D/f

wireless man
29th June 2008, 12:39
Hi Everbody
I have just joined the sight and wonder if anyone can fill me in on the use of D/F.
I wasnt aware until I read a book about Marconi RO's that much use was made of it in shipping.
What were the stations used the ranges and accuracies of the plots?.
Hope you can all help.
Regards
Max
(wireless man)

K urgess
29th June 2008, 14:20
Welcome aboard from East Yorkshire, Max.
Plenty of us around in the crew that used D/F in anger.
Usually in the Western Approaches when the weather was 10/10s and nobody had a clue which side of the Scillies we were.
I'm sure you'll get some tales. Mostly it was just something you did when asked and nothing out of the ordinary.
Cheers
Kris

tedc
29th June 2008, 15:46
Hi Everbody
I have just joined the sight and wonder if anyone can fill me in on the use of D/F.
I wasnt aware until I read a book about Marconi RO's that much use was made of it in shipping.
What were the stations used the ranges and accuracies of the plots?.
Hope you can all help.
Regards
Max
(wireless man)

Hi Max!

Tricky business using df - seem to remember that it was easy to get a 180 degree error as you had to back up the loop with a small aerial which was supposed to change the ping to show the right bearing of the two possible.
as Fubar says, it was used quite frequently - especially as many mates would take an opportunity to "check out" our skills.

If I recall correctly you often had to get someone to transmit so that you could "read" their bearing - or you could use one of the call sign transmitting stations.

Memory is thin now 50 years on.....!.

TABNAB
29th June 2008, 16:34
Hi Everbody
I have just joined the sight and wonder if anyone can fill me in on the use of D/F.
I wasnt aware until I read a book about Marconi RO's that much use was made of it in shipping.
What were the stations used the ranges and accuracies of the plots?.
Hope you can all help.
Regards
Max
(wireless man)

Used D/F frequently on ships not fitted with radar - there were quite a few in 1950's ! Brought "Lombardy" up the channel in 1955 from Start Point to Dover pilot in thick fog - bearings every hour for 36 hours or so. Not unusual in those prehistoric days !
Also used it to verify distres casualty "Romana" in South Atlantic - she was about 25 miles out in her QTH.
Now I'm feeling really old......

R651400
29th June 2008, 16:58
Pre 60's it was also possible to get d/f bearings from coast stations which the ships had to pay for. QTF Frequency 410 kc/s .

wireless man
29th June 2008, 20:13
Hi Guys
Thanks for those replies. It looks as though these were non directional beacons or were shore stations giving you bearings on your transmissions perhaps both.
What sort of range or accuracy could be expected. I suppose the deck officers plotted the bearings.
What was it like down in Africa.
Cheers
Max

IAINT
29th June 2008, 21:13
Hi Max

Used DF continuously on the Norwegian coast bound for MO I RANA to load ore in the winter, due to bad weather/fog and no sights for the mates. Must have done a decent job as we got there in the end. I actually enjoyed using
the DF - it's true.

Had to use 410 kc/s a lot offshore for homing in the choppers.

Regards
Iain T

ChasD
29th June 2008, 21:47
Hi Wireless man ! D/F beacons were fitted in most of the larger navigational aids, lighthouses, lightships and so on. In the older ships the D/F was located in the radio shack, it was the formal practice for the bridge to ring down (or yell !) and ask for a bearing on such and such and the R/O would take the bearing and send it back up to the bridge. More commonly, and certainly my practice, if D/F's were needed, I would take a selection of bearings up to the bridge and plot the relevant position on the chart with the OOW. Accuracy could be variable depending on a variety of factors, most importantly the accuracy of the "Correction Chart" which gave the system/equipment error on any bearing. If you have never seen one of these, its a double sine wave, the coordinates of which need to be applied to the bearing taken. Like anything there was a bit of a "knack" interpreting what you got. As with any position fix, the size of the "cocked hat" was a good indication of how much of a "cock-up" you had made of the bearings ! In later years the systems were more automated and usually fitted on the bridge, though I usually did the "radio navigation" when needed to back up the OOW. I've attached a couple of extracted pics of the equip't to give an idea of the gear in use. First is the simple rotating loop handwheel which was attached to a simple loop aerial aloft feeding a suitable receiver. Second is the later "Belini Tosi" type fed from crossed loop type arrangement aloft shown in the third pic.
Hope this helps
Regards,
ChasD

R651400
1st July 2008, 07:23
Every deep sea Blue Funnel ship I sailed with excepting one had only D/F as it's principal radio navigation device.
D/F was good for it's time but there were shortcomings.
From memory, Bellini-Tosi systems required a separate single wire sense aerial. Accuracy was over a certain and short range. The need for a calibration chart. Night effect error meant use only during daylight hours. Quadrantal error if bearings were taken when the ship was rigged differently from when the D/F was calibrated. Coastal refraction when taking bearings from other than known radio beacons. Maybe there are more?
At the behest of a Greek 2nd mate to double check his sun-gun sights, I took bearings at enormous distances off the Brazilian coast on a RCA rotating loop D/F and was impressed at how accurate the results actually were or maybe how inaccurate the 2nd mate's calculations were!

trotterdotpom
1st July 2008, 10:37
People hanging wire aerials all over the ship, especially close to the DF loops, didn't help the accuracy of the equipment.

