Null fill

Null fill is used in radio antenna systems which are located on mountains or tall towers, to prevent too much of the signal from overshooting the nearest part of intended coverage area. Phasing is used between antenna elements to take power away from the main lobe and electrically direct more of it at a more downward angle in the vertical plane. This requires a phased array. Changing the relative power supplied to each element also changes the radiation pattern in this manner, and often both methods are used in combination.

References

"Analysis of Antenna Null-fill and Broadcast Coverage." Myron D. Fanton. ERI Technical Series, vol. 6, April 2006.
"The Tide is Turning." Charles Rhodes.
"A Study on Null-Fill Array Antenna for Service Coverage Expansion in PCS Band" Youngseok Ko

Analog television broadcasting topics

Systems	180-line 405-line ( System A ) 441-line 525-line ( System J , System M ) 625-line ( System B , System C , System D , System G , System H , System I , System K , System L , System N ) 819-line ( System E , System F )

Color systems	NTSC PAL PAL-M PAL-S PALplus SECAM

Video	Back porch and front porch Black level Blanking level Chrominance Chrominance subcarrier Colorburst Color killer Color TV Composite video Frame (video) Horizontal scan rate Horizontal blanking interval Luma Nominal analogue blanking Overscan Raster scan Safe area Television lines Vertical blanking interval White clipper

Sound	Multichannel television sound NICAM Sound-in-Syncs Zweikanalton

Modulation	Frequency modulation Quadrature amplitude modulation Vestigial sideband modulation (VSB)

Transmission	Amplifiers Antenna (radio) Broadcast transmitter/Transmitter station Cavity amplifier Differential gain Differential phase Diplexer Dipole antenna Dummy load Frequency mixer Intercarrier method Intermediate frequency Output power of an analog TV transmitter Pre-emphasis Residual carrier Split sound system Superheterodyne transmitter Television receive-only Direct-broadcast satellite television Television transmitter Terrestrial television Transposer

Frequencies & Bands	Frequency offset Microwave transmission Television channel frequencies UHF VHF

Propagation	Beam tilt Distortion Earth bulge Field strength in free space Knife-edge effect Noise (electronics) Null fill Path loss Radiation pattern Skew Television interference

Testing	Distortionmeter Field strength meter Vectorscope VIT signals Zero reference pulse

Artifacts	Dot crawl Ghosting Hanover bars Sparklies

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Null fill

References

See also