DSL Interference on 75M Band
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| Jul 27th 2011, 01:26 | |
W7YVTotal Topics: 0 Total Posts: 0 |
Recently, my neighbor had a DSL modem installed using VDSL techology. This created S9+10 noise in the 75M band at my QTH. Fortunately, I was able to work with my neighbor (very cooperative) and the local phone company to resolve the issue. In short, the phone company switched the technology from VDSL to ADSL+ and the problem went away. Interestingly, I had to start at the corporate top level to get any attention. Tedious but it worked out in the long run. Question: has anybody encountered a similar problem? I am aware of reports that point to the switching power supply of the modem as the problem. In this case, it was tried and failed as a fix. The problem is the broader spectrum of VDSL. |
| Jul 27th 2011, 17:03 | |
w1rfiSuper Moderator Total Topics: 0 Total Posts: 0 |
What company was involved? If you can email me the contact information, I'd like to work on the bigger problem. The two flavors of VDSL standards are supposed to include spectral masks for the Amateur bands, so if this is not being implemented universally, I'd like to take that up with the industry. ARRL has received few VDSL reports. Part of the problem may be that there is some severe unbalance on the phone lines in the house doing the radiating, as if this were a universal problem, there would be a lot of reports. You can post the company name here, but it would not be appropriate to post the contact info without permission to do so. 73, Ed Hare, W1RFI ARRL Lab Technology forums moderator |
| Jul 28th 2011, 22:30 | |
0007055157H80Total Topics: 0 Total Posts: 0 |
Ed, I think I was/am experiencing the same thing. I am not sure if it is vdsl, but my neighbor had a qwest dsl modem installed recently and S9 + "bend my meter needle" signals appeared in the 75 meter and MARS freqs (in the same range). Fortunately, my neighbor and I are good friends and it appears that they had a bad unit. A new unit was installed and the noise was abated (not gone, but greatly reduced). If you would like, I can try to get model numbers, etc. If this is going to be a coming issue, then it needs to be nipped right away. Mike AB7ZU |
| Aug 7th 2011, 17:55 | |
W7YVTotal Topics: 0 Total Posts: 0 |
Ed, et al.. The company was Qwest and the location is Taylorsville, UT. I had to go "to the top" in Regulatory Affairs before I got some response and, then, the response was pretty good. If there is some kind of spectral mask that is applied, it sure did not work for me. In the main distribution box (where fiber meets the neighborhood), they had hundreds of ADSL slots and hundreds of new VDSL slots. My neighbor was the "first" to get VDSL. Qwest simply wired him back down to an open ADSL slot and my problem went away. When those ADSL slots are full, then, as they say, "there goes the neighborhood." As for the modem, the same modem works for both technologies and was, therefore, not changed out. I've read the FCC test data submitted by the modem manufacturer. From their point of view, it isn't a modem problem (and I agree). It is the spectral density of the signal radiated from the physical phone wires emerging from the ground. My horizontal loop antenna, on the east leg, is only about 50 feet from my neighbor's upstairs bedroom window which is where the WAN terminates. We think that the house phone wiring has an imbalance which could have been causing radiation of the signal. At this point, who cares 'cause my problem is fixed - for now. |
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