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IowaCowboy
Iowa native
Premium
join:2010-10-16
Springfield, MA
kudos:1
Reviews:
·Verizon Broadban..
·Comcast

[CDV] Noise on CDV line (and HAM radio may be to blame)

Had issues with static on the line, called Comcast and CSR verified the issue, tech comes out, says the signal is fine, and then he takes off. Tech told me there are some HAM radio operators in the area and he troubleshooted the neighbor but it was her equipment that was getting the interference. After the tech left, I ran an errand and the neighbor in our duplex said someone from down the street knocked on my door (after seeing the 2 Comcast trucks parked outside my house) and told my neighbor that he is having trouble with his cable as well. I know there are a couple of HAM radio operators in the area according to the techs. Another neighbor also had a truck roll but it was her equipment. My TV downstairs is acting up as well (might be the TV according to the techs) but the bedroom is working just fine.

Downstream
DCID Freq Power SNR Modulation Octets Correcteds Uncorrectables
Downstream 1 213 693.00 MHz 0.90 dBmV 37.09 dB 256QAM 17581811 213 28
Downstream 2 214 699.00 MHz 1.01 dBmV 37.36 dB 256QAM 4440615 209 53
Downstream 3 215 705.00 MHz 0.60 dBmV 37.36 dB 256QAM 5948375 240 64
Downstream 4 216 711.00 MHz 0.44 dBmV 37.64 dB 256QAM 5734229 177 78
Reset FEC Counters
Upstream

UCID Freq Power Channel Type Symbol Rate Modulation
Upstream 1 1 30.00 MHz 36.00 dBmV DOCSIS2.0 (ATDMA) 5120 kSym/s 64QAM
--
All of my CPE (including my EMTA) is customer owned. The only Comcast owned equipment in my house is the CableCards in the two TiVO boxes I own.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
hams would interfere with the return band...forward(tv) wouldnt be affected...
--
I'm better than you!


IowaCowboy
Iowa native
Premium
join:2010-10-16
Springfield, MA
kudos:1
Reviews:
·Verizon Broadban..
·Comcast
said by gar187er:

hams would interfere with the return band...forward(tv) wouldnt be affected...

That explains it as I could hear the called party ok but the called party could barely hear me. There must be ingress somewhere on the node.

They used to use RG6 Quad Shield back in the days of the analog only dual cable system (with the old A/B switches) but with the new system, they use standard RG 6 cable. My house is mostly RG6 Quad Shield but the underground line has been replaced with standard RG6 cable. Maybe they need to use RG 11 in areas with a lot of HAMs or go back to RG6 Quad Shield.
--
All of my CPE (including my EMTA) is customer owned. The only Comcast owned equipment in my house is the CableCards in the two TiVO boxes I own.


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:19
said by IowaCowboy:

Maybe they need to use RG 11 in areas with a lot of HAMs or go back to RG6 Quad Shield.

Damaged cable, loose connectors, and poor shielding in CPE cause more issues than ingress on standard dual shield cable.
--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:19
reply to gar187er
said by gar187er:

hams would interfere with the return band...forward(tv) wouldnt be affected...

There are a couple HAM bands that can cause forward interference, but the majority are in the return spectrum.
--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
reply to IowaCowboy
11 has nothing to do with helping avoid ingress......tri shield is fine for 99% of applications, the 1% being in headends and telecom rooms....
--
I'm better than you!

Kearnstd
Space Elf
Premium
join:2002-01-22
Mullica Hill, NJ
kudos:1
reply to IowaCowboy
have to wonder what would happen if the cable system started to scramble the HAMs. if its leaking one way then it can leak RF the other way too I think
--
[65 Arcanist]Filan(High Elf) Zone: Broadband Reports


mb

join:2000-07-23
Washington, NJ
Reviews:
·Comcast
·Verizon Online DSL

1 edit

1 recommendation

reply to IowaCowboy
First thing you should do is disconnect your house telephone wiring from the back of the comcast modem and plug a different telephone directly into it. If the problem goes away you are dealing with either phone wiring problems in the house, or, a cheap telephone that can't deal with rf energy from the ham transmitter, if it is even that to begin with.

