In a May, 1932, commencement address President Roosevelt called for “bold, persistent experimentation” to correct the faults of the American economic system.

The same concept, persistent experimentation, must be applied to correct a fast approaching National Technical Event, the US Digital Transition.

It may come as a shock to our readers that the FCC’s calm seems to be utterly disconnected from the difficulties experienced so far:

• Less than spectacular test results produced in the community-wide analog shutoff in Wilmington, NC conducted three months ago.
• The selected transition date, middle of February, occurs when the weather in most of the country is the coldest and iciest, an absolute no-no for antenna-array installation or even antenna re-orientation work.
• The new DTV channel allotments demonstrates a complete disregard for co-channel and adjacent channel interference protection for CATV systems receiving distant DTV stations.

The Boston-Cleveland-Washington, DC triangle of the American Northeast is saturated by TV stations boasting several hundred analog UHF stations that will leave the air on the DTV transition day. In this high density section and other critical areas the digital channel allocation research neglected to pay any attention to interference conflicts.

The danger of co-channel interference could have been significantly reduced or completely eliminated by a more carefully conducted DTV channel allocation process, based on simple common sense tools such as Biro Engineering’s proprietary Co-Channel Signal Direction Sheets.  The computer-aided interference study can produce fail-safe results.  It is a fast and moderately priced approach available for CATV systems as well as for the FCC.

The following four (4) wide area samples demonstrate the existence of severe digital co-channel interference under thecurrent DTV channel allocations conditions.

SITE: Webster, Massachusetts COORDINATES: 42/17/06 71/51/32 Co-Channel Signal Direction Sheet for
CH 45	CH 31

Undesired Channel 45, Hartford, is only 9 miles further away than the desired Channel 45, Norwich.  The probability of co-channel interference is even greater because the Channel 45, Hartford transmit antenna doubles the height of the Norwich antenna tower.

On Channel 31 interference conditions are even worse.  The undesired Channel 31, Hartford is practically equidistant with the desired Channel 31, Boston and Hartford has four-times the output power of Boston.  Co-channel interference is caused by a  poorly selected DTV channel allocation.

SITE: Newburgh, New York COORDINATES: 41/30/22 71/58/13 Co-Channel Signal Direction Sheet for
CH 45	CH 33

In the case of  Channel 45 the co-channel offender is practically equidistant with the desired Channel 45, New York. Also, the desired Channel 45, Hartford has double the output power of the desired New York station.

On Channel 33 co-channel projected interference conditions are practically the same as on Channel 45.  None of this degradation would have developed with a more carefully conducted channel selection or FCC channel allocation approval.

SITE: Williamsport, Ohio COORDINATES: 40/24/34 80/58/16 Co-Channel Signal Direction Sheet for
CH 26	CH 50

The undesired Channel 26, Cleveland signals arrive practically from the same distance as desired Channel 26, Pittsburgh.    The probability of a severe co-channel interference is higher than 75%.

The chances of co-channel interference on Channel 50 are somewhat better, although it must be noted that the undesired Channel 50, Pittsburgh operates with an output power twice as high as  desired Channel 50, Akron.

SITE: Palmerton, Pennsylvania COORDINATES: 40/48/09 75/30/15 Co-Channel Signal Direction Sheet for
CH 31	CH 32

On Channel 31 the desired station, Scranton is jut 9 miles closer than the undesired.   Consider also the fact that Channel 31, Philadelphia operates with 200 kW output power versus Scranton’s 100 kW.  The probability of co-channel interference is close to 75%.

On Channel 32, line-of-sight is much better toward Philadelphia than toward Scranton, significantly increasing the chances of co-channel interference.

CONCLUSION

It is not our intention to over-simplify DTV reception difficulties, but it must be noted that all the recently published articles in leading newspapers deal exclusively with the problems of the 20 million TV household which receive their TV programs by rooftop antennas and rabbit-ears.  Nobody is paying attention to the anticipated difficulties of Cable TV systems, serving more than 75 million household, which are required to carry distant DTV stations.

What will you do on the morning of February 17, 2009?  Our best bet: Answering telephone calls of angry subscribers, asking: “What is wrong with your pictures?  Why do we lose occasionally the sound?  What is that snow in the background?" (Digital  co-channel interference).

Federal agencies, such as the FCC, are like battleships.  It takes them a long time to make a turn, get the ship properly oriented.

To restore confidence in the FCC, they should revise the DTV channel allocations with the acceleration of a speed boat and re-grant  DTV stations higher output power and/or extend the analog cutoff date to a more practical early summer time slot.

Biro Engineering’s specialized technical services can respond to your inquiries in days, not weeks, and our computer aided phased-array design can reduce or totally eliminate those nasty over-the-air DTV reception interference problems.

For emergency engineering services:
Call: (609) 883-9866
E-mail: steven@biroengineering.com
Web site: www.biroengineering.com

Biro Engineering
P.O.BOX 2175
PRINCETON, N.J. 08543