Getting In Sync
Database administrators have also agreed to what is essentially real-time synchronization between databases, far better than the FCC requirement of only once every 24 hours.
Asked how that translates into actual sync times, several of the database technical folk indicated all databases should be synchronized about every 10 minutes or so given vagaries with database calculations once the registration is received, server loading and internet routing.
However, this does not address how often TVBDs must attempt a query of a database for available channels; the rules call for only once every 24 hours and the TVBD is permitted a 24-hour grace period if the attempt fails. This could mean up to almost 48 hours for a TVBD operating without checking the databases, but there are a few factors in place to minimize interference potential due to this.
First is the requirement TVBDs check their location via GPS every 60 seconds, and if it’s determined the TVBD has moved more than 50 meters from the location it last attempted to query a database (whenever it made the attempt), it must do so again.
Second is the fact that when a TVBD does download channel availability information, that information is for the following 48 hours, not just for the moment of the query.
The final interference avoidance mechanism is possibly one where the TVBDs query the databases far more often; in fact this is something the database administrators are actually advocating and advising TVBD manufacturers and service providers to do. Having the TVBD query as often as every 15 minutes or so could permit it to take advantage of channels that have just been released from a reservation or channels that are open for the specific time of day or night the TVBD attempts to operate.
The Ground Rules
As wireless mic (IEM, intercom and IFB) users, it’s necessary to understand the ground rules for operation now that TVBDs will be sharing the spectrum. There are two classes of wireless mic users as of January 2010:
1. Unlicensed users operating under Part 15, Subpart H rules. In short, the maximum permissible RF power output is limited to 50 mW in both VHF and UHF, and there are some minimum requirements that must be met before an unlicensed user can register in the database for additional channels.
A) The unlicensed user must first populate the two reserved TV channels with 6-8 wireless frequencies;
B) Populate any other usable TV channels that are unavailable to TVBDs with 6-8 wireless frequencies;
C) Request on the FCC website (not yet active but in the advanced development stage) to register for additional TV channels in the database at least 30 days in advance. This 30 days provides for a comment period in case anyone has objections, though unless there is some major public detriment, it’s unlikely the FCC would deny the request. Once the FCC approves the request, the FCC will place the approval in the ULS for the geo-location databases to reference. Once the approval is granted, the unlicensed user can then register in one of the databases.
Aside from the fact that in most cases there simply isn’t 30 days advance knowledge of an event, a registration request on the FCC website concludes with the applicant certifying there will be 6-8 frequencies in each of the TV channels noted in A and B above. This certification will be the legal equivalent of signing a federal document, with all that implies. So claiming a large number of frequencies in order to warehouse additional spectrum when that will knowingly not be the case could lead to some unpleasantness should the FCC audit the registration request and find it to be knowingly false.
Part 15 users wishing to request registration will have to first acquire an FCC Registration Number (FRN), which is free and can be obtained from the FCC website in a matter of minutes. The FRN is a permanent identifier the user will reference whenever they request registrations, and it is recommended to acquire one now. (See the end of this story for the web site.)
2. Licensed users operating under Part 74, Subpart H. These are users that are also Part 73 broadcasters, content producers for TV and film, and cable studio operations. Although 50 mW remains the maximum RF power level for VHF equipment, these users can utilize UHF equipment up to 250 mW. These users can register directly in a geo-location database, at any time, and do not need to certify their use of the reserved channels or other channels unavailable to TVBDs first.