UH-OHH! RFI FROM A NEIGHBOR! Radio Frequency Interference (RFI) is a problem that usually surfaces in one form or another in a ham's life. The situation we most often hear about is when a device in your neighbor's home malfunctions when it unintentionally picks up energy from your transmissions. Who hasn't heard a story about an irate neighbor whose TV picture gets scrambled during the big game or who say's you're tearing up his telephone? An angry telephone call from an unhappy neighbor in the middle of your favorite operating activity can spoil a good mood real fast. But RFI problems can also turn the tables on a ham: when a neighbor's electrical device causes interference to your reception. Both cases can easily lead to conflict. In the former case, your transmissions quickly become the subject of scrutiny. But if you set up and operate your station in accordance with FCC rules, there's not much else you can do with your own equipment. After all, your equipment is *supposed* to radiate. However, in the latter case, it is the unintentional transmissions from a device in your neighbor's home that are causing a problem for you. In either case, the neighbor usually doesn't like to hear that their equipment is faulty. Resolving RFI problems with a neighbor requires a level of tact, diplomacy, patience, instruction, and perhaps even negotiation. The ARRL provides some handy information for resolving these issues on their RFI/EMI web page at: http://www.arrl.org/tis/info/rfigen.html. The FCC also has some very good information on their interference handbook page: http://www.fcc.gov/cib/Publications/tvibook.html. Covering this topic in detail is beyond the scope of this article so I will simply describe a recent episode that happened to me. I began to notice pulses of very strong buzzing on 160 through 10 meter band frequencies, especially strong in the 40 meter band. These pulses were 10 to 20 dB over S9 and very regularly spaced about 1 second apart. Let me tell you, this was completely wiping out copy from all but the most powerful signals! This sounded very much like the noise an automatic battery charger makes when the battery is charged, the clips aren't firmly connected to the battery terminals, and the charger begins to cycle itself on-and-off. I quickly peeked under the table at my own charger, but the pulses I heard in the radio didn't match the flashing light on my charger. Hmmmmm, did I have any other chargers? Any other devices on my home that pulsate? I turned off light dimmers, TV's, my computer, sensor lights, etc, to no avail. Eventually, I just turned the radio off and hoped it would go away (Ha!). But no, it was always there, day and night, throughout the summer and early fall. Then, I remembered that my next-door-neighbor and good friend Chuck, KF4DTT, had a battery and charger, too. Yes, I thought, perhaps his battery clips need to be refreshed or something simple like that, and my hopes rose. Finally, I decided it was time to go on a hunt. It was a warm, sunny, Sunday afternoon, and my desire to listen in to the ECARS net on 7255 KHz was thwarted once again. Let the hunt begin! I tuned my HF rig to the highest frequency where I could still hear the noise, which was the upper portion of the 10 meter band. I connected my HF beam and started swinging it around to determine what direction brought the strongest signal. Hey, this worked: I found one direction where the pulses were strongest: It wasn't Chuck's house! Good thing I didn't go bug him! My beam was pointed through the woods in my back yard directly at a shed in another neighbor's yard. Maybe he had a battery charger in there on his garden tractor! This type of noise is best hunted with an AM mode receiver, on the highest frequency possible. I scooped up my trusty HT, which can tune to the AM aircraft band around 120 MHz. I also turned on my baby monitor, grabbed its receiver, and headed out the door. Baby monitor? Yes, that's right: I set up the base unit next to my radio gear (where all the speakers are) and carry the handset around the house when I want to monitor the HF, scanner, etc. Now armed with these tools, I could sniff out the buzzing signals using the AM receiver, and simultaneously monitor what the HF radio was picking up using the baby monitor. I headed out the back door toward the neighbor's shed. No signals yet on the HT... As I approached the rear property line and the shed, I discovered a ham's nightmare: my neighbor had installed an electric fence. Actually, this was a good thing, although it didn't seem that way at the time. Electric fences are notorious sources of RFI. Could I have found the problem already? I knelt close to the wires and brought my HT's antenna close to one of them. Sure enough, it began to receive the same noise pulses, and they exactly matched the timing of those I was hearing on the baby monitor. Hurrah! I had found the offending noise maker! Now, all that remained for me to do was to quickly cut the wires to the fence behind the neighbor's house and skeedaddle before he saw me do it! Heh heh heh! I'm kidding, of course, although it was tempting. Stage one of the process was complete: I had found the noise source. Stage two, however, brought a pang of trepidation: how to get the neighbor to understand my problem and contribute to a resolution. This can have two outcomes, one good, one very bad. I didn't know this neighbor very well, and that amplified my anxiety. Well, before I knew it, I was headlong into the process: the neighbor's two charmingly alert dogs had heard me and came to investigate, barking gruffly. These are the same ones that always come out to bark at me when I go jogging by this neighbor's house at night. After a year, they don't bark at me too much anymore, but now, I was no longer out in the street, I was nearly in *their* territory (Darn, didn't bring my steel cosh for protection!) Suddenly, the same fence that caused me consternation just a minute ago became my salvation from puncture wounds, rabies, and doctor bills! HA haww, can't get me! Wait a minute: here's comes the neighbor to investigate the