2GHz transition
Apr 1, 2008 12:00 PM, BY JIM BOSTON AND ROLAND HOFFMANN
This is the year broadcasters and Sprint have vowed to accomplish several key milestones. In response to the current plans to complete the relocation of all BAS users by August 2009, the FCC has allowed an extension to March 2009, and may consider a further extension to August 2009.
Some DMA clusters, including top 30 markets, have relocated in March 2008. This means broadcasters must be ready for the cutover or risk mobile satellite system interference. In a worst-case scenario, a station could end up paying for the relocation itself.
Midpoint status
Most stations are halfway through the eight-phase process, which includes:
- Phase 1. Market kickoff 100 percent complete.
- Phase 2. Inventory submission 100 percent complete.
- Phase 3. Inventory verification 100 percent complete.
- Phase 4 (halfway point). Quote submission 95 percent complete. Broadcasters select vendors, obtain quotes and develop estimates.
- Phase 5. Frequency relocation agreement (FRA) 65 percent complete. The relocation contract includes the agreed to quote package. Creating the FRA can take from two to more than eight weeks.
- Phase 6. Purchase orders and vendor fulfillment beginning stages. Many broadcasters negotiate dock swapping at this stage. This is a process to exchange FRA equipment on the vendor's dock for something else. Here, stations can trade spare or portable equipment.
- Phase 7. Equipment installation beginning stages. Stations install the equipment, perform tower work and system commissioning and complete their staff's training. Stations can go live with digital narrow in place sometimes long before the DMA cutover.
- Phase 8. Retune and market closeout beginning stages. Stations in a DMA cluster retune to the new BAS channel plan. If a station has problems, the DMA cluster reverts to the old channel plan and reschedules the cutover. Stations send the old equipment to Sprint for destruction and settle the final financial aspects of the FRA.
Checklist
Let's look at some ways to ensure a positive project outcome. The following sections will cover antenna and tower studies, filters, LNAs, transmission control and cables, transmitters, receivers, remove slaves and antenna controllers, spectrum monitoring, central controllers, IFB, fixed links, portable equipment, cutover and implementation, and dock swapping.
Antennas and tower studies
Sprint generally does not pay for replacement antennas. The company only pays for antennas when filter or remote control issues make it necessary. Stations often need to replace remote antenna controllers (slaves) to facilitate spectrum monitoring back at the station or central control point along with standard telemetry. These slaves often are incompatible with existing antenna pan/tilt units. In these cases, Sprint may agree to cover a complete replacement.
Most antennas are slated only for feed upgrades where the LNA is replaced with a new phase-stable unit and PCS/AWS filtering.
Some antenna vendors will not build filter switching as part of feed upgrades. This means you'll probably have to replace the antenna if you need filter switching. Filter switching is often needed for Ch 1 or Ch 2 to use during the transition phase. For those channels, you also may need pre- and post-relocation filter switching. (See the Filters section below.)
If you are replacing the antenna, be sure the replacement feed horns have the same polarity as the original system. Also, consider the need for a tower study if other equipment will be added to the tower. Ask the tower manufacturer whether a study is required. If so, Sprint will pay for it.
A note on portable and spare antennas: Sprint will generally not pay to replace single golden rod antennas. However, the company will generally pay to replace dual golden rod antennas.
If you need a tower study, provide the information to your engineering firm early. The firm will require a lot of data, and it may take you a while to gather it. The engineering firm will assume that the tower is in proper plumb and alignment and has correct bolt tightness, without significant deterioration or damage to any components. If you know of any tower issues, be forthright and admit them.
Filters
Filters or switches located at ground level do not constitute a reason for an antenna replacement, because new filters and switching are installed in the same location. If this is the case, consider an up sell and pay the difference out of pocket. Then install filters and switches in front of the LNA. That way, the filters will prevent overloading and other linearity problems.
Omni antennas mount on ENG trucks using COFDM modulation allow trucks to transmit as they travel down the road. Diversity receivers at the other end maximize your chance of recovering the signal of a vehicle in motion. But all COFDM receivers have increased ability to recover signals where the multi-path characteristics are changing with location.
Digital modulation provides better rejection of unwanted adjacent signals, so channel filters may not be needed. However, if your site is close to a cell tower, then all bets are off. A cell transmitter can radiate 1500W to 2000W of power, and if close enough to your site, problems can develop. Consider mounting your equipment higher than the cell antennas to reduce the amount of cell RF reaching the antennas.
Stations that use a Ch 1 and Ch 2 must install the new BAS filter only after their market cuts over. New users of the abandoned old Ch 1 and Ch 2 frequencies will most likely not occupy the frequencies immediately, so you will likely have time to schedule the necessary tower work.
Ch 10 users need a special BAS filter. The standard filter combines three parallel and cascaded filters: the Ch 1 to Ch 7 band pass filter, a stop band filter between Ch 7 and Ch 8, and a second Ch 8 to Ch 10 band pass filter. To simplify the filter design, the Ch 10 filter has a gentle roll off skirt, making that channel unusable. A special Ch 10 BAS filter adds a brick-wall filter for Ch 10.
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