DTV Repack Is Causing ‘Harmful Interference

[FireMarshalRob]

Long Island T Band is getting hammered since about 4am. Some public safety users systems are virtually unusable. FCC has been notified..... not holding my breath.

 

[INDY72]

Unless it results in millions of dollars in property damages, a large loss of life, or huge lawsuits that actually do look winnable where the FCC would have to pay up.... The FCC is not going to blink once at this "reporting". And Congress is sure as he** not gonna give a flying frick unless it can be used as a political weapon of the nuclear scale in the election cycle.

 

[W1KNE]

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.

This happened in Scranton-Wilkes Barre PA, where WNEP-TV went from RF 50 to RF 16. Fully constructed their facility, including tower modifications and what not. They were "Phase 4" (switch on August 02, 2019). When they turned on 16 for the overnight testing, almost immediately NYPD started receiving interference. NYPD requested the FCC push their deadline back and work to come up with a solution. The eventual solution was WNEP-TV switched from 16 to 21, requiring a second TV antenna swap along with RF equipment that was in the transmission chain. (The transmitter itself is a broadband model and changing frequencies is done via software). They were tolled to Phase 9, and then eventually 10. (And for the record the TV antenna weighs between 10,000 and 20,000 lbs, so it's not an easy change.)

This first occured in 1998 when WCVB-TV in Boston turned on their high powered channel 20 transmitter. The first summer tropo opening, started wiping out T-20 in southern Jersey. This was one of the first cases where an ATSC signal caused this type of interference. (WCVB-TV has switched to 33. as part of the repack., however WBZ-TV now occupies channel 20).

 

[INDY72]

At this point, the EPA, FCC, DOEd, IRS, and "The FED" all need nuked and redone from the ground up. With "The FED" never being reborn. That is IMHO. And some folks that are actually in the world of communications at the top of the FCC, not just a pen pushing, bean counting, business head...

 

[phillydjdan]

Nice to see our GOOBERment working for us...

 

[12dbsinad]

"puts salesman hat on with no RF background theory" all users on T band need to go digital, that will solve it..

If only I had a dollar for every consultant and salesman that pitched that one liner over the years...

 

[RFI-EMI-GUY]

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..

The FCC used to be comprised of experienced Engineers and Technicians who worried about such annoying and trivial "science" things as out of band emissions, RF Propogation, R6602 and Carey Curves, filter bandwidths, inter-modulation, receiver spurious responses.

The industry fought back and filled the FCC with Lawyers who are concerned with words not physics.

 

[rr60]

The most common tropo events set up paths from the NY NJ Metro area are from the Southwest to the Northeast towards New England. The other common path is from Metro area extending from the Northwest to the South Southwest towards ACY, Chesapeake and Norfolk.

Both set up as overwater paths and coastal areas and extend inland.

Within the last two weeks 3 openings have occurred, one S-SW two NE.

The new factor this year is the recent FCC mandated and funded move by many TV stations to new RF channels.

While undoubtedly there are many new moves on RF 14-21, I looked at CH19 RF 500-506.

I have found two new DTV channels. One in Boston area at 1300’ w a million watts and one in Norfolk area at 1000’ and a million watts.

My conclusion is now two paths exist to potentially shut down PS Comm’s for those using any freq between 500-506 MHZ along those paths.

A side note, as a result of speaking w several systems folks. Systems that have a low footprint and low antenna elevation and remote receivers were getting by. Super sites with high antenna elevations were exposed to more video RF and wiped out.

My opinion. The last and final door has been opened. PS T-Band users are being shown the way out the door with a gentle push.

Here is some more background. Do not overlook this paragraph.

“The remaining channels (14-17, 19 and 20) cannot be used to reposition broadcast television unless all of the hundreds of land mobile licenses using frequencies within those channels are moved ... and to where?“

Why the repacking of digital television won't work

www.kmrichards.com

 

[W1KNE]

I have found two new DTV channels. One in Boston area at 1300’ w a million watts and one in Norfolk area at 1000’ and a million watts.

Channel 19 existed in Boston prior to the repack, just on a different station. (WGBH). Boston in fact lost a T-Band channel, when 18 entered into a channel sharing agreement with another station. 19 and 20 in Boston were both here prior.

 

[WA4A]

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...

The FCC has had no idea what they are doing with RF telecommunications since before they came up with assigning 27 mHz to the Citizen's Band back in the 1950s! Digital broadcast TV is a dismal failure that the FCC still keeps tinkering with since they have no idea how to provide a useful broadcast service to the general public. God help us when regular AM and FM broadcasters go silent! The FCC are lawyers, not engineers or practical thinkers.
The whole system of RF communications is misunderstood and is simply something to auction off to the next highest bidder who has no idea what they are buying, i.e. the 220 mHz amateur band or the legacy VHF and UHF Television channels fiasco. Give me back my analog television!

DE WA4A

 

[belvdr]

Give me back my analog television!

No thanks.

