Com-Power Active Monopole Antenna for EMC/EMI radiated emissions measurements

The AM-741 Active Monopole antenna has a rod height of 41 inch (104 cm) and is used for radiated emissions measurements according to various EMC standards.
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The AM-741 Active Monopole Antenna can detect frequencies from 9kHz to 30MHz (and has the potential to operate at heights of 60 MHz).

You can adjust the telescoping rod from 23 cm all the way up to 105 cm (approx. 41 inch). The telescoping rod is also removable, making it easier to transport and carry with you. The AM-741 has an active matching network because of its low-noise preamplifier, therefore its antenna has an increased signal-to-noise ratio and is super-sensitive.

The AM-741's adjustable telescoping rod has a high electrical impedance, so during impedance matching you'll need a high-input impedance combined with a 50Ω output impedance (for connecting your measurement equipment).

The antenna's preamplifier has an internal 6 VDC NimH battery which is fully rechargeable. The preamplifier can also be charged with the supplied power adapter. There are amplifier saturation, low battery, and power indicators on the front panel.

Each of its antennas are individually calibrated to SAE ARP958 regulation by NIST equipment, of which we also include the appropriate certificate and data with the product. The matching network is calibrated using the ECSM Method.

The complete AM-741 antenna weighs 4.3kg. It has a matching network enclosure which is latched to a polished aluminum counterpoise.

Its N-type antenna connector travels through a gap in the middle of the counterpoise. The output port connector is secured to the matching network's sturdy enclosure. The output cable is fitted with a ferrite between the antenna output and the bracket (with an impedance of 20 to 30Ω at 20 MHz).

The antenna has a threaded hole on the matching network enclosure, used to attach the antenna to any tripod. The AT-220 antenna stand is our suggested support for the AM-741 antenna. The AT-220 (which we also supply on our website) allows you to change the height of the antenna so that it's level with ground plane heights from 80 to 100 cm.


The Active Monopole Antenna is mainly used for measuring radiated emissions, generally under 30 MHz. This antenna model is often used for CISPR 25 automotive tests, MIL-STD 461 (RE102), RTCA DO-160 (section 21, A-E) and other EMC standards. It is mandatory for most testing procedures that the counterpoise and ground plane (on which the Equipment Under Test (EUT) is installed) be bonded directly when performing the tests.

For radiated emissions testing, the RF voltage from a 50Ω source is transferred to the first leg of a T-connector, the second leg has a 50Ω impedance, and the third leg is a dummy antenna which simulates the rod's high impedance.

Active Antenna Factor Graph

The Antenna Factor is used by EMC and RF antenna engineers to describe the electric field strength needed to produce 1 Volt at the antenna terminals. Using the sum of Measured Voltage + Antenna Factor you can calculate the Field Strength of the antenna. Also, the Antenna Factor shows what the antenna's received voltage is when an electric field is present. As shown in the graph below, the AM-741 has a typical Active Antenna Factor of between -1.2 and -0.3 [dB(m-1)], and an average Antenna Factor of 12.6 [dB(m-1)]. Furthermore, it's maximum Antenna Factor Variation is ±1dB (between 9 kHz and 30 MHz).

Active Antenna Factor AM-741 Active Monopole Antenna

VSWR Graph for Active Monopole Antenna AM-741

The Voltage Standing Wave Ratio (VSWR) is a function of the reflection coefficient (which is used to describe reflected power from an antenna). Most commonly, the VSWR of a transmitting antenna is measured and examined upon tuning and installation. This measurement is required, to assure that damage isn't made to the antenna's transmitter if it receives an unexpected electrical impedance. This damage occurs because an antenna/feed line impedance which is non-matching prevents the antenna's full power being reached. The AM-741 has a typical VSWR of between 1.01 and 1.329 :1 at its output port. The Average VSWR at its output port is 1.06 :1. VSWR Graph - AM-741 Active Monopole Antenna

AM-741 Product Datasheet

Datasheet PDF
Technical Specification
Manufacturer: Com-Power
Antenna Type: Active Monopole Antenna / Vertical Rod Antenna
Model: AM-741
Frequency Range: 9 kHz to 30 MHz (usable up to 60 MHz)
Specifications: MIL-STD-461, RTCA DO-160, CISPR 25 and more
Nominal Impedance: 50 Ω
Battery Type: 6 V NimH (rechargeable)
Average Battery Life: 10-12 hours (new, fully charged battery)
Active Antenna Factors (typical): -1.2 to -0.3 (average: -0.5) [dB(m-1)]
Antenna Factor Variation (maximum): ±1 dB (9 kHz to 30 MHz)
Dynamic range: 103 dB @ 1 MHz [1 kHz bandwidth]
Lower Limit of Field Strength Measurement: 7 dBμV/m (2.2 μV/m) @ 1 MHz [1 kHz bandwidth]
Upper Limit of Field Strength Measurement: 110 dBμV/m (0.35 V/m) @ 1 dB compression
VSWR (output port): 1.01 to 1.329 (average: 1.06) :1 (typical)
Return Loss (output port): 17.0 to 41.1 (average: 33.1) dB (typical)
RF Connectors: N-type (female)
Telescoping Rod Element: Adjustable from 23 cm to 105 cm (approximately) Standards specify 104 cm / 41 inch
Tripod Mounting: 1/4 x 20 inch threads hole
Size of Base Plate: 60.5 cm x 60.5 cm (23.8" x 23.8")
Size (Amplifier section): 18.8 cm x 41.4 cm x 7 cm (7.4" x 16.3" x 2.75")
Weight: 4.3 kg (9.5 lbs)
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