Even though SDI is more immune to extraneous noise and low frequency components (hum) problems can still exist. As with analog signals, once you have noise in the signal, it is extremely difficult and costly to remove. Jitter caused by induced noise effects can compound problems created by unstable signal sources, poor re-clocking systems, cable attenuation and can be the demise of digital signals. HD-SDI Serial Digital signal transmissions at 1.485Gbps over a cable contain a range of low to high frequencies like analog signals and are subject to analog-type distortions like induced noise as well as unique digital distortions related to sampling and quantizing.
Using the Allen Avionics HD-SDI Ground Loop Eliminator you can eliminate the potential for this kind of data loss. See (Outgoing Video) The model HD-SDI Ground Loop Eliminator supports the four transmission rates of SMPTE 259m and SMPTE 292m 1.485Gbps HD SDI.
FYI Here is a brief comparison of the differences between 3G SDI vs HD SDI:
HD SDI optical terminal appliances are designed and manufactured for serial digital optical transmission devices with increased reliability and performance in the television field. Meanwhile, the 3G SDI digital video optical terminal equipment is an enhanced edition of HD SDI.
HD-SDI signal formats range from 19.4 Mbps to 1.485 Gbps. 3G SDI signal formats vary from 19.4 Mbps to 2.97 Gbps. HD SDI is the common name for the 1.485Gbps serial interface. SMPTE adopts SMPTE424M, a new standard that increases the SDI data rate two times to 2.97 Gbps, which is 3 Gbps (3G) SDI.