I believe EMI is screwing with my Uverse...

[Jeff7181]

I moved my Uverse RG from one room to another so I could put it on my UPS. The only problem is that the CAT3 cable from the phone jack runs right under my air conditioner. It's one of those compact ones they put in apartments and condos (not a window air conditioner).

Anyway, it seems as though every time the A/C kicks on, I lose my connection for a few seconds. I think it's the initial large current draw of the compressor kicking on that creates enough EMI that it screws up the signal.

So, in your opinion, if I switch from CAT3 to CAT6, would the improved cable design likely be enough to better tolerate the EMI, or should I use shielded CAT3 instead?

 

[azazel1024]

shielded would eliminate any possible emi. Cat6 is significantly more resistant than cat3 is, but it is not immune to EMI.

 

[Jeff7181]

I've been cautioned in the past about using shielded cable because terminating it improperly can actually hold EMI in rather than keep it out. Do I need to use metal RJ-45 ends if I use shielded cable?

 

[Cerb]

If EMI from the AC unit is capable of doing that, shielded cable won't do you any good.

Shielded cat 5 and 6 are for RF shielding, well into the double-digit MHz range, on top of needing special equipment to make sure use of. For 60Hz or 120Hz EMI, you'd need a thick copper pipe grounded right there by the AC unit.

If it is that EMI, you probably just need your phone wiring redone anyway. Or, better yet, ditch DSL .

 

[imagoon]

I would check to make sure the issue isn't the power dip as the AC starts causing the modem to freak also.

 

[Jeff7181]

I would check to make sure the issue isn't the power dip as the AC starts causing the modem to freak also.

It's plugged into a line conditioning UPS, so I don't think it's related to a voltage drop.

Actually now I'm questioning whether it was related. I thought I noticed a correlation between when the A/C turned on and when I had performance issues, but now I think it was just coincidence. Yesterday evening I had no problems for several hours, then I had big problems for several hours. The A/C turned on an off probably a dozen times over the course of the evening and into the night, but sometimes it worked fine.

I have a service call in with AT&T and they're supposed to dispatch a tech tomorrow, but I may cancel if it stays stable until then.

 

[Jeff7181]

If EMI from the AC unit is capable of doing that, shielded cable won't do you any good.

Shielded cat 5 and 6 are for RF shielding, well into the double-digit MHz range, on top of needing special equipment to make sure use of. For 60Hz or 120Hz EMI, you'd need a thick copper pipe grounded right there by the AC unit.

If it is that EMI, you probably just need your phone wiring redone anyway. Or, better yet, ditch DSL .

It's Uverse, and Comcast has grossly oversold the lines in my area so their service sucks, as does any cable provider that piggy-backs on Comcast's infrastructure. Those are really the only two companies that have any infrastructure where I live and AT&T is able to provide better service than Comcast.

 

[imagoon]

It's plugged into a line conditioning UPS, so I don't think it's related to a voltage drop.

Actually now I'm questioning whether it was related. I thought I noticed a correlation between when the A/C turned on and when I had performance issues, but now I think it was just coincidence. Yesterday evening I had no problems for several hours, then I had big problems for several hours. The A/C turned on an off probably a dozen times over the course of the evening and into the night, but sometimes it worked fine.

I have a service call in with AT&T and they're supposed to dispatch a tech tomorrow, but I may cancel if it stays stable until then.

Does the unit alarm every time the AC starts? If not the modem is seeing a dip. Even with the alarm it will see a dip unless the unit is a AC-DC-AC unit which is fairly rare at home. Some of the trashy modems out there don't have the caps needed to make it through sometimes.

 

[Cerb]

It's Uverse

Which, by description, is DSL.

Comcast has grossly oversold the lines in my area so their service sucks, as does any cable provider that piggy-backs on Comcast's infrastructure.

And I thought it was bad here, with Cox constantly upping their rates, and AT&T providing random service quality...

Since you can move the modem, what happens if you plug it in as close as possible to where the line comes in, without the rest of your phone wiring hooked to it (and thus no cabling going near the AC unit, though I also suspect it's not EMI)? My guess is still that it's either a pair issue outside the house, or an in-house wiring issue (if the phone wiring predates broadband DSL being common, it's not uncommon for it to be a problem).

 

[azazel1024]

If EMI from the AC unit is capable of doing that, shielded cable won't do you any good.

Shielded cat 5 and 6 are for RF shielding, well into the double-digit MHz range, on top of needing special equipment to make sure use of. For 60Hz or 120Hz EMI, you'd need a thick copper pipe grounded right there by the AC unit.

If it is that EMI, you probably just need your phone wiring redone anyway. Or, better yet, ditch DSL .

Errr no. The shielding with grounding effects a faraday cage around the internal wires. Due to it being a complete foil wrap, it is effective all all wavelengths/frequencies, not just really high or low ones.

Yes you'd need metal ends, but only so long as the RJ45 ports accept grounding. If not, you'll have to manually attach the foil to ground on each end.

Also, yes, if it is not properly grounded it'll function as an inductor, which will trash the signal going through the twisted pair.

 

[imagoon]

Errr no. The shielding with grounding effects a faraday cage around the internal wires. Due to it being a complete foil wrap, it is effective all all wavelengths/frequencies, not just really high or low ones.

Yes you'd need metal ends, but only so long as the RJ45 ports accept grounding. If not, you'll have to manually attach the foil to ground on each end.

Also, yes, if it is not properly grounded it'll function as an inductor, which will trash the signal going through the twisted pair.

Yeah that is certainly not true. Lookup Transfer impedance.

http://www.interferencetechnology.com/differential-transfer-impedance-of-shielded-twisted-pairs/

This is why there are several types of STP. Sheet vs screened vs weaved, aluminum vs steel vs copper. You choose the characteristics for the environment. Before you use STP you are supposed to use a radiation detector to determine what EMI you need to block and choose the cable appropriate for the job.

Transfer impedance is why Subs use ELF. The lower the frequency, generally the difficulty is shielding goes up.

You also only ground STP on one end. Industry practice is at the patch panel. Grounding both ends is dangerous and can induce currents that fries equipment. It can also cause ground loops that will radiate noise in to the twisted pairs.

 

[Jeff7181]

Problem solved with the new Motorola NVG589. Guess it was the old gateway flaking out rather than the cabling after all.