Craig Birkmaier wrote: > Not only this, but it is NOT correct to lump > all video services together. Which is why I didn't lump them together. I said specifically high quality TV, not the portable kind. With an analog design, it's perfectly possible for a TV station to use its 6 MHz channel for radio, perhaps during the day. It can create 30 200-KHz FM radio channels, or perhaps 15 to allow for poor receiver selectivity, and deliver an equivalent of 33+ KW output for each radio program (for 1 MW TV transmitter). Then revert back to TV at night. Same transmitter, same transmitting antenna, different exciters. The effect is more robust radio channels during the day, and less robust TV channel (AM-VSB) at night, for the same transmitter. But oh wow, now my radios might have to work over the UHF band too. You rob Peter to pay Paul. With a digital scheme, you can do something similar *or* you can use hierarchical modulation or DVB-H to transmit radio and TV simultaneously on the same 6 MHz band. So what? You're still robbing Peter to pay Paul. There's no free lunch. If you transmit radio, you have to reduce the TV channel. Either in bit rate or in robustness or both. And at the same time, your radio channels are also compromised, compared to what they could be if you did not have TV running simultaneously. Check the ETSI EN 300 744 spec to see how degraded QPSK is when it's run in HM rather than by itself. Instead of detracting from the TV channel and from the radio channels, the small aggregate bandwidth used for radio can be collected in a small sliver of spectrum. Aside from providing more optimized services for both applications, other advantages of doing this are (1) radio receivers can be made cheaper, because they can be optimized to operate over a considerably smaller set of frequencies, and (2) receiving antennas can also be optimized, because they can be designed for higher gain in with a simpler structure (because you'll only have a narrow range of wavelengths of interest to the radio receiver). So once again, there are tradeoffs. And the difference between analog and digital, once again, is not so huge after all. Just because something was not done in the past does *not* mean that it couldn't be done. And just because something *can* be done now does not mean it should be done. > The only sharing of infrastructure between Radio > and TV is when we put both TV and Radio antennas > on a common tower. Sharing of infrastructure for transmission was discussed above. As far as reception, I use the same receiving antenna for TV and FM, and the lead serves as a decent MW and SW antenna as well. Same infrastructure. So this is not by any means a new concept, Craig, and all the same considerations apply now as they always have. Bert ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.