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- เผยแพร่เมื่อ 28 พ.ย. 2024
- The plastic pipes I have used to make coils have never been a problem, UNTIL NOW! By (bad) luck I ran into a type of plastic pipe that does NOT work for a crystal radio coil. It seems to have a filler that interacts with radio waves lowering the inductance of the coil to 1/3rd the calculated/expected value (don't know what other ill effects it might have.)
Crystal Radio Coil Sizing: • Crystal Radio Coil Siz...
Calculator: m0ukd.com/calc...
UPDATE: The most common fillers used in plastic include
Calcium carbonate (CaCO3) Magnetic susceptibility (χ) −3.82×10−5 cm3/mol
Talcum Mg 3Si 4O 10(OH)2
Barium sulfate Magnetic susceptibility (χ) −71.3·10−6 cm3/mol
Wollastonite CaSiO3
Magnetite Fe2+Fe3+2O4 Ur = 5.0 Magnetic
From ChatGPT (for what it's worth).
ME:
plastics now contain a lot of fillers such as Calcium carbonate, Talcum, Barium sulfate, Wollastonite, Magnetite, etc. given the relative permeability of these, how do they affect the use of plastics with this fillers as RF cores. Engineering level answer please.
ChatGPT Answer:
The use of fillers such as calcium carbonate, talcum, barium sulfate, wollastonite, magnetite, etc., in plastics can significantly impact their electromagnetic properties, especially when used as RF (Radio Frequency) cores. The relative permeability of these fillers plays a crucial role in determining the effectiveness of the plastic composite as an RF core. Here's how different fillers can affect the performance:
Calcium Carbonate (CaCO3):
Impact on Permeability: Generally, calcium carbonate has a relatively low permeability compared to some other fillers. This can influence the overall permeability of the composite material.
Effects on Dielectric Properties: Calcium carbonate is known for its dielectric properties, which can affect the electrical performance of the material. It may contribute to changes in the dielectric constant and loss tangent.
Talcum:
Impact on Permeability: Talcum has a low permeability, and its use in plastics can contribute to enhancing the magnetic properties of the composite material.
Dielectric Properties: Talcum may also influence the dielectric properties of the material, affecting factors such as the dielectric constant and loss tangent.
Barium Sulfate (BaSO4):
Impact on Permeability: Barium sulfate has high density and can significantly affect the permeability of the composite material, making it more suitable for certain RF applications.
Dielectric Properties: Barium sulfate is generally considered a good dielectric material, and its use may contribute to maintaining stable electrical properties.
Wollastonite:
Impact on Permeability: Wollastonite has a low permeability, making it a potential candidate for enhancing the magnetic properties of the plastic composite.
Dielectric Properties: Wollastonite can influence the dielectric properties of the material, and its use may contribute to changes in the dielectric constant and loss tangent.
Magnetite:
Impact on Permeability: Magnetite is a magnetic material with high permeability, making it a suitable choice for applications where magnetic properties are crucial, such as RF cores.
Dielectric Properties: Magnetite can affect the dielectric properties, and its use may contribute to changes in the material's electrical characteristics.
In engineering terms, the choice of filler depends on the specific requirements of the RF application. Designers need to carefully consider the trade-offs between permeability, dielectric properties, mechanical strength, and other factors to optimize the performance of the plastic composite as an RF core. Additionally, the concentration and dispersion of fillers within the plastic matrix are critical parameters that can influence the overall electromagnetic behavior of the material. Experimental characterization and testing are often necessary to fine-tune the formulation for a particular RF application.
I've looked into the magnetic susceptibility of the most common fillers used in plastics. They range from near zero (talcum), to very magnetic (magnetite).
The most common fillers used in plastic include:
Calcium carbonate (CaCO3) Magnetic susceptibility (χ) −3.82×10−5 cm3/mol
Talcum Mg 3Si 4O 10(OH)2
Barium sulfate (BaSO4are rhombic crystals (cuboid) Magnetic susceptibility (χ) −71.3·10−6 cm3/mol
Wollastonite CaSiO3
Magnetite Fe2+Fe3+2O4 Ur = 5.0 Magnetic
Finding values for most materials is very difficult as only the CRC handbook publishes them, and many are reported using different measurement standards.