If you still get the problem, it could possibly be rf from a nearby ham radio transmitter getting into a "leaky" cable system reaking havoc with the modem connection, but I'd bet a kidney that if this was the case the modem would lose sync giving you more than static on your audio.

There is no legitimate reason why a nearby ham radio, or any other type of transmitter for that matter should be interfereing in any way whatsover with anything that Comcast is sending to it's customers. If they are, it is again a cable system issue.

I'd bet a kidney that it was an incompetant or lazy tech just blowing smoke. In the old days you could see and hear interference on a tv channel if there was ingress, but with digital tv, and more so with digital voice I say BS. There are so many different things that could cause the type of issue you are seeing and the most common is crappy routing of the digital data that is carrying the voice info.

In any case, it can be a complex issue that may require intensive troulbeshooting.
--
"When will they ever learn? When will they ever learn?"
Pete Seeger 1961


Jeremy W

join:2010-01-21
said by mb:

First thing you should do is disconnect your house telephone wiring from the back of the comcast modem and plug a different telephone directly into it. If the problem goes away you are dealing with either phone wiring problems in the house, or, a cheap telephone can't deal with rf energy from the ham transmitter, if it is even that to begin with.

If you still get the problem, it could possibly be rf from a nearby ham radio transmitter getting into a "leaky" cable system reaking havoc with the modem connection, but I'd bet a kidney that if this was the case the modem would lose sync giving you more than static on your audio.

Exactly. Once it hits the modem, the phone audio is digital. So like you said, interference with the cable network would cause the modem to lose sync, not static on the phone line. The problem has to be with the internal phone wiring.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4

1 recommendation

reply to Kearnstd
cable RF can egress from the plant and interfere with outside systems...which is why CLI leakage is done....but again, most HAMs are in the return band.....so carrier levels are not high, meaning its not as strong a signal leaking out that would affect the HAM/CBs....
--
I'm better than you!


jseymour

join:2009-12-11
Waterford, MI
reply to Kearnstd
said by Kearnstd:

have to wonder what would happen if the cable system started to scramble the HAMs.

That's easy. Some enterprising ham would identify the source of the interference, and probably contact the cable operator to ask them to fix it. If the cable operator failed to address the problem w/in a reasonable time frame, eventually that ham, or another, would file a complaint with the FCC and the FCC would oblige them to address the interference problem, or start paying penalties.

As often as not, probably more often than not, the fault is with the equipment suffering the interference, not with the ham radio operator(s) or their equipment. Or at least that's the way things used to be. I've been out of the hobby for over a decade, now.

Jim


Cjaiceman
Premium,MVM
join:2004-10-12
Parker, CO
kudos:2
said by jseymour:

said by Kearnstd:

have to wonder what would happen if the cable system started to scramble the HAMs.

That's easy. Some enterprising ham would identify the source of the interference, and probably contact the cable operator to ask them to fix it. If the cable operator failed to address the problem w/in a reasonable time frame, eventually that ham, or another, would file a complaint with the FCC and the FCC would oblige them to address the interference problem, or start paying penalties.

As often as not, probably more often than not, the fault is with the equipment suffering the interference, not with the ham radio operator(s) or their equipment. Or at least that's the way things used to be. I've been out of the hobby for over a decade, now.

Jim

Jim, you hit that one on the head, and nothing has really changed. I had some cranky neighbors a couple years ago that when a local HAM (about 1 mile line of sight) would fire up his HF rig they would get lines on all the channels on their TV. They complained with the FCC, which came out, inspected his rig and found no faults. They "suggested" to them to stop using cheap TVs and cabling, and since their TV falls within Part 15 rules, they had to accept it, or shield the TV from the interference. They moved about 3 months later

And no one else around has said anything about interference from him, he even went around asking people if they have noticed interference on the phone lines and TVs, everyone else has said no.
--
TorDek: "DSLR... Here, were not just experts... were also vindictive bastards..."


nerdburg
Premium
join:2009-08-20
Schuylkill Haven, PA
kudos:1
reply to IowaCowboy
said by IowaCowboy:

Had issues with static on the line, called Comcast and CSR verified the issue, tech comes out, says the signal is fine, and then he takes off.

Static on CDV is not caused by RF signal problems. First thing you would check is the phone, then the phone wiring. If everything looks fine, the EMTA should be swapped.