A Belated Look at Equipment Reliability
We planned the translator installations using the best information available. Unfortunately, no effort had yet been made to broadcast over such a large, mountainous area with a high concern for preserving audio quality. There were no successful examples for us to copy and no unsuccessful efforts from which to learn. We drew from experience with two-way radio and aircraft communications. We listened to advice from TV engineers – some of which proved to be completely wrong for FM. Finally, when we began to talk with Jon Sawyer of Television Technology Corporation (TTC), we learned a great deal about the electronic design of translators and the propagation of radio waves. His information proved to be totally on target.
Even good advice didn't answer every question. In solving the remaining problems, we adopted both conventional and unconventional strategies – the modular tower system being noticeably unconventional.
Now that the translators have been operating for more than 20 years (some as long as 30 years), it is appropriate to consider their service records in order to see which ideas were successful and which were not. Although this particular era of broadcast technology is waning, there may be value in what we observe.
Repeated Problems with Solar Power
We had embraced the growing popularity of solar-electric power generation. In only a short time, however, many of the solar translators went off the air. The electrical generating and storage capacity proved inadequate during the winter months. Having been careful to follow the manufacturer's guidelines, we were unprepared for the failures.
Looking back at the events and circumstances, five factors seem pertinent:
Inadequate database. A computer program determined the specifications for the solar panels and batteries. This program, operated by the vendor of the solar panels, relied on solar insolation data from U.S. Weather Bureau recording stations. KSOR's solar-powered translators were located far from the nearest of these stations, and at significantly higher elevations. The program did not adequately compensate for these differences.
Greater power consumption than anticipated. The data that we provided for the computer run was based on preliminary specifications for the solar model of the XL-FM translator. After the prototypes were built and debugged, the power consumption was more than originally predicted.
Increased hours of operation. The station was popular, and there were requests for the broadcast day to begin earlier. We were not yet aware of the slim margin of solar sufficiency during the winter months and the impending deterioration of the solar panels and batteries.
Unsuitable solar panel construction. The solar panels were manufactured with a covering of silicone. In the late 1970s, this was the industry standard for protecting the panels from the harsh elements of weather. Unfortunately, after a few seasons, the silicone delaminated at the corners and then along the edges. At one site, pieces of the silicone laminate broke off and fell to the ground.
At Iron Mountain, I replaced the solar modules when I was there as the silicone lamination on those old modules was coming apart (now they use low-iron glass) and there were breaks in the intercell connections on several of the modules. . . (Todd Cory, email, February 6, 2008)
Accelerated battery deterioration. Given the first four factors, it was inevitable that each of the solar-electric installations would eventually run short of power, even if only temporarily. When there was no solar power, the batteries continued to provide electricity to the translator without interruption. At a certain point, however, the battery voltage would drop below its operating range. The result was irreversible damage to the batteries due to heightened plate sulfation. Then, with decreased electrical storage capacity, the solar-electric system was even more vulnerable to low levels of insolation. Each incident led ever more quickly to the deterioration of the batteries.
At this late date, two solutions come to mind. One is to include a disconnect that removes the translator from the battery bank when the voltage nears the lower limit of its operating range. The other is to oversize the battery bank and solar panels. A more experienced and authoritative source of advice would have been a great advantage in selecting the solar-system components, but the technology was new and practical experience was still in its infancy.
These days it would be no big deal to design a solar powered power source for a translator with LVD (low voltage disconnect) and sufficient storage to run the gear for 30+ days w/o any charging input. (Todd Cory, proprietor of Mt. Shasta Energy Services, email, November 4, 2008)
Damaged Antennas and Towers
At elevations above 6,000 feet, some translator sites have experienced extensive damage, while other sites have demonstrated limited harm from what seemed like an equivalent exposure to the extremes of weather. Some sites appeared to receive no damage at all. At first, these observations were puzzling.
Storm damage can be seen to relate to these three factors:
Towers. At sites where antenna damage has occurred, at least one nearby tower is higher than the damaged antenna. Towers gather a large amount of ice during the winter. At high elevations, it is common to see ice shields protecting antennas. Falling ice is inevitable. Severe storms bring winds that are able to propel chunks of ice horizontally with destructive force. The result is bent and broken antenna elements.
Venturi effect. When a fluid (air, in this case) passes through a restricted area, the pressure decreases, and the velocity increases. The pressure decrease is what makes a carburetor work. The velocity increase adds destructive power to winter storm winds. A mountain constricts the space through which air is moving, thus making it move even faster. The more prominent and abrupt a mountain's silhouette, the greater the Venturi effect.
Consolidated snow. A barrier to the wind, such as a stand of trees, a building or a prominent feature of terrain, may facilitate the accumulation of snow. Then, in springtime, rising temperatures begin to consolidate the snow into a smaller, more compact mass that increasingly resembles a block of ice. As consolidation progresses, the diagonal brace of an antenna tower may be left supporting an area of snow as its bottom surface rises above the ground due to shrinkage. Consolidated snow can be far too heavy for the braces to support. Small deformations from each season are cumulative, in some cases resulting in severe bending.
If an antenna site is barren, storm winds effectively sweep the snow away. With a minimal accumulation of snow, tower braces aren't damaged by the springtime thaw.
Chestnut Mountain - 5,814 feet. This site is slightly below the danger zone. The transmitting CL-FMs have full exposure to winds from the south and east, but there are no towers to provide wind-bourn ice from these directions. On the remaining sides, trees are higher than the antennas. Significant snow buildup would seem a possibility under the receiving antenna, but there is no evidence of damage to any of the towers or antennas.
Stukel Mountain - 6,421 feet. This site is barren of trees. Extreme winds sweep the snow away from the ridge, preventing buildup. The translator towers have not been damaged. The KSKF tower, however, little more than 100 feet to the south, stands high above the antennas. As Todd Cory relates, ice and even roof tiles can become dangerous projectiles in strong winds. This has led to extensive antenna damage.
Park Mountain - 6,892 feet. There are only a few small trees. The wind is free to blow away any buildup of snow, and there are no other towers at the site. No tower or antenna damage is evident.
Walker Mountain – 7,106 feet. Even when the wind becomes fierce, the trees are high enough to protect the antennas from wind-borne projectiles. On the other hand, the crowding of trees significantly reduces the wind speed near the ground, so snow can accumulate to a considerable depth. There is serious tower damage but no antenna damage.
Grizzly Peak – 7,724 feet. A small tower 60 feet to the north of the translator vault is a source of wind-blown ice that has bent five elements on the CL-FM antennas – one near the point of breaking. There is evidence of extreme wind speed. This is the only site where a vertical tower member has been bent by the direct force of the wind itself. No damage is seen from snow consolidation because the barren surface minimizes the buildup of snow.
Grey Butte – 7,974 feet. The translator antennas are in the lee of the green communications building. This would provide a shadow from the dominant northwest wind sufficient to build deep snow. Additionally, there is no protection from wind-driven ice leaving the antennas that are above and immediately behind. There is extensive tower and antenna damage.