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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 24th Apr 2021, 10:25 pm   #21
ChristianFletcher
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Default Re: Woodsons of Aberdeen SR124

Thanks John interesting history
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Old 24th Apr 2021, 10:48 pm   #22
turretslug
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Default Re: Woodsons of Aberdeen SR124

I don't think you will cause harm by plugging in an ECC83/12AX7- there are the three obvious double-triode candidates with this heater configuration, the ECC81/82/83, 12AT7/12AU7/12AX7 siblings and for this application of AF amp and low-power Hartley BFO, the ECC83/12AX7 is a good guess and getting the wrong one of the three won't make anything go bang with the high-value anode resistors, rather the audio may end up low level or distorted or the BFO may just not work.
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Old 25th Apr 2021, 10:30 am   #23
David Simpson
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Default Re: Woodsons of Aberdeen SR124

During my time working on Fishing Boat's electronics, the older Woodsons/Marconi/Kelvin Hughes/etc. R/T equipment was run off the boat's 24V DC supply. Hence the use of Rotary PSU's or Dynamotors for Tx & Rx HT's, with Vh derived from the 24V.
Once the likes of Sailor Radio eq. took over - their Rx's were transistorised & the Tx HT's were sourced from an internal static inverter. The Sailor T66 Rx for example could work off 12 or 24V depending on link changes in the incoming plug circuitry.

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Old 25th Apr 2021, 10:38 am   #24
ChristianFletcher
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Default Re: Woodsons of Aberdeen SR124

One ECC82 later and the only potential replacement I had in stock and it’s working very well on MW and Longwave. Feeding via a long wire at the moment

https://youtu.be/tIn_aLfEjts

Does anyone have any ideas regards the electrical construction of a receiving loop. I can roll copper pipe into a circle but how many turns are in the loop? There is a picture of the loop in the circuit diagram but I’m not sure how big the loops were or if they were tuned at all. Look like they were screened perhaps I can use some thick coax cable I have to had. How big were the loops on a ship ?
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Old 26th Apr 2021, 2:02 pm   #25
Keith
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Default Re: Woodsons of Aberdeen SR124

Christian,

If you make a shielded loop don't forget to leave a gap in the shield to avoid a shorted turn. Back in the days of top band DF hunting I made one by threading a length of 6 core telephone wire though an aluminium loop about a foot in diameter. Then joined the appropriate ends to get one continuous coil and put a variable capacitor across the whole thing to tune it. Worked very well.

Great choice of music for your video, btw!
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Old 26th Apr 2021, 6:28 pm   #26
ChristianFletcher
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Default Re: Woodsons of Aberdeen SR124

Thanks Keith

I think I would roll a C shape with the open part of the C at the top. What I’m not sure about is the size of the loop and if I need to do any matching. It would need to cover LW and medium wave but my understanding of loops it’s they have very narrow bandwidth. I did have look at medium wave receiving loops and some of these are enormous. The only other stuff that came up was those loops that you put next to a radio to increase the signal level
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Old 27th Apr 2021, 8:14 am   #27
ChristianFletcher
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Default Re: Woodsons of Aberdeen SR124

My final thoughts on this radio is the the actual model number for my radio 124 is actually incorrect. I suspect one of the digit should have been blacked out so for the 12 volt version it would read SR-12 and for the 24 volt version it would read SR-24. But if the transmitter section is ignored it does appear to fit the circuit diagram. With a ECC82 fitted in place of the missing valve 8 the set works very well and is a sensitive and lively performance. The noise of the rotary converter is somewhat annoying if not an interesting bit of vintage technology.

I have decided not to proceed with anymore restoration for now as the radio is working well enough for occasional use and due to its midget size it’s not a easy thing to work on.

Full video here for anyone interested in the story of this set. I would be interested in trying to build a loop antenna if any information on how to do this can be provided. Thanks

Resurrection video here https://youtu.be/cF_E5FSS_kg
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