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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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7th Sep 2018, 8:32 pm | #1 |
Pentode
Join Date: Aug 2005
Location: North Warwickshire, UK.
Posts: 108
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Vintage aerial loading coils
Hi Team, I have built a simple one valve receiver using a book by F J Cam "A beginners guide to radio." The two coils used in the set are just hand wound of 60 turns and 40 turns. My set works very well but I have some factory made coils by Seaford and Ecclips and also "What are the wild waves saying. They are all numbered from 45,60,75.100,150,200;250 and 300. My question is which coils would work better together in the Tuning and reaction positions of the input cct. Phew regards Brian
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12th Sep 2018, 6:22 pm | #2 |
Rest in Peace
Join Date: Sep 2010
Location: Ripley, Derbyshire, UK.
Posts: 785
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Re: Vintage aerial loading coils
Hello Brian,
I think the only way to find out the answer to your question is simply to experiment with what you have got, and try different combinations in the two positions. Generally, the reaction coil (I'm assuming one of the two is for that purpose) would be no more than about one third of the number of turns compared to the tuning coil, so that gives you some sort of basis to start with anyway. Try the reaction ones with the connections one way, and then reversed to get the phasing right. With the connections phased correctly, things should be a lot livelier than if the phasing is the wrong way round. The "What are the wild waves saying?" ones are known as De Forest coils. I had quite few of those in my childhood in the 1940s. They seemed to be more efficient in terms of sharpness of tuning than any of the others. Probably worth a few bob today(?). Tony. Last edited by boxdoctor; 12th Sep 2018 at 6:29 pm. |
16th Sep 2018, 8:05 pm | #3 |
Pentode
Join Date: Aug 2005
Location: North Warwickshire, UK.
Posts: 108
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Re: Vintage aerial loading coils
Hi Tony , thanks for your reply, I will have an experiment with the coils and respond shortly . Regards Brian
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18th Sep 2018, 6:01 pm | #4 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,858
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Re: Vintage aerial loading coils
Can anyone answer Brian's query about manufactured coil numbering, please ?
I have a box of old TRF coils, some with their Inductance written in uF, and sometimes their resistance in ohms, some have both. But then other coils just have numbers on them . i.e. A lovely bakelite enclosed LEWCOS with just a fitted label with "60" stamped on it. Another - a Quality Radio one, has just "50" stamped on it - a wee one which my LCR meter tells me is 58uH. I'd like to know if any of these would do as a loading coil for a Crystal Set for LW. Guess its a lazy approach, not working out the formula & attempting a rewind. Regards, David |
19th Sep 2018, 11:03 am | #5 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Vintage aerial loading coils
"What are the wild waves saying" are usually Igranic coils, the number on them denotes the number of turns, the graph on them shows the maximum wavelength typically using a 500pF or 1,000pF capacitance and the minimum wavelength with little or no capacitance.
Typical example.... Coil number "50" Turns = 50 Inductance = 130uH Self capacitance = 38pF Self resonant wavelength = 133 metres Wavelength with 500pF = 498 metres Wavelength with 1,000pf = 693 metres All according to this: https://www.kevinchant.com/uploads/7..._catalogue.pdf There's another source on the web that gives slightly different figures for the maximum wavelength here: https://mullard.org/blogs/news/82719...d-waves-saying Lawrence. |
22nd Sep 2018, 9:58 pm | #6 |
Pentode
Join Date: Aug 2005
Location: North Warwickshire, UK.
Posts: 108
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Re: Vintage aerial loading coils
Thanks team for your replies I have now made a dual coil fitment and have tested some of my coils with it. I expected that the tuning coil would have had the most turns on it but in this particular cct the reaction coil works best when it has the most turns on it Any how this is what I have found out for my set A coil 150will be used for 1040 to 1620 metres - a 200 coil for 2030 to 2900 mtrs - a 250 coil for 2560 to 3580 and a 300 coil for 2670 to 3500. The most useful coil seems to be the 150 I have tuned to the Asian station using the 150 coil in the tuning position with the 250 in the reaction position. and radio 5 live using the 150 coil in the tuning position and a 200 in the reaction slot. I expected to tune into the radio 4 station but cannot get a signal using a 150 coil. I will try and find a combination and a longer aerial next week. Thanks for all your help on this experiment. Regards Brian
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28th Sep 2018, 1:32 pm | #7 | |
Rest in Peace
Join Date: Sep 2010
Location: Ripley, Derbyshire, UK.
Posts: 785
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Re: Vintage aerial loading coils
Quote:
However, it was nearly 70 years ago! I do remember the graphs on the coils. They looked to have been individually drawn for each coil, or was that what the makers wanted the customer to think by the style, and the insipid colour of the ink, I wonder. Tony. |
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