Technical Information

About WVIZ/PBS’s Analog Transmission:

WVIZ/PBS operates on television channel 25 which is 536 MHz to 542 MHz. The visual signal (the picture) is transmitted on a frequency of 537.26 MHz and the aural signal (the sound) on a frequency of 541.76 MHz. These frequencies are 10 kHz higher than the normal operating frequencies for channel 25 so as to reduce interference from or to nearby stations. The visual transmission employs VSB-AM (vestigial sideband amplitude modulation) while the aural transmission employs FM (frequency modulation). WVIZ/PBS broadcast its audio in stereo using the BTSC (Broadcast Television Systems Committee) system, a (L+R)(L-R) system very similar to FM radio. Besides stereo, this BTSC system will also support surround sound based on Lt, Rt encoding such as Dolby’s Pro Logic system. The stereo subcarrier is at 31,468 Hz with a pilot at 15,734 Hz. WVIZ/PBS also broadcasts a SAP (second audio program) channel on an audio subcarrier at 78,670 Hz. WVIZ/PBS broadcasts with an ERP (effective radiated power) of 2.14 megawatts on the visual transmission and 214 kilowatts on the aural transmission. The visual and aural signals are routed to a single 6 1/8” hard coaxial transmission line and sent up the tower to a pylon antenna situated 1,000 feet above average terrain. The WVIZ/PBS transmission plant is located on Ridge Road in North Royalton, Ohio. Programming is sent from our originating studios on Brookpark Road to our transmission plant via an STL (studio to transmitter link) microwave operating at 7.025 MHz to 7050 MHz.

Frequently Asked Questions:

This page will answer technical questions you have about WVIZ/PBS and will attempt to answer any technical questions you may have about television technology in general. Please use the “Feedback” selection on our homepage and select “Engineering” to send us your question. I will return your answer by e-mail and, if the topic is of general interest, I will also post the answer here.

When will WVIZ/PBS begin broadcasting DTV?

WVIZ/PBS has remaining transmitting tower issues that need to be resolved before it can begin broadcasting in digital. WVIZ/PBS has been granted an extension to the FCC’s deadline of May 1, 2003 when public television stations were to begin digital broadcasting. WVIZ/PBS continues to pursue the resolution of its tower issues and hopes to begin digital broadcasting late this fall or early next spring.

Why doesn’t the sound on WVIZ/PBS match the picture?

Imagine tuning into WVIZ/PBS and hearing someone speaking as if they were reading and what they’re saying has nothing to do with the picture on the screen. Well this has actually happened to a small number of WVIZ/PBS viewers.

When stereo sound capability was added to the US system of television (NTSC), the ability for TV stations to broadcast two additional “hidden” audio channels was added as well. I use the word hidden because these additional channels cannot normally be heard by TV viewers. One of the additional channels is known as the Second Audio Program channel or SAP channel and the other is known as the Professional channel or PRO channel. The SAP channel is typically used for special services to viewers while the PRO channel is typically used by the TV stations for internal purposes. Of course TV stations are not required to use either of these channels. Some stations make use of the PRO channel to send audio and directors’ comments to reporters in the field doing “live shots”. Few stations make use of the SAP channel.

WVIZ/PBS does not use the PRO channel but we do make good use of the SAP channel by broadcasting services to the visually impaired community in northeastern Ohio. Some of WVIZ/PBS’s programs are come to us with an additional audio track called a Descriptive Video or DVE. This DVE track is a monophonic version of the regular stereo or surround program soundtrack but with the addition of a narrator occasionally superimposed on it. The narrator describes any action taking place on the screen that is helpful to understanding the program but that could be missed by visually impaired people. For example, the narrator might say, “Jane gets up from the table and walks across the room to the window. She pulls back the curtain and looks outside.” Whenever this special DVE soundtrack is available on a program that WVIZ/PBS is broadcasting, we broadcast the DVE track on our SAP channel. We currently have about XX hours per week with DVE service.

During all the times when there is no DVE soundtrack available for the programs we are broadcasting, we broadcast the Cleveland Radio Reading Service, or CRRS, on our SAP channel. The CRRS is a radio station like service where volunteers read the daily newspapers, other periodicals and books for the benefit of the visually impaired. Since the majority of WVIZ/PBS’s programming does not have a DVS soundtrack available, most of the time our SAP channel is carrying the CRRS.

Viewers with visually impaired family members (or those just curious) who want to listen to WVIZ/PBS’s SAP channel, must have a stereo capable TV or VCR. These TV’s and VCR’s will have some way to switch from the main, stereo sound of a TV program to the SAP channel. Your best bet to find out how the SAP channel works on your particular TV or VCR is to look it up in your owner’s manual. Unfortunately, every make and model has a different way to switch to the SAP channel and back. It would be impossible for me to offer any sort of directions here except for a few very general clues. First of all, with most (but not all) models, the switch between the main, stereo channels and the SAP channel is done with the remote control. Secondly, look on the remote control for a button that is labeled “Audio”, “MTS”, or “SAP”. What happens when you push these buttons varies greatly from set to set so you’ll have to watch the screen and try to logic it out. Finally if you don’t see any of the button labels above, look for a way to get into your set’s menus and look for any of those same labels as menu items. If you are unsure of what you’re doing, DON’T TOUCH IT. Read your owner’s manual or call the store where you bought your set.

Getting back to my original thought where someone tunes in WVIZ/PBS and hears sound that doesn’t match the video, you can probably figure out what is going on in these situations. Occasionally a TV or VCR will inadvertently get switched from the main, stereo audio to SAP audio. It may happen when children play with the remote control or by someone just pushing the wrong buttons by mistake. It’s not easy to know when this happens because most channels do not broadcast SAP. When you are watching a station that is not broadcasting SAP and you switch your TV or VCR to SAP, nothing happens. Your set knows that there is no SAP to switch to on the channel you’re watching. The problem is that your set has now been put into a mode where it will provide you SAP sound whenever SAP is available. As you surf through the channels, everything sounds normal until you switch to a channel that has SAP which will very likely be WVIZ/PBS. Suddenly you are hearing someone at the Cleveland Radio Reading Service read the grocery adds from the newspaper while you watch NOVA.