barking... Actually, the dogs weren't all that aggressive, it's just that we had not been properly introduced. I quickly shoved the diagonal cutters and devil horns back into my pocket, greeted the neighbor, and after some short chit-chat, I told him about my trouble and the hunt. Scott is a good-natured person, and he became genuinely concerned that his fence seemed to be causing a problem. I was able to demonstrate to him, using the HT and the baby monitor, that the noise was definitely coming from the fence in a gentle, non- accusatory way that was easy for him to accept. I even suggested that he try turning on the AM broadcast or CB radio in his Jeep so he could see that this problem affected services other than Amateur Radio. He declined, but it would have made a good demonstration for someone less receptive. The dogs followed cautiously behind us as we made our way over to his house. He disappeared under the house for a moment as he switched off the fence. The HT went silent and the reception on the HF radio became clear on the monitor: now *both* of us had positive proof that the fence was the culprit. Actually, Scott's job in the military involved working in a power generation facility, so he was conversant in electrical terms. As it turned out, his familiarity with CB radio helped stimulate his concern for interference and an appreciation for Amateur Radio, and suddenly I found myself breathing easier and describing the interesting facets of the hobby. I described how I had read about hams facing RFI problems and how common it was for an electric fence to radiate noises, since it was so much like a loop antenna. The usual faults are cracked insulators, shorts from bushes or fallen branches, or corroded splices where an arc can be generated. Scott turned the fence back on and we began to walk the fence line looking for problems. Half the battle of stage 2 was over: the neighbor was very cordial and sympathetic (whew!). And the dogs were coming closer for a friendly sniff to get more acquainted. This particular fence is an inexpensive kit for homeowners to use for keeping pets (dogs) from going out of their yards. Scott had installed it earlier in the year after his dogs learned how to break through the previous 'invisible fence' product. The new fence uses aluminum wire on PVC posts. These all looked fine, and he had neatly installed and connected a ground rod where the power unit was, all in accordance with the instructions. The kit also provides 2 sets of spring-loaded hooks, for creating an opening in the fence for a driveway. These hooks are chrome-plated mild steel. Got the picture? Here were dissimilar metals exposed to the weather, making intermittent contact. As we approached the first set of hooks, the noise got louder on the HT. We knelt down to inspect the joint where one hook clipped in to a loop in the aluminum wire. I could see the tell-tale white residue of corrosion on the aluminum wire on either side of the contact point of the hook, which had also begun to rust. When I placed the HT antenna next to the joint, we could both see the signal bars appear in the display. This joint was generating an arc every time the power unit sent a pulse to the fence. I turned off the HT and we could even hear a faint arcing sound! Scott disappeared into the house one more time. When he re-appeared, he was carrying a small rat-tail file and quickly cleaned all of the hook-and-wire junctions. There were a total of four junctions in the whole fence. Success! Even though the HT could faintly pick up a bit of noise, the baby monitor went silent and we knew the HF rig in my house was no longer picking it up. This kit was a guaranteed noisemaker: a ham headache in a box going on sale all over the country, I'm sure. I pointed out that I thought he had done a very nice job of installing the fence and that I was not blaming him at all for the problems. As is frequently the case, the poor design and inexpensive construction of the consumer device was at fault, not the neighbor. Boy, was I thankful I had a nice neighbor. Together we hashed out a couple of ideas to improve the hooks, but he insisted that he would simply clean the joints from time-to-time to take care of the problem. In the course of our inspection, Scott showed me a spot in the yard where his cable TV line had been exposed by the dogs that had dug it up. Following that, one of his kids went exploring the hole with a shovel and managed to chop the cable in two. Gee, no TV for the kids that afternoon. One of the youngsters had even come to the window, asking if I was the repairman (the real repairman wasn't due until the next day). I just smiled, and this gave me an idea. As a show of appreciation for Scott's good nature and concern over the RFI problem, I offered to make a temporary splice for his cable, using a scrap of cable I had at home in the garage. This time, I disappeared to retrieve a tool bag and a piece of cable. While I was home, I tuned the HF rig to the ECARS net frequency on the 40meter band. The reception was beautiful and static- free. When I returned, we both listened to the check-ins from mobile and fixed stations from all around the east coast as we set to work together to splice the cable. He became even more fascinated as I revealed that I had an HF rig in my car and used this service to keep in touch with friends at home during trips that I had made that summer. The sun was still shining brightly as I packed up my tool bag to head back home. My heart was light as I said goodbye to Scott and patted the canines on their heads. My problem was resolved, I got to know my neighbor better, develop a new friendship, and promote Amateur Radio. Oh yes, Scott's kids got to watch TV, too. Scott also happens to own the wooded parcel of land immediately behind my own parcel. He offered me permission to use any of the land for antennas as I saw fit (wow!) I checked into the ECARS net when I returned home, enjoying some of the best copy I have had in months. The dogs still occasionally bark a little when I run by at night, but I just look at them and smile. --...MARK_N1LO...--