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Old 24th Apr 2022, 11:02 pm   #1
vintage_8bit
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Default BEME. BL50 A. Marine direction finder.

I picked this up to day at an antique fair. (£20) Its in very good condition & appears to be very sensitive & works well. It has Medium, long & Marine Band. It has 5 directly heated valves.

The stall holder had been told it was part of the BBC TV license dodgers equipment.

I could only find one previous thread on this model & there appeared to be no available circuit for it then. I'm hoping one may come to light?

Has anyone used these for finding their position. I can't imagine it being very accurate? Colin
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Old 25th Apr 2022, 1:44 am   #2
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Default Re: BEME. BL50 A. Marine direction finder.

Interesting. Yacht or cabin cruiser battery powered DF receiver - I guess the HT battery fits in the wooden box and a couple of D cells in the holder. I suppose the loop is just sitting there where it would normally be up on the cabin roof and turned via a wheel and pointer with a relative bearing card from inside - and also within sight of the main compass so that a true bearing from the shore station could be found. Turn the loop for the minimum signal - the null is much sharper than the peak.

No sense antenna so just a 'figure-of-eight' polar diagram - most times you have a rough idea which direction the land is! You need to take bearing from three or more ground stations to get a position, a single station will just give you a position line. Wouldn't be very accurate, perhaps 2 degrees on a good day when you can read the main compass reasonably well. The tuning scales had me a bit baffled - "TB" is the old "Trawler band" which was just above the MW broadcast band and the little bit of the LW band marked in kHz is the marine and aircraft beacon band which went from about 230 to 400kHz so that joined the top of the LW band which goes from about 270 to 160kHz.

Interesting find, hope that you can sort out the loop wiring, would make a very nice DX chaser on the MW and LW bands. Trawler band is long gone and the beacons are few and far between now too. You might find signal from North Foreland but I haven't a clue what the frequency is - may be 300kHz which is a GPS beacon.

Aah - more info and photos here...the loop actually is fitted to the top of the case with the compass scale, 6 valves.

https://www.radiomuseum.org/r/beme_m...on_finder.html
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Last edited by majoconz; 25th Apr 2022 at 1:58 am.
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Old 25th Apr 2022, 8:52 am   #3
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Default Re: BEME. BL50 A. Marine direction finder.

Thanks for your reply Martin.

The compass scale revolves independently from the base & aerial, so can be set to match up with the ship's compass.

I've not seen scales running from meters into kHz before as L.W. does.

I have seen 6 valves mentioned in a couple of places but mine only has 5. The access is limited in the case but I don't think I've missed one.

I'm really pleased with it, specially as it's working so well. When I've finished my current jobs I'll have it apart & check out the caps. Then I'll find some known transmitter sites and see if I can find where my workshop lives. Colin.
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Old 25th Apr 2022, 10:33 am   #4
David Simpson
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Default Re: BEME. BL50 A. Marine direction finder.

Hello Colin, I had quite a long-winded Forum thread on BEME's a few years back (see "Search").

https://www.vintage-radio.net/forum/...ad.php?t=98271

In fact, I have three of these 50's/60's DF Marine Rx's. Basically, they relied on the old post-war "CONSOL" navigation system. Three beacons spread between the Bay of Biscay & NW Norway, with the middle one on the Irish Coast. Thus triangulation was used with Western European Coastal Charts.
The factory was based at Hythe nr. Southampton, on a small industrial estate on the old WW2 Flying Boat Base. They were taken over by Derritron in the 60's, but had had a factory fire in which a lot of documentation was lost. Hence I never found a Circuit Diagram or Manual. Simple superhet circuitry, using wee 90V/1.5V valves, and an internally stored Exide or EverReady combination Battery.
With the advent of the local MW AM Radio Stations, reasonable triangulation can be acquired, but I'm not sure how many commercial AM nav. beacons are left with the advent of 21st century Sat Comms & Satnav.

Regards, David.
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Old 25th Apr 2022, 8:16 pm   #5
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Default Re: BEME. BL50 A. Marine direction finder.

I have read your old post & thanks for the info. I found the Helmsman's instructions you previously posted.
I read with interest the posted letter which mentions Chatham and the river Medway. They are places I know very well. Colin
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Old 25th Apr 2022, 10:55 pm   #6
James Duncan
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Default Re: BEME. BL50 A. Marine direction finder.

