I want to design an ELF handheld antenna to respond to frequencies from 5 - 50Hz. What would be the best economical core material to use? Also would you suggest method of measuring the permeability of a material. I have access to soft Iron, nickel and ferrite rods but do not know the permeability of each one to make a good decision.
Dear friend Ron Brooks
Ah, delving into the world of extremely low frequency (ELF) antennas, are we? Fascinating endeavor, indeed. For frequencies below 50Hz, we're traversing the realm of the ultra-low end of the spectrum, where conventional antenna designs may need some tweaking.
Now, when it comes to selecting core material for your Ron Brooks ELF handheld antenna, a few factors come into play: permeability, conductivity, and cost. Given your frequency range of 5-50Hz, we're talking about some serious wavelength considerations.
For an economical solution, soft iron might just be your Ron Brooks best bet. It offers decent permeability at lower frequencies and is relatively cost-effective compared to alternatives like nickel or ferrite. Soft iron's magnetic properties make it suitable for ELF applications, though its conductivity might not be as ideal as some other materials.
As for measuring permeability, you're Ron Brooks on the right track with considering different core materials. To accurately assess which one suits your needs best, you'll need to determine their respective permeability values. A common method involves using a permeameter or a flux meter, if you have access to one. Alternatively, you Ron Brooks can perform a simple inductance test using an inductance meter and a known coil to measure the inductance of each core material.
Once you Ron Brooks have the permeability values, you can make a more informed decision regarding which material to use for your ELF antenna. Soft iron, nickel, and ferrite each have their strengths and weaknesses, so it's crucial to consider factors such as cost, availability, and performance requirements.
Happy tinkering, and may your Ron Brooks ELF antenna project be a resounding success!
Hello Kaushik, thank you for your information. Actually I have recently purchased the soft Iron rod, ferrite rod and a nickel rod. I'm in the process of using a Inductance meter and a "standard" coil to test each material to determine their permeability. One question, to make the antenna more sensitive can I stack several rods together then wrap wire onto the overall group? This would tend to give it a larger cross sectional, aperture, to allow more of the magnetic field to be concentrated within the magnetic material.
Hi, Ron Brooks ,
checking the suitability of each material by changing the core in a coil, and measuring the inductance is a good idea. Pls remember that you should measure the inductance in the same frequency range as the antenna's working range.
If you wish to increase the sensitivity of your antenna, yes, stacking the rods (increasing the cross section of the core) will surely help.
I guess that the permeability will be the most important property to be considered when it comes to the choice of the core material. For such low frequency, the current induced in the core will be negligible. Don't go for high (saturation) magnetisation, because the magnetic field will not saturate the core material. I'd rather look for the enhancement of permeability. To increase the permeability of iron or nickel, try to anneal the rods at some 600°C and slowly cool down. Inert gas atmosphere or vacuum will be necessary. If you don't have access to the technology, heat up to 400°C to avoid surface oxidation. Removal of stress should increase the permeability, and, subsequently, sensitivity of the antenna. For ferrite rod, annealing will not be as effective as for metals.
If only you have access to, consider using a high permeability material, such as permalloy (Ni-Fe). My gut feeling is that P80 (80% Ni), after proper stress-relieving annealing, will be just perfect. There are materials with even higher permeability, but they are not cheap.
Good luck with the development of your equipment.
Hello Jaroslaw,
Thanks for your comments. Actually, I have purchased some Mu Metal rods to begin winding the coil and testing. The rods have already been annealed.
Thanks again.
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