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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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18th Mar 2019, 7:02 pm | #21 |
Heptode
Join Date: Dec 2014
Location: Limerick, Ireland.
Posts: 901
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Re: Long Wave Coil Rewind
Coupling is indeed why the inductance is proportional to N squared.
A wave wound coil won't be hugely different inductance to a multilayer solenoid of the same length and inductance. It will need some more turns for same inductance. It will use more wire and have lower capacitance. |
18th Mar 2019, 9:57 pm | #22 | ||
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,765
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Re: Long Wave Coil Rewind
Quote:
Life certainly gets complicated with tapping multilayer coils, where mutual inductance becomes very significant. The recent thread about 'Q', which started off with a simple request for a 'Q' meter and drifted off into the clouds indicates just how complicated life can get. I often wonder how the 'cottage industry' of small firms that used to abound who made coils - Repanco, Weyrad, Denco, Osmor et al - managed to devise and manufacture their coils (and in some instances, coil packs). Most were, I think, quite small outfits with maybe half a dozen employees at most. I doubt that they had much in the way of complex test equipment, or were mathematical geniuses. It makes their achievements all the more remarkable and called for much manual dexterity. (I wonder if today's boffins have ever subjected any of those vintage coils to close and rigorous examination, not that there'd be much point in doing so).
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David. BVWS Member. G-QRP Club member 1339. |
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18th Mar 2019, 10:17 pm | #23 | |
Tetrode
Join Date: Apr 2015
Location: Chester, Cheshire, UK.
Posts: 62
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Re: Long Wave Coil Rewind
Quote:
A very interesting read and some fine craftsmanship by the looks of things. I'm considering ordering one of these devices to get the initial readings from the good coils: www.ebay.co.uk/itm/LCD-1999-3-1-2-BM4070-LCR-Meter-Capacitance-Resistance-Inductance-Self-discharge/233022521025?hash=item3641397ec1&enc=AQADAAADAFjVr DbVsZ8oH%2F8PNHtt9VX4%2Fw7FZcmMuqsX8uaFEduVhpK7Ibl 2x8LW5Yhmj3LyqFuqj1%2FZGSbcv7Kcc%2B5ryC%2B3SfmInNa rGTFo5r443JkYRgSVxYNzvupRFiPNoYnNqbNBkGu98HF2FPtET jyN%2FbhKo%2Bf1Tb7CID9HjaGANJb%2B%2BoYwZRdFZYZLtQw 1nsnJJqVU750ebSsFl5JJlNw5cZFJu%2BW1iy%2BHRd26t7BbM S5sEiOG9xVL7Ps3oV7uonweYRnfiMYCePu0lfLNWF53twVS2lE soIST1PVClaR4%2FQ%2FxyRNPr19FxZpxzOxz%2F548irLTm4d cNxuZUlfi8cq9y3b6LpGdmN0pd%2BPxup3l3R0sHCMIZS7%2FL 4n3dmRXqMSdKEwdmQcXICrOfXrQpdKnFnTSKUQuiOR5EZ9M%2F X1eDwCHbCMWOfGfmZOCcflZJ6WLafYIHk3J4JhoHgiVv1bxHNB 5WLluNeuzurdNrc9Q5CNqy2z4raUGMalIbwm3AZ%2BLVFZKUXa OagR1TyYxbEZFmQWzX1Z0ZRZZkjevB4HjRDN95quzTr6MTT%2B 5n175eyXhvh6KRJTraNoRVUwnpPXNpr1mYvvmMhoDvPDFqX4pR 2lEyrt0a3JySB72qlrb0EIcJFF9u9VYm0WuVWNyDcxa4mJkqIp j8%2B%2BOJ2glNnblZKKCgdaWHu%2BGJxfk1yg68eUjdUqWvHB AcsIcQrDhz4k48SpKBvp9OcHXB2%2BUyJU7sCmxZuwY1JbinDr scuq3d5yHUyCjtjIDMlrC4bSsBEATjlVZnYRj3hSduRisqJxap 4gm6SBbxTGBlaDvhs2iZZoVqoXyL1mKYb2zOCBDD5MZkTn%2BZ 6uiBaba40y6QzBNjDc79%2Fv%2FAa%2BzIEFi%2FiyJJSS59X7 ILPnTFiJOKfM4t38NZ5Z04q1zH7B%2BsvZYOWuXx5c7DYJQj9J lDEb79MHjhdGgJk9DQYfp4RolUt2fgpT9Ayso64%2BWexrCPtE Z%2FIvqBovAXAAX9tAd%2BQsMk0A1sc21xw%3D%3D&checksum =233022521025fed6b46ba7dd476f8c274d702cc0d077 I am a little sceptical of how well this device will work given the price compared to some of the others on offer (I did baulk at some of the prices quoted at RS components for similar apparatus) so if anyone can offer a testimonial on that particular LCR meter I would be interested to know. Paul |
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18th Mar 2019, 10:39 pm | #24 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Long Wave Coil Rewind
Quote:
Lawrence. |
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19th Mar 2019, 11:08 am | #25 | |||
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,088
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Re: Long Wave Coil Rewind
Quote:
I've been designing coils and transformers professionally for 28 years (among other things). I regard myself as still learning my job. That applies particularly to high-Q, air-cored inductors where my company gets very few enquiries (I can think of only 3 which made it to getting an order in this time). It's been fun, but I have gaps in my detailed knowledge, and bigger gaps in experience, when it comes to RF. So this thread is of particular interest! Quote:
Quote:
Self-capacitance tends to be rather lossy capacitance; a dry, unimpregnated coil paralleled with 300pF of external capacitance will generally show higher Q than the same coil, impregnated, with 270pF external capacitance. By how much I don't have a feel for - if Paul the OP gets this far I will be really interested in results! |
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19th Mar 2019, 11:55 am | #26 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Long Wave Coil Rewind
The Osmor factory in the '60's was a 65,000 square ft job according to WW archives.
Lawrence. |