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Glenn Research Center	NA2XAA through NA2XGZ
Dryden Flight Research Center	NA2XHA through NA2XOZ
Langley Research Center	NA2XPA through NA2XZZ
Ames Research Center	NA3XAA through NA3XGZ
Goddard Space Flight Center	NA3XHA through NA3X0Z
NASA Headquarters	NA3XPA through NA3XRZ
Jet Propulsion Laboratory	NA3XSA through NA3XZZ
Marshall Space Flight Center	NA4XAA through NA4XEZ
Stennis Space Center	NA4XFA through NA4XJZ
Wallops Flight Facility	NA4XKA through NA4XUZ
Kennedy Space Center	NA4XVA through NA4XZZ
Johnson Space Center	NA5XAA through NA5XGZ

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Glenn Research Center	KHA940 through KHA944
Dryden Flight Research Center	KHA910 through KHA914
Langley Research Center	KHA935 through KHA939
Ames Research Center	KHA905 through KHA909
Goddard Space Flight Center	KHA915 through KHA919
NASA Headquarters	KHA900 through KHA904
Jet Propulsion Laboratory	KHA920 through KHA924
Marshall Space Flight Center	KHA945 through KHA949
Stennis Space Center	KHA950 through KHA954
Wallops Flight Facility	KHA955 through KHA959
Kennedy Space Center	KHA930 through KHA934
Johnson Space Center	KHA925 through KHA929
Spare Call Signs	KHA960 through KHA969

Applicable only to fixed operations.

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Glenn Research Center	PBA320 through WPBA335
Dryden Flight Research Center	WPBA230 through WPBA244
Langley Research Center	WPBA305 through WPBA319
Ames Research Center	WPBA215 through WPBA229
Goddard Space Flight Center	WPBA245 through WPBA259
NASA Headquarters	WPBA200 through WPBA214
Jet Propulsion Laboratory	WPBA260 through WPBA274
Marshall Space Flight Center	WPBA336 through WPBA350
Stennis Space Center	WPBA351 through WPBA365
Wallops Flight Facility	WPBA366 through WPBA380
Kennedy Space Center	WPBA290 through WPBA304
Johnson Space Center	WPBA275 through WPBA289

Applicable only to land mobile radio systems operations, i.e. repeater operations.

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1. The Center or JPL Spectrum Manager exercises complete control of the assigned block of call signs and reserves the right to cancel or make changes as appropriate. The Center Spectrum Manager must maintain a complete and accurate record of all call sign assignments. Additional call signs may be made available by the National Spectrum Program Manager upon receipt of a request supplemented by documentary proof that the call sign allocation cannot satisfy existing call sign requirements.

2. One or more call signs may be assigned by the Center or JPL Spectrum Manager to any operation remotely located from the Center where the spectrum manager exercises responsibility for the NASA Radio Frequency Assignment (NRFA) specifically issued to NASA representatives of commercial contractors, research institutes, colleges and universities under contractual jurisdiction of the activity.

3. Upon receipt of an NRFA, the Center or JPL Spectrum Manager will make all call sign assignments required by operations on such radio frequencies from the call sign block allocated to the Center or JPL, regardless of the organization or commercial activity conducting the operation.

4. Prior to the assignment of an initial radio call sign, the Center or JPL Spectrum Manager must first determine that a valid requirement exists and that no previous assignment of an experimental call sign has been made to this operation.

5. Upon receipt of a request for an additional call sign, the Center or JPL Spectrum Manager will review the requirement to determine the feasibility of expanding the initial call sign assignment in lieu of the assignment of an additional identifier.

6. Duplicate assignment of the same call sign to different operations is not authorized.