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 Post subject: Tube for Crystal Radio Coil
PostPosted: Dec Thu 17, 2020 4:06 pm 
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I am not much for crystal radio building but for some reason I always have my eye open for alternatives to the standard toilet paper roll for winding a coil on.

these are readily available in Walmart's produce department, they have produce plastic bags rolled around them. There are usually one or two empty during every visit and they really don't mind if you ask for the empties.\

Measurements 3.5" by 1.75" and they are about 3/16 thick


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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Thu 17, 2020 4:56 pm 
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Location: Wayside, NJ Monmouth
I use them. Good to dry them out in a Low Temp Oven for a couple of hours to be sure the moisture is driven out , then coat with a sealer. I use spray shellac.


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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Thu 17, 2020 8:23 pm 
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I've used 1-1/2" diameter PVC pipe for coil forms.

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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Thu 17, 2020 9:48 pm 
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IF your replicating a $1.00 crystal radio then a paper tube is O.K. If less loss in a solenoid winding is desired polystyrene tubing is a better choice. For example:

https://genplex.com/plastic-tubing-mate ... ene-tubing

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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Thu 24, 2020 6:09 pm 
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Joined: Aug Mon 18, 2008 3:17 pm
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Location: Dallas Tx.
Clear plastic food jars would be a lot better.
Thickness relates to losses, lower Q coils.
I have a couple good coils made from plastic mailing tubes.
You could wind larger diameter wire on the thick forms, then remove the former for a higher Q stand alone coil.


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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Fri 25, 2020 11:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1239
Location: St. Louis, MO, USA
Awhile back I got some generic toilet paper with really hard inner rolls. I may use these for coil forms. Reynolds makes a plastic film for covering food that has a long hard plastic inner roll.

Dennis


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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Sat 26, 2020 12:05 am 
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I believe that the number of turns in any particular coil is dependent upon the diameter of the form they are wound around. Using the most convenient or cheapest of such -unless pretty close to the specified size- would require formulating an adjustment in the turns number, or suffering with a loss of efficiency.

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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Sat 26, 2020 3:01 am 
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Location: Phoenix, AZ
FWIW, several months ago I was turning down some new black ABS pipe on my lathe to make a piece for a different (non-radio related) project. I was surprised to find, underneath the skin, that the body of the pipe wall is made of some sort of lighter material with a microscopic cellular structure ... the wall is sort of like a bonded sandwich. It had been many years since I last turned ABS pipe to make an adapter, and I don't remember pipe having this composition in the "old days" - the wall was simply solid ABS. It appears that 'they' changed the recipe. If I were looking for plastic pipe to use as coil form material, I think I would avoid current production ABS ... I suspect it might be lossy.
R/ John


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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Dec Sat 26, 2020 3:32 am 
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Location: Arvada, CO, 80004
Quote:
Tube for Crystal Radio Coil


Title Confused me just a little!

Try medicine bottles :?: :!:

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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Jan Fri 01, 2021 4:48 pm 
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Joined: Aug Sat 29, 2009 12:06 pm
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Location: Milford, CT
I’ve used paper towel tubes. I paint them with yellow glue and let it dry between coats. I typically put 7 coats of glue inside and out. It’s a bit time consuming but the end result is excellent.


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 Post subject: Re: Tube for Crystal Radio Coil
PostPosted: Mar Sat 27, 2021 1:01 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1530
Location: Auburn, AL
UV201 wrote:
FWIW, several months ago I was turning down some new black ABS pipe on my lathe to make a piece for a different (non-radio related) project. I was surprised to find, underneath the skin, that the body of the pipe wall is made of some sort of lighter material with a microscopic cellular structure ... the wall is sort of like a bonded sandwich. It had been many years since I last turned ABS pipe to make an adapter, and I don't remember pipe having this composition in the "old days" - the wall was simply solid ABS. It appears that 'they' changed the recipe. If I were looking for plastic pipe to use as coil form material, I think I would avoid current production ABS ... I suspect it might be lossy.
R/ John


It’s usually larger diameter DWV/sewer pipe that comes in “cell core” variety. They do this to reduce weight, without compromising strength/rigidity too much. Usually product is labeled as solid or cell core. I’ve only ever seen the cell core pipe in 4” and larger sizes. Pressure rated pipe, I would imagine would be solid throughout.

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