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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 29th Dec 2016, 10:18 am   #1
Sparky67
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Default Transmitter ID

Can anyone ID this LF Tx please? Is it a commercial unit, or could it possibly be homebrew? Due to where it is (photo taken through a window) unfortunately this is the only view available.

Thanks.
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Old 29th Dec 2016, 12:05 pm   #2
Peter.N.
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Default Re: Transmitter ID

Looks like an HF linear amp to me, the multi ways switch suggests that its for ham radio use. Never seen one like that though.

Peter
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Old 29th Dec 2016, 12:08 pm   #3
G3PIJpeter
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Default Re: Transmitter ID

Two, possibly three 807s in view. Don't think it's commercial. Tank inductor and variable capacitor look distinctly LF. Possibly a home-brew MW RF section from a local pirate radio station of the 1960s? It looks to be 'plugged in' - can you see where the cables go from the plugs on the rear panel? The latest edition of the VMARS 'Signal' has an extensive article on low-power land-based MW pirate radio activity.
- Peter
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Old 29th Dec 2016, 1:36 pm   #4
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Default Re: Transmitter ID

Hi,
Though it is many years since I have seen one in the flesh, your photo looks very much like the RF section of a Redifon LF beacon transmitter as used in airfield NDB's, marine navigation beacons etc., generally operating in the band 150 - 450kHz or thereabouts.
If this is the case, the design dates from the late 40's/early 50's and used multiple paralleled 807's as these were available in huge quantities at the timer.
The transmitter would be CW or MCW and keyed by a mechanical keyer based on a "record player" type of mechanism using a 12" brass disc with the station callsign in morse cut into the edge as notches, which were then read by a microswitch attached to a roller running on the edge.
The transmitter was designed for extreme reliability and generally operated continuously - often for many years without interruption.
Redifon supplied many LF beacon transmitters over the years, with large numbers going to sites in Africa and the Middle East as commercial avaiation got off the ground in the years after WW2.
And then again I might be completely wrong!
cheers
Peter G8BBZ
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Old 30th Dec 2016, 1:36 am   #5
Peter.N.
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Shows how much I know.

Peter
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Old 30th Dec 2016, 9:57 am   #6
G3VKM_Roger
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Default Re: Transmitter ID

Quote:
Originally Posted by G8BBZ View Post
Though it is many years since I have seen one in the flesh, your photo looks very much like the RF section of a Redifon LF beacon transmitter as used in airfield NDB's, marine navigation beacons etc., generally operating in the band 150 - 450kHz or thereabouts.
I'd be inclined to agree with you, Peter, it does have the beacon-look about it and the tuning components visible would be about right for MF use, it looks to have a tapped secondary winding so would be designed to use a standard antenna.

I did think of Decca Navigator gear but that would be nearer 130-160 kHz and would be bigger and more powerful.

Let's hope for some more photos, I love a mystery!

73

Roger/G3VKM
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Old 30th Dec 2016, 11:00 am   #7
GW3OQK Andrew
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Default Re: Transmitter ID

Seems its an end-of-year guessing game until we see the front. It looks like a 1.6 to 3 Mc/s crystal controlled marine band transmitter of about 50 watts AM to me.
73 and HNY
Andrew
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Old 30th Dec 2016, 11:28 am   #8
lesmw0sec
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Default Re: Transmitter ID

Looks a bit home-made to me. Note the hand annotations on the sockets and the fact that the chassis is just finished with emery or the like.
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Old 30th Dec 2016, 1:26 pm   #9
G6Tanuki
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Default Re: Transmitter ID

There don't look to be enough turns on the coils for it to tune the beacon-band between MW and LW.

Also I'd have expected a beacon TX to be 19-inch rack mount, which this one doesn't look to be.

The guess at a "fish-phone" transmitter is a good one - there were quite a few small manufacturers of these in the 1950s-1970s: "Woodsons" in Aberdeen being one of the better known ones.
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Old 30th Dec 2016, 3:02 pm   #10
David Simpson
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Default Re: Transmitter ID

The cabinet seems to have well louvered sides for ventilation. Probably needed it for heat dissipation from the bunch of 807's. It might well have been a marine band shore station.
I worked for Woodsons briefly back in the 80's, but by then their range of marine band HF R/T's were Sailor 10's series AM, or later 100's series SSB's.
I've a Woodsons Spey Tx from the 50's/60's era, 807's and all, but the cabinet is cast aluminium & gasketed. As it would have been a vessel installation.
I also note that the valves have no rayon restraining shrouds. So not expected to be subjected to off-shore storms.
Coastal Radio Ltd also had a liking for 807's in their marine band HF AM R/T's.
We really need a shufti at the front panel, please.