BTW: Gray PVC often has some amount of iron oxide in it. Any plastic that is gray, red or black may have iron oxide in it. It isn't an intentional addition it is something that comes as an impurity in other stuff.
At the general hardware and large home improvement stores in my area of the US, PVC conduit is grey and, very occasionally, white. Water PVC pipe comes in 2 flavours - pressure and Drain & Vent. They are both white, but the pressure pipe is a much denser material. I have had fairly good results using both of those - haven't used grey conduit. One can sometimes find blue or green pipe at the contractor suppliers, but they are in the larger sizes (4"+) and usually marked for waste or sewage use. My best results, though, have been with varnish soaked cardstock and 3D printed forms.
Nothing like the classic cardboard tube dipped in varnish.
Interesting. I would avoid anything with white paint too. White pigment is usually made from different metal oxides. Black is bad if it's made with conductive carbon. Lamp black is fine, it's made from non conductive oil soot.
The most common white pigment by far is titanium dioxide, which is an excellent insulator at DC. At RF the dielectric constant may be a problem.
You can avoid all these problems by using cardboard mailing tubes. They can be painted with urethane varnish to stiffen them up.
True, and I have done that. Their major drawback is they can be crushed and deformed more easily. That's what happened to my first crystal radio.😢
@@tsbrownieNot the junk paper towel tubes. Use the very stiff mailing tubes which are very stiff.You can get them at Walmart, Staples, etc.
I've also used the tubes that were in rolls of carpets and fax paper tubes used to be really stout.
It is amazing that you found that out. The interesting thing is that metal conduit affects the magnetic field of the wiring it is meant to contain so you would think that plastic conduit would be free of any impurities that would do so.
I agree. Surprised me.
I say also stay away from the gray pipe cuz that's also used for condo electrical because it may have some filler in it maybe because it's used for electrical usage in Lowe's carries that
The immediate suspect for that electrical conduit is something conductive. That being the case, a slit down the length, breaking the hoop, should greatly reduce the effect on an inductor wound on the pipe. Just like how transformer cores are made of laminated iron sheets, not solid iron.
In the distant past, I used ABS "drain" plumbing pipe and it was OK. I suspect the conduit pipe is actually conductive as far as the RF is concerned. Lower inductance is hard to do with anything that is not conductive in nature.
BTW: Some "fake" diodes will work OK. The problem is you don't know what you are going to get with them. If I get some time, I might build a crystal radio and try a few diodes to see what they do compared to a 1N34
I know there are equivalents to the 1n34a, but I won't recommend something I have not tried myself. If my videos get 500k views, and only 1% fail, that's 5,000 people. I am compiling non-diode detectors, but there's always something that comes up that needs to get done first.
@@tsbrownie If I do the experiment any time soon, I will come back with my results
@@kensmith5694 Please do.
@@tsbrownie I just did a simple experiment and I found that basically nothing works as well as a 1N34
I have a crystal radio set up right now with just enough antenna that I can hear a station and understand what is being said.
With the 1N34 it works well enough. At least it did until I dropped my earphone and it broke. I did get some diodes checked before that.
I loaded the output with a 6.8K for the listening test.
I put a 0.68 across (and no headphone) for a volt meter check.
If you want you can copy and paste what follows to format it better
1N34, Clear, 100mV
1N4148, OKish, 75mA
1N5408,Weak, 10mV
R107,Weaker, 30mV
1N4007,Barely, 20mV
1N5819,Leastm30mV
As you can see the audio vs voltage on the 0.68uF don't track very well.
I may repeat this test later with a lot more antenna.
Have a very good whatever it is you do this time of year and a great newyear
@@kensmith5694 Thank you for the holiday wishes. Same for you and yours. I appreciate all the effort in getting and testing those diodes. I too prefer the 1n34a, it was purpose built for AM audio frequency detection. There's an equivalent made in the old days from Eastern Europe that's pretty good, but after that the pack falls short pretty quickly.
Thanks for your Video, appreciate your insight, crystal radios are extremely interesting, enjoying your Channel, peace out 😎✌
I'm thinking that that brand of plastic conduit has a metal filler that is used to suppress the ac wave from the power line.
What about the standard, round paper-board box of "Quaker's Oats"?
Boy Scouts and school kids have been building "Crystal SETS" with the coil and other parts attached to the Old, familiar Oat Box, for about 100 years! All those radios work GREAT!!!!
