Institute for Telecommunication Sciences / Research / Table Mountain / Coordination of Nearby Transmitters
Coordination of Transmitters Near the Radio Quiet Zone
The Table Mountain Field Site is designated by the FCC as a “Radio Quiet Zone” and is protected by Federal and State regulation from strong external radio signals. This restriction ensures that the Department of Commerce laboratories and research affiliates can study the characteristics and propagation of electromagnetic radiation in a real-world environment with minimal interference from uncontrolled sources of external radio interference.
This web page provides guidance for the coordination of offsite transmissions that may impact the Table Mountain Radio Quiet Zone. See also 47 CFR § 1.924 - Quiet zones.
Researchers who use the field site will coordinate the onsite transmitters when requesting access to the site. Frequency coordination is not needed for computer peripherals, such as wireless keyboards, mice, printers, etc.
Table Mountain Radio Quiet Zone
Licensees and applicants planning to construct and operate a new or modified station at a permanent fixed location in the vicinity of Boulder County, Colorado are advised to give consideration, prior to filing applications, to the need to protect the Table Mountain Radio Quiet Zone from interference. To prevent degradation of the present ambient radio signal level at the site, the Department of Commerce seeks to ensure that the field strengths of any radiated signals (excluding reflected signals) received on this 1800 acre site (in the vicinity of coordinates 40°07′49.9″ North Latitude, 105°14′42.0″ West Longitude) resulting from new assignments (other than mobile stations) or from the modification or relocation of existing facilities do not exceed the values given in the following table:
| Frequency Range | Field Strength (mV/m) | Power flux density (dBW/m2) |
|---|---|---|
| Below 540 kHz | 10 | −65.8 |
| 540 to 1600 kHz | 20 | −59.8 |
| 1.6 to 470 MHz | 10 | −65.8 |
| 470 to 890 MHz | 30 | −56.2 |
| 890 MHz and above | 1 | −85.8 |
Note: Equivalent values of power flux density are calculated assuming free space characteristic impedance of 376.7Ω (120πΩ).
Advance consultation is recommended, particularly for applicants with no reliable data to indicate whether the field strength or power flux density figures in the above table would be exceeded by their proposed radio facilities. In general, coordination is recommended for:
- Stations located within 2.4 kilometers (1.5 miles) of the Table Mountain Radio Receiving Zone;
- Stations located within 4.8 kilometers (3 miles) transmitting with 50 watts or more effective radiated power (ERP) in the primary plane of polarization in the azimuthal direction of the Table Mountain Radio Receiving Zone;
- Stations located within 16 kilometers (10 miles) transmitting with 1 kW or more ERP in the primary plane of polarization in the azimuthal direction of the Table Mountain Radio Receiving Zone;
- Stations located within 80 kilometers (50 miles) transmitting with 25 kW or more ERP in the primary plane of polarization in the azimuthal direction of Table Mountain Receiving Zone.
Frequency Coordination Applications
If the transmitter is within the radius described above, provide the following:
- Transmitter name
- Transmitter owner
- Transmitter site ID (USID)
- Transmitter coordinates
- Distance from Table Mountain Receiving Zone (from vicinity of 40-07-49.9 N lat / 105-14-42.0 W lon)
- Project description
- Transmit frequencies
- Duty cycle
- Signal bandwidth
- Modulation type
- Transmitter power (per polarization)
- Antenna model
- Antenna gain
- Polarization
- Beamwidth
- Main beam direction (toward Quiet Zone)
- Other beam directions (not toward Quiet Zone)
- Transmitter height (electrical center) above ground level
- Mechanical downtilt
- Full antenna radiation patterns (0–359 degrees, horizontal/vertical)
Send this information to frequencymanager@ntia.gov. Allow 5–15 business days for a full propagation analysis to be performed with the information provided. Field strength will be calculated at the crossroads in the vicinity of coordinates 40°07′49.9″ North Latitude, 105°14′42.0″ West Longitude. Upon a favorable outcome (does not exceed TM limits), the frequency manager will provide a Letter of Successful Coordination to be submitted along with your application to the FCC.
The FCC will not screen applications to determine whether advance consultation has taken place. However, such consultation may avoid the filing of objections from the Department of Commerce or institution of proceedings to modify the authorizations of stations that radiate signals with a field strength or power flux density at the site in excess of those specified herein.
This coordination is based solely on technical information submitted to our office and not on the actual measured signal.
Questions
In advance of filing applications with the Commission, applicants are urged to communicate with the Radio Frequency Manager by sending an email to frequencymanager@ntia.gov or call 303-497-4220.