DTV Repack Is Causing ‘Harmful Interference

milf

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What is DTV
Digital Tele Vision... Where all the Television stations had to move off 700 MHz and went to the new digital format. Now apparently things are not all daisy's and sunshine yet... Many years later.
 

MTS2000des

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Really shows how out of touch the FCC is, they're too busy pandering to the telecom cartels to notice that incumbent part 90 and part 22 systems that have been in use for decades would get clobbered when they approve the moving of a megawatt ERP DTV transmitter on the same band. This is like iDEN interference times 1000.
 

gmclam

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DTV, as it relates to this article, is over-the-air Digital TeleVision. On June 9, 2009 most of the analog (NTSC) signals were turned off moving people to ATSC 1.0. Even if you get your TV from cable, many cable operators, especially in rural locations, get their signals off the air that they then "sell" to you.

That action back then also reduced the physical number of over-the-air TV channels. The top channel was 69 and became 51. You see, along with the move to digital came "logical channels". That station you've been watching that called themselves "channel 3" or "channel 10" was most likely no longer brodcasting on the same channel when they moved to digital. So you could have channel 58, even though the physical channels stopped at 51.

Now comes ATSC 3.0 (yeah we skipped past 2.0). And the government (and cell companies) learned that over-the-air TV could be further "compressed" into even fewer channels. It was decided that TV only needs channels 2 to 36 and they could "give back" channels 38 to 51 (which opens up the 600MHz band). To make this happen TV broadcasters have had to "repack" their channel usage into the newly restricted space.

Most scanner listeners know of the "T band" (Television band) of TV channels 14 to 20, frequencies from 470-512MHz, that have been "shared" for years by TV and public safety radio. Well, this repacking has put TV signals back into some of those places and now the public safety radio operators are complaining about interference. What did everyone expect?

These changes have largely happened to a) give cell companies more spectrum; b) generate revenue for the general fund; c) provide more abilities for our native over-the-air televison signals.
 

Reelfishguy

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The TV repack was the result of Congress passing in 2012 the Middle Tax Relief Act which authorized the FCC to auction off the upper TV channels. This forced about 1,000 TV stations to change frequency. It was not a simple thing for them such as just changing a crystal or whatever, but many had to purchase new transmitters, antennas, combiners, and many other things although they were compensated for some of those expenses by the federal government. Unfortunately some of the TV stations drew the short straw and had to relocate to TV channel 14 (470-476 MHz). Those stations certainly did not want that channel assignment because of the potential interference to the 450-470 MHz UHF land mobile users. Congress thought the FCC could find "other spectrum" for the Public Safety users in the T band but that did not happen. Apparently they did not even consider allocating funds for the Business and Industrial users in that band to go to other frequencies. I am aware of one the TV stations that was forced to change to TV channel 14 that caused major interference when they first tested their channel 14 transmitter. In essence it rendered all the UHF land mobile users within several miles of their transmitter useless. The noise floor at several sites increased by 35-40 db even with their existing 450-470 MHz band pass filters. Prior to their initial channel 14 testing they had conducted an extensive PIM study on their tower. They were scratching their heads about how to resolve this interference problem. Then a few months later they tested the channel 14 transmitter again, but there was no interference--where did it go?? Well the PIM remediation work had been done of their tower which involved changing many bolts, nuts, grounds, and other things. We think that remediation work solved their problem. We have all heard of weird things happening such as rusty guy wires and other things. The thing is what would have happened if they had not had the PIM study done. I think this is a case where a land mobile user does not have any control of what happens external to their equipment. For all parties involved, thank goodness this interference went away.
 

Septa3371CSX1

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New this tropo season is TV19 in the New Jersey area from Norfolk Va area. Public safety using 500 MHZ TRS being knocked off the air. Subs have little or no idea and no short term plans.
This might be the one causing issues with Delaware County, PA. Lately they've had problems on Sector 7 (501.850).
 

r60

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Hearing additional reports of not only TRS but conventional systems also being impacted today.

TV 19 occupies in a perfect world 500-506 MHZ.
 

GTR8000

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NYPD is experiencing interference on the Staten Island zone frequencies, and issued a memo regarding it.

The NYPD SI channels are in the 482 MHz range, i.e. DTV Ch 16. Also in the 482-488 MHz block are all FDNY and FDNY EMS channels, all channels of the UHF SmartZone system and the UHF site of the P25 system, and all six NYMAC interop channels.

