"mm" wrote in message
...
What is the difference between scanning for chhannles and going
directly to one?

I thought that letting a VCR or DVD recorder or TV scan for channels/
stations was only to compile a list in advance of channels a device
could receive, by checking out every station and noting which had
signals.

And that pushing 1 3 on the remote would go to channel 13 whether one
had scanned for stations or not, whether digital station frequencies
had changed since the last time one scanned or not. As effectively as
if one scanned the whole spectrum, and then channeled up or down to
get to 13.

Am I right about the paragraph just above?

Well, I don't know about over there in the U.S. but here in the UK, if you
pressed "1" and "3" on the remote control, it would just cause the TV / DVDR
/ PVR to go to the thirteenth channel storage position, in which could be
stored the frequency information for any channel, anywhere in the band. So,
that could be any valid channel that you had chosen to store in that
location, or just as easily, some arbitrary channel frequency that you can't
receive at your location. Scanning for channels causes the tuner to move up
from the bottom of the band to the top, stopping each time that it finds a
channel that it can receive, and then storing the frequency information for
that channel in the next available 'slot'.



And that for timed recording, when the dvd recorder goes to channel 13
directly, it looks for it if necessary, just like scanning does. And
if it gives some reception, though bad reception, even though the
transmitter is only 10 miles away, it's not because it's off
frequency?


I think that you are perhaps getting confused between a channel's name, and
the actual physical channel that it's broadcast on ? Even over there, I
think that VHF has long gone, hasn't it ? We have channels here called
"Channel Four" and "Channel Five", but they have never been broadcast on VHF
channels 4 and 5. They have always been up in the UHF band on various
physical channel numbers between 21 and 68, in different parts of the
country.



Or are digital tuners different from analog, in that scanning first is
essential?

Thanks.

Digital is way way different from analogue. Take everything that you ever
knew about how analogue TV was transmitted, and just forget it. Digital
transmissions are 'lumped together' into blocks of frequencies called
multiplexes. Within a single multiplex, there may be many channels, and no
single one is independently identifiable, because various techniques are
used to 'mix' the data from individual stations to produce a form of spread
spectrum transmission containing encoded interleaved data. In order to
resolve this into individual stations, a channel scan has to take place
initially, and as each multiplex is found, the information about what is in
that multiplex, and how to get it out, has to be decoded and stored and used
to build the EPG that is a fundamental part of digital TV

Arfa