We use an antenna and a converter box to get TV in the work breakroom. After TV went all digital, looks like we lost KTTV FOX 11 and KCOP 13 completely. Before the switchover, the digital channels must have been on UHF frequencies but after June 12, the must have moved to VHF. I can still pick up channels 2, 4, 5, 7 and 9 just fine. I don't know why they wanted to move back to their old channel number since there is now virtual channel ID....seems like the reception was better when they were on UHF.
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My Issue with Digital TV
- Thread starter Neel
- Start date
K
kenrayc
Guest
Actually KABC 7 and KCAL 9 also should have moved back to VHF. Even though UHF is better , The high VHF should work fine, It's the low VHF 2-6 that's horrible at DTV.
A lot of these stations that returned to high-VHF are running in temporary medium-power situations until they can get approval for more power. Issues with international borders seem to be what's delaying these applications from being approved. I also read on another site (from a respected broadcast engineer) that FM radio may cause interference to even the high-VHF DTV's.
Once the FCC is aware of this issue, they may start doing research on higher ERP levels for high-VHF DTV's. But, knowing the FCC, that may take a while.
Also, remember the right receiving antenna will also make a difference.
Once the FCC is aware of this issue, they may start doing research on higher ERP levels for high-VHF DTV's. But, knowing the FCC, that may take a while.
Also, remember the right receiving antenna will also make a difference.
K
kenglish
Guest
I suspect that many problems, especially in the big cities, are due to FM Broadcast stations interfering with VHF reception.
Channel 6 is, for all intents and purposes, a "First Adjacent Channel" to the low end of the FM band. Those high-powered FMs are probably causing havoc there.
Channels 7-13 are, by design, almost exactly twice the FM frequencies....88 x 2= 176 MHz, 108 x2= 216.....the VHF High Band is 174-216 MHz.
It's likely that the RF tuners (the first stage of all receivers) themselves are generating second-order distortion when receiving high-level FM signals (they can also act funny when hit by strong signals elsewhere in the spectrum, but affecting different channels than 7-13). According to Charlie Rhodes, an RF expert and former member of the ATSC committee, tuners USED TO have an FM "Trap", or FM Rejection Filter, built right inside. That, of course, was in the days when TV sets were bigger, and the tuner itself was as big as a Christmas fruitcake.
As tuner modules became smaller, and more sets were used exclusively on Cable, the FM Traps went away. Many folks didn't need them (they were on Cable, or far away from FM transmitters), and the ones who DID need them probably didn't even recognize the symptoms of FM overload, so they didn't demand them.
Additionally, especially as it concerns the "Channel 6 issue", the low end of the FM band (adjacent to TV Channel 6) was restricted to lower powered stations (the so-called "Educational Allotments"), so there was a "buffer" between TV and FM. That is no longer the case, as high-power authorizations are granted across the band. Additionally, "FM Booster" and low-powered FM stations are often placed all over the map, not just at traditional transmission sites, so you might have a strong FM BCB signal coming at you from a nearby school, water tank or cell tower.
The long-term solution may be, to install an 88-108 MHz rejection filter ("FM Trap") on the input of each receiver, or at a point after the antenna, but common to all the sets. Very high FM signal-strength areas, such as those near the transmitter sites, might even require the traps to be placed right on the back of the sets and converter boxes, perhaps with some broad-band attenuation, too (bringing the levels of all signals back to their design-levels). Inexpensive filters cost less than $5.00, and attenuators can be had for a dollar or two each.
The 88-108 MHz FM Traps might cause some trouble with channel 6 reception though, just due to manufacturing tolerances, so a trap designed for 95-108 MHz may be better....IF there are few/no high-powered FM transmitters below 95 MHz. Otherwise, a tunable trap might be needed (in addition to the broader trap) to notch-out those particular FM channels. Something like that might have to be custom-manufactured for stations on a market-by-market basis, for cost and complexity reasons.
Trouble is, right now, the (88-108 MHz) FM Traps appear to be unavailable. The ones we have purchased are not available from the original supplier, and are back-ordered (for another month) from the only other (MCM Electronics) supplier we found. The 95-108's are available, though. Traps and attenuators used to be stock items at Radio Shack, but are discontinued, though you might be able to find them at local electronics shops.
The short-term solution may be for stations to move back to their pre-transition UHF channels until filters are available to the affected viewers (Or,... "fat chance" wise...., turn all the FM stations down to 10% piower).
You can read Charlie's article at the "TV Technology" magazine website, by clicking on their "Digital Edition", then going to pages 32-33 of the (current) June 10 issue. "Testing for DTV Interference" is the title.
