Loop Antennas vs. B-Probes: Similarities and Differences

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Discussion Overview

The discussion centers on the differences and similarities between loop antennas and B-probes (magnetic probes), focusing on their operational fields (far field vs. near field) and characteristics such as antenna factor, impedance matching, and efficiency. The scope includes technical explanations and conceptual clarifications regarding their functionality and applications.

Discussion Character

  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that the primary difference between a loop antenna and a B-probe is their operational fields, with loop antennas functioning in the far field and B-probes in the near field.
  • Another participant notes that loop antennas extract maximum power from the magnetic field, which can distort the local field, while B-probes sense the voltage induced on the loop with minimized current to reduce field influence.
  • It is mentioned that there are different types of B-field probes, including simple coils for sensing AC magnetic fields and Hall Effect sensors for detecting both AC and DC magnetic fields.

Areas of Agreement / Disagreement

Participants express differing views on the extent of the differences between loop antennas and B-probes, particularly regarding their operational principles and characteristics. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

There are unresolved aspects regarding the definitions and implications of standard features such as antenna factor and efficiency in the context of B-probes compared to loop antennas.

Massi
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Hi
the difference between a loop antenna and a magnetic probe (B-Probe) is only that the loop antenna works in far field and B-Probe works in near field? The standard features of magnetic antenna (antenna factor, impedance matching, radiation patterns, efficiency, ecc) have the same definition in the case of the B-Probe?
Thanks !
Regards
Massi
 
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Welcome to PF.
A loop antenna and a B-probe differ in the external circuit and so in the flow of energy.
The loop antenna extracts the maximum power from the magnetic field and so significantly distorts the local field.
The B-probe senses the voltage induced on the loop, while minimising the current. That reduces the influence of the probe on the field.
 
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Thank you!
 
Massi said:
Hi
the difference between a loop antenna and a magnetic probe (B-Probe) is only that the loop antenna works in far field and B-Probe works in near field? The standard features of magnetic antenna (antenna factor, impedance matching, radiation patterns, efficiency, ecc) have the same definition in the case of the B-Probe?
Thanks !
Regards
Massi
Welcome to the PF.

In addition to Baluncore's comments, keep in mind that there are two different kinds of B-Field probes. The simplest is a small coil that is used to sense AC magnetic fields. It may be a single turn, shielded loop probe, or it can also consist of a number of turns for higher sensitivity (at the expense of lower bandwidth). But to sense DC and AC magnetic fields, a Hall Effect sensor is generally used. Does that make sense?
 
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ok I see, thank you!
massi
 

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