WTKR in Norfolk, Virginia was recently moved from Ch 40 to Ch 16 as part of Phase 10 of the repacking, and undoubtedly is the culprit here.

What a mess. But hey it's okay, because T-Band is getting auctioned off soon anyway, right?!? :rolleyes:
 

fleef

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Really shows how out of touch the FCC is, they're too busy pandering to the telecom cartels to notice that incumbent part 90 and part 22 systems that have been in use for decades would get clobbered when they approve the moving of a megawatt ERP DTV transmitter on the same band. This is like iDEN interference times 1000.
Pandering to telecoms- when WE, the public, are supposed to own these airwaves.
 

MTS2000des

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This is what happens when government becomes by the corporations and not the people. We didn't learn from rebanding, and what a mess that was (and still is). This is being kept relatively quiet because it isn't "terrorism" that's causing multiple public safety systems trunked and conventional, on UHF T-band, to become useless. Nevermind the rest of the part 90 SMRs. No one cares because their cellphone works so they can spend hours posting narcissistic images of themselves and tweeting every time they flatulate.

Meanwhile, the cartels gobble up spectrum left and right. How could no one from the FCC OET not see this was going to be a problem? Oh that's right, they were all furloughed. Silly me.
 

gmclam

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IMHO the company that now calls itself AT&T is largely to blame. And after convincing the government that they should hold these auctions (because lawmakers would have "extra" money to spend too), they didn't even bid on the newly created space.
 

phillydjdan

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As we speak it is totally drowning out T-Band users just outside Philadelphia in the 506-508 range. Just a constant warble over top of the mobiles and base radios and nothing at all from portable radios. We're talking about cops and firefighters completely unable to use thier channels. I think the FCC really dropped the ball on this. It's like they forgot what RF can do...
 

MTS2000des

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This isn't just dropping the ball, it's borderline criminal negligence at the least. So why isn't the EB chief ordering the offending licensees from ceasing and desisting operation immediately? Let some ham guy with a spurious emission pop up on the repeater input of a single conventional repeater and he/she gets a knock at the door.

A few high powered DTV put a -80dbm (or stronger) carrier on dozens of life safety radio services and nothing happens. Consequence free USA, sponsored by corporate slime.
 

12dbsinad

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I anyone knows what the REAL intent of the FCC was, it was to "manage" the airways for access to all.

Now, it's just corporate sludge that when it gets thrown enough money at and sucked off the best, the hell with anything or anyone else. It'll never change..
 

r60

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NYPD is experiencing interference on the Staten Island zone frequencies, and issued a memo regarding it.

The NYPD SI channels are in the 482 MHz range, i.e. DTV Ch 16. Also in the 482-488 MHz block are all FDNY and FDNY EMS channels, all channels of the UHF SmartZone system and the UHF site of the P25 system, and all six NYMAC interop channels.

WTKR in Norfolk, Virginia was recently moved from Ch 40 to Ch 16 as part of Phase 10 of the repacking, and undoubtedly is the culprit here.

What a mess. But hey it's okay, because T-Band is getting auctioned off soon anyway, right?!? :rolleyes:
Seems to me the table has been set. The table will be run on Public Safety use of T-band.

Even if Congress were to agree to repeal on giveback the band is now largely unusable in many large population centers.

IMHO UHF-T band is done. What is left to save? Not much.
 

GTR8000

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Public safety was always second fiddle to TV stations on T-Band, going back 50 years to the early 70s when they first allowed public safety in some markets to share the spectrum. It's still that way today, if you read Part 90 it lays out the protections that the TV stations have in that band. I realize that some aren't familiar with that, and automatically assume that "well of course public safety must have the priority/protection in the band!", but that's not the case.

In any event, the giveback fiasco notwithstanding, T-Band is still viable in most markets. Yes, during periods of strong tropo ducting it can wreak havoc with certain systems, but frankly that's nothing new. Morris County NJ has been dealing with that crap for years on Ch 15. The fact that the recent completion of the repack shuffled around a few more stations over the past few months has created some new challenges in some markets is obviously unfortunate, and could've been avoided, but it hardly means that T-Band is done for public safety. Again, the elephant in the room is the giveback, but I'm speaking about the T-Band as it stands today.
 
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r60

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No question. However you have to wonder how NYC DoItt feels about this. Could certainly impact planning on many levels.
 
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