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Why are ferrite rod antennas inefficient (for sending and receiving), one would asume stronger magnetic field makes them more efficient?
I know there are core losses at higher frequencies, but i am reasoning if you have a air-core antenna and ferrite rod antenna with magnetic field as much as MILLION times stronger than without a core, isn't ferrite atenna supposed to be stronger and more efficient for the same input power?
Tnx for the answer, i just don't understand what you mean by "they saturate easily"? As far as i know ferrite cores can be highly magnetized.
I don't think saturation is problem AT ALL. As Ian Poole from radio-electronics.com writes:
"Ferrite rod antennas are normally only used for receiving. They are rarely used for transmitting anything above low levels of power in view of their poor efficiency. It any reasonable levels of power were fed into them they would soon become very hot and there would be a high likelihood that they would be destroyed."
1 Answer
- Robert JLv 73 years agoFavorite Answer
At appropriately low frequencies, a ferrite rod antenna will be far more effective than an air cored coil of the same volume.
That's why they are generally the standard antenna for long wave / medium wave portable radio receivers.
They are not good for higher frequencies as ferrite materials become increasingly lossy with increasing frequency.
The loss becomes so high the core has no useful effect. Actual iron ferrite starts to show losses at around 500KHz - 1MHz and is totally unusable at 10MHz or less, depending on material grade.
Also, they saturate easily so are not practical for transmitting at more than very low powers.
