On Monday, September 2, 2019 at 7:57:21 AM UTC-5, Scott Dorsey wrote:
Because there's a lot of 60 Hz trash on the cable shield, possibly because
it's not properly bonded.
Get a real technician out. Likely the "interference" they are referring to
is 60 Hz trash on the cable shield, and it's caused by the cable not being
properly bonded to ground at your house. When the ground isolator is removed,
the system is being grounded through your TV set (which also provides a
path to discharge lightning and other inadvertent transients), and so the
cable folks don't see the 60 Hz trash. This is an unsafe condition.
--scott
Scott,
The cable is definitely not bonded to house ground. I found an article that discusses this:
https://www.mikeholt.com/mojonewsarc...s~20030214.htm
"As the 820.33 FPN explains, one purpose of 820.33 is to limit the potential differences between CATV and other metallic systems (see Figure 820-14 un820-14 820-40D.cdr). So, connect the coax shield to the main grounding system."
and
"[820.40] When grounding the coax sheath:
Use an insulated grounding conductor listed for the purpose.
Use a grounding conductor made from a corrosion-resistant conductive material. If copper, it must not be smaller than 14 AWG."
Although 14 gauge copper wire is apparently large enough, do you have any information regarding whether increasing this to 10 or even 6 gauge would have an effect on the hum in my system?
The Cox technician who came out last Friday scheduled a return visit Thursday morning to ground the cable. Since he did not demonstrate understanding beyond his limited training, I expect that I will do a better job bonding the cable shield to house ground than he would. I certainly have more at stake in the outcome than he does.
Bob