[mythtv-users] Electrical power in my cable line? Is that bad?

Keith Pyle kpyle at austin.rr.com
Tue Sep 11 01:03:34 UTC 2007

Thanks to Brian Wood, David Brodbeck, and others for their help in 
diagnosing my hum bar problem.  For the benefit of others on the list, I 
did two things that seems to have solved the problem (based on a limited 
number of recordings).  First, I checked and improved the cable TV 
grounding.  The cable installer had clamped a ground wire from the 
incoming splitter to the conduit between my electric meter and the 
distribution panel.  However, he neglected to notice that the conduit 
was painted.  There was a 145 ohm resistance to ground due to the 
paint.  Fixing this substantially reduced the hum bar, but it still 
seemed slightly present.  I'm not convinced this is the best grounding 
option and need to check a bit more.  The second change was to create a 
temporary, crude isolation transformer from a couple of 75-300 ohm 
baluns (one Radio Shack 15-1253 and one 15-1140).  I haven't seen a hum 
bar with this in place.

I'm now looking for a better isolation option.  I've seen some mention 
of the MAGIC (Mondial Antenna Ground Isolation Circuit) splitter as 
being a good one.  If anyone has an opinion on this or other isolation 
options, let me know.



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