Did you lose Digital TV channels? Do a rescan, double rescan, and check your antenna. - AVS Forum
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post #1 of 16 Old 06-13-2009, 12:20 PM - Thread Starter
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Update 6/16/09

- Concurrent with the June 12, 2009 Digital TV transition, some DTV stations are changing their digital broadcast channel number. If you are an existing DTV viewer, and are now having issues receiving stations you previously received, one possible solution is to do a rescan on your Digital TV receiver. This applies to both CECB's or HDTV STB. In some cases you may have to completely delete all stations, unplug the unit, and do a new set up from scratch. See unit specific topics in the CECB Forum and the HDTV Technical Forum.

- Concurrent with the June 12, 2009 Digital TV transition, a number of DTV stations moved from their temporary channel number, in some cases on the UHF band 14 and higher, to their permanent channel number on VHF channels 13 and lower. A problem can occur when the antenna being used is a UHF only model; the VHF station may not be picked up. In those cases, an antenna with VHF capability must be added and its signal combined with the UHF antenna, or a combination VHF/UHF antenna must be used. See the HDTV Locals Forum for info on DTV final channel assignments and individual topics for local TV markets across the country:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=45



From the FCC

WASHINGTON, D.C – Consumers having difficulty receiving certain television
channels following the June 12 transition to digital TV should try these two tips for better
reception: “double rescanning”, and double-checking and relocating their antennas. Meanwhile,
local broadcasters are working to resolve those issues that originate with their signal.

Double Rescanning
Many consumers already know about the need to run the “scan” function on their digital
converter boxes or digital TV sets periodically following the June 12 digital TV transition.
Scanning searches for and “remembers” the available digital broadcast channels.
But in some cases where stations moved their digital frequencies on June 12, simple
scanning may not be enough. There is a procedure – sometimes called “double re-scanning” –
that can clear your box’s memory of saved channels. These earlier scans may have saved channel
information that is now incorrect.
There are five simple steps to a double re-scan for a converter box or digital TV, which
are as follows:
1. Disconnect the antenna from the box or digital TV
2. Re-scan the box or digital TV without the antenna connected. As with any scan
follow the on-screen instructions or owner’s manual for your device
3. Unplug the box or digital TV from the electrical outlet for at least one minute
4. Reconnect the antenna to the box or digital TV and plug the unit into the electrical
outlet.
5. Rescan the box or digital TV one more time.

Double Check & Relocate Your Antenna
You must have a “VHF/UHF antenna. “Rabbit ears,” rods, or other elements are needed
to pick up channels 2-13 (VHF), and a circle, bow-tie, or other element is needed to pick up
channels 14-51 (UHF). Some antennas marketed as HDTV antennas don’t perform well on VHF
channels; some antennas are VHF or UHF-only.
For the best reception of channels 2-6, extend the rods all the way out. For the best
reception of channels 7-13, reduce the length of the rods to 12-18 inches.

Location, Location, Location
The location of an indoor antenna is key. And one of the most popular spots for indoor
antennas – on top of the TV – may not be the best. Consumers having trouble with digital TV
reception should try moving their antennas to one of these locations:
• Near a window
• As high as possible
• Away from other electronic equipment, including computers, VCRs, DVD
players, converter boxes, and the television itself
• Change the direction the antenna is facing
• Rooftop antennas may be needed in some instances
Consumers may need to run the “scan” function again on their converter boxes after
moving the antenna

'Better Living Through Modern, Expensive, Electronic Devices'

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post #2 of 16 Old 06-13-2009, 04:52 PM
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With the appropriate VHF/UHF antenna. www.antennaweb.org
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post #3 of 16 Old 06-14-2009, 12:39 PM - Thread Starter
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Quote:
Originally Posted by Mizzou! View Post

With the appropriate VHF/UHF antenna. www.antennaweb.org

Yes, antennas have also been an issue for some DTV viewers.

Why?
- Concurrent with the June 12, 2009 Digital TV transition, a number of DTV stations moved from their temporary channel number, in some cases on the UHF band 14 and higher, to their permanent channel number on VHF channels 13 and lower. A problem can occur when the antenna being used is a UHF only model; the VHF station can not be picked up. In those cases, an antenna with VHF capability must be added and its signal combined with the UHF antenna, or a combination VHF/UHF antenna must be used. See the HDTV Locals Forum for info on DTV final channel assignments and individual topics for local TV markets across the country:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=45

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post #4 of 16 Old 06-16-2009, 04:53 AM
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For those markets where real broadcast channels changed, it seems that certain boxes don't automatically clear out the old data. I've personally observed this behavior with my DirecTV HR20 which required deletion of the old data before it would accept the new channel assignments.


