fact can't remember having to repair one. Usually gave good accurate results. Never really trusted the Lodestar ADF.

I seem to have been lumbered quite a few times with doing a swing for calibrations. At least twice off Robben Island in Table Bay and several times on the Aussie coast.

Ron Stringer
24th March 2009, 16:27
When I worked for MIMCo at South Shields, there was a steady demand for recalibrations from ships that had been in the repair yards of Palmers, Middle Docks and Brigham & Cowan, as well as for first calibrations of newbuildings from Redheads and Hawthorne-Leslie.

The repair jobs almost always got finished on Friday nights so, depending on the tides, the calibration off the beacon at Souter Point was either a Friday evening, or Saturday morning, overtime bonanza. Very popular amongst the technicians and much competed for (league table kept of how many evening and how many weekend calibrations had been given to each guy).

The first calibrations on newbuildings usually fell to the technician that had been fitting out the radio room. In the lean days of the 1960s, with mortgages to pay, every bit of overtime counted.

The actual calibration process (almost always with a MIMCo B-T D/F) was interesting but not particularly challenging. Some of the later, all-aft vessels with heavy-lift derricks, or multiple goal-post masts took a bit of sorting out but as long as the weather stayed fine, it was a cushy number. When the wind got up, especially when it was Northeasterly or Easterly, getting off into the pilot boat was a much more challenging experience.

Klaatu83
24th March 2009, 17:01
By 1989 RDF receivers were no longer required. However, if your ship still had one, it was required to be able to work and still had to be tested every year. The only problem was that the radio beacons were steadily being shut down, so there were getting to be fewer and fewer places where one could test an RDF.

Our captain on the Sealand Quality decided to calibrate our RDF against visual bearings while we were passing by the lighthouse on Sable Island, off the coast of Nova Scotia. He was to record the RDF bearings in the chartroom while I was to call out the visual bearings as we passed the light. All well and good, except that it happened to be a February night in the middle of a blizzard. I spent over an hour and a half out on that miserable bridge wing in the freezing cold and snow and, although we passed within five miles of the light, I never saw a thing.

Shipbuilder
24th March 2009, 19:00
I always hated DF and have been lumbered with a number of calibrations. I always felt that they demanded far too much of it after not putting enough into the calibration. A number of times, when I have suggested to the old man that we could do with a calibration, they have said "OK, we'll do the port side off Dakar southbound and the starboard side on the way back! I never liked that idea and am not even sure a surveyor would accept it, different times, different trim of ship. Another time when I asked old man, he said OK, he would sail in a circle while we did it. About halfway round, they started hoisting all the derricks and in my opinion ruined it all. Often, years ago, when called in the night for DF off West Africa, my comments about night effect were dismissed with "that's only at sunset and sunrise," but I have always though that the sky waves were coming down on top all night!
Another thing that would annoy me was that a small X would be pencilled on the chart where the old man thought we were and DF bearings would be taken until such a time as they fell on top of the X and then everyone was happy.

Another time, when we couldn't find a small island, I was called for DF and it showed it broad on the beam. "must be something wrong with it," was the cry, until sheepish c/o comes in saying he can see top of island visual but faint - on the beam!

Have calibrated several times off Robben Island against my advice, saying experience from Union-Castle said mountain messed it all up. All these Robben Island calibrations were, in fact rubbish, anyone else found that? We never even took check bearings of Robben Island in U-C, so I never knew for sure. It may have simply been one excuse is as good as another.

Most accurate DF I ever sailed with was aboard REINA DEL MAR. It was in the radio room and we often got noon positions on it in the Med.

Bob

Naytikos
25th March 2009, 07:42
I don't know if my experience was common but on every ship, regardless of nationality or flag, I was expected to take D/F bearings when the mates got lost or had no horizon. On a couple of ships the D/F receiver was in the radio room anyway; in most cases they expected me to plot the bearings on the chart as well. The same applied to Loran.
As I recall, on British ships it was only necessary to have a couple of check bearings in each quadrant for the Safety Certificate to be renewed, however with other flagged ships it would be up to the classification surveyor. ABS and DNV usually liked to see a new calibration chart each year but it was always possible to find a beacon at some time in the couple of months preceding the annual safety survey.
Joining one VLCC two months after delivery I found, a few weeks later, the calibration chart to have a wavy line from 000 to 359 entirely to the left of centre. At the next port, the company Port Captain, who had been in attendance during the trials, just shrugged and asked 'does it matter?'
I found the Bellini-Tosi loop assembly was mounted about 5 degs off from the fore-aft line. This was an excuse, the next time we passed close to a beacon, to stop the ship and line her up with the beacon dead ahead so I could realign the loops. That meant teaching my wife to find a null on the goniometer and telling me via walkie-talkie when I had it right.
Those were the days!
I agree with the Sahib; no problems with the Lodestone but the Lodestar was a can of junk.

