Realistically, COFDM ENG Systems have about half the range as analog systems, but provide a much cleaner picture, with virtually no chroma amplitude or phase changes. KCNC-TV has a range of about 44 to50 miles with their helicopter in the Digital Mode, and about 90 to 100 Miles in the Analog Mode. Their vans incorporate high gain, directional antennas to insure range.
WPIX-TV reported that at an altitude of 3000 feet, they sent back pictures of the Cape May water tower from a distance of 125 statute miles before running out of signal.
Some other stations use COFDM ENG Systems with (~6 inch) LOW GAIN, OMNI-DIRECTIONAL antennas, and suffer a DRASTIC LOSS in RANGE.. Some of the most popular units use "EZ FLEX-402" transmission line, with a loss typically 4 times greater than conventional 1/2" HELIAX line. The net result is a system that has about 1/10th the gain of a typical analog ENG transmit antenna, with a transmission line that has 4 times the loss. This makes for great local and some moderate coverage, but only about 1/5th the range of an analog system with a high gain, directional antenna.Your Receive and Transmit Antenna System can be the weakest link in your digital system. Call us at 1-888-828-8775 for further information..
Things that Reduce COFDM Range:
High gain LNAs can hinder COFDM reception. High signal levels at the receiver result in intermod between the many COFDM carriers present in a single channel COFDM Channel.
LNAs with little headroom may be ok for a Analog Signals, but greatly reduce the range of Digital Signals.
Virtually all highly selective RF filters designed for analog applications DISTORT COFDM Signals by adding Group Delay. This can increase the Bit Error Rate.
If standard copper or aluminum filters are used, extremes in temperature cause passband shifts that can cause even moderately strong digital signals to "freeze". This is due to corruption of soft decision stream information as the passband shifts..
Out of Band or Off Frequency Signals can also corrupt the soft decision stream.
To get the most from your COFDM System:
Keep Group Delay to a minimum with Temperature Compensated Gaussian Filters
Use LNA Systems that incorporate an LNA with High Linearity ( high IP3 )
Our specially designed COFDM-LNA/Filter Systems keep unwanted signals out, and their minimal Group Delay and High Linearity give you maximum performance and range.Rather than re-invent the wheel, use these links to gain a deeper understanding of COFDM (Coded Orthogonal Frequency-Division Multiplexing). Many times the "C" is dropped, and COFDM is referred to as OFDM.
Explaining Some of the Magic of COFDM (BBC)
COFDM for U.S. HDTV Broadcasting:
FCC Rejects Sinclair Request for COFDM DTV Standard - FEB 2000
COFDM DTV Exciters for US HDTV - MARCH 2000
COFDM for European Consumer Market:
COFDM for Terrestrial Broadcasting. (BBC)
COFDM vs. PAL
Call 1-888-828-8775 for more info.