 

[prcguy]

Considering all the hurdles, the original switch from analog TV to ATSC digital television went remarkably well and the end result is a vastly superior picture, no picture noise, tons of new channels and very little loss of signal after initial problems were ironed out. It took over the air TV from the stone age to the future almost overnight.

The current repack is different and seems to be a mistake, only to allow the FCC to sell frequencies.

The FCC has had no idea what they are doing with RF telecommunications since before they came up with assigning 27 mHz to the Citizen's Band back in the 1950s! Digital broadcast TV is a dismal failure that the FCC still keeps tinkering with since they have no idea how to provide a useful broadcast service to the general public. God help us when regular AM and FM broadcasters go silent! The FCC are lawyers, not engineers or practical thinkers.
The whole system of RF communications is misunderstood and is simply something to auction off to the next highest bidder who has no idea what they are buying, i.e. the 220 mHz amateur band or the legacy VHF and UHF Television channels fiasco. Give me back my analog television!

DE WA4A

 

[W1KNE]

Considering all the hurdles, the original switch from analog TV to ATSC digital television went remarkably well and the end result is a vastly superior picture, no picture noise, tons of new channels and very little loss of signal after initial problems were ironed out. It took over the air TV from the stone age to the future almost overnight.

The current repack is different and seems to be a mistake, only to allow the FCC to sell frequencies.

I agree with the first part and disagree with the second.

To the other commenter who said to bring back analog TV, as someone who has actually worked on the transmission side of analog TV, I am very glad it's gone. You have no idea how complicated setting up, adjusting and maintaining an analog TV signal really is, unless you're the one on the low powered side of the transmitter. And on the receiving end, the multi-path and noise were terrible, unless you had the most perfect setup or lived 10 miles from the tower. ATSC is a lot more forgiving on that.

To the broadcasters, many of them, the repack has been a major boom. Don't forget that the ATSC conversion for most stations happened between 1999 and 2002, so for many stations, they are running on 18-20 year old high powered IOT (Inductive Output Tube) transmitters. The repack has allowed the stations to replace the aging and dangerous technology with newer, much better built, solid state transmitters. No more 30-35kV DC in our transmitter! We measure the quality of our signal in ATSC by SNR (signal to noise ratio) and EVM (Error vector magnitude). The signal to noise I get on our current brand new GatesAir transmitter is better than anything I ever got on our older Harris. The EVM is also the lowest I've seen in a modern transmitter. It's no comparison. We also got an increase in power from 625kW to 922kW, at the same height, so our coverage has improved too.

Now my situation is more of the norm than not, but yet, some stations did end up taking a "hit" due to the repack. Some stations sold their spectrum and went to Low Band VHF, which can be a killer for ATSC. (Both of the PBS affiliates near me did. One went to 5, the other to 2).
Some stations decided to move their transmitters to not so market central locations because of corporate disputes with large tower companies.
But that's not the norm, and most who repacked came out a winner. Especially on the back end equipment end.

Sometime I will compile a list , only in the markets that it matters, of who left T Band and who went.

 

[prcguy]

I was recently on a crew swapping out an old analog 100kW UHF TV transmitter that had been "upgraded" to ATSC and was running 20kW to a brand new "repack" transmitter and antenna on VHF lo that I turned up and put on the air. Yes, a lot of stations got free $$ to upgrade equipment. Yes, a lot of mistakes were made with clueless station owners not knowing or understanding the impact of going from 20kW on UHF into a very high gain antenna to 10kW into a modest VHF lo antenna and the huge loss in coverage. Oh well, they got a new shiny transmitter and the new rigid line coax is really pretty. Never mind they lost a ton of customers.

Bottom line is the FCC initiated the repack to make big $$. That is the only reason the repack exists and I think it stinks.

I agree with the first part and disagree with the second.

To the other commenter who said to bring back analog TV, as someone who has actually worked on the transmission side of analog TV, I am very glad it's gone. You have no idea how complicated setting up, adjusting and maintaining an analog TV signal really is, unless you're the one on the low powered side of the transmitter. And on the receiving end, the multi-path and noise were terrible, unless you had the most perfect setup or lived 10 miles from the tower. ATSC is a lot more forgiving on that.

To the broadcasters, many of them, the repack has been a major boom. Don't forget that the ATSC conversion for most stations happened between 1999 and 2002, so for many stations, they are running on 18-20 year old high powered IOT (Inductive Output Tube) transmitters. The repack has allowed the stations to replace the aging and dangerous technology with newer, much better built, solid state transmitters. No more 30-35kV DC in our transmitter! We measure the quality of our signal in ATSC by SNR (signal to noise ratio) and EVM (Error vector magnitude). The signal to noise I get on our current brand new GatesAir transmitter is better than anything I ever got on our older Harris. The EVM is also the lowest I've seen in a modern transmitter. It's no comparison. We also got an increase in power from 625kW to 922kW, at the same height, so our coverage has improved too.

Now my situation is more of the norm than not, but yet, some stations did end up taking a "hit" due to the repack. Some stations sold their spectrum and went to Low Band VHF, which can be a killer for ATSC. (Both of the PBS affiliates near me did. One went to 5, the other to 2).
Some stations decided to