NFL Event Frequency Coordinator Tools

White Space Devices (TVBD)

I did a little bit of playing with radio mapping software and made a set of maps that says a LOT about the future of licensed wireless mics at large events as TV Band Devices (TVBD), also known as "White Space Devices", start showing up on the market!

I mapped the signal coverage of 3 devices; an unlicensed Fixed TVBD running the maximum FCC allowed power and antenna height, a typical licensed wireless mic at 100 mW and a 250 mW device running the maximum power allowable to a licensed device under Part 74 (250 mW). While I did NOT look at unlicensed wireless microphones allowed to run up to 50 mW, note that many licensed low-power devices, like intercom beltpacks, operate at these power levels (between 10-50 mW ERP) because of battery and size limitations.

The coverage areas for all devices are centered around the same location; in this case Cowboys Stadium in Dallas as I was working on Super Bowl stuff.

Additionally, I show the FCC specified protection radius around the site that Fixed TVBD must protect. Keep in mind my software only allows me to create concentric circles at a specified radius, so I added circles on 1 KM increments from the center of the venue.Please note: TVBD are only required to protect the center most circle!

The maps show the received signal level calculated using the Longley Rice method specified at F(50,50) for 3 different devices transmitting from the same location. It does NOT allow for any additional losses other than Free Space path loss at 500 MHz - meaning it doesn't take into consideration losses from other people standing around a transmitter that is worn on a coaches or referees belt!

Unlicensed TVBD, as specified in the FCC Report & Order at 4 Watt ERP and a transmit antenna 30 meters above ground

Typical licensed wireless mic (Part 74 Licensed device), as used at any NFL event: 100 mW ERP, the TX antenna worn on belt 1 meter above ground

Part 74 Licensed device, 250 mW, operating with the TX antenna worn on a belt 1 meter above ground (maximum power allowable under the FCC Part 74 Rules)

All 3 maps have the receive antenna 2 meters above the ground and I cut off all calculated receive signals levels that are below -114 dBm; which is the minimum signal that a TVBD was supposed to be able to sense when sensing was a requirement for TVBD. Note that this cutoff signal level is BELOW the minimal signal level that is needed to receive a usable signal from the mic or intercom!

Compare the FCC specified protection distance (inner most circle) that the TVBD must protect to the actual distance that the fixed TVBD can legally cover and then to the area that a typical LICENSED wireless mic or Coached Intercom beltpack can cover and you see how much trouble we are in! Especially since the FCC removed the requirement for TVBD to sense other users to keep from interfering with them!