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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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29th Dec 2016, 10:18 am | #1 |
Heptode
Join Date: Feb 2008
Location: Great Barr, Sandwell, West Midlands, UK.
Posts: 584
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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. Last edited by Sparky67; 29th Dec 2016 at 10:24 am. |
29th Dec 2016, 12:05 pm | #2 |
Dekatron
Join Date: Jul 2008
Location: Charmouth, Dorset, UK.
Posts: 3,601
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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 |
29th Dec 2016, 12:08 pm | #3 |
Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
Posts: 319
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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 |
29th Dec 2016, 1:36 pm | #4 |
Pentode
Join Date: Oct 2005
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 199
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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
__________________
Peter G8BBZ |
30th Dec 2016, 1:36 am | #5 |
Dekatron
Join Date: Jul 2008
Location: Charmouth, Dorset, UK.
Posts: 3,601
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Re: Transmitter ID
Shows how much I know.
Peter |
30th Dec 2016, 9:57 am | #6 | |
Heptode
Join Date: Jun 2012
Location: Southeast Norfolk, UK.
Posts: 772
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Re: Transmitter ID
Quote:
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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30th Dec 2016, 11:00 am | #7 |
Pentode
Join Date: Apr 2011
Location: Swansea, Wales, UK.
Posts: 143
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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 |
30th Dec 2016, 11:28 am | #8 |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
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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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30th Dec 2016, 1:26 pm | #9 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
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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. |
30th Dec 2016, 3:02 pm | #10 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,838
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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 |
30th Dec 2016, 10:10 pm | #11 | |
Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
Posts: 319
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Re: Transmitter ID
Quote:
Peter (the G3PIJ version) |
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31st Dec 2016, 12:09 am | #12 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,838
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Re: Transmitter ID
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 |
31st Dec 2016, 10:43 am | #13 |
Heptode
Join Date: Feb 2008
Location: Great Barr, Sandwell, West Midlands, UK.
Posts: 584
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Re: Transmitter ID
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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31st Dec 2016, 11:53 am | #14 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,838
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Re: Transmitter ID
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 |
31st Dec 2016, 12:23 pm | #15 |
Heptode
Join Date: Feb 2008
Location: Great Barr, Sandwell, West Midlands, UK.
Posts: 584
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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. |
31st Dec 2016, 1:33 pm | #16 |
Pentode
Join Date: Apr 2011
Location: Swansea, Wales, UK.
Posts: 143
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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 |
8th Jan 2017, 3:36 pm | #17 |
Tetrode
Join Date: Jan 2008
Location: Shetland, UK.
Posts: 79
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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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