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British Columbia Frequency Modulation Communications Association
The Cabling Project
The hardline is in the ground! In late August 1996, one of the largest projects in BCFMCA history was completed after many years of delays. In the span of one weekend, all of the coax feeding all of the repeaters on the top of Mt. Seymour was replaced.
This project was in the planning since the early 1990's, and after finally purchasing the new materials in the fall of 1995, Mother Nature decided to put all of our plans on hold for another season (it snowed). Once the snow melted in 1996, the planning resumed and a timeline set for completion, we were determined to get it done this year, one way or another. A contractor was lined up and schedules cleared for August 25-28.
On the Friday, with the help of an excavator from D&D Excavating and Rick, VE7EMT, the trench was marked out and the old and water damaged coax was unearthed. All existing coax was contained inside two 4" PVC conduits running from the shack to the tower. Concrete was found extending approximately 4m outwards from the shack, partially encasing the existing conduit. When the conduit was punctured near the shack, approximately 150 liters of water was released. Due to the lack of sealant at the tower end, water had been allowed to enter the conduit and collect in the low areas. This water had no where to go and hence, the coax was forever doomed to sit in a water bath. Water damage was the suspected cause of the high VSWR found on many of the original runs and this was confirmed after further examination of the old coax.
Saturday brought out most of the BCFMCA Executive, FET, EZD, SEY, and SPV, to do the preparations for the new cable. For the reasons mentioned above and upon consultation with LeBlanc and Royale Telecom, Sinclair Labs, and Andrews, conduit would not be used again for the new hardline. In order to get the hardline into the shack, the existing conduits were broken open and as much concrete as possible was removed from around the sides. At the tower, the conduit was squared off with the base and the trench widened by hand. All the old coax was removed from the tower, trench, and shack, and preparations to the trench were completed. To protect the new hardline from damage by rocks and hard earth during backfilling, the trench was smoothed out then lined with a layer of river sand.
Sunday was the big day, lots of work was accomplished by FET, EZD, EMT, SEY, and HSK. Approximately 330m of 7/8" Andrew LDF5-50A Heliax, 50m of 1 5/8" Andrew LDF7-50A Heliax, and 35m of 12/2 AC wire was placed into the trench. All of the hardline was covered with river sand to protect it and to aid in drainage. After the hardline was placed, VSWR checks were done on the hardline and antennae as they were reconnected. The new Sinclair antenna for the ACS link was installed on the tower and almost all of the other machines were put back into operation by the time darkness fell. During the following week, D&D Excavating did the final back-filling of the trench.
Over the next few weeks, the rest of the new antennae were installed. The new Sinclair SRL-310-C4 antenna for VE7RPT-70cm was installed by FET, EZD, and EMT. LeBlanc and Royle Telecom did the installation of the new Sinclair SRL-210C4 on VE7RPT-2m, and the old antenna was exchanged with the one on VE7RAG-2m. All hardline runs were "swept" with a graphical SWR analyser to ensure a good match.
After many years in the making, the "Cabling Project" was finally completed and the tower was looking a lot cleaner. We've put an end to any more water problems, we hope, and the new hardline should last for many years to come. In total, there are 8 runs of 7/8" Heliax (including 1 spare) and 1 run of 1 5/8" Heliax. The 1 5/8" still needs connectors and when we get these, this run will be used for VE7RPT-1.2GHz freeing up another run of 7/8".
The Inside Cabling Project
Once all the work was completed outside the building, we turned our attention inside. All of the machines have "jumpers" from the Heliax to the duplexers and then to the repeaters themselves. Over the years a number of different types of coax were used with a variety of connectors and adapters. It was our goal to replace everything with something that was relatively flexible, didn't consume lots of space, could handle the power levels, and had the proper connectors.
When we originally talked to Dan, VE7DES, he recommended that we look into using RG-142 if we were ever to replace everything. RG-142 met all of our criteria, it was small (about the size of RG-58), it was fairly easy to work with, it was a double braid cable offering 99% shielding, and it could handle the high power from VE7RAG-2m and VE7RPT-2m.
When all the old jumpers were removed, a number of them were found to have loose or improperly installed connectors. This was another source of potential problems in the form high VSWR and intermod that was being eliminated. A large number of adapters were also removed which helped reduce unwanted and undesirable loss of signal and power. The new RG-142 was custom cut for each run and the proper crimp connectors were installed.
Once this project was completed, electrically the repeaters were working much better, unfortunately some of them were working too good. With the new antenna and feedline, VE7RPT-70cm was receiving so well that it started suffering greatly from intermod. As a result, the squelch on this machine has been turned up to compensate until a better solution can be worked out. VE7RPT-2m had suddenly become so sensitive that it was almost unusable. The additional filters on the receiver were placed back into service and much of the problem reduced. The problems you still hear regarding interference on VE7RPT-2m and VE7RAG-2m from the BC Ambulance Service (EHS) are an ongoing battle/mystery and we hope to take more action in the new year.