Communal aerial amplifiers like "Pantenna" should have eliminated the problem, but the folk who couldn't understand why they couldn't pick up Radio Luxembourg from Japan still insisted on running their own aerials.

Dubious connections of some of these aerials, particularly if the radio was still connected to the Pantenna socket, downgraded reception for everyone else on the particular line. I even found occasions where some "expert" had removed the wall plate and connected his aerial to the communal aerial and shorted the whole system out.

The best way of receiving from these aerials seemed to be a home-made coil of wire wrapped round a cardboard toilet roll holder dropped over the rod aerial of the radio.

John T.

G4UMW
1st July 2008, 12:41
At college I trained on the Marconi Lodestone (all manual) and at sea used the Marconi Lodestar (automatic). However, the best DF I ever used was made by ITT - unfortunately I don't recall the model number. It had a digital display which could be switched to show tuned frequency, ship's head (slaved from the gyro compass) and true or relative bearing. It also had a small (about 2 in diameter) CRT which displayed the received signal as a radial line extending from the centre of the tube to the edge where the bearing could be read against a scale. The CRT trace gave a useful indication of the accuracy of the bearing - a strong signal showed up as a single line whereas a weak or refracted signal displayed an ellipse. The wider the trace, the less accurate the bearing.

King Ratt
1st July 2008, 15:05
During WW2 the Plessey Company with the RN developed an HF DF system which also displayed signals as a strobe on a CRT. The unit was called FH4 and vied with radar in detection and destruction of U boats.
See the article at http://www.naval-history.net/xGM-Tech-HFDF.htm

mikeg
1st July 2008, 15:52
Picture of my ancient ADF receiver. Still can mark a position well with it using NDB's (Non Directional Beacons - aviation) Needs 12VDC int/ext. Good fun (POP) (or is it being very sad) to take it in a car or boat and lay bearings on a chart to fix a position.

Mike

charles henry
1st July 2008, 16:16
Only df I ever sailed with was the Bellini Tosi type with crossed loops, the US ships prefererance was single loop. In my experience if conditions were reasonable (Otherwise I would not give a bearing) it could be an extremely accurate device. My fondest memory of df-ing was in a tanker coming on our way home in foul weather.. socked in with rain and clouds there had not been a sight for four days. One evening I got three VERY GOOD bearings plus an iffy one. It put us 60 miles west of our dead reckoning. The second mate and I had quite an arguement leading to a five pound bet. (The old man held the money). Next day we got a sight and I got my money.
Sneakily I had also verified my bearings using the "Consul" system (But I'M showing my aged
de Chas(Pint)

K urgess
1st July 2008, 16:38
Didn't you just love counting all those dots and dashes, Chas.
Good system though.

Kris

mikeg
1st July 2008, 16:39
Didn't you just love counting all those dots and dashes, Chas.
Good system though.

Kris

Better than counting sheep if you need to get to sleep [=P]

Lewis
1st July 2008, 16:46
As 3rd Mate on the Gosforth, I had never seen the Belini Tosi type DF before I joined her. Previous ships all had the Marconi Lodestar (I think). I didn't have to use it in anger until leaving the St Lawrence heading for St John's Newfoundland. Passing Cape Race in fog with no radar (u/s) I had to stay on the bridge after midnight to operate the D/F as the 2nd Mate (ex Nigerian National) had no idea how to operate it. He couldn't get the hang of picking up the silent sector and taking the bearing on that. As we had only Cape Race for a bearing, we kept heading East until we were convinced that Cape Race was well behind us and then turned North. After coming off the bridge, didn't sleep too well until we cleared the fog and managed to get a good fix using two shore stations.

NoMoss
1st July 2008, 17:44
I used to fancy myself at taking DF bearings. I calibrated the DFs on several ships.
Once half-way through a round the world trip, crossing the north Pacific from China to Canada on a Great Circle route it was 'thick as a hedge' most of the way across. Many ships were broadcasting their position, course and speed and I took bearings on all of them and passed them to the chartroom to compare with our dead reckoning position. I couldn't understand ships broadcasting their speeds in thick fog as they were obviously not slowing down at all.
One US warship gave me a laugh as at the age of 19 I didn't know the name of the bird on the crest of the US and USS Bald Eagle was an unlikely name for a ship!

One Old Man in Union Castle was well know for being mean and he got me to take check bearings off Robbin Island so that he could send a message using the Aldis lamp to a friend ashore as we swung the ship.

On one ship the 2nd Mate used to like taking DF bearings so I did the visuals as we swapped roles.