As posted at http://www.broadcastingcable.com/art...e_Re_scan_.php

FCC Pushing 'Double Re-scan'

Involves having consumers clear out their boxes' memories before re-scanning

By John Eggerton -- Broadcasting & Cable, 6/15/2009 1:09:28 PM MT

The FCC says some stations in Chicago and Philadelphia may have to apply for power boosts and are in discussions with stations there about their various technical issues, but that it is currently focused on consumer-based fixes for reception problems, including promoting what it is calling the “double-rescan.”

That is having consumers clear out their boxes' memories before re-scanning, a process the commission says is having success, particularly in Chicago. Our teams are beginning to put the word out on the technique, says FCC spokesman Rick Kaplan.

Kaplan says that some consumers who were having problems with both channel 2 and channel 7 in Chicago, for example, were having problems with their boxes because both those stations went from a high UHF to a low VHF channel. "There are some converter boxes that, if you just do a normal re-scan, they won't be able to replace the old digital channel with the new one. So, you actually just have to clear the box out."

He says that the double re-scan has worked "very well" in Chicago with channel 2. The FCC has a person from the D.C. office now in the market who says the call center has been able to resolve "about 90% of the calls that way,” says Kaplan. He said L.A. has had success with the double re-scan as well, where according to field staffers there. 80%-90% of calls about KTLA reception have been resolved.

To double re-scan, says Kaplan, viewers need to unplug the antenna, then scan so it picks up nothing, then unplug the converter or DTV set, plug it back in, then rescan.

But for viewers still having trouble, says Kaplan, the FCC is talking with stations about possible long-term solutions from their end. If stations have to officially ask for more power, the FCC will take that seriously, he said. But that will also include figuring out who the boosted power might interfere with, and what dominoes that might trigger elsewhere.

"We want to figure out how to get it right," he says. "We don't want to rush, but don't want to delay, either." But while the commission is working with stations on their end, a process that won't be immediate if it involves adjusting power levels, the FCC "wants to make sure all consumer avenues are exhausted."
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post #5 of 16 Old 06-16-2009, 05:04 AM
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Quote:
Originally Posted by Mizzou! View Post

With the appropriate VHF/UHF antenna.

Quote:
Originally Posted by Ken H View Post

Yes, antennas have also been an issue for some DTV viewers.

As well as possibly needing a higher tower, relocating or reorienting the antenna or adding a rotator and maybe even a signal booster.

All in all, some could be looking at hundreds of dollars in upgrades and alterations.
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post #6 of 16 Old 06-16-2009, 08:26 AM
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Quote:
Originally Posted by Ken H View Post

Yes, antennas have also been an issue for some DTV viewers.

Why?
- Concurrent with the June 12, 2009 Digital TV transition, a number of DTV stations moved from their temporary channel number, in some cases on the UHF band 14 and higher, to their permanent channel number on VHF channels 13 and lower. A problem can occur when the antenna being used is a UHF only model; the VHF station can not be picked up. In those cases, an antenna with VHF capability must be added and its signal combined with the UHF antenna, or a combination VHF/UHF antenna must be used. See the HDTV Locals Forum for info on DTV final channel assignments and individual topics for local TV markets across the country:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=45

Hi! I need suggestions to solve my problem. I have had a vhf/uhf/fm antenna on my roof for about 15 years as a backup for the occasions when my cable system is out. I normally use cable, but have a switchbox so I can go over to the antenna when needed. After the switch to digital broadcast, I rescanned my digital TV and tried the antenna(I'm in New York, zipcode 11746) and found that I get about 8 channels very well. The problem is that I don't get 2 major channels--CBS(ch2) and NBC(ch4). I rotated the antenna a bit with no result. I didn't expect it to help because according to the sites I visited that provided channels I should receive, direction, distances, signal strength), CBS and NBC come from the same location(NYC), direction and distance(33 miles) as the others and have the same signal strength, yet I get nothing for CBS and a black screen with a weak signal message for NBC. Fox, ABC, PBS and more are all good. I'm thinking it must be the antenna. Any ideas? Thanks!
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post #7 of 16 Old 06-16-2009, 01:40 PM
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Quote:
Originally Posted by KJHarris View Post

