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Old 10-31-2017, 11:50 AM
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Why is ATSC on VHF so damn finicky?

Why is reception of ATSC on VHF, especially low-VHF, such an enormous pain in the ass compared to ATSC on UHF? In the analog days, my grandparents, who live in something of a fringe area, had a hell of a time picking up some of the NTSC UHF stations. Now with ASTC, the situation seems to be reversed, with any station on UHF coming in just fine and the handful of VHF stations in the Detroit and Flint/MBS markets being nearly impossible to receive.

More importantly, why the hell would the FCC approve a standard that doesn't work very well on VHF? In a place like Michigan, VHF stations were a must in getting adequate coverage of our geographically large markets.

Take for instance the upper lower peninsula and eastern upper peninsula of Michigan. Traverse City, Cadillac, Sault Ste. Marie, St. Ignace, Cheboygan, and Petoskey all rely on Traverse City stations (with full power translators between the Soo and the Straits filling in the gaps). Providing a quality signal to that vast area was feasible with VHF, it's near impossible to do with UHF. The local stations have resorted to sharing sub-channels to try and make up for the inadequate coverage. Still, if I lived in St. Ignace, I'd be pissed that FOX is only available in standard def on a subchannel of another station...
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Old 10-31-2017, 01:11 PM
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Quote:
Originally Posted by benman94 View Post
Why is reception of ATSC on VHF, especially low-VHF, such an enormous pain in the ass compared to ATSC on UHF? In the analog days, my grandparents, who live in something of a fringe area, had a hell of a time picking up some of the NTSC UHF stations. Now with ASTC, the situation seems to be reversed, with any station on UHF coming in just fine and the handful of VHF stations in the Detroit and Flint/MBS markets being nearly impossible to receive.

More importantly, why the hell would the FCC approve a standard that doesn't work very well on VHF? In a place like Michigan, VHF stations were a must in getting adequate coverage of our geographically large markets.

Take for instance the upper lower peninsula and eastern upper peninsula of Michigan. Traverse City, Cadillac, Sault Ste. Marie, St. Ignace, Cheboygan, and Petoskey all rely on Traverse City stations (with full power translators between the Soo and the Straits filling in the gaps). Providing a quality signal to that vast area was feasible with VHF, it's near impossible to do with UHF. The local stations have resorted to sharing sub-channels to try and make up for the inadequate coverage. Still, if I lived in St. Ignace, I'd be pissed that FOX is only available in standard def on a subchannel of another station...
Ben, I live in a semi-fringe area 30+ miles from all seven Cleveland television stations' towers, and do not receive two of them OTA. The problem is that the two stations I cannot get are on VHF DTV channels, while the others, every one of them, are on UHF DTV assignments. The only way anyone in this area can get channels 8 and 19 (FOX and CBS from Cleveland) is to have cable, satellite or a streaming video player such as Roku. I am using a Roku player and now get reception from every Cleveland TV station, including the two I do not receive OTA. I will probably use this system indefinitely, doing away with OTA television antennas altogether. I no longer use the cable connection, but I must still have a cable account so the Spectrum (formerly Time Warner Cable) TV application used with my Roku will receive local TV channels.

Low-power or full-power translators would solve, once and for all, the reception problems channels 8 and 19 (on VHF DTV channels 8 and ten, respectively) have in the area east of Cleveland along the south shore of Lake Erie, where I live, but the stations' owners flatly refuse to install such translators, probably for financial reasons. (Channel 8 did have a translator on channel 31 which it installed shortly after the start of the DTV transition, but it has since been deactivated.) The transmitter for one of Cleveland's UHF stations, along with its RF spectrum, were sold recently, the plan being to eventually put the station in question on a subchannel of CBS channel 19. I don't know if this has been done yet, as I no longer have cable (Spectrum cable in my area has been 100 percent digital since the third of this month) and the "MyTV" subchannel showing on the channel guide for my Roku player only receives a channel it refers to as "CLE 43".

BTW, if I could no longer receive FOX channel 8 in my area it would be no loss whatsoever to me, as I don't watch the OTA main channel. However, I do watch the Antenna TV subchannel on channel 8.2, although it irks me that the subchannel carries endless (or so it seems) strings of commercials promoting channel 8, as I do not care beans for that channel ever since FOX Broadcasting bought it out and switched it from CBS to FOX some time in the '90s. CBS was moved to a UHF station (channel 19) which, despite their 3.7-megawatt NTSC (now 9.5 kW ATSC) signal, does not reach much of the greater Cleveland area OTA, particularly the region east of the city along the lakeshore.

When TV was converted to ATSC from NTSC, the FCC should have, IMO, outlawed the use of VHF channels for DTV and reassigned the entire VHF TV band to some other service such as police, fire, etc. that really needs the spectrum space.

Sheeesh!
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Last edited by Jeffhs; 10-31-2017 at 01:27 PM.
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Old 10-31-2017, 02:36 PM
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If they transmitted near the same power on VHF as allowed on UHF there would probably be no problem other than co-channel interference from distant stations.