The FCC is acutely aware of these VHF issues, although they may need to "research" the solutions before applying any "across-the-board fix".
Channel 6 is, for all intents and purposes, a "First Adjacent Channel" to the low end of the FM band. Those high-powered FMs are probably causing havoc there.
Channels 7-13 are, by design, almost exactly twice the FM frequencies....88 x 2= 176 MHz, 108 x2= 216.....the VHF High Band is 174-216 MHz.
It's likely that the RF tuners (the first stage of all receivers) themselves are generating second-order distortion when receiving high-level FM signals (they can also act funny when hit by strong signals elsewhere in the spectrum, but affecting different channels than 7-13). According to Charlie Rhodes, an RF expert and former member of the ATSC committee, tuners USED TO have an FM "Trap", or FM Rejection Filter, built right inside. That, of course, was in the days when TV sets were bigger, and the tuner itself was as big as a Christmas fruitcake.
As tuner modules became smaller, and more sets were used exclusively on Cable, the FM Traps went away. Many folks didn't need them (they were on Cable, or far away from FM transmitters), and the ones who DID need them probably didn't even recognize the symptoms of FM overload, so they didn't demand them.
Additionally, especially as it concerns the "Channel 6 issue", the low end of the FM band (adjacent to TV Channel 6) was restricted to lower powered stations (the so-called "Educational Allotments"), so there was a "buffer" between TV and FM. That is no longer the case, as high-power authorizations are granted across the band. Additionally, "FM Booster" and low-powered FM stations are often placed all over the map, not just at traditional transmission sites, so you might have a strong FM BCB signal coming at you from a nearby school, water tank or cell tower.
The long-term solution may be, to install an 88-108 MHz rejection filter ("FM Trap") on the input of each receiver, or at a point after the antenna, but common to all the sets. Very high FM signal-strength areas, such as those near the transmitter sites, might even require the traps to be placed right on the back of the sets and converter boxes, perhaps with some broad-band attenuation, too (bringing the levels of all signals back to their design-levels). Inexpensive filters cost less than $5.00, and attenuators can be had for a dollar or two each.
The 88-108 MHz FM Traps might cause some trouble with channel 6 reception though, just due to manufacturing tolerances, so a trap designed for 95-108 MHz may be better....IF there are few/no high-powered FM transmitters below 95 MHz. Otherwise, a tunable trap might be needed (in addition to the broader trap) to notch-out those particular FM channels. Something like that might have to be custom-manufactured for stations on a market-by-market basis, for cost and complexity reasons.
Trouble is, right now, the (88-108 MHz) FM Traps appear to be unavailable. The ones we have purchased are not available from the original supplier, and are back-ordered (for another month) from the only other (MCM Electronics) supplier we found. The 95-108's are available, though. Traps and attenuators used to be stock items at Radio Shack, but are discontinued, though you might be able to find them at local electronics shops.
The short-term solution may be for stations to move back to their pre-transition UHF channels until filters are available to the affected viewers (Or,... "fat chance" wise...., turn all the FM stations down to 10% piower).
You can read Charlie's article at the "TV Technology" magazine website, by clicking on their "Digital Edition", then going to pages 32-33 of the (current) June 10 issue. "Testing for DTV Interference" is the title.
The FCC is acutely aware of these VHF issues, although they may need to "research" the solutions before applying any "across-the-board fix".
A related issue with the new Digital standard is that there's a great discrepencacy between the FCC station coverage maps and where a station's signal can be received. In the Providence and Boston markets, for example, several stations here went on nightlight service (notable chs 2, 4,5 in Boston and ch. 6 in Providence), and displayed the new FCC coverage maps, showing areas that were gained with the transition. Now even they are seperate adjacent markets, Boston is only 45 miles away (and even less between their transmitters in Needham, MA (for Boston) and Rehoboth, MA (for Providence), so there has always been a large overlapping of signals. However,now that digital has arrived, at least two Providence stations foolishly have a signal null to the northeast facing Boston, so they get weak or no signal even as close as 12 miles from Rehoboth. The FCC maps on the other hand show a strong signal for the nulled areas. Many in the area received these stations with a strong signal in analog, but are at wit's end trying to figure out why with a powerful outdoor antanna cannot get the signals so close to the stations. The Boston stations come is very good throughout most of the Providence area because they do not null signals. To make matters worse, Boston's NBCstation, WHDH ,is having major signal issues as noted on this board, and Providence's NBC station, WJAR, can't be received well or at all because of signal null. The FCC, after resolving the lower DTV VHF signal issues, should look into the inconvenience for viewers of stations severly nulling their signals when the issue is not interference. Cable and satellite are already restricted from carring out of market stations, OTA viewers should not have to put up with the inconvience of stations nulling their signals to adjacent and nearby viewers.
