# Df



## david.hopcroft (Jun 29, 2005)

Does anyone remember taking DF bearings that were really relied on at the time ? Especially the AEI (Siemens) Rotating Loop like the one below. 

I was coasting one of Stricks on a 'dark and stormy night' on passage Hull to Liverpool north about. Don't think they had a Decca. We were light ship bouncing around a fair bit, and I was up every half hour through the early hours taking bearings from an east coast North Scotland group. It was a effort trying to hold the DF Loop steady enough. I called out the bearings each half hour and thought no more about it. Later the Mate told me that they were small 'cocked hats' but all maintain a steady course and speed. I felt quite proud of that

David
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## sparkie2182 (May 12, 2007)

The "Night Effect" possibly accounting for the cocked hat plots, David.


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## Ron Stringer (Mar 15, 2005)

*DF Bearings*

On a December Atlantic crossing aboard the 'Cairngowan' from Quebec to Grangemouth, heavy cloud cover made it impossible to obtain any sights, neither solar nor astral, for the whole of the first 7 or 8 days. By this time we were approaching the West coast of Scotland and, having no electronic aids more advanced than the Marconi 'Lodestone' DF, I was called upon to take bearings.

The only relatively strong beacon that could be received was that on the Butt of Lewis. A series of bearings taken over several hours indicated that we were well to the South of our intended track. This was treated with some scepticism in the chart room - after all I wasn't their regular Sparks, just a last-minute reliever. But the DF plots were pencilled in on the chart, well separated from the accepted DRs. 

I was only doing the one trip on the vessel and had not had to use the DF on her before, so was less than sure of the accuracy of its calibration. We had loaded a fair bit of deck cargo so it was quite possible that she did not have the same reradiation configuration that she had 2 or 3 weeks earlier when I had checked it while coasting between Grangemouth and the Tyne.

Still, I stuck to it and as other beacons came into range, the DF fixes continued to show us well to the South. After a lot of mumbling and muttering, it was decided to alter course. This was done and the following afternoon we saw the DF bearing of Butt of Lewis move abaft the beam onto the starboard quarter. When the radar picked up Cape Wrath fine on the starboard bow just a few hours later, there was great relief all round.

Our original course would have landed us somewhere around Uig.


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## Troppo (Feb 18, 2010)

By the time I went to sea (1980) the DF's main purpose was as a broadcast rx for the bridge...


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## david.hopcroft (Jun 29, 2005)

Another occasion was not really vital, except to the recipient. On passage on the Mobil Astral from Oz back to the Gulf, I was called one evening in the middle of the Indian Ocean by the 'George Champion' - one of Universe Tankships. They had been ahead of us around Oz. His fridge gas had leaked and they had no freezer ! Did we have a spare cylinder. Yes, we did. 

They waited for us, and first thing next morning, I did a DF on 512 on him which put them a few points off. We altered and checked again later. When we saw him, the Capt said 'On the nose Sparks' 

Think the George Champion were quite pleased too !

David
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## Baulkham Hills (Jul 11, 2008)

On ships I sailed on there was some occasions where D/F bearings were relied on. I was on a ship called the Victoria U sailing from the States to the West coast of Africa. For a few days before landfall off West Africa it was overcast and no sights were taken. When we eventually came in sight of land it was not clear where we were, a D/F bearing clarified our position. 
The other times were coming down the Red Sea from Suez, radar did not show up the coast clearly so D/F was used to identify where Jeddah was. Of course these were all before GPS.
I always sailed with the Bellini Tosi systems of one type or another so seeing a picture of the simple loop was interesting.
The first time I did a complete calibration was on my first ship as an R/O after the six months as junior. I had joined the ship that day and we swung around the Bar light vessel off Liverpool at midnight.
It was an interesting correction curve but I would not like to swear by it's accuracy. I did quite a few complete calibrations in subsequent years which turned out pretty good. On one ship the loops were struck by lightening and required replacing and calibration afterwards.
For the annual survey I seem to remember 2 bearings per quadrant were required. 
There was a story about a ship off New York in fog which followed a D/F signal from a pilot vessel directly ahead and ended up sinking it. I never found out if it was true or not.
In my PMG exam 1/2 convergency error came up on the paper but I never had need to apply the error in practice. I would say that before Radar and GPS systems D/F must have been quite important and this was reflected in all the rules and regulations it was afterall an aid to navigation and also used in distress.

Cheers


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## Naytikos (Oct 20, 2008)

I never sailed with a rotating loop, but took bearings 'for real' several times.
On a 1600grt freighter North-bound across Biscay in thick fog; eventually got a very nice cross bearing right on the 100-fathom line South of Ushant which tallied with the echo-sounder. The mates were impressed but the ancient skipper, who happened to have a Trinity House pilotage certificate for the Thames as well, thought it was all black magic.
Another occasion was on a Bank boat from Ymuiden to Hamburg in fog. This was before all the mines had been cleared; no doubt other SN members will recall the booklet of chartlets showing supposed safe routes up the Dutch/German coasts.
The last one I can remember was on a VLCC awaiting ship-to-ship discharge off Galveston in a howling gale. The anchors wouldn't hold and there are a lot of unlit oil-rigs in the area. The U.S. did not seem well-served by marine DF beacons, so a combination of aircraft beacon bearings and Loran-A had to suffice. I spent 30 hours in the wheelhouse and insisted on plotting the positions myself.


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