Have you tested those?
They work the same as plastic cores of the same diameter, but are much more fragile. My first core was paper and it got crushed. All that work gone in an instant!
Electrical conduit is always 'doped' so as to be fire-resistant. Designed to char, but rather than "catch fire" it's often designed to give off CO2 when it gets hot. Bad idea.
As for un-doped PVC, I'm still not a fan, because it has a high susceptibility to absorbing and retaining atmospheric moisture (ie, hygroscopic) - and worse still, the moisture content will vary day by day as the relative humidity changes! Guaranteed to affect performance.
This effect can be mitigated by slowly drying in a warm oven then quickly painting with a xylene-based thinned lacquer while still warm... but that's "a lot of squeeze for very little juice".
For a coil former using modern materials, I prefer PET, the plastic used in soft-drink bottles.
Soft drink bottles themselves are usually not the best option, as the walls are thin and lack the strength needed to support a coil... BUT!
There are many other products packed and marketed in the same material, but much stronger, much thicker walls.
From soup to shampoo to peanut butter, there are many excellent options and the only prep work needed is removal of labels with some turpentine, then a wash in warm soapy water.
I haven't measured or researched the permeability of PET, but it has a gazillion uses in the electrical hobbyist's workshop - especially if, like me, you also play silly games with extremely high voltages!
Did you say the name is "Clips-All?" As in, clips all noise? Meaning it is a special type of electrical conduit that includes electrical noise suppression? Well, we know that that is the way the pipe acts, but I am wondering if the brand name is a clue to it intentionally having special noise suppression properties. Might be fun to test/research that.
"Alfred Gerard develops the product that gave Clipsal its name, an adjustable, one size “clips all” metal conduit fitting. The company achieves several manufacturing breakthroughs, including the first all-Australian electrical switch."
Using the methods to calculate the inductance of a single-layer solenoid given on page 6-1 and page 6-3 of Reference Data for Radio Engineers, Fifth Edition, I get about 1.5 microhenries for the inductance of the coil of #19 wire wound on the white tube. You might want to double-check your calculations. (This still leaves a discrepancy, but a smaller discrepancy, between the measurement and the calculation.)
I also get different answers from different calculators, but the answers are consistently grouped around a mean, and that mean is far enough from the measured inductance on that pipe (by half or so) such that is is clear there are pipes that will greatly skew the inductance of a coil wound on them.
When you were making your tests did you give any consideration to the wall thickness of the pipe? I would think that thin wall pipe (drain, waste, vent) would work better than sked 40 water supply pipe. In this respect, would thinning the wall thickness on a lathe improve the performance of plastic electrical conduit?
It will depend on the relative permeability of the plastic of the pipe. PVC with neutral fillers (like glass) is pretty close to air, so thicker or thinner won't affect the RF signal. I've used thick and thin and if it is a factor, it is much smaller than other things like well wound coil, correct diode, clean connections, etc. Thicker will be mechanically stronger and less prone to deformation and damage.
The blue pipe,is that pex pipe.?
@@skybot9998 PVC drinking water pipe.
@@tsbrownie thanks.👍
if you are outside the range would you end up getting content above and below the am radio like the noise from the hetrodyning oscillator in intermediate stages of a standard radio or the pulse width modulations of a power supply or even the waves given from the human body (what a therimin detects to work or why you can cause interference with reception when touching antennas).
electrical pipe even plastic has to have something to act as shield to reduce the emf leakage.
you dont want radio and electrical noise radiating from the wires.
the sewer pipes would have anti microbial coatings that may be a problem.
Outside the AM band, generally the RF power levels are a lot lower.
@@kensmith5694 i was thinking if you wound the coil too long you may be able to tune to 400 khz witch is below the am 540 khz or if you wound the coil too short you may get to 2 or even 3 mhz witch is then in the ham bands.
the shielding material used in the plastic pipes may have the same effect as longer or shorter coils
@@ejonesssThe AM stations are many thousands of watts. Hams etc are much lower power.
@@kensmith5694 the video was talking about am receivers right? so you might pickup something outside of the band it is like you trying to use a japanese fm radio here in the united states or a usa fm radio in japan because of the differences in the bands you may be able to tune outside of the band.
@@ejonesssThe receive something. there must be a transmitter. To receive on a crystal radio, there must be a reasonably strong transmitter.