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Old 05-20-2008, 01:04 PM
Bo Bo won $500 in our forum's Most Engaging Poster Contest - Tenth Edition (Apr-May 2014). 

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Location: Ohio
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Quote:
Originally Posted by Canes2006Champs View Post
why is this happening? what purpose does the news in digital tv give us?
It all comes down to money. The radio spectrum vacated by analog TV signals after February 17, 2009 will generate billions of dollars in revenue for the Federal treasury because its use is being auctioned off to wireless companies for new services.
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Old 05-20-2008, 02:33 PM
 
Location: DC Area, for now
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Quote:
Originally Posted by Bowie View Post
After next February there won't be any analog signals to receive over the air, so that's a feature that was expendable.

This is likely to be the case. On a Digital TV forum I visit, an engineer for one of the local stations here says that his station is running its digital signal through a lower power transmitter than the analog signal. Once they flip the switch to shut off the analog signal forever, he says they'll bring the digital signal up to full power.
I read that this isn't fully the case. Some low power local stations will still be analog after Feb. and the costs to go digital are far beyond their financial capabilities to meet. Besides, I didn't want a box for the transition that would make the analog unavailable. As it stands, if I want to watch something on CBS, I need to go analog because the digital is too choppy.

Good to know that the current signals are not necessarily what will be there in the end. Thanks
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Old 05-20-2008, 04:16 PM
Bo Bo won $500 in our forum's Most Engaging Poster Contest - Tenth Edition (Apr-May 2014). 

Over $104,000 in prizes has already been given out to active posters on our forum and additional contests are planned
 
Location: Ohio
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Quote:
Originally Posted by Tesaje View Post
I read that this isn't fully the case. Some low power local stations will still be analog after Feb. and the costs to go digital are far beyond their financial capabilities to meet.
I didn't want to muddy the water by bringing that up, but you're correct. Around here, the low power programming choices are home-shopping, music videos and fire-and-brimstone preachers. There's nothing on them that I will miss when I don't have the capability to tune them in anymore.
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Old 06-09-2008, 08:46 AM
 
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Can we expect digital reception to improve as the result of analog transmitters being switched off? Our antennas are still being bombarded by analog signals in the same band as the new digital transmissions. Couldn't their presence be causing automatic gain control circuits to lower the input gain of broadband "front end" of amplifying or receiving equipment? If so, that would also cause amplification of the digital signals to be attenuated. Once analog transmitters are switched off, gain of receiving equipment would be able to adjust higher, perhaps improving reception of digital stations. I would think mast-mounted preamps and indoor antennas that have built-in amplification would have automatic gain controls, to keep strong signals from clipping or distorting and from burning out components downstream. I am not familiar with the design of the converter boxes or digital tv sets, but they might also suffer from the presence of the strong analog signals because of automatic gain control in their front ends.
I live 45 miles SE from DC stations, can get a digital station most any time, but cannot predict which it will be. Some days I can get several stations. I have highest-gain Winegard UHF-only antenna, highest-gain Winegard mast preamp, rotator atop 35-foot mast, magnavox converter box. Local newspaper report states that DC stations are already using their ultimate rated power for their digital transmissions, as well as their final locations on their towers. My reception so far is so iffy that I am holding out hope that switching off the analog transmitters will set me free.
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Old 06-09-2008, 09:57 AM
 
Location: Hopewell New Jersey
1,393 posts, read 7,118,492 times
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Quote:
Originally Posted by sm_vermn View Post
Can we expect digital reception to improve as the result of analog transmitters being switched off? Our antennas are still being bombarded by analog signals in the same band as the new digital transmissions. Couldn't their presence be causing automatic gain control circuits to lower the input gain of broadband "front end" of amplifying or receiving equipment? If so, that would also cause amplification of the digital signals to be attenuated. Once analog transmitters are switched off, gain of receiving equipment would be able to adjust higher, perhaps improving reception of digital stations. I would think mast-mounted preamps and indoor antennas that have built-in amplification would have automatic gain controls, to keep strong signals from clipping or distorting and from burning out components downstream. I am not familiar with the design of the converter boxes or digital tv sets, but they might also suffer from the presence of the strong analog signals because of automatic gain control in their front ends.
I live 45 miles SE from DC stations, can get a digital station most any time, but cannot predict which it will be. Some days I can get several stations. I have highest-gain Winegard UHF-only antenna, highest-gain Winegard mast preamp, rotator atop 35-foot mast, magnavox converter box. Local newspaper report states that DC stations are already using their ultimate rated power for their digital transmissions, as well as their final locations on their towers. My reception so far is so iffy that I am holding out hope that switching off the analog transmitters will set me free.

This can get complicated real fast ...

