lowvolttech
Member
Will a ground loop cause Signal to Noise issues such as a robotic voice in a CATV VoIP system?
CATV VoIP robotic voice
- Thread starter lowvolttech
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zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
A ground loop in the coax won't directly affect the sound of the voice, but if it introduces enough uncorrectable bit errors the vioce quality will difinitely suffer. So, yes, it could, but it's not too likely... how's the TV part?
robotic sound in voip is usually caused by network latency and jitter. Is the voip service the one provided by the cable co, or is it a 3rd party such as vonage or packet 8? I have also seen this problem when the user's computer has a virus or application running that is maxing out the internet connection. Try turning all computers off and see if the problem goes away.
lowvolttech
Member
voip
voip
The voip is cable company provided. Usally its a system Signal to Noise issue. The house had a RG-59 drop that was not grounded. I know that the drop was no good but it just got me thinking about ground loops. Knowing that they cause hum bars. I wondered if it would cause issues with voice. Most likely it is a return issue as the subscriber can hear who ever is calling. But the person on the other end hears robotic or under water voices.
voip
The voip is cable company provided. Usally its a system Signal to Noise issue. The house had a RG-59 drop that was not grounded. I know that the drop was no good but it just got me thinking about ground loops. Knowing that they cause hum bars. I wondered if it would cause issues with voice. Most likely it is a return issue as the subscriber can hear who ever is calling. But the person on the other end hears robotic or under water voices.
lowvolttech
Member
They just had internet and voice.
egnlsn
Senior Member
- Location
- Herriman, UT
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- A/V/Security Technician
Or there is an issue with the return path causing low signal there. That could cause such symptoms.
lowvolttech
Member
Yeah an old 59 drop will kill return and with bad shielding will cause SNR spikes.
egnlsn
Senior Member
- Location
- Herriman, UT
- Occupation
- A/V/Security Technician
Which brings up a good point. It isn't so much the fact that the cable is Series 59 as it is the construction of the cable that is the issue. CATV needs 100% shielding from the headend to the premise device. So much of the Series 59 cable that is out there is older, copper-braid cable, most of which has 85% shielding at best. I've seen some as low as 65%. The cable used MUST have a layer of foil BONDED to the dielectric plus a braid.
Just as important as the cable itself is the connectorization of the cable. If a connector is loose, corroded, plain old junk, or not made up properly, ingress can occur. The return path is more susceptible to ingress than is the forward path. We used to be able to see ingress in pictures in the form of multiple images on locals, herringbone, and other forms of interference on certain channels. Now, with many systems going digital, the channel (say, ESPN) that is on analog channel 20 is now one of the channels digitally modulated to NTSC channel 112 (112-4). If the settop box is mapped so that when the sub goes to channel 20 (as indicated by the display), the STB tunes to NTSC channel 112-4 and he watches ESPN. The interference that he would have normally be seen on channel 20 will not be seen on 112-4.
But, the return path will suffer regardless.
Now, if there's a levels issue in the outside plant, that's another story...
Just as important as the cable itself is the connectorization of the cable. If a connector is loose, corroded, plain old junk, or not made up properly, ingress can occur. The return path is more susceptible to ingress than is the forward path. We used to be able to see ingress in pictures in the form of multiple images on locals, herringbone, and other forms of interference on certain channels. Now, with many systems going digital, the channel (say, ESPN) that is on analog channel 20 is now one of the channels digitally modulated to NTSC channel 112 (112-4). If the settop box is mapped so that when the sub goes to channel 20 (as indicated by the display), the STB tunes to NTSC channel 112-4 and he watches ESPN. The interference that he would have normally be seen on channel 20 will not be seen on 112-4.
But, the return path will suffer regardless.
Now, if there's a levels issue in the outside plant, that's another story...
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