Tai Pan
25th March 2009, 14:41
It was usual in Bluies to calibrate every voyage using another passing Bluie. Usually in the Indian Ocean. never could get an old man to do a 360 degree turn, however he would pint towards the other ship then swing the stern after passing. could only do one side of course but with plenty of Bluies around did not take long to do the other side.

charles henry
25th March 2009, 14:55
Interesting comments and certainly shows the difference both in ships and attitudes since my seafaring days. "Overtime???" what a difference, we did all the things like batteries, message abstracts, repairs etc on off watch time, never thought there was anything odd about that.

Found the "feel" of the loadstone goniometer far too soft making it difficult to be sure of the zero width.

Three days of dead reconning and then four "EXCELLENT" bearings, big arguement with the 2nd mate who felt it was a slur on his dead reconning.
Next day good sights - I won a five quid bet..... ah.... memories
de chas (Pint)

M29
25th March 2009, 17:55
Hi all
Lodestone was a lovely d/f, big dial and very reliable. Never had to fix it.

The Loadstar ADF was also very reliable and if the feedback system was set up properly, the Auto mode worked very well.

In our company, the Lodestone was located in the Radio Room, but as soon as the ADF came in, the installation was in the chart room.

When sailing on the Dart Container ships, the D/F was totally useless due to the calibration changing depending upon how many boxes on deck, and what was in them. We were constantly taking check bearings and the Radio Surveyors in Soton made regular visits. I'm not sure if this was ever resolved as I moved on.

Worse case of poor maintainance I ever saw was when I sailed on a British Rail Ferry for a summer. The loops had several layers of white lead over the insulators and clearly the d/f had not been checked for a couple of years! This was not the only problem in the Radio Department of this ferry and I think if I listed them, many of you would not believe me!

Best wishes

Alan

Trevor Clements
25th March 2009, 18:45
Weren't those Inspectors hot on it though? I was 'ticked off' by Cardiff SRIO a couple of times for not keeping the calibrations up to date. However in my defence it wasn't always easy to get one of the Mates to go up on the monkey island to do the compass readings. We had Decca Navigator on my last ship and they only used DF as a last resort.

Lodestone was easy compared to an RCA DF on the T2, especially when someone (accidentally on purpose) reversed the leads on the rotary converter.
Trevor.

K urgess
25th March 2009, 18:50
Aaah! Memories.
Lead paint all over the DF loops and insulators.
A good excuse for a bit of bronzy. [=P]

Nick Balls
25th March 2009, 18:59
Never had much success with them deep sea myself. However some years ago once got "lost" in a yacht in the southern north sea in dense fog . VERY embarrassing for a professional mariner BUT DF saved the day ! We used what I seem to recall was the Aeronautic Beacon for Schipol Airport and followed that signal straight past the invisible breakwaters into Imuiden ,A small hand held device . The other members of the crew who were not professional were very impressed !!!! I was just glad to get up to the pub !!!!

R651400
25th March 2009, 20:10
Aaah! Memories.Lead paint all over the DF loops and insulators.A good excuse for a bit of bronzy. [=P]
Insulators?? On the sense aerial??

K urgess
25th March 2009, 20:16
Each semi-circular loop section of the Bellini-Tosi was made out of bronze on the one's I saw and were insulated from the junction boxes at the top and bottom by blocks of red insulating material. They may well have been for shock absorbing as well.
I seem to remember "Do Not Paint The Insulators" being cast into part of the base.
These were quite often painted over by over-enthusiastic paint gangs.
Marginally better, but only just, were the ones that had been highly polished as a makee-workee for idle apprentices. [=P]

R651400
25th March 2009, 20:20
. ...ah loop isolation/insulation.

Mimcoman
26th March 2009, 11:57
I was once on watch in the radio when the mate came in and said that it appeared that the df loop had been bumped and knocked off centre "so me and the cadet have adjusted it back so that it's exactly on the ship's fore/aft line again."

Happy days...