An analog NTSC signal is basically 4 MHz wide,not including the blank guard band at each end of each channel allocation. However within that 4 MHz signal are "slots" where little or no info is present...lack of sounds carriers, chroma etc etc. The digital stuff sorta sits in those little no info slots. That is why both signals can "co-exist" in the same band without interferring with one another. In the precence of extremely strong input signals it might be possible to "over load" the front end of a poorly designed RF small signal amplifier that dosen't have enough "head room". If that happens, the amplifier will no longer be operating in a Linear fashion and as a result additional by products (intermodualtion distortion) will result. Many of those additional "products" will be outside the pass band of the rf filtering in the reciever. Some however will also be downconverted and pass through that pass band responce curve of the reciever...and the short story of that is that it will degrade the demodulated signal, AND, the down conversion mixer will also add it's own garbage to the mix because of all these addition signals.

A number of years ago the FCC was actually doing live on air broadcast testing to see the results of the at that time proposed signal "interlacing".
(Remember there were a number of competing modulatio schemes.) Part of the testing involved cranking the transmitter power way up and down to actually test, on actuall test reciever TV's located around Washington, in order to gauge what the viewable effects would be. The results were that even with some pretty lousy tv front ends the noticable effects were very small even in the opinion of "professional viewers".

Bottom line is I doubt you will notice any change with or without the analog transmitters on line.



Sorry to bore the snot out of the rest of you...

Last edited by JBrown; 06-09-2008 at 10:26 AM..
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Old 06-09-2008, 12:27 PM
 
Location: Utah
115 posts, read 336,055 times
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Quote:
Originally Posted by Canes2006Champs View Post
Im kind of angry about this, I've got a small tv in my room, one my mom used in college and was built in 1982, that still works terrific and has a great picture, no cable hooked up to it but i use it to watch sports, and the simpsons, king of the hill etc, on regular tv, and now it wont work unless I pay for a converter box? forget that! why is this happening? what purpose does the news in digital tv give us?
Canes, from what I have learned the major reason for the switch to digital is primarily because of the 911 attack in New York. Fire and rescue had a heck of a time with communications between departments and agencies so freeing up or vacating analog frequencies will enable fire and rescue across the country to expand their capabilities and be able to communicate throughout the various interagencies during a major disaster such as Katrina. The added bonus to this is that our TV reception and quality will vastly improve!
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Old 06-09-2008, 01:15 PM
 
Location: Hopewell New Jersey
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Quote:
Originally Posted by Moose Hollow View Post
Canes, from what I have learned the major reason for the switch to digital is primarily because of the 911 attack in New York. Fire and rescue had a heck of a time with communications between departments and agencies so freeing up or vacating analog frequencies will enable fire and rescue across the country to expand their capabilities and be able to communicate throughout the various interagencies during a major disaster such as Katrina. The added bonus to this is that our TV reception and quality will vastly improve!

I've heard that before.....NOT SO...
The change over to digital was in the works and finalized LONG before 911. I helped build some of the prototype equipment and was invovled in the FCC DC testing...back in the 80'and into the 90's.

As far as the communications between the various departments in NYC. Also not true. That was the result of each department insisting on having it's OWN radio system with different codes,channerls,scramblers etc etc etc... That little aspect of things didn't get much news play and it was advantagous for them to deflect the questions but it's the ugly truth. In the end it all came down to each department treating other departments as if they were an enemy. In the end the public suffered the stupidity .
Our Armed forces do the same crap...each branch has their own version of every piece of equipment...dumb and wasteful.



Last edited by JBrown; 06-09-2008 at 01:34 PM..
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Old 06-10-2008, 02:31 PM
 
Location: West Virginia
12,629 posts, read 32,258,590 times
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Comcast can not answer this......I recieved my coupons in the mail. & I also recieved a letter from Comcast there are 5 channels that I now recieve that I will not recieve without the box. So I go buy the box...get home hook it up per directions....NO SIGNAL!!! Go figure......
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Old 06-10-2008, 05:07 PM
 
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The convereter boxes being sold are not cable boxes. They won't allow you to receive anything from Comcast. You need to rent a box from Comcast, or buy a QAM tuner (assuming Comcast is not encrypting their channels), to get those.
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Old 06-10-2008, 05:16 PM
Bo Bo won $500 in our forum's Most Engaging Poster Contest - Tenth Edition (Apr-May 2014). 

Over $104,000 in prizes has already been given out to active posters on our forum and additional contests are planned
 
Location: Ohio
16,904 posts, read 33,644,625 times
Reputation: 13871
Quote:
Originally Posted by pcity View Post
You need to rent a box from Comcast, or buy a QAM tuner (assuming Comcast is not encrypting their channels), to get those.
Cable providers in the US are not allowed to encrypt the signals of local broadcasters on their systems. (The rule requiring it is called digital must-carry.) The local channels have to be made available in the clear (unencrypted) for viewing by a subscriber's QAM tuner.

You're also correct that the set-top boxes sold in stores are not QAM tuners, they are ATSC tuners. ATSC tuners can only receive signals over the air. As far as I know, there are no set-top QAM tuners available for sale, but most modern digital TV sets are equipped to tune in QAM channels on cable. Since some are not QAM-tuner equipped, this is an important feature that you should look for when purchasing a digital TV, if you are a cable subscriber.
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