THE STORY OF THE 146.94 INTERFERENCE, May 2-3, 2013
I know I haven't "blogged" for a while, but I thought this might be a good subject to start back with, since it involves one of my repeaters being OFF for for over two days. Lots of folks have asked about it. Those of you who were kind enough to subscribe to my 'blog will get the 'news' first ! :-)
Thursday morning, as I was starting my day, I received word that someone was transmitting continuously on 146.34 MHz, causing the repeater to be "locked up" until the time-out timer took care of things. Sometimes, when someone would attempt to "kerchunk" the repeater, there would be just enough of a signal reset that the repeater would come back up again for the duration of another time-out cycle. At this point, I decided that the best thing to do was to remotely command the repeater off. I did not consider this decision lightly. 94 and .47 are my two busiest repeaters with daily activity from the wee hours of the morning until some of the second shift folks go home late in the evening. However, the signal into the repeater was quite strong, and anyone who tried to have a QSO on .94 would be "scrubbing" the offending signal until the time-out occurred. Some of the .94 regulars moved to 146.625 while this problem existed (hint...146.625 does pretty good on its own...). I hoped that the person who had left their radio keyed up would find it and the problem would go away. I checked the repeater several times during the day and the signal was still there.
On the Thursday night 145.47 net, I mentioned that .94 was off and asked everyone to listen on 146.34 and let me know if they heard a continuous carrier at their location. There was a ham from Jellico that said he had a weak signal at his location...I didn't get his call sign. But I thought..."from that far away? getting to the .94 site in Sevier County?" But he was RIGHT...
A question was asked to me..."Why don't you just turn on a tone?" First of all, it is not my policy to have continuous tone squelch on any of my repeaters except 927.0625. This is my policy for several reasons. The most important one is that it makes the repeater less "user friendly." Travelers thru our area could find one of my repeaters with a QSO in progress, but be unable to join in or call for help if they do not know the correct tone. Only one of my repeaters (147.075) has a controller which could announce the tone, but those are not cheap and typically do not fare well in lightning prone environments. The use of tones on a repeater is not a magic fix for all problems, but it does help with intermittent problems. I will occasionally use a tone on 145.47, 146.625, or 146.73 in order to keep them on the air (118.8 Hz). There *is* a tone decoder on .94, but I do not have it operational yet. I may try to finish that this summer. However, a tone decoder would NOT have helped with today's particular problem, as the offending signal was continuous, and everyone would have had to have been stronger than it was to overcome it and keep the repeater receiver unmuted.
After the first full day (Thursday) with the offending signal still going strong, I decided to try to find it. Friday morning, I met up with Danny, N4ZAA, who had already been tracking the signal and took me to a spot in Northeast Knox County where it was the strongest. I had a 4 element VHF yagi antenna with me and attempted to "shoot an azimuth" to where the signal was coming from. From there we went to North Knox County, Union County, and Anderson County. The tests were inconclusive, as we would see several "peaks" in the signal from different directions. In the mid-afternoon, we were joined by Cleve, KB4UAL, and Frank, W4NCS, who also had a directional antenna. Through a series of several stops, we found our way Northward into Union County and Claiborne County. We found the signal in several places, and it was quite strong, but never strong enough for us to say that we were getting very close to it. I traveled to several high locations in the area that I knew from my two-way radio days. I went to tower sites that I haven't seen for 20 plus years. It was a beautiful day and the scenery was great, but we weren't getting close enough to the problem signal yet. Todd, KA4OAK, joined us when he returned to the area after working out of town for the day. He had also heard the signal in several places, but we were still were not close enough.
When we traveled into Kentucky on US 25 (thru the tunnel), we got a very strong signal. However, it disappeared rather quickly in either direction that we traveled. We received some reports via 145.47 from the Middlesboro, Kentucky area. At this point, Cleve and I decided to split up. He went to the home of a local ham who had a beam antenna to check the direction from his location, and I traveled to Pine Rock mountain to see if I could get a clear direction from the top of the mountain. Both of us determined that the signal was coming from West of the Middlesboro-Pineville area. By this time, it was getting dark, and we had just about decided to give up and go home to Knoxville. However, a breakthrough happened. I found a ham on 146.55 simplex that was in London, who told me he had the offending signal "full-scale." Additionally, Bo, KI4VMR, was on 145.47 (which had been serving as our coordination frequency) and told us that he had the 146.34 signal full scale on his portable two meter radio with the antenna removed. He was right in the area. I met back up with Cleve and Frank, and we headed up US 25 from Pineville to Corbin. By now it was fully dark.
By this time, Bo had to go to work. Elizabeth, KJ4NRY, volunteered to lead us to the area where Bo lived. We met on US 25 and traveled toward Corbin. By now the 146.34 signal was strong enough that we could hear it on our hand-helds inside our vehicles. As we approached Corbin, it became strong enough that Cleve could not attenuate it using a selectable attenuator pad (guess who forgot his?) and we could indeed hear the offending carrier without antenna attached to our portables. It was time to look around.
I was familiar with the tower that we could immediately see as we came close to Interstate 75, as a very close friend of mine is the Chief Engineer of the radio stations that utilize the tower for their signal delivery. We drove to the entrance of the studio building adjacent to the tower. We could not attenuate the signal at all whatsoever. I made a phone call to my friend, who was now in Knoxville winding down for the evening. He called the station owner, who traveled to the site and let us into the building after we explained the situation. He knew all of the equipment inside the building and went immediately to the equipment that we and he suspected was the culprit. The removal of the AC power confirmed our suspicions...the 146.94 interference was finally gone after over two days!!!
The offending equipment was a UHF amateur repeater with a two meter remote base. Was this interference intentional? Of course not. We did not pursue troubleshooting any further after the AC power feed was unplugged; that is the discretion of the site owner and the owner of the repeater. By this time, it was almost midnight, and Cleve, Frank, and I had a hour plus trip back to Knoxville.
I was unable to restore .94 to service until I got back in range of my UHF control receiver at the 94 site. I was able to access my control receiver for the .94 site on Caryville Mountain as I traveled South on I-75. When I successfully commanded 146.94 back on, there were folks waiting. One said..."Its back!!" We had a great coming-home roundtable QSO until I made it back home a little after 1 AM.
I'm happy to say that the WB4GBI 146.94 repeater is back on the air serving the ham radio operators of East Tennessee, just like it has since 1967 and that's the way I want it to be.
I want to say a HUGE Thank you to all of these Amateurs that made this "mission" a success:
Danny, N4ZAA
Cleve, KB4UAL
Frank, W4NCS
Todd, KA4OAK
Bo, KI4VMR
Elizabeth, KJ4NRY
and to all the others that helped us along the way with signal reports, directions, and monitoring.
On a separate note, THANK YOU to all of your for your prayers, concern and caring during the passing of my Mother. She went home to Heaven last Friday. It still hurts and probably will for a long time. A friend once told me..."Your mother is your 'rudder.' " She left a wonderful legacy to myself, my brother and my sister. We were her proudest accomplishments. I know where she is, and I will see her again someday. I hope I continue to make her proud until then for the rest of my life.
73 de Tim WB4GBI
Tim Berry
www.wb4gbi.com
www.wb4gbi.com