Radiomariner
27th March 2009, 00:08
Each semi-circular loop section of the Bellini-Tosi was made out of bronze on the one's I saw and were insulated from the junction boxes at the top and bottom by blocks of red insulating material. They may well have been for shock absorbing as well.
I seem to remember "Do Not Paint The Insulators" being cast into part of the base.
These were quite often painted over by over-enthusiastic paint gangs.
Marginally better, but only just, were the ones that had been highly polished as a makee-workee for idle apprentices. [=P]

The "Do not paint" sign was often totally unreadable due to multiple
layers of paint!
I recall an occasion when it had been decided to remove the thirty odd coats of paint completely from the loops. The result was extremely unsightly so a new coat of paint was decided upon. I was called upon to show the Indian sailor where not to paint, the red insulators. It was getting dark when I inspected the job which looked good. Next morning discovered that the insulators had been highlighted in red paint!

I think it was the same ship we had been through a swarm of very small flies.
Hundreds of these flies were trapped behind the dial of the Loadstone Goniometer (The earlier version with the white dial) Took it all apart but rubbed the plate with the scale on too hard, the printed graduations came off!

K urgess
27th March 2009, 01:01
I think it was the same ship we had been through a swarm of very small flies.
Hundreds of these flies were trapped behind the dial of the Loadstone Goniometer (The earlier version with the white dial) Took it all apart but rubbed the plate with the scale on too hard, the printed graduations came off!

That immediately reminded me of the smell of roasting copra bugs on Bankboats when they sought warmth as we progressed into the northern latitudes. Had to vacuum them out of various bits of valve equipment. (EEK)

Tai Pan
27th March 2009, 10:25
On Esso Bedford I had an american type rotating loop RCA DF. This was in the wheelhouse. A tube extended from the deckhead to the deck. half way down a table jutted out with the RX controls and above this was a wheel to turn the loop. as you stood there with both hands on the wheel, looked like a U-Boat commander about to torpedo something. came in use once, was in bay of biscay homeward to Fawley, i was taking a bearing of La Rochelle and it was on the nose- curious, went ourside, checked the direction of the loop, that was fore and aft, said to 2nd Mate ( who was a 100% richard cranium) why are we going to france, his comments , stupid sparks etc, i held my ground, he relucantly went to the compass and found that the auto pilot had got its knickers in a twist and yes we were heading for france. Gave me great delight to give him the two fingers.

R651400
27th March 2009, 11:10
I had probably the same RCA DF on "World Peace" and used to help out our 2nd Mate with his solitary noon sightings.
Far cry from Blue Funnel with five sun guns on the bridge at midday!
Sailing down the Brazilian coast and well beyond the limits of accuracy I noted he preferred and marked my sightings to his own.
I've always had great faith in the swinging loop and wonder why Marconi adopted the the Bellini Tosi system which I feel was a lot less accurate.
Preference to all things macaroni perhaps?

K urgess
27th March 2009, 13:18
I sailed with a Siemens R19 on the Cerinthus (Hadleys Sunshine Cruises) and found it accurate and relatively easy to use once it had been freed up.
Never forget to apply the clamp again after taking bearings or even leave it unattended unless you're good at unravelling cat's cradles of halyards.
I believe Macaroni purchased or took over the rights to the Bellin-Tosi system sometime in the 1920s or maybe earlier.
According to Danielson & Mayoh "The rotating method of direction finding suffers from the disadvantages that the size of the loop (and hence the magnitude of the resultant signal) is necessarily limited and that the loop must be located near to the position at which bearings require to be taken - and electrically this may not be the best position."
I wish I hadn't opened that book. I've got another headache. (Whaaa)
Just found the reference in "Wireless at Sea - The First Fifty Years" published by Marconi in 1950 - "Early in 1907 E. Bellini and A. Tosi began their experiments - each on different lines, but with a common aim - designed to attain directivity in wireless signalling. In February 1912 the Marconi Marine Company secured the patents of Bellini and Tosi, including those for the wireless direction finder."
The Battle of Jutland came about because the east coast direction finding stations saw movement in one of Germany's capital ships and this information was passed on to the Admiralty. It's not made clear whether the Germans had perfected direction finding technology during WWI.
The first recorded use of direction finding in a distress was in 1921 when it was instrumental in the rescue of the crew of the Norwegian steamer Ontaneda.
Not a lot of people know that. [=P]

Cheers
Kris