K urgess
1st July 2008, 18:58
Swung off Robben Island a few times doing DF calibrations.
Quite interesting in a VLCC.
Why was it that I seemed to join ships where no calibrations had been done in the past 12 months. (Cloud)

BobClay
1st July 2008, 19:10
Shoreside DF beacons were usually in the 300 Khz range, this was usually the frequency zone where the correction curve was made (it could be significantly different at 410 Khz due to differing electrical lengths of the rigging etc).

Range in daytime would not usually be much above a few hundred miles, maybe less. It was of course longer at night, but made very unstable by differing propagation routes.

DF was a very good fallback in it's day when you had days of fog (North Pacific crossing from Canada to Japan I remember well, the old man was very happy to see the Decca Navigator start twitching as we got near Japan, but we weren't that far out thanks to the Lodestar).

Getting check bearings each year prior to the radio survey could be a pain on occasion. Many times I would annoy the 2nd mate when we were swinging around the hook in sight of a beacon. Once we made a 500 khz curve by using the lifeboat radio and a lifeboat when at anchor. It differed dramatically from the standard 300khz curve.

It became something of an ornament when early SatNav sets appeared on the bridge (not GPS, the old once and a while system with low orbiters).

It was a good simple bit of kit though, and good enough when you don't see the sky for days on end and are looking for landfall.

Moulder
1st July 2008, 19:44
..........Why was it that I seemed to join ships where no calibrations had been done in the past 12 months. (Cloud).......

Wot! You as well Kris??
:rolleyes:


(Thumb)

Tai Pan
2nd July 2008, 09:36
On Esso Bedford I had a rotating loop DF (RCA), i was messing about with it in the bay and found that La Rocelle was bearing 0 or dead ahead, I asked the 2nd mate ( a real big head and major bollox), why we had changed course, your a total nut case sparkes we are heading for Ushant, i replied I think something is wrong, great sigh from him, however he checked the auto pilot and yes, we were heading straight for France. I really enjoyed that one.

R651400
2nd July 2008, 10:26
On Esso Bedford I had a rotating loop DF (RCA), Sounds like the same D/F on World Peace. It was actually a complete unit that stood in the wheelhouse. I only used it to keep the mate off our very timid 2nd mate's back with his noon sightings, I'm sure 2nd mate moved them to my d/f readings.
No noontime "dance-hall floor" bridge like Blue Flue with everyone zapping away on sun-guns from skipper to senior middy whose knees used to quake waiting for the inevitable question on his reading!!

Tai Pan
2nd July 2008, 13:15
Sounds like the same D/F on World Peace. It was actually a complete unit that stood in the wheelhouse. I only used it to keep the mate off our very timid 2nd mate's back with his noon sightings, I'm sure 2nd mate moved them to my d/f readings.
No noontime "dance-hall floor" bridge like Blue Flue with everyone zapping away on sun-guns from skipper to senior middy whose knees used to quake waiting for the inevitable question on his reading!!

Sounds like it. Look like a submarine periscope, with a wheel just obove head height and then the rx jutted out obout chest high. You got the bluie bridge opera to a tee. the 2nd mate had already worked it out and let the mate know.

charles henry
2nd July 2008, 14:17
Didn't you just love counting all those dots and dashes, Chas.
Good system though.

Kris

It wasnt the dits and dahs that were the bother, t'was the sometimes very long silence in between. As you say it was a good system (Pint) de chas

David Davies
2nd July 2008, 15:10
Used hand held Seafarer DF frequently on continuous light ship beacons such as Tongue and Sunk L/v in foggy conditions. The practice was to put the beacon dead ahead and home in whilst listening for its fog signal. Approaching The Sunk from Galloper under sail on port tack (2 blasts on Norwegian reed horn), with contious beacon dead ahead and listening for its fog signal. The DF signal (UK?) became very loud and DR said we had done the distance but no fog signal, and then we heard voices, out of the fog loomed the red hull of the Sunk L/V, We shouted our disapproval at those on deck and cranked away on our Norwegian fog horn which roused them to activity and started their fog signal. I know that this practice was not approved in the orals but under sail with no engine noise, hearing is a good aid to navigation.

Mimcoman
2nd July 2008, 18:04
It wasnt the dits and dahs that were the bother, t'was the sometimes very long silence in between. As you say it was a good system (Pint) de chas
I can still picture myself and the Skipper on the trawler Newby Wyke counting the dits and tapping away silently on the radio room desk to try and keep in sequence for when the dahs started. Tap...tap...tap...

Ron Stringer
3rd July 2008, 08:32
The practice was to put the beacon dead ahead and home in whilst listening for its fog signal.

A practice that, when it was followed by larger vessels, was much feared by the lightship crews. Several lightships were run down and severely damaged or even sunk by ships that 'homed' down their beacon transmissions but failed to make allowance or take action in order to avoid colliding with the source.

Tai Pan
3rd July 2008, 09:19
I can still picture myself and the Skipper on the trawler Newby Wyke counting the dits and tapping away silently on the radio room desk to try and keep in sequence for when the dahs started. Tap...tap...tap...

why was it that nobody came to the radio room until you were counting dots etc on consul, then the whole ships company seemed to want to see you?.(K)