frequency-shift modulation 
frequency-shift signaling 
frequency-shift telegraphy 
frequency source 
frequency spectrum 
frequency spectrum congestion 
frequency stability 
frequency standard 
frequency synthesizer 
frequency tolerance 
frequency translation 
Fresnel diffraction pattern 
Fresnel reflection 
Fresnel zone 
front-end noise temperature 
front-end processor (FEP) 
front-to-back ratio 
FSDPSK 
FSK 
FTAM 
FTP 
FTS 
FTS2000 
full carrier 
full carrier single-sideband emission 
full-duplex (FDX) circuit 
full-duplex (FDX) operation 
full duration at half maximum (FDHM) 
full modulation 
full-motion operation 
full processing 
full width at half maximum (FWHM) 
fully connected mesh network 
fully connected topology 
fully intermateable connectors 
functional component (FC) 
functional profile 
functional signaling 
functional signaling link 
functional unit 
function signal 
fundamental 
fundamental mode 
furcate 
fuse 
fused silica 
fusion splice 
FWHM 
FX 
gain 
gain hit 
gain medium

FM capture ratio 
FM improvement factor 
FM improvement threshold 
FM threshold effect 
FM threshold extension 
FO 
footprint 
forbidden character 
foreign exchange (FX) service 
foreign instrumentation signals intelligence (FISINT) 
format 
Fortran 
fortuitous conductor 
fortuitous distortion 
forward busying 
forward channel 
forward echo 
forward error correction (FEC) 
forward propagation ionospheric scatter (FPIS) 
forward scatter 
forward signal 
FOT 

floppy disk 
flops 
flowchart 
flow control 
flow control procedure 
flow diagram 
flowline 
flutter 
flux 
flywheel effect 
flywheeling 

Fourier analysis 
four-wire circuit 
four-wire repeater 
four-wire terminating set 
fox message 
FPIS 
fractional frequency fluctuation 
fractional T1 
frame 
frame alignment 
frame-alignment recovery time 
frame alignment signal 
frame-alignment time slot 
frame check sequence (FCS) 
framed interface 
frame duration 
frame frequency 
frame grabber 
frame pitch 
frame rate 
frame relay 
frame slip 
frame synchronization 
frame synchronization pattern 
framing 
framing bit 
framing signal 
Fraunhofer diffraction pattern 
Fraunhofer region 
free net 
free routing 
free-running capability 
free space 
free-space coupling 
free-space loss 
freeze frame 
freeze frame television 
F region 
frequency 
frequency accuracy 
frequency aging 
frequency allocation 
frequency allotment 
frequency-analysis compaction 
frequency assignment 
frequency assignment authority 
frequency averaging 
frequency band 
frequency band allocation 
frequency-change signaling 
frequency coherence 
frequency compatibility 
frequency departure 
frequency-derived channel 
frequency deviation 
frequency dispersal 
frequency displacement 
frequency distortion 
frequency diversity 
frequency-division multiple access (FDMA) 
frequency-division multiplexing (FDM) 
frequency drift 
frequency-exchange signaling 
frequency fluctuation 
frequency frogging 
frequency guard band 
frequency hopping 
frequency-hopping spread spectrum 
frequency hour 
frequency instability 
frequency lock 
frequency modulation (FM) 
frequency offset 
frequency of optimum traffic (FOT) 
frequency of optimum transmission (FOT) 
frequency prediction 
frequency range 
frequency response 
frequency response curve 
frequency scanning 
frequency sharing 
frequency shift 
frequency-shift keying (FSK) 
FM 
FM blanketing 
FM broadcast translator 
FM capture effect