Hi! I need suggestions to solve my problem. I have had a vhf/uhf/fm antenna on my roof for about 15 years as a backup for the occasions when my cable system is out. I normally use cable, but have a switchbox so I can go over to the antenna when needed. After the switch to digital broadcast, I rescanned my digital TV and tried the antenna(I'm in New York, zipcode 11746) and found that I get about 8 channels very well. The problem is that I don't get 2 major channels--CBS(ch2) and NBC(ch4). I rotated the antenna a bit with no result. I didn't expect it to help because according to the sites I visited that provided channels I should receive, direction, distances, signal strength), CBS and NBC come from the same location(NYC), direction and distance(33 miles) as the others and have the same signal strength, yet I get nothing for CBS and a black screen with a weak signal message for NBC. Fox, ABC, PBS and more are all good. I'm thinking it must be the antenna. Any ideas? Thanks!

Hey KJ,

Give us a few more specifics about your situation. Are you using a digital tuner in your TV, or a converter box? If the latter, which model?

Does your tuner/converter box have a bar graph or numeric signal strength or quality meter function. If so, how close are the readings for Fox 5, NBC, and CBS? Do the signal readings bounce up and down noticeably?

Are there other houses nearby that might be giving strong reflections of the signals from NYC?

Do you have any splitters, amplifiers, or other devices in the feed line run from your antenna to your receiver?

Have you visually inspected your antenna? Does it look normal, or are there missing elements, or possibly broken connections? Coaxial cable can go bad after years of service, too.

Are any of your neighbors watching over the air TV? Do they have the same problems with those channels?

----
Multipath interference can be strongly channel number dependent, due to the differences in path lengths as a function of wavelength.

Can you confirm that your digital tuner is actually tuned to RF channel 33 for virtual channel 2, and to RF channel 28 for virtual channel 4?

If you were looking down the boom of your antenna in its present location, would you be able to see straight to distant treetops, or would a nearby building or hill be in the way?

I'm sure this is not the case for you, but I'll mention that often I'll see rooftop combo antennas pointed 180 degrees from where they should. These people seem to think that longer horizontal elements should point to the transmitters as if they were an arrow, whereas the shorter UHF elements should face the direction of the TV stations. These folks surely will get some reception, but not what they should - especially on UHF.

Others may laugh at me for this idea, but, if you are handy, you *could* make a $10 Youtube coat hanger antenna in about a half hour. If you had one, you could set it in a West-facing window and check reception of 2 and 4 using that antenna. If your rooftop antenna/feedline are working as they should, that setup *should* outperform the homemade antenna on all channels. If the home-made 4-bay equals or exceeds your roof-top combo antenna, then something is not up to snuff with the latter.
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post #8 of 16 Old 06-16-2009, 01:57 PM
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Originally Posted by ProjectSHO89 View Post

But while the commission is working with stations on their end, a process that won't be immediate if it involves adjusting power levels, the FCC "wants to make sure all consumer avenues are exhausted."

Translation: We're hoping that if we drag our heels long enough, more folks will give up and subscribe to pay TV services (cable, DBS), and we won't have to OK OTA power level increases in all those markets.
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post #9 of 16 Old 06-16-2009, 02:28 PM
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Thanks for the response. As soon as I get a little time, I'll go up on my roof and take a close look at the antenna and cable for physical problems. They are 15 years old after all. Also, there is an amplifier plus splitter close to the antenna where the line first enters the house, and another amplfier plus splitter at the far end of the line to feed the TV and an FM receiver. The TV is a Panasonic plasma with digital tuner. I set the antenna's UHF end pointing to the stations in the direction that gave the strongest VHF reception a few years ago and marked the pole and the brackets and I can see that it hasn't moved. I tried the "real" channels for CBS(33) and NBC(28) and no difference. I'm just puzzled that since the stations still all broadcast from the same place, and the ones that I receive are good why 2 and 4 won't come in. I think my tv does have a signal strength function--I'll get to check it. As far as my location, it's a built up residential area with homes of different heights and some trees, and of course as you get in closer to NYC there are more and taller buildings over the 35(approx.) miles.
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post #10 of 16 Old 06-16-2009, 03:35 PM
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Quote:
Originally Posted by KJHarris View Post

I rotated the antenna a bit with no result. I didn't expect it to help because according to the sites I visited that provided channels I should receive, direction, distances, signal strength), CBS and NBC come from the same location(NYC), direction and distance(33 miles) as the others and have the same signal strength, yet I get nothing for CBS and a black screen with a weak signal message for NBC.