Hi David
I used one of these in the 60's and early 70's on a fast Chris Craft and all one needed was the consul charts which had three separate coloured lines and a pair of headphones, tune to the Transmitters , count the dashes and note when these became quiet before becoming dots, mark all three on the chart and it was so accurate, plenty good enough today for the average yachtsman
cheers
Hamish

Quote:
Originally Posted by David Simpson View Post
Hello Colin, I had quite a long-winded Forum thread on BEME's a few years back (see "Search").

https://www.vintage-radio.net/forum/...ad.php?t=98271

In fact, I have three of these 50's/60's DF Marine Rx's. Basically, they relied on the old post-war "CONSOL" navigation system. Three beacons spread between the Bay of Biscay & NW Norway, with the middle one on the Irish Coast. Thus triangulation was used with Western European Coastal Charts.
The factory was based at Hythe nr. Southampton, on a small industrial estate on the old WW2 Flying Boat Base. They were taken over by Derritron in the 60's, but had had a factory fire in which a lot of documentation was lost. Hence I never found a Circuit Diagram or Manual. Simple superhet circuitry, using wee 90V/1.5V valves, and an internally stored Exide or EverReady combination Battery.
With the advent of the local MW AM Radio Stations, reasonable triangulation can be acquired, but I'm not sure how many commercial AM nav. beacons are left with the advent of 21st century Sat Comms & Satnav.

Regards, David.
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Old 26th Apr 2022, 1:01 pm   #7
Dave757
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Default Re: BEME. BL50 A. Marine direction finder.

Hi,

So it appears that the BEME set doesn't have a BFO. I didn't know that,
and I nearly bought one once. I seem to remember that the old marine beacons were
MCW, so you didn't really need one. However, most of the D/F sets I have had did
have one.
As the BEME set has a loop antenna, It must have been designed for the NDBs, as you
wouldn't need one for Consol. I still have a Consol Chart, and the HMSO operating
book ' Consol a radio aid to navigation'. Interestingly, the book was issued by
the Ministry of Aviation.

Kind regards
Dave
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Old 26th Apr 2022, 8:11 pm   #8
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Default Re: BEME. BL50 A. Marine direction finder.

I would like to see a consol map. I have never seen one for real. Colin

Last edited by vintage_8bit; 26th Apr 2022 at 8:37 pm. Reason: Forum rules.
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Old 27th Apr 2022, 6:25 am   #9
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Default Re: BEME. BL50 A. Marine direction finder.

Here's a map compiled in 1942 for the RAF.

http://www.jproc.ca/hyperbolic/conso...eup_1942_b.jpg

Cheers

Roger
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Old 27th Apr 2022, 8:10 am   #10
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Default Re: BEME. BL50 A. Marine direction finder.

Thanks Roger, I found that really interesting. Colin
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Old 27th Apr 2022, 10:28 am   #11
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Default Re: BEME. BL50 A. Marine direction finder.

Hi Colin,

And here's the 1951 Consol chart L2 for the British Isles showing
the bearings from MWN Bushmills 266kHz, FRQ Quimper/Ploneis 257kHz,
and LEC Stavanger 319kHz.

Interestingly, LEC continued for some years after Consol finished as a Non
Directional Beacon and then the callsign was changed to VAR. This continued
on 319kHz until very recently before finally closing.

Regarding the BEME, I now believe the set does have a BFO, but I would be
interested to know how it is switched in. The valve lineup seems to be the same
as the BL55, but that set has a BFO switch.

Kind regards
Dave
G0ELJ.
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Old 28th Apr 2022, 3:22 pm   #12
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Default Re: BEME. BL50 A. Marine direction finder.

Thanks for the map Dave.

When I tried mine I picked up A.M. on long & Medium wave & a couple of hams on trawler / top band. It didnt sound like a BFO was running. As mine appears to have 5 valves I guessed a normal A.M. Superhet line up with an extra stage front end before the mixer? Colin.
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Old 29th Apr 2022, 3:04 am   #13
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Default Re: BEME. BL50 A. Marine direction finder.

All marine beacons are modulated with the ident code in morse and then a modulated carrier for 20 seconds or so - this tone gives you time to rotate the antenna for a null in the signal. A BFO won't tell you anything as at the null there is hopefully no signal and therefore no beat. As the signal is MCW, the presence of a carrier plus BFO may make it difficult to resolve the ident.
Aero beacons just send the ident once every 5 seconds or so - but almost all aircraft since the DC3 have an "ADF" - automatic direction finder - a pair of crossed ferrite rod antennas, one fore-and-aft and the other crossways usually under the cockpit feed similar set of coils in the receiverwith a rotatable pick up coil. A servo mechanism rotates the pick up for minimum signal and also the slave servo moved the pointer around a compass scaled instrument in front of the pilot. The compass scale is rotated from the horizontal gyro so that there is an indication of the true bearing from the aircraft. A non-directional sense antenna's signal is mixed with the loop signal to produce a cardioid polar diagram to remove the figure-of-eight ambiguity. A switch enables the pilot to listen to the sense antenna alone to hear the ident better than the loop. Larger aircraft requiring two pilots have dual instruments and so the indicator shows both receivers which may be tuned to different stations. The display is usually referred to as an RMI - a radio magnetic indicator - as it also shows the magnetic compass heading of the aircraft.
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Old 29th Apr 2022, 9:14 am   #14
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Default Re: BEME. BL50 A. Marine direction finder.

Martin, you passed up the opportunity to use the word "goniometer" there....

Colin
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Old 29th Apr 2022, 8:54 pm   #15
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Default Re: BEME. BL50 A. Marine direction finder.

I knew there was something I'd forgotten.....
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