VIDEO HUM BARS
Causes:
So you just finished installing a new video distribution system and everything
looks great. Wait a minute, what is that green (or blue, or grey, etc.) bar that
is slowly floating up through the picture. If this sounds familiar, you are
experiencing a video hum bar.
There are a couple of different causes for hum bars. If the source electrical
power is too low, the video devices may have a problem regulating their
power supplies. This issue can be compounded by sources that output DC
offsets that place additional loads on the video distribution system. A
second source of the problem is differential ground voltage potentials,
which cause AC power to flow through the video cable grounds. This is
commonly referred to as “Ground Loop”.
The hum in the system might also be induced into the video cabling by
being routed too closely to an AC power cable.
Remedies:
1. The signal and AC power cables should never be bundled together.
2. Have a qualified electrician find and repair any defective AC outlets that
may be causing AC Ground Loop currents.
3. Use a distribution amplifier with isolated input grounds in order to break
the Ground Loop.
4. If the video source has DC voltage on the video output, inserting a DC
voltage blocker in line can eliminate problems in the distribution network.
SPECIFICATIONS
Connectors:
5 RCA in, 5 RCA out
Channels:
3 Video
2 Audio
Video Bandwidth:
>300 MHz
Audio Bandwidth:
20 Hz to >1 MHz
Dimensions:
1.25” x 3.9” x 1.5”
(2.3 including mounting tab)
Mounting Holes:
1.8” spacing, 0.15” diameter
NOTE: The three video channels may be used for three
individual composite video signals if desired.
DCB101 TYPICAL WIRING APPLICATION
INSTALLATION INSTRUCTIONS
Unpack the DCB101 from the box. Place the adapter in a suitable location
close to the source unit. The user will need to supply a patch cable from the
source to the DC isolator. Plug a cable from the DCB101 to the distribution
amplifier. This will remove the DC offset from the source Video and Audio
channels. If the DC offset was the cause of the hum bar issue, this should
eliminate the problem. The unit may be secured to a wall with user supplied
screws.
Installation is complete.
HD SOURCE
HD
Distribution
Amplifier
HD Monitor
or Projector
HD Monitor
or Projector
HD Monitor
or Projector
HD Monitor
or Projector
Breaking the DC path between the Video
Source and the Distribution Amplifier can
sometimes eliminate annoying hum bars.
