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systems of other services which are also allocated on a primary basis. New systems
cannot be introduced into that frequency band if they will result in interference to a
system operating with a primary allocation. A secondary allocation to a service allows
systems to operate in a band on the condition that it does not cause interference to, nor
claims protection from, systems operating on a primary basis. However, systems
operating on a secondary basis can claim protection from interference from other
systems operating on a secondary basis.
D.3.2 Consequences of Exceeding PFD Limits
If the PFD levels do not meet the PFD limits given in the NTIA manual, the NTIA will not
grant frequency authorization except as noted in paragraph D.3.1.
If the PFD levels do not meet the PFD limits given in the ITU-R RR, then the mission is
subject to the conditions given in Article 4.4. Article 4.4 states “Administrations of the
Member States shall not assign to a station any frequency in derogation of either the
Table of Frequency Allocations in this Chapter or the other provisions of these
Regulations, except on the express condition that such a station, when using such a
frequency assignment, shall not cause harmful interference to, and shall not claim
protection from harmful interference caused by, a station operating in accordance with
the provisions of the Constitution, the Convention and these Regulations.”
D.3.3 Calculation of PFD Levels
The calculation of PFD levels requires the following data for the spacecraft:
a. Maximum transmitter power contained in the reference bandwidth (i.e., 4 kHz or
1 MHz), under all conditions and modes of modulation measured at the antenna
input. Please see paragraph D.3.3.1 below.
b. Transmitting antenna gain pattern.
c. Transmitting antenna mainbeam pointing characteristics, including any
intentional or unintentional antenna mispointing.
d. Orbital altitude (nominally circular orbits are assumed for this analysis).
The PFD at an angle of arrival, α, is calculated as shown in
Equation D-1Equation D-1 with R(α) found using Equation D-2 and Equation D-3. The
geometry is shown in Figure D-1:
Equation D-1:
where:
Gt ( ) PtB
PFD ( )
= 10 log
2
4πR
( )
Revision 10 D-4 450-SNUG