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Loop Antenna FAQ's

As part of our commitment to provide you with information that adds value to your work, A.H. Systems is continuously producing articles and application notes on specific uses of our products. Our complete library of technical articles and application notes is available below for public use as an open reference for the RF engineering community. If you need information on a topic you don’t see here or you require additional technical support, we can help. Contact support to talk with one of our engineers for answers.

Common Questions

A small loop antenna is sensitive to the magnetic field and not the electric field. The loop antenna’s voltage output is proportional to the magnetic field that it’s in.

The circular loop antenna is considered small if its diameter is less than λ /10, it is small in comparison to wavelength.

Shielding effectiveness tests requires a 12” (30 cm) electrostatically shielded loop antenna for both the transmit and receive antennas. Our models would be the SAS-563P passive transmit loop antenna and the SAS-563B active receive loop antenna.

No, our active loop antennas are a receive only antenna. Any attempt to transmit power with damage the antenna.

A vertically orientated loop antenna has a large figure eight pattern and there is a sharp null when rotated 90 degrees.

The active loop antennas have a 12VDC NiMH 2000mAh battery assembly (P/N 2351-3).

Every hour of charge will result in two hours of operation for up to 10 hours of charging. Charging for up to 24 hours will not damage the battery.

Approximately 40 hours.

That will depend on the amount of usage (charge/discharge cycles). A typical battery pack should last 3 to 5 years; ≥ 500 charge cycles (IEC 61951-2)

The battery storage temperature rating is -20 to 50 C.

NiMH battery voltage can drop significantly during storage due to self-discharge. We strongly recommend checking the voltage of your stored batteries, or cycle them, at least once every 6 months.

The SAS-564 Loop antenna produces a magnetic field that has a flux density of 1.4 * 104 picotesla per ampere (pT/A) of current flowing in at an axial distance of 1 Meter from it's center. In decibels, this is 83 dB(pT/A) The field intensity change in dB is twenty times the log of the change in current at a given distance.

The effective gain of a passive loop antenna is generally lower than that of a full-size antenna like a half-wave dipole, especially for electrically small loops. The gain is primarily determined by the antenna's physical design, including its circumference, the number of turns, and its orientation, and is a measure of its efficiency in a specific direction. A larger loop or a higher number of turns will provide more gain, but will also reduce the antenna's bandwidth. Mathematically based off of the antenna factor, the gain of the SAS-564 loop antenna would be -200 to -28 dBi.
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