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EFM Series
Elevated Feed-point Monopole Series

These elevated feed-point monopole antennas have been designed for HF receiving applications as either a standalone element or as an element in an array.
Each antenna operates from 1.5 to 30 MHz. For enhanced performance, models EFM-6,12 or 18 can be used together to provide separate low, mid, and high band receiving elements.
The antenna consists of a rugged stainless-steel radiator having a solid insulator fitted at the feed point that is located above the base of the antenna. An impedance transformer/matching network provides suitable impedance transformation to a 50-ohm coaxial cable input. The position of the feed-point combined with the transformer impedance ratio allows optimum performance over a selected operating bandwidth.
The antenna is mechanically stabilized by non-conductive guy wires.
A radial earth mat of any length, consisting of up to 64 copper wires can be fitted to the base of the antenna to stabilise antenna impedance and radiation patterns.

FEATURES / BENEFITS

  • Rugged, high-reliability construction with stable performance
  • Proven design, installed in multiple locations over many decades
  • Stainless steel construction for harsh environments
  • Cyclonic wind rating
  • Element performance can be optimized for specific operational requirements, frequency sub-bands, or array configurations using RFS state of the art simulation and optimization algorithms
  • Hinged base construction allows ease of maintenance and installation

 


EFM-18 shown

Technical features

Electrical Specifications

ModelEFM-18EFM-12EFM-6
Frequency Range MHz1.5 - 32
Optimum Frequency Range MHz3-136-2011-32
PolarizationVertical
Elevation Radiation PatternRefer to plot
Azimuth Radiation PatternOmni Directional
Maximum Power Rating kW0.25 RMS
Mismatch Loss dBTypical <3dB
from 4 MHz to 10 MHz
Typical <2.5dB
from 7 MHz to 18 MHz
Typical <2.5dB
from 15 MHz to 32 MHz
Mismatch Loss NoteMismatch loss/bandwidth properties can be adjusted to suit customer operational requirements
Input ConnectorN-type socket
Impedance (unbalanced), ohmsΩ50

Mechanical Specifications

Antenna Height m (ft)18 (59.1)12 (39.4)6 (19.7)
Wind Survival Rating (no ice) km/h (mph)337 (209)

Temperature Specifications

Operating Temperature Range °C (°F)-20 to 70 (-4 to 158)

Material

Material - GuysPhillystran or equivalent (option: Insulated Stainless Steel)
Material - RadiatorsStainless Steel Tube
Material - Earth MatUp to 64 copper radials, or mesh ground screen when used in array configuration
Material - InsulatorsDelrin

PACKAGING INFORMATION

Shipping informationPacked weight [kg]Packed size [m]
EFM-183706.0 x 0.3 x 0.15 and 1.2 x 1.2 x 0.6
EFM-122306.0 x 0.2 x 0.15 and 1.2 x 1.2 x 0.6
EFM-61156.0 x 0.2 x 0.15 and 1.2 x 1.2 x 0.4

External Document Links

Notes