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Red SVT value (resistance) - All LEDs flashing + No Internet Access when router installed

posted Jan 7, 2010, 2:07 PM by Josh Madrone   [ updated Nov 9, 2012, 4:30 PM ]
The install had to be a pole installation because it was a mobile home, and to find good LOS. It was a long cable run - up to 130' +/-, but not over 150'. 
  • The modem did lock and 
  • provisioning was successful
  • the LEDs on the modem were all flashing continually
  • SVT values were not acceptable. 3.5 Ohms of resistance (Red) and Attenuation was not normal for length of cable
  • it failed an Internet Access Test and Customer Access Test when a router was installed
  • Without router, there was basic connectivity with 30% packet loss (5% is max acceptable)
  • Visual Cable test showed grounding problems
    • Ground block was mounted to pole, not building, leaving 130' of cable not grounded
  • Modem-Short Cable Test - PASSED (now we know it's an on-site cabling issue)
  1. Grounded Antenna to ground pole using cold water clamp and #10 AWG wire (I did not have any ground straps on hand)
  2. Removed ground block from pole and installed on outer wall of mobile home near entrance hole for coax
  3. Ran #14 AWG solid copper wire from antenna to ground block (there was no #17 messenger wire attached to coax to use), effectively grounding cable run.

SVT values now all green. 1.5 Ohms resistance (to be expected with such a long cable run). Good cable attenuation. All other values green.


There is a reason for the process shown in the Trouble Isolation Checklist's Modem Offline Matrix and Poor Performing Matrix. USE THEM!!! I spent hours attempting to fix other things rather than following those Job-Aids to the "T".