Regards, David
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Old 30th Dec 2016, 10:10 pm   #11
G3PIJpeter
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Quote:
Originally Posted by David Simpson View Post
The cabinet seems to have well louvered sides for ventilation.
The photo was taken through a window in the side of what appears to be a garage. The 'louvres' visible on the right-hand side of the cabinet seem to me like the inside of a 'up-and-over' garage door. The 'louvres' extend past the framework of the equipment. So it's a chassis with an open frame around it (? ? - need more photos !). Some commercially-made kit from the early 1950s was distinctly 'home-built' in appearance and often used surplus components.

Peter (the G3PIJ version)
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Old 31st Dec 2016, 12:09 am   #12
David Simpson
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Please Sparky67, as Peter says - we need more photos. Where is it located ? Are there any other Forum guys near you who could perhaps help you sus this place out ?

Regards, David
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Old 31st Dec 2016, 10:43 am   #13
Sparky67
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Well, I think G8BBZ wins this (unintentional) end-of-year-quiz. This photo was taken some time ago on an airfield which is shown as having an NDB and probably is, or was, the NDB transmitter. I *believe* the NDB facility has been upgraded in recent years, so this may be a stand-by Tx, or may just be redundant. Next time I visit I will see if I can get some other photos.
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Old 31st Dec 2016, 11:53 am   #14
David Simpson
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Good on yer Sparky 67, I like quizzes. Do you not fancy putting on a Sgt Bilko hat & contacting the airfield owners or Air Traffic authorities and asking them if they wished to part with the obviously redundant Tx ? If you don't fancy it for yourself, I'm sure that quite a number of Forum guys would.
In making contact, it might lead to other items of valuable vintage airfield equipment being acquired. Otherwise it might end up in a (spit - spit) skip !
Should WEEE regulations be a stumbling block with the airfield authorities, you might like to read this month's VMARS' Signal Journal. It contains a large interesting article on WEEE, and a much smaller supporting article by myself - regarding the acquisition of a Paragraph 47 Exemption Certificate. Someone as well qualified & experienced as yourself would have no problem in acquiring one, I reckon. In fact, I suspect that many Forum/BVWS/ VMARS folk would be qualified to apply. Reclamation/Recycling of old airfield equipment is better than Skips & subsequent Landfill.

Regards, David
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Old 31st Dec 2016, 12:23 pm   #15
Sparky67
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Default Re: Transmitter ID

I am now a little more intrigued! Will see what I can find out next visit.

Somewhere in the depths of my memory, when I was flying from this airfield in the early 1970s, I vaguely recall looking through a window and seeing a T1154, sans case, probably doing the same job. That NDB helped me enormously when returning to the airfield through ever-lowering cloud and squally showers one day.

Yes, the VMARS dialogue on WEEE made me smile a little... Been there, done that. In my opinion, a valid awareness and discussion point.
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Old 31st Dec 2016, 1:33 pm   #16
GW3OQK Andrew
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Default Re: Transmitter ID

For the exercise I scaled the size of the big coil against the length of the 807, reckoned on 46 turns, and used an on-line calculator to calculate it's inductance. It came to 50 microhenry.

Resonated with 1000pf the frequency is about 1 MHz in the broadcast band. With fewer turns selected by the rotary switch and less on the variable capacitor it will be resonating on the marine band 1.6 upwards.

In my experience marine and NDB transmitters for 525 KHz and down to 300 kHz had many more close-wound turns and always used Litz wire. 100 uH or more would be usual.

I think the louvres are in the side of it's cabinet and I see a wire going to the insulator on top. Maybe below it in the rack is its modulator and power supply. Sparky I hope you can visit it again one day.

73
Andrew

Last edited by GW3OQK Andrew; 31st Dec 2016 at 1:42 pm. Reason: mistaken calc
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Old 8th Jan 2017, 3:36 pm   #17
gm0ekm cecil
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Default Re: Transmitter ID

Looks very much like a Redifon NDB transmitter. I dismantled a Redifon transmitter very similar quite a few years ago, which contained identical metal parts holding the variable capacitor and switch. The louvered cabinet is also similar to the G54 I took apart. ..... Cecil.
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