To my understanding that KABC is broadcasting two HD feeds and one SD feed on VHF7. Does this cause reception issues at all?
In Columbus Ohio all the stations are still on their current digital signal VHF/UHF channels and did not move back or change VHF/UHF channels with the exception of WSYX might move form VHF13 to UHF48. Until WCPX-LP48 get their act together.
In Columbus Ohio all the stations are still on their current digital signal VHF/UHF channels and did not move back or change VHF/UHF channels with the exception of WSYX might move form VHF13 to UHF48. Until WCPX-LP48 get their act together.
The reception is not an issue of having 2 HD feeds on KABC (or any channel for that matter), however the picture does take a hit. When LiveWellHD started on KABC 7.2 they tried to have the clearest picture for both KABC 7.1 (the main LA ABC affilate) and LiveWell on 7.2. Obviously, both channels suffered greatly having a washed out, dull and blocky picture. They have since lowered the bandwidth to 7.2 to pump up their main 7.1 which makes even having HD programming on the subchannel a joke. Any quick or sudden camera pans or fast movement and you see blocks on 7.2. They'd be better off showing SD programming formatted to 16:9 much like what PBS-World does on many PBS subchannels.willcail said:
Neel Mehta said:
I did my first channel scan Friday afternoon, and couldn't get KABC (and a couple of the UHFs), and KCBS-DT was actually in KCAL's 9.1 spot. That, of course, was because KCBS is now using KCAL's old digital allocation (43), KCAL moved back to 9; KCBS's digital allocation was originally at Channel 60. Signal strength-wise, KNBC and KTLA came in the strongest (with at least 80-85 percent strength), with KCBS not too far behind. KTTV and KCOP, depending where I positioned the antenna, just came in and out. Back to KNBC and KTLA for a second...the ironic thing about them was that their analog signals were very spotty where I live, but their digital signals are far superior now.
I did a re-scan on Saturday morning...all the stations but KCET, KOCE, KVEA (Telemundo), KAZA (Azteca) came in with little to no problems.
willcail said:
WSYX has petitioned the FCC for ch 48, which doesn't make sense, as Pittsburgh's WPXI is on ch 48. Proximity to WPXI was the reason WCPX-LP used to get a construction permit to move to ch 25. Still, if WSYX were to be granted the channel change, and WCPX had not moved to ch 25, there's nothing WCPX can do. WSYX has priority, and WCPX would have to find another channel.
Displacement rules say an LP can be displaced if there's a station within 265 km on the same channel. I think it's more a technicality to let LPTV stations shuffle around than anything based in reality.
In the analog world, Columbus to Pittsburgh spacing wasn't a major problem. Exhibit A: WCMH and WTAE.
- Trip
In the analog world, Columbus to Pittsburgh spacing wasn't a major problem. Exhibit A: WCMH and WTAE.
- Trip
K
kenrayc
Guest
DTV spacing can be done on adjacent channels, In Sacramento KVIE PBS now on ch. 9 and KXTV 10 ABC are on the same stick at Walnut Grove CA. same way with UHF that used to be separated by 6 channels on the same site now doesn't have to be.
re: WMAR.....did you get WJZ DT before the switch? If you did,try a rescan. WMAR DT is now using the same facility that WJZ DT was using on RF channel 38. Did you get WMAR DT before the switch when they were on RF channel 52?....Do you have a UHF antenna? WBAL DT and WJZ DT are back on VHF channels 11 and 13. WMAR DT is not directional and operates with 1MW at around 1000 feet. Hope you figure out your problem. I would think at 30 miles with a decent outdoor antenna you should be able to pick up all the Baltimore signals no problem.
F
FreddyE1977
Guest
dhett said:
KDKA-TV is now running digital on UHF Channel 25, so the short-spacing issue remains
vacuum tube said:
Yes, and I still do. Same case with WBAL DT pre and post switch.
I did tonight, to no avail.
Yes.
On the roof? Yes. The VHF-UHF assembly is 75 to 80 feet above sea level FWIW.
Even with an antenna that's as old as the house (24 years)? Even with thick, tall woods beginning +/- 30 feet from the back of my house, and rising into the line of sight between my antenna and Baltimore? FWIW I get WJLA-DT perfectly but the trees are not in the antenna's line of sight towards Washington so at least I can get ABC programming that WJLA doesn't preempt. BTW I have a Samsung purchased new shortly after the original February deadline, and also BTW it got WTTG perfectly and KYW and WRC less than perfectly pre switch, now it gets their nightlights.
ixnay
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