Townsquare Media''s Tri-Cities cluster (Richland/Kennewick/Pasco, Wash.) provides a great example of “engineering strategy” that you should know about. They built an N+1 site known as “Finley” that serves all four of the company''s FM stations in the market (KXRX, KEYW, KOLW and KORD). Market Engineer Tim Schall described the system for this article.
"Finley" backup site with frequency agile transmitter serves four stations.
The N+1 site is basically composed of a Nautel VS2.5, and a two-bay Bext TFC2K, which is a broadband antenna. Each of the four stations has a licensed auxiliary for 2 kW ERP. All four stations are currently received at the site by their normal microwave channels. Each STL receiver feeds a composite switcher input—and naturally the output of that switch in turn feeds the composite input of the VS2.5.
In order to turn up the site, Tim establishes an IP connection to the transmitter, and then using the Nautel AUI he simply selects a particular profile. A profile is configured in the transmitter for each station—in this case, all that really needs to change is the frequency. Also configured in the profile is a logic high output that is wired to a particular input select on the composite switch. When each profile is selected, the appropriate composite feed is sent to the VS. The station chosen then comes up at the right frequency, TPO, and with the correct audio.
One interesting change that Tim plans in the near future is making use of another available feature in each profile: receiving audio via a Shoutcast or Icecast stream. Townsquare maintains a full 25 Mbps IP radio link to the site. By installing four Barix Instreamers at the common studio location, he''ll be able to have the VS grab the correct audio for each station, replacing the composite STL receivers and switch. This will allow Tim to re-allocate the four STL receivers at their associated main transmitter sites as backups.
As you can tell, quite a bit of time and resources have been invested in this site. I asked Tim for a couple of examples when it came in handy. “Recently, there was a lot of tower work to be done at the KORD site. There are three FMs on that tower. The other two are owned by another company. To maintain NIER compliance, only one station could be on from the tower while the work was being done and it had be at greatly reduced power. Townsquare Media moved the operations to our Finley site and actually got better coverage from there than we would have at the power level necessary from the main site,” said Tim. “There was another instance when the power failed at the KEYW site and it (Finley) was pressed into service. There is no backup generator at KEYW.”
Broadband antenna at the "Finley" site serves as backup for all four stations.
Even with the advantages of an N+1 site, Tim has some warnings that he wants to pass along. “If someone were to build a site like this, or even if I were going to build another one, I would insist on having the discussion of station priority. That is to say, if something happens and two stations are down at the same time, which station gets the backup? My market manager has made it clear which station gets this site if that should happen,” said Tim. Again, this is part of the engineering strategy, but one that is decided along with your local manager and PD.
The approach you take toward establishing an alternate site depends upon the resources available to you. That, in turn, depends upon what is at stake in your particular business circumstance. In smaller markets it may be that you''ll have less to work with, sure. However, that should not be an insurmountable obstacle. Look at tower space that''s under lease or otherwise available inexpensively, figure out a way to make space in the racks for a frequency-agile transmitter, and determine a backup means of getting program audio out to another site. Use your imagination and study what others have done. Borrow their best ideas to help solve your own. That''s how it''s done.
Irwin is RF engineer/project manager for Clear Channel Los Angeles. Contact him at firstname.lastname@example.org.