We have Ch 8 WFAA here on RF 8, and KFWD 52 on RF 9. WFAA is the ABC affiliate, been on the air here since 1950. They transmit an ERP of 37.9 kW. At a distance of about 27 miles I receive the VHFs just as strong, 95-100% signal quality as the UHFs. I am using a 30+ year old RadioShack (Antenna Craft) TV antenna that has good VHF gain, unlike a lot of the newer antennas that all but ignore VHF. The The local Fox affiliate, KDFW 4 transmits on RF 35 with an ERP of 153 kW. The differences in power allowed may well have something to do with the reception issues some people have. Then there are the so-called "digital" antennas that have no or very little reception of VHF.

Anyway they are supposed to move more stations down to VHF with the repacking. We have at least one here, KHPK-LD 28 that has moved to RF 10.

I do know that for some odd reason Dish network is suddenly promoting OTA TV by offering to remove the local channels from the Dish subscription with a $10 a mo savings, and will even send a technician out and install a new TV antenna, FREE! I have no idea why or what they are up to but they must think there's a good future for OTA TV, unlike in 2009 when there was a sudden "spectrum shortage" and some were talking about OTA just going away because the RF spectrum was too valuable to give away.
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Old 10-31-2017, 02:53 PM
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My grandparents are using a Winegard 7698P which ought to have decent gain in the H-VHF region. We don't have any L-VHF stations in south-east Michigan anymore...
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Old 10-31-2017, 03:06 PM
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Here's a TV fool report for their location:

http://www.tvfool.com/?option=com_wr...00134b9f3ba862

Some of the Detroit stations seem to have gone missing from the TVFool database, but my point can still be made. WJRT blinks in and out all the time, WILX, WJBK, and CBET, which came in just fine in the analog era, haven't been picked up since the analog shutoff.
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Old 10-31-2017, 05:31 PM
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A number of interesting articles here by Charles Rhodes, who I believe participated in the early ATSC standards work. A number of ATSC "pitfalls" are analyzed here:

http://www.tvtechnology.com/author/c...odes/2/article

jr
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Old 10-31-2017, 05:48 PM
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Sorry to be negative. Dont get me started on DTV .LOL .Because. its a failed format.I said this before that I used too get all channels the analog way and some came in just with the antenna lugs.New I dont receive crap with this crappy new system.VHF or UHF.Its a pile of crap that was unloaded too sell off the TV channel bandwidth to the telecom people and other wireless companies. .Thanks to the MSM for the brainwashing the public saying its better then regular TV.Fake news BS..

End of my rant.

Last edited by centralradio; 10-31-2017 at 05:54 PM.
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Old 10-31-2017, 08:32 PM
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Sorry to be negative. Dont get me started on DTV .LOL .Because. its a failed format.I said this before that I used too get all channels the analog way and some came in just with the antenna lugs.New I dont receive crap with this crappy new system.VHF or UHF.Its a pile of crap that was unloaded too sell off the TV channel bandwidth to the telecom people and other wireless companies. .Thanks to the MSM for the brainwashing the public saying its better then regular TV.Fake news BS..

End of my rant.
How far away are the local transmitters anyway? Have you run a "tv fool" analysis?

http://www.tvfool.com/?option=com_wrapper&Itemid=29

When the going gets tough, the tough get BIGGER ANTENNAS

jr
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  #9  
Old 10-31-2017, 10:07 PM
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Sorry to be negative. Dont get me started on DTV .LOL .Because. its a failed format...
That's too bad you have such bad results. It's 100% all good here. No airplane fading, no static noise slowly crawling up the picture from noisy power lines and other sources, no ghosting from multipath. Don't miss any of that. With a good antenna and tuner DTV works great. I even pull in a station from Oklahoma with the same picture quality as the locals and the OK station is about 100 miles away, on RF 12, KXII 12. Over 110 channels total. Much more efficient.
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Old 10-31-2017, 10:24 PM
centralradio centralradio is offline
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Originally Posted by jr_tech View Post
How far away are the local transmitters anyway? Have you run a "tv fool" analysis?

http://www.tvfool.com/?option=com_wrapper&Itemid=29

When the going gets tough, the tough get BIGGER ANTENNAS

jr
Thanks Jr. . The closes is about 15 miles and the others very from 20 to 35 miles since I'm in the center of the state.The VHF station is the 15 miles away station.

Last edited by centralradio; 10-31-2017 at 10:33 PM.
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Old 10-31-2017, 10:32 PM
centralradio centralradio is offline
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Originally Posted by Ed in Tx View Post
That's too bad you have such bad results. It's 100% all good here. No airplane fading, no static noise slowly crawling up the picture from noisy power lines and other sources, no ghosting from multipath. Don't miss any of that. With a good antenna and tuner DTV works great. I even pull in a station from Oklahoma with the same picture quality as the locals and the OK station is about 100 miles away, on RF 12, KXII 12. Over 110 channels total. Much more efficient.

