Communications Audit UK Ltd is a company that leads the field in the design and manufacture

of highly specified and highly reliable antenna multicouplers

for more information please visit us at








CommsAudit design and manufacture very reliable high performance Receiver multicouplers for the RF community. CommsAudit Antenna HF VHF UHF Multicouplers provide multiple outputs from a single input and this enables a number of receivers to share one antenna input with minimum loss of signal performance, this is normally referred to as multicoupling. When specifying a multicoupler there are a number of key points to consider:

Intermodulation.  Intermodulation products are formed when two signals of different frequencies are mixed abd the additional signals are formed at frequencies that are not in general at harmonic frequencies (integer multiples) of either.  The largest intermodulation products appear at ƒ1+ ƒ2 or ƒ1- ƒ2 (referred to as second-order intermodulation) and at 2ƒ1-ƒ2 or 2ƒ2-ƒ1(third-order intermodulation).  Intermodulation figure can be shown as the input level or as the output level for that point this should be specified and can be termed input intercept point (IIP) or output intercept point (OIP).  When considering multicoupler performance specifications it should be noted that some vendors will quote OIP2 and OIP3 and if this is done it refers to the output of the multicoupler and includes the gain figure.

A basic low performance multicoupler with no input protection and poor port-to-port isolation

Basic Low Performance Multicoupler Block Diagram

Isolation.  Port-to-port isolation stops RF leakage between the channels of a multicoupler.  Output port-to-port isolation is an important parameter as it is possible for receivers connected to a multicoupler to have antenna ports with (local oscillator) emissions that can cause problems for other receivers connected to the multicoupler.  Isolation figures should be quoted under all-out impendence conditions i.e. (open through to short) as an open or shorted multicoupler port would cause a reduction in the output port-to-port isolation.

High Performance Multicoupler Block Diagram

Noise.  The noise figure (NF) measures degradation of the signal to noise ratio (SNR) caused by the components in the RF signal chain.

Input protection. Large input signal protection is essential in any HF signal distribution system and is desirable at VHF, UHF and L-Band frequencies.  Protection from electrostatic discharge such as a nearby lightning strike and EMP is also essential. Huber Suhner EMP protectors are normally used with all Commsaudit multicoupler installations.

Voltage Standing Wave Ratio (VSWR).  The ratio of the maximum/minimum values of standing wave pattern along a transmission line to which a load is connected. VSWR value ranges from 1 (matched load) to infinity for a short or an open load. In addition to signal distortions, inefficiency and standing waves, RF energy reflected by impedance mismatching between a transmission line and its load can also damage the signal source, such as a power amplifier.

Phase Match.  Optional phase matching of outputs can be useful if the multicoupler is to be used with direction finding (DF) or Super resolution Direction Finding (SRDF) systems .

Phantom Power Optional Phantom power through coax, to power active antennas and or masthead amplifiers

BITE. Built in test equipment, this is important so that you can monitor the performance of a multicoupler remotely, on a small system it may be a fount panel LED and an alarm contact on the rear panel. On a large system full board level diagnostics should be available to monitor the multicoupler remotely via Ethernet

High Performance Multicoupler Block Diagram


CommsAudit uses a number of in house proprietary designs and a program of continued research and development to produce the most technically advanced receiver multicouplers and antenna distribution systems.  All our multicouplers incorporate a low noise figure with outstanding linearity and high isolation this has established CommsAudit as a leader in the field of HF, VHF and UHF L-Band SHF receiver multicoupler design and manufacture.

Applications: HF, VHF UHF antenna signal distribution for sigint, radio monitoring receiver systems and multi receiver installations.


For more information please visit us at

CommsAudit is ISO 9001 registered for the design and manufacture of RF multicouplers

© CommsAudit Limited 2007
PO Box 78
GL52 6ZU
United Kingdom

Communications Audit UK Limited reserves the right to alter the specifications