ELECTRO-METRICS ALP-11
(ALP11-1)
DESCRIPTION AND USE ELECTRO-METRICS
ALP-11 LOOP ANTENNA
1.0 Description
The ALP-11 Loop Antenna is designed to obtain magnetic field measurements from 20
Hz to 50 kHz. It can be used up to 500 kHz with any 50
instrument since it is designed and
calibrated for use in a 50
system. The antenna is suited for use in compliance testing to MIL-
STD-461A/B/C, CISPR standards, plus other government and federal standards.
The antenna incorporates a balanced faraday shield that reduces response to electric fields
to a vanishingly small amount. This allows the antenna to obtain practically pure magnetic field
measurements.
The antenna is designed to work into a 50
system and the calibration chart is based on
this use. The calibration chart gives values of antenna factor for finding magnetic field strength
H.
NOTE:
The calibration chart in Figure 1 only extends to 100 kHz.
However, the antenna factor from 100 kHz to 1 MHz remains
almost constant at 1.8 dB(S/m).
To find the field strength H in dB(µA/m), add the factor in dB(S/m) to the measured two-
terminal input voltage on the 50
instrument in dB(µV).
To find the flux density B in dB(pT), add 2 dB to the field strength H reading.
The ALP-11 Loop Antenna is, electrically, a magnetic dipole and thus having a dipole
pattern must be oriented for best sensitivity.
The base plate has a 5/8-11 threaded receptacle for mounting to the Model TRI-136
Tripod. This allows the loop antenna to be mounted either vertically or horizontally with respect
to a horizontal plane.
