2GHz transition
Apr 1, 2008 BY JIM
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.
LNAs
LNAs are commonly powered by the receiver, a standalone power supply or a power line from the remote control slave. A portable or spare LNA usually does not have a remote control slave. This requires that new radios be equipped with a diplex kit or that you provide a standalone bias-T power supply. Many portable and fixed link receivers include it, but some central receivers only provide this feature as an option.
Transmission and control cables
ENG receive
antennas can be quite complicated devices, especially when filter switching and
other bypass options. The authors have seen antennas that can have seven
different configurations switched between. Add local serial and parallel
control and one or two LNAs, and the antenna can weight in at a few hundred
pounds.
Antenna control cables have not changed much since the 1980s. Typically, this means you can reuse existing cables — unless you change antenna manufacturers. Keep in mind that some of the major vendors' OEM antennas are from the same manufacturers. However, even if you use the same manufacturer, the pin-out may change to support new features. Also, manufacturers sometimes use a serial control protocol to compensate for the need for more conductors.
If you use fiber on the tower, you will need new electrical-to-optical and optical-to-electrical interfaces. Sprint may agree to cover this if the overall cost is comparable.
Consider your path carefully. Digital LNAs have gains in the 20dB to 30dB range. The minimum signal required at the bottom of the cable run is 4dB to 5dB C/N. A 7/8in transmission line has a loss of about 1.86dB/100ft @ 2GHz, and a 1-5/8in line has a loss of about 1.13dB/100ft @ 2GHz. While the LNA sets the noise floor, the attenuation of the line determines the noise floor increase at the receiver.
Transmitters
A 10W+ analog transmitter will usually be replaced with a 5W digital one. A 10W or lower power analog transmitter will be replaced with a 1.5W digital transmitter. Digital 5W transmitters may require an external power amp and revert to lower power without it. Some two-part transmitters optionally bypass the PA from the truck unit.
If you are replacing a multiband radio, Sprint may have allowed for a new 2GHz radio while disabling the analog 2GHz part of the old radio.
Receivers
Most receivers
provide for front panel telemetry, and some even overlay that information on a
monitor video output.
Remote slaves may supply LNA power. However, if you need the receiver to power the LNA, ensure your quote includes that option. Another option in most radios is 2-VSB, 4-VSB or 8-VSB. COFDM is better at overcoming multipath effects, but VSB has as much as a 3dB lower C/N ratio requirement. If distance is important, VSB modulation is a plus.
If the receiver feeds a transmitter, use the ASI feed instead of the IF output. The IF output will have more errors, and ASI has a fixed 19.3Mb/s rate with more FEC.
Sprint allows you to upgrade to single-input diversity receivers. Manufacturers are likely to work with you to enable additional inputs at competitive prices. While diversity receivers have many advantages, by their nature they generally do not support VSB.
Remove slaves and antenna controllers
Remote slave units at
the receive site talk to the central controller and control the receive
antenna. These units need to be robust to drive antenna position, filter
switching and provide LNA power. They are also used to accept receiver spectrum
data and package it along other receiver and antenna telemetry and send it back
to the central controller.
Antennas are lightning targets. Sprint will cover the cost of surge suppressors, even if they are considered an extra option.
Remote slaves use modems for two- or four-wire systems. Some are configurable on-site. Others need to be specifically configured, and you need to spell that out in your request for quote (RFQ). Consider purchasing spare modems.
Spectrum monitoring
Digital receivers require spectrum monitoring, so be sure your new equipment includes the necessary software and hardware. The receiver and remote controller protocol needs to be compatible to provide spectrum monitoring features. Also, be sure your link supports a fast enough refresh rate to maintain the spectrum display. This typically requires at least a 19.2Kbaud link.
If your receive site is at the station without a central controller, you are eligible for standalone spectrum viewing on a PC.
Central controllers
Central controllers
control multiple receive sites at once, and they are generally touch-screen
devices. They also display receive signal health characteristics, as the old
method of looking for best video in the analog world doesn’t necessarily make
for the most reliable signal in the digital world.
Central controllers manage multiple remote slaves. Sprint will allow one modem per remote slave line. Modems are housed either in the central controller or connected via USB or Ethernet. Stations with a single controller usually get USB connectivity. Those with multiple controllers get Ethernet.
IFB
IFB for DENG remotes is like IFB for satellite remotes. You need mix-minus feeds between studio and talent, even over cell phone links.
Do not give up any two-way radio capability. In some cases, Sprint may pay for continuous duty two-way radios for IFB. Stations currently using Pro Channel are eligible for Pro Channel 3 receivers, which provide side-tone or secondary audio to eliminate backhaul delay issues.
Cell phone users, keep in mind that FCC rule 47 CFR 64.402 encourages wireless operators to provide priority access service (PAS) to emergency responders. This means that in the future, you might be covering the biggest stories without cell phones. If that happens, do you have a backup plan?
Fixed links
Many of these issues are also appropriate for fixed links. Work through each of the questions and issues for those links too.
Portable equipment
Many stations use portable equipment for stationary applications. If so, hopefully the expense to install the new equipment was included in your project as Sprint typically covers these costs.
Cutover and implementation
You can move your fixed link to the new frequency immediately after you install the new equipment, as long as it does not cause interference. Otherwise, you will have to stay on the old channel until your DMA cluster cuts over.
Before starting installation, discuss your LAN topology, including IP address schema, with your vendors and integrator. Provide them with detailed information about any custom antenna mounts or other unique issues. Schedule the integrator only after you receive all equipment and hardware, and provide clear dock swap documentation to the installers.
If you install a BAS filter during the first tower climb, you must not use Ch 1 or Ch 2 until the cutover. However, you can continue using the existing PCS filter until after cutover. Then you can schedule the tower crew for a second climb. You will need to schedule the tower crew on cutover weekend to replace channel filters, if you agreed to operate nonswitched channel filters in the current band plan.
Once you have a cutover date, coordinate site access, power reductions or off-air time with joint tenants and building managers. Remember to start the license modification process early. Otherwise, you may delay the cutover for the entire DMA cluster.
Dock swapping
Most manufacturers allow broadcasters to swap equipment in the vendor's quote for other equipment. Often the broadcaster will exchange extra spare and portable equipment for something now considered more desirable. The newly selected equipment is shipped in lieu of the gear originally quoted by the vendor to Sprint. As far as Sprint is concerned, it has agreed to give the vendor a certain amount of money based on a vendor's approved quote. Whatever agreement you and the vendor come to for exact equipment is between the two of you.
However, be careful. Some equipment vendors may prohibit this process or will charge you hefty restocking fees. The reason is that Sprint has already paid for some equipment to be built in advance of actual orders. Now some vendors want to minimize the amount of product left on the shelf when this project is completed.
Final thoughts
Many stations are now in a quiet period in their projects where the FRAs are still winding through Sprint's approval process. Don't waste this downtime. Recheck your plans, and be sure you haven't forgotten something. When it does come time to move, you don't want to discover that a key component has been overlooked. You will save yourself the embarrassment of holding up everyone in your DMA.
Jim Boston is a West Coast consultant, and Roland Hoffmann is a project management consultant and provides project governance services.