Transmission Info

[Frank Stelloh]

I would like to find a website that describes the method of modulation used for HDTV and also the meaning of "1-1", "12-1", etc as it applies to channel assignment. It appears that I cannot detect the presence of an HDTV station with an analog receiver and I would like to get more info on the modulation method (like QPSK, etc?).
Thanks,
Frank

[Pat]

The encoding is "8VSB".  That would make a good Google search term to find out the gory details.  The VSB part means "Vestigal Side Band".

The number before the dash is decided by the station, but I'm not sure of what rules there may be.  CBS58, for example chose "1" deliberately, believing the lowest number would be of marketing value and also believing they would lose the number 58 in the future.  The other local stations are choosing to use their analog channel numbers.  This info is broadcast in the HD data stream in a segment called PSIP.  You are supposed to be able to enter either the actual digital channel number or the number before the dash to tune the station.

The number after the dash refers to the sub-channel, which can range from 1 to at least 5, and maybe more, broadcast on a single digital channel.  Exception: the number zero refers to an analog channel, if any is specified by the PSIP.  If your box can receive both analog and digital channels, then channel 1-0, for example, will tune channel 58.

[oflaherty]

Frank -- If it is very technical information on digital TV modulation that you want I'll suggest two sites:

The Guide to Digital Television
http://www.digitaltelevision.com/publish/dtvbook/toc.shtml
Look at Chapter 9: Engineering & Transmission

And Zenith
http://www.zenith.com/index.asp?url=./sub_hdtv/hdtv_index.html
Start with "DTV Explained" ..then try the "Technical Papers" section including the "VSB Tutorial"

Warning — they are both very, very technical.
---
Sean at TMJ

http://www.digitaltelevision.com/publish/dtvbook/toc.shtml http://www.zenith.com/index.asp?url=./sub_hdtv/hdtv_index.html

[P a u l]

And if you are really finding it difficult to fall asleep one night, try reading a few pages of this http://www.tektronix.com/Measurement/App_Notes/DigitalTV/25W-7203-3.pdf