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Old 7th Sep 2018, 8:32 pm   #1
Brian4radio
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Default 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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Old 12th Sep 2018, 6:22 pm   #2
boxdoctor
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Default 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.
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Old 16th Sep 2018, 8:05 pm   #3
Brian4radio
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Default 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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Old 18th Sep 2018, 6:01 pm   #4
David Simpson
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Default 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
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Old 19th Sep 2018, 11:03 am   #5
ms660
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Default 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.
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Old 22nd Sep 2018, 9:58 pm   #6
Brian4radio
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Default 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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Old 28th Sep 2018, 1:32 pm   #7
boxdoctor
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Default Re: Vintage aerial loading coils

Quote:
Originally Posted by ms660 View Post
"What are the wild waves saying" are usually Igranic coils
Lawrence.
Thank you Lawrence, I stand corrected on that.
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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