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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 2nd Nov 2020, 5:43 pm   #1
G6Tanuki
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Default "RF" unit coils.

A while back I acquired a "RF" unit for 1 at a car-boot-sale.

It's not a switch-tuned RF24, rather it's a tunable one. It's had its front-panel Hammerited, ID-plate removed, a Belling-Lee coax socket replaces the Pye-plug, vanes have been pruned from the tuning-capacitor rotors, and the coils have all been messed-with - my suspicion being that someone tried to 'modify' it into a 2-Metre or VHF-Air-band converter.

It's never going to be original, but I was wondering if anyone with one of these units could count the turns on the RF coils for me so I can rewind them?

[I've got a set of unmolested Wingrove&Rogers variable capacitors to replace the mutilated ones].
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Old 2nd Nov 2020, 8:42 pm   #2
Ed_Dinning
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Default Re: "RF" unit coils.

Hi G6, I might have a set of coils from one of these units.
It was stripped to convert it to the WW 1155 bandpass convertor, Mail me if you have no luck and I'll see if I can find them

Ed
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Old 3rd Nov 2020, 11:34 am   #3
Orakle42
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Default Re: "RF" unit coils.

Ah, the RF26! once very popular for Band 3[ITV] to Band 1 conversion. I still have one somewhere, I will try to find it.

Orakle42
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Old 3rd Nov 2020, 12:09 pm   #4
Orakle42
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Default Re: "RF" unit coils.

Re my previous post,found it! however, it has been messed with. Although quite tarnished it is complete with case & all its variables although the EF50 is missing and the rewound coils can be seen. Some pictures are attached for interest, but sorry, I cant offer any help on the original coil data.

Orakle42
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Old 3rd Nov 2020, 4:36 pm   #5
M0FYA Andy
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Default Re: "RF" unit coils.

I believe the chassis is silver-plated, hence the blackened look.

Andy
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Old 3rd Nov 2020, 6:45 pm   #6
G6Tanuki
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Default Re: "RF" unit coils.

Yes there was quite a bit of silver-plating in these, and it does go dark after 70+ years.

I'm going to do some 'grope and hope' coil-rewinding on mine, with luck I can get it to play on 50MHz or 70MHz.

If not, part of me is tempted to rebuild it as a 50MHz transmitter - with a couple of VR91 as VFO/driver and a little QV04/7 [CV309] as PA. Should be good for 10 Watts RF out!
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Old 3rd Nov 2020, 6:53 pm   #7
llama
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Default Re: "RF" unit coils.

It might be (have been...) an RF26 or RF27. I think I have unmolested ones of each. I'll have a look tomorrow - and try to spot a component or two that will help tell whether yours is a '6 or '7!
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Old 3rd Nov 2020, 11:52 pm   #8
AlanC
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Default Re: "RF" unit coils.

I used to have an RF27 back in the 70's, it was intact when I got it. I modified a homebrew shortwave receiver into a 7.5Mc/s IF system and ran it like that- in effect a dual conversion receiver. It covered 4 meters without any mods (as I remember), and was actually quite hot- I could hear the Buxton beacon GB3BUX no problem from home in Sheffield. Lovely Muirhead tuning drive with illuminated cursor, and I remember the underchassis components where all very heavily varnished- it was a 'tropicalised' unit.

The RF units were plug-in front ends to the R1355 'Gee' navigation receiver that was standard fit on the Lancaster bomber. RF24 and 25 were switch tuned, 26 and 27 were tunable.

Cheers
Alan G0NFY
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Old 4th Nov 2020, 8:50 am   #9
M0FYA Andy
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Default Re: "RF" unit coils.

OK, G6, the information exists!
The coils in the RF26 and RF27 are different, so first you need to ascertain which unit you have. If you haven't already got it, download AP2557A from the VMARS archive, work out which unit you have and which coils you need info on, and determine the Air Ministry Stores Reference Numbers from the parts list.

In this instance, Section 10D of AP1086 is very helpful and contains the coil details, when you know the coil references I'll extract the information.

Andy
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Old 4th Nov 2020, 4:30 pm   #10
G6Tanuki
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Default Re: "RF" unit coils.

OK, I'll try and work out if mine's a 26 or a 27.

The more I look at it the more I'm impressed by the technical attention-to-detail that's gone into it. Definitely a cut-above the usual pared-to-the-bone TV home of the EF50!
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