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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Digital is at full strength, but reception may improve on Feb. 17.
I wrote to channels 9 and 4 in DC and asked if they were at full power on digital. Both wrote back immediately to say that they were, but one answer confused me. It said 100% power broadcasting on UHF ch. 34. But after the switchvoer they would be back on channel 9. Just as two network stations he named in Baltimore are doing. Does this mean that a standalone converter box, or my I-forget-the-brand DVDR with HardDrive is capable of receiving the same digitial station at different times on different frequencies?? It scans frequencies looking for one that calls itself channel 9?? Is this why it takes so long to tune in a digital channel? Will tuning be quicker when it goes back to the traditional channel 9 frequency? The Channel 9 man said that he thought I would have greater sucess when they moved back to the VHF frequency. Is that because VHF generally has longer range? Thanks |
#2
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Digital is at full strength, but reception may improve on Feb. 17.
On Thu, 08 Jan 2009 11:52:05 -0500, mm wrote:
I wrote to channels 9 and 4 in DC and asked if they were at full power on digital. Both wrote back immediately to say that they were, but one answer confused me. It said 100% power broadcasting on UHF ch. 34. But after the switchvoer they would be back on channel 9. Just as two network stations he named in Baltimore are doing. Does this mean that a standalone converter box, or my I-forget-the-brand DVDR with HardDrive is capable of receiving the same digitial station at different times on different frequencies?? It scans frequencies looking for one that calls itself channel 9?? More or less. See http://en.wikipedia.org/wiki/Virtual_channel Is this why it takes so long to tune in a digital channel? Not really. Once it has learned where to go, it just tunes it in. Will tuning be quicker when it goes back to the traditional channel 9 frequency? Probably not. The Channel 9 man said that he thought I would have greater sucess when they moved back to the VHF frequency. Is that because VHF generally has longer range? Modulo your antenna configuration. Lots of folks have been sold "HDTV antennas" that are optimized for the UHF range (470 - 698 MHz). Channel 9 is down at 190 MHz. Some gain vs channel charts he http://www.hdtvprimer.com/ANTENNAS/comparing.html So, you may have a stronger signal at your location as compared to the UHF station but may lose more through the antenna. -- Rich Webb Norfolk, VA |
#3
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Digital is at full strength, but reception may improve on Feb. 17.
I wrote to channels 9 and 4 in DC and asked if they were at full power
on digital. Both wrote back immediately to say that they were, but one answer confused me. It said 100% power broadcasting on UHF ch. 34. But after the switchvoer they would be back on channel 9. Just as two network stations he named in Baltimore are doing. Does this mean that a standalone converter box, or my I-forget-the-brand DVDR with HardDrive is capable of receiving the same digitial station at different times on different frequencies?? Yes, although you might have to tell it to "scan for channels" again after the switcheover on The Big Day. It scans frequencies looking for one that calls itself channel 9?? Yup. There's no longer a fixed relationship between the "channel number" in the signal, and the frequency at which the signal is being transmitted. Is this why it takes so long to tune in a digital channel? Probably not. Analog TV signals transmit a full frame of video 30 times a second (two interlaced fields, at a 60-field-per-second rate). You can start watching the signal as soon as the tuner gets the RF pathway set up. Digital TV works differently. It doesn't send the complete picture very frequently... typically only a few times a second. The other (intermediate) frames are described during transmission in terms of differences from the most recent complete frame... or sometimes in terms of differences from the most recent complete frame and the *next* complete frame (the one not yet actually transmitted). This saves a lot of transmission bandwidth, which is part of how it's possible to send a high-definition picture over the same amount of RF bandwidth used to send a standard-definition analog signal. What this means is that the TV set can't start displaying a meaningful image until it has waited long enough to receive at least one, and often two of the occasional "complete" frames. Depending on how the station is choosing to encode its digital transmissions, this could take a second or more. Will tuning be quicker when it goes back to the traditional channel 9 frequency? I'd tend to doubt that. The Channel 9 man said that he thought I would have greater sucess when they moved back to the VHF frequency. Is that because VHF generally has longer range? That might be part of it. It might be that their "full power" UHF transmitter actually has lower power output than their "full power" VHF transmitter. It might be that their VHF antenna is better (higher gain, or in a better location) than their UHF antenna. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#4
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Digital is at full strength, but reception may improve on Feb. 17.
