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pgoelz
join:2001-12-26
Rochester, MI

1 edit

pgoelz

Member

Re: Hum bars

I think I have pretty much eliminated anything inside the house.... it is there when I connect the incoming cable directly to one TV and it is there when I disconnect just that TV from the rest of the system.

The edges of the hum bars are quite sharp and well defined so I don't think this is a simple sine wave AC line leakage to the cable shield. Looks to me more like a failed power supply cap in a line amp somewhere.

I can't dismiss grounding totally though. One thing I didn't mention was that about a year ago (and well before I think the problem started) I went over the grounding of everything entering the house. I was upgrading the grounding and bonding of the incoming AC, the water pipes, cable and telephone and my ham antennas for lightning protection. In the process I discovered that the incoming cable service was grounded to a separate (but physically close) ground rod from the rest of the house. That was not code so I bonded that ground rod to the ground rod for the rest of the house (which is also bonded to the water service). That should not have affected anything (and I am pretty certain the hum bars did not appear at that time).

My first suspicion was that they appeared when I swapped out my old 400MHz amplified splitter for a new 1GHz version. But as I said earlier, they remained virtually unchanged when I physically removed it and went straight to one TV.

Since "hum bars" seems to be a recognized term, I'll give CC a call and see what happens. But before that, I want to try one more thing.... running a totally new and separate (and totally isolated) piece of coax from the drop side of the grounding block to a TV.

Paul

Robotics
See You On The Dark Side
Premium Member
join:2003-10-23
Louisa, VA

1 edit

Robotics

Premium Member

Ive had that here at the house. And it ended up being a bad cable between the box and TV.
Maybe you have a bad cable somewhere??
Just a thought.

NSA_CIA
@charter.com

NSA_CIA to pgoelz

Anon

to pgoelz
Do you see 1 hum bar or 2?

1 hum bar tends to be 60 Hz, a neighborhood power supply or house issue is the most likely cause.

2 is 120 Hz and tends to happen when AC to DC power packs fail (which are in all cable line amps and nodes).