Third-wire deck cable selection guidelines
The third-wire deck cable is relatively short, but runs through an extremely noisy environment. It may be the biggest contributor of system noise and can cause significant impairment of the telemetry link between the Sonar Head and Processor Unit.
We recommend using a high-quality telemetry cable, such as the RG214 coaxial cable or an impedance-controlled shielded twisted-pair cable. The chosen cable should be similar to those of antennas with carrier frequencies up to around 1 MHz.
The third-wire deck cable installed on fishing vessels is primarily coaxial, but twisted-pair cables have been used in a few cases. Each type of cable has its pros and cons. But, regardless of the cable construction, an overall shield is required to minimize noise.
Twisted-pair cables are the only effective means of minimizing noise from low-frequency magnetic fields (primarily originating from power cables). However, unshielded twisted-pair cables have limited effectiveness in rejecting noise at higher frequencies and should not be used. Shielding provides an electrically conductive barrier to prevent electromagnetic interference.
Coaxial cables have less attenuation and can be used over a wider range of frequencies than twisted-pair cables. Coaxial cables are most suitable for single-ended circuits with the outer shield grounded and acting both as a shield and as the signal return. To minimize noise, use a shielded coaxial (triaxial) cable with appropriate shield grounding techniques.