Monopole Antenna for EMC Testing

An active monopole antenna consists of a short vertical radiator directly coupled to a high-input-impedance, low-noise amplifier. The active stage buffers the antenna, minimizes mismatch losses, and enables electrically short elements to operate over very wide bandwidths.

Com-Power AM-741R is an Active Monopole Antenna operating over 9 kHz to 30 MHz (usable up to 60 MHz). Its removeable telescoping rod element is adjustable from 23 to 105 cm (approximately). Most standards specify a rod height of 104 cm (41 inches). Due to the high impedance of the rod element, a matching network with a high input impedance and 50Ω output impedance (for connection to the measurement equipment) is needed. 

The AM-741R provides this and also incorporates a low-noise preamplifier, thereby increasing the sensitivity and signal to noise ratio of the measurement system. The preamplifier can be powered by its internal, rechargeable 6 VDC NimH battery pack or the supplied charger/power adapter. The front panel has indicators for RF ON/OFF, power, battery low, amplifier saturation, as well as charging status. The matching network enclosure is secured to the bottom side of the of a 60.5 cm square, polished aluminum counterpoise.

The AM-741R Active Monopole Antenna is used for radiated emissions measurements, typically below 30 MHz. It is commonly used for tests according to RE102 of MIL-STD-461, Section 21 of RTCA DO-160, CISPR 25 (automotive), and other various standards.

 Includes:

• Telescoping rod: Adjustable from 23 cm to 105 cm (approx. 41 inches for compliance with most standards)
• Low-noise preamplifier: Enhances signal sensitivity and SNR
• Power Indicators: RF ON/OFF, battery low, amplifier saturation, and charging status
• Mounting: 1/4"-20 threaded hole for tripod mounting (compatible with Com-Power AT-220)

Applications:

• Compliance with standards such as:
• MIL-STD-461 (RE102)
• RTCA DO-160 (Section 21)
• CISPR 25 (Automotive)
• Other sub-30 MHz emission tests

Grounding & Installation

Standard Grounding: Counterpoise must be bonded to the ground plane where the EUT is installed

MIL-STD 461 Grounding:

• Output cable shield must be grounded via metallic bracket
• Ferrite (20–30Ω @ 20 MHz) must be centered between bracket and antenna
• Optional AMS-741 Grounding Kit available, includes:
• Ferrite-fitted cable
• Grounding bracket
• Elbow adapter