Thanks Ed.Wow you are lucky.It is a bad experience and thats why I'm probably so negative over DTV. I see the benefits of it but its useless if I cant get even one channel.I probably have put up a 50 foot mast antenna to get anything here.If it was the other way around .I would cut the cable and go OTA.For $36 bucks on cable and thats all its worth to me.
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Old 11-01-2017, 12:06 AM
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This issue has come up on video karma multiple times, and I will now give the same answers I have before:

1) The FCC planning factors did not take into account the level of environmental noise present in the VHF bands
2) at low VHF antennas are less efficient than they could be due to size limitations
2a) at low VHF antennas are less directional and more susceptible to ghosts
2c) the ATSC 1.0 system depends on the capability of the receiver equalizer to handle ghosts, especially moving ones. ATSC 3.0, like DVB, will have a specific ghost immunity (guard band) depending on the particular choice of coding parameters for a subchannel; the broadcaster will determine at what delay range / level of ghosting the viewer will lose signal
3) During the transition from analog, the power could not be boosted due to interference with analog co-channel stations. Power could be boosted now, but in order for the more tightly packed digital co-channels not to interfere with each other, they would all have to boost simultaneously. Practically impossible both technically and economically.
4) Near the Canadian and Mexican borders (read, the complete tiers of northern and southern states), power cannot be changed without international agreement.
5) Because of antenna size problems, cell phones must use UHF. The cell phone providers have much more money and clout than the broadcasters these days, (there are many more cell phone customers producing much more revenue than the advertising that supports OTA TV customers, plus many people today are completely unaware that you can get OTA, but they all want mobile phones) so the spectrum negotiations go in favor of mobile.
6) Maybe ATSC 3 allocations and repacking will be a chance to raise VHF power, and maybe broadcasters will use more robust, more highly coded, (but lower bit rates) for at least some of their services; or some combination of the above. It remains to be seen.
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Old 11-01-2017, 12:23 AM
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I would also note that VHF over the horizon is subject to smeared ghosting (energy spread over a range of delays), which analog viewers can look through, but is hard for digital systems to handle. In Europe, digital broadcasting typically repeats national feeds on multiple transmitters and different RF channels, so everyone lives within the horizon of one. This does not fit the American broadcasting model of big stick transmission to large local markets. ATSC 3.0 has specific signal features that facilitate use of single frequency networks (SFNs) where a market can be covered out to its legal limit by use of multiple transmitters spread over the coverage area but on the same RF channel; but in this case, DXing may become more difficult for those outside the designated area, since each transmitter has only enough power to cover its locality.
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Last edited by old_tv_nut; 11-01-2017 at 12:26 AM.
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Old 11-01-2017, 09:59 AM
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WPVI (WFIL 1947-72) has remained on low band channel 6, having to increase power (more than one FCC construction permit) in order to overcome undersized antennas and higher noise levels that pixellate DTV by causing bit error rates. Prior to the transition to ATSC, WPVI 6 reached NYC, all of NJ, DE, northern MD and well into the Poconos and Appalachians.

The VHF band is so loaded with noise from switch-mode power supplies, both radiated from fluorescent and LED lamps with electronic ballasts and drivers. The harmonic content of the non-sinusoidal current drawn is pretty harsh, just move a portable FM radio close to one and see.

But with DTV that shows a poor signal level, the only way you can tell WHY is to check you location with a spectrum analyzer(I don't own one0 or a SDR-Sharp application that turns your laptop into one. Signal to Noise is more relevant with ATSC.

Any CFL/fluoescent lighting system with a real iron-core transformer, like old T12 lamps is a radio-friendly system. Don't upgrade to "energy star"

I agree it was a bad idea to keep VHF for DT yet dead spots still exist for UHF and VHF does seem to work there. I sent a Winegard HD7697 and CM7777 preamp with my neighbor to the hunting camp in Sullivan County and all he could get was two VHF channels from Binghampton, NY. and not any of the Wilkes-Barre Scranton area transmitters now both on VHF and UHF.

Prior to Wilkes Barre getting local UHF in 1952, all TV in NE PA came at least 50 miles from channel 12, (pre-transition) of WBNG, if at all.
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Old 11-02-2017, 11:21 PM
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I hadn't done a TV Fool report in a while; some interesting data to mine. Generally, the farthest distance I'm seeing are the Baltimore stations at 65.1 miles. I see a number of stations which have popped up in the deeper fringes that I didn't know about. Hmmm...could cause me to try Dx'ing some night.

I'm torn on ASTC. It means a lot more to watch than we used to have, and a whole lot clearer than my stepmother gets with her dish. But the pixelation-I know I'm asking a lot for some of these stations. I have a decent Winegard on the chimney with a booster and rotor. I'd have to add height to see much more of a difference & I don't think that's happening anytime soon.
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