I feel your pain. I'm in similar situation but in a different state. I looked up your zipcode, and TVFool.com does indicate your "missing" stations are on par with your "good" stations, location-wise and power-wise. It lists them as 3rd and 5th out 10 stations listed at the same broadcast location. On the other hand, the FCC reception tool at http://www.fcc.gov/mb/engineering/maps/ classifies your missing stations as "weak signal" and lists them way down at 9th and 10th position. I've found the fcc tool to be more realistic than the tvfool tool. Also, on the fcc.gov tool, you can click on each station to see a detailed map of their signal coverage. So...those 2 stations just have weak signal where you are.
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post #11 of 16 Old 06-16-2009, 04:56 PM - Thread Starter
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First post updated.

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post #12 of 16 Old 06-16-2009, 11:03 PM
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One doesn't necessarily need a VHF/UHF combination antenna to receive both VHF and UHF broadcasts.

I use a dipole only on two Insignias, both antennas are placed by my outside window (inside, that is), and pick up VHF stations 6 and 12, and all the UHF stations.

My UHF only antenna was working the other day picking up VHF 12, but today the signal is breaking up on a windless clear night. This antenna is in about 20 ft. from the outside window, and the signal on this station is average, so with a better signal, the UHF antenna should be able to pick it up.

But agreed, the best way to go if one doesn't have an amplified antenna is with a combination VHF/UHF antenna with a fine tuning knob/dial, and ideally a UHF reflecting plate that can be rotated 360 degrees.

In my area, VHF 6 and 12 may be boosting their signals, and if that happens, my UHF only antenna should be able to get these stations. Prior to the digital transition, the UHF antenna was pulling in these VHF stations very well.

As has been said before, location is very important. (My residence faces OPPOSITE to the broadcasting towers, so the only thing I have going for me, as far as reception goes, is that I live a few floors above ground level. I did notice that turning on a light connected to a CFL bulb causes a flicker on the picture reception. I will experiment with sneezing and see if that affects reception, too.)
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post #13 of 16 Old 06-17-2009, 07:38 AM
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Quote:
Originally Posted by ninja1 View Post

I feel your pain. I'm in similar situation but in a different state. I looked up your zipcode, and TVFool.com does indicate your "missing" stations are on par with your "good" stations, location-wise and power-wise. It lists them as 3rd and 5th out 10 stations listed at the same broadcast location. On the other hand, the FCC reception tool at http://www.fcc.gov/mb/engineering/maps/ classifies your missing stations as "weak signal" and lists them way down at 9th and 10th position. I've found the fcc tool to be more realistic than the tvfool tool. Also, on the fcc.gov tool, you can click on each station to see a detailed map of their signal coverage. So...those 2 stations just have weak signal where you are.

Appreciate that information. As you pointed out, that site shows poor signal for those 2 stations. I guess since they originate in the same place as the "good" ones, some strange land elevations or treed areas or buildings cause the problem. In any case, I only switch to antenna if the cable goes out, which isn't very often so if it does happen my wife and I can manage with the "good" stations.
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post #14 of 16 Old 06-17-2009, 02:46 PM
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Any evidence out there that a double rescan makes a difference on the Zenith or Insignia CECBs? Frankly I am dubious that it would make any difference, since it seems you can manage all the channels manually.
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post #15 of 16 Old 06-17-2009, 03:17 PM
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I believe the double rescan is an attempted "foolproof" method to avoid the confusion between a "find and add new stations" rescan, and a "erase everything and start from scratch" rescan.
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post #16 of 16 Old 06-17-2009, 07:27 PM
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Double rescan is recommended when the full scan fails to clear the channel memory. I had a problem getting rid of temporary test channels last November. They were automatically deleted on my TR40 when the test was over, but the CM7000 kept them. A full scan didn't clear them, nor did deleting the extra channels first before doing a full scan. I had to delete all channels, shut the box off, and do one more full scan on startup.

In Portland, four stations changed frequency last Friday, and the call center reported problems with scanning not working as expected. Some people scanned 3 or 4 times before the scan finally worked. If the old channel doesn't clear out properly, many boxes cannot add a channel with the same virtual frequency as an existing one.
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