Per Dave Platt:
Digital TV works differently. It doesn't send the complete picture very frequently... typically only a few times a second. The other (intermediate) frames are described during transmission in terms of differences from the most recent complete frame... or sometimes in terms of differences from the most recent complete frame and the *next* complete frame (the one not yet actually transmitted). This saves a lot of transmission bandwidth, which is part of how it's possible to send a high-definition picture over the same amount of RF bandwidth used to send a standard-definition analog signal. Would it be technically feasible to have a set with, say, six tuners - each tuned to one of the user's "Favorite" channels and near-instant response when hopping between those already-acquired channels? -- PeteCresswell |
#5
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Digital is at full strength, but reception may improve on Feb. 17.
Would it be technically feasible to have a set with, say, six
tuners - each tuned to one of the user's "Favorite" channels and near-instant response when hopping between those already-acquired channels? Sure. You could build this out of off-the-shelf gear today, at least if you're satisfied with composite or S-Video quality. Buy half-a-dozen of the "converter boxes" now available. Tune each one to a different channel. Feed the six A/V outputs to a six-input A/V switchbox, and run the output to your screen and speakers. There *might* be converter boxes with composite or HDMI outputs, to go to a high-definition monitor, but I haven't see any myself. In principle you could build the necessary tuners, MPEG decoders, and banks of memory into a single chassis. I doubt that you'll see such a device on the consumer market, though - insufficient demand and high cost. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#6
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Digital is at full strength, but reception may improve on Feb. 17.
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#7
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Digital is at full strength, but reception may improve on Feb. 17.
On Thu, 08 Jan 2009 14:49:28 -0500, Rich Webb
wrote: On Thu, 08 Jan 2009 11:52:05 -0500, mm wrote: I wrote to channels 9 and 4 in DC and asked if they were at full power on digital. Both wrote back immediately to say that they were, but one answer confused me. It said 100% power broadcasting on UHF ch. 34. But after the switchvoer they would be back on channel 9. Just as two network stations he named in Baltimore are doing. Does this mean that a standalone converter box, or my I-forget-the-brand DVDR with HardDrive is capable of receiving the same digitial station at different times on different frequencies?? It scans frequencies looking for one that calls itself channel 9?? More or less. See http://en.wikipedia.org/wiki/Virtual_channel Is this why it takes so long to tune in a digital channel? Not really. Once it has learned where to go, it just tunes it in. Hmmm. It takes 3, maybe 4 seconds to change from one channel to another. Will tuning be quicker when it goes back to the traditional channel 9 frequency? Probably not. The Channel 9 man said that he thought I would have greater sucess when they moved back to the VHF frequency. Is that because VHF generally has longer range? Modulo your antenna configuration. Lots of folks have been sold "HDTV antennas" that are optimized for the UHF range (470 - 698 MHz). Channel 9 is down at 190 MHz. Some gain vs channel charts he http://www.hdtvprimer.com/ANTENNAS/comparing.html So, you may have a stronger signal at your location as compared to the UHF station but may lose more through the antenna. I"m willing to wait until the changeover to work on that some more. I get Baltimore digital channels fine, and I'm just using a 6 foot piece of single strand wire, plugged into the center of the coaxial connector on the back of the DVDR, and lying on the floor of my bedroom. I usually use an amplified antenna in the attic, but it broke and then I injured myself and had to have surgery at the end of August. I'm getting put back together again in another surgery this coming Thursday, and in a few weeks I'll be able to climb up to the attic and change antennas if necessary. Until then I'll live with only Baltiomre stations. The lack of the amplified antenna might be the reason I'm not getting DC digital, even though I can still get most DC analog channels pretty well. The DVDR seems to have a better analog tuner than most of my tvs Thanks. |
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