If you have a Ground Loop Hum in a combined A/V setup, the video coax is typically the source, and can usually be eliminated using a Coax Ground Loop Isolator (such as
this one from Jensen). However, if you are using a large multi-port coax splitter upstream (i.e. a 6-port or 8-port, for multiple household TV’s),the combined signal attenuation from that single splitter PLUS a ground loop isolator, might be sufficient to block some TV channels. One solution (short of using a coax signal amplifier) is to use TWO coax splitters in series, with the FIRST being a 2-way splitter feeding the A/V setup needing the Ground Loop Isolator, and the SECOND splitter for the remaining TV’s (assuming they are not part of a full A/V system, thus no ground loop issues). The reason this works is that the FIRST 2-way splitter reduces signal strength by ~3.5 db, (~50% signal loss),which is still usually sufficient, even with the Ground Loop Isolator, for all digital and analog channels. The SECOND coax splitter “halves” the signal yet again for all subsequent TV’s, but even that (~75%) net signal reduction is likely still sufficient for all channels, as long as no Ground Loop Isolator, or further splits, are inserted downstream. The SECOND splitter should have the least number of ports necessary, and if any of the ports are unused, they should be capped with a 75 Ohm terminator (
such as these). Here’s a picture of the configuration.
I struggled with a Ground Loop Hum for years, which Frontier Service Techs couldn't resolve (they re-grounded, and even replaced ONT box, and replaced the 8-port splitter, all while assuring me I had sufficient signal).
