By Ed Schumacher WA9GQK
With AT&T U-verse service becoming more established in our area, some of my experiences with it may be of interest to other hams. My first incident of RFI with the system was actually interference between two components of the AT&T equipment itself! I am classifying this as RFI because it did involve a radiated signal from one device interfering with another and is not carried over the connecting cables.
Backing up for just a moment here, the system installed basically consists of a separate modem that separates the telephone (VOIP), internet and cable television signals all being received off of your original copper wire telephone feed. The television is routed to digital receivers at each set, two being included in the basic package, with one master DVR box usually located at the first set closest to the modem location. The VOIP telephone is distributed via original wiring to all the phone jacks. The internet can be distributed via phone wiring, new cable or a wi-fi. There is also a battery backup unit located with the modem.
A short time after our system was installed, I became aware of a tapping sound on the television audio and soon determined that it was present on most signals (goood luck trying to find any dead air time on most network channels in order to listen for this with non-stop wall of sound). I eventually noticed the tapping matched the pulse of one of the LEDs in the modem and simply repositioning the modem eliminated it.
The next incident was a little more serious. Now I was chasing a dx’pedition which gave me plenty of opportunity to operate several different bands on phone and CW as well as a couple of times with the amp. It didn’t take long to finally completely blow away the U-verse. This was eventually easily solved by rerouting the CAT-5 cable (unshielded of course, you didn’t really think AT&T was going to install shielded CAT-5 did you?). The main offending mode was CW which apparently the modem saw as confusing digital signals on the input (can’t copy code?). Also, high power simply overloaded the line and caused the same thing, modem lockup. Keeping the AT&T cable away from proximity to my feedlines cured this problem. The tech who came out advised me they do have shielded cable but it is not on the trucks for general installation in homes. At least he knew what ham radio was, his brother is a ham.
All is well with the world now, right? NO. Annoying burbles have been appearing in our bands for years now with the digital revolution but the one that was parking right next to the 20 meter Salvation Army daily net frequency was really starting to annoy me. However, I had lost the use of my old portable short wave radio and it seemed every time I went out to the mobile, the signal had moved or something. Finally the day came when I had the time to do some driving around and I could copy the offending signal on the mobile rig. It didn’t take much driving around to definitely locate the signal back to my QTH for sure. By this time I did have another portable SW receiver which was also capable of copying the signal and imagine my dismay when it zeroed in on the very northwest corner of my house! A veritable antenna! To keep this story short, the receiver on the upstairs tv was putting out an incredible amount of trash via the power cube back onto the house wiring.
I eventually tried one of those little snapon ferrite cubes from Radio Shack and the signal was reduced enough to live with but still not completely gone. Now comes the big mistake. I found that the tech who did the original installation had left another power cube that had not only a ferrite cube snapped and tie wrapped on the low voltage cable, but it also had a large core on the 110v cord with the cord wrapped through it several times. AHA! (did I steal that from Oprah?). AT&T must have had some problems and maybe this was a fix for me too. Finally got everything together and connected and guess what? 20dB over S9 noise was what!
The next time I had the hours that I knew talking to AT&T would take, I made the fateful call. In the meantime I found yet another issue for them to fix. My vintage all analog Signal One transceiver would knock out the VOIP phone on 40 meters. My Ten-Tec Orion at the same power level did not. A low pass filter had no effect and I also verified that it was the signal off of the antenna and not something radiated in the shack which is right below the location of the U-verse equipment in the room upstairs.
Of course the phone tech had to attempt what I told him would be useless procedures of reprogramming the modem over the lines. This only shifted the burble up frequency and did nothing to stop the 40M signal getting into the totally unshielded equipment. After blowing him off the phone three times with the radio he finally accepted this and contacted his supervisor for “permission” to send out a real live tech. All of this ate up a good hour or more to prove that I knew what I was talking about and the phone tech had no grasp of the technicalities involved, obviously not a radio guy.
Imagine my disappointment when upon arrival and listening to my explanation, the real live tech told me that 1. no one in their department knew anything at all about rfi issues, read no training whatsoever, and 2. he knew of no parts, filters or anything else for curing rfi being available from the company. He asked me what I could think of instead! After showing him my tests, demonstrating the offending signals and my filter on the receiver power cube, describing the loss of phone service when running the particular transmitter, etc. he just flat out stated that I knew more about this stuff than he or anyone else in his department including his supervisor! He also allowed that he thought this ham radio stuff was just about the coolest thing he had ever seen and told his supervisor the same thing in very excited tones.
I went back upstairs and removed the “filtered” AT&T cube from the one receiver (the tech took one look at it and said that those had caused interference problems between the modems and the DVRs and weren’t being used anymore) reinstalled my ferrite snapon and watched the noise drop way back down and went for a cold beer. He also told me that most of the technicians had finally been told about the tapping noise problem finally and knew to solve it the same way I did. What a relief, I followed accepted company practice!
I am now waiting for a burst of inspiration which may be some time in coming as I write this. If and when I solve all of this to my complete satisfaction, rest assured that AT&T will not be the first folks I go running to with the answers. At least not for free. I will get it all published in a ham radio forum and then offer my services to AT&T as a retired old dog engineer with some common sense and real world experience. The price? Still up in the air but believe me, it will be worth my while for the time and aggravation. Oh, the manufacturer of this mighty fine equipment? This is all the better stuff they went to from CISCO. Guess CISCO could use a couple of old engineers over there too, any takers? My first advice to them is get out of the ham bands and then shield the boxes. I would be embarrassed if something I designed for a system interfered with another part of the same system. And they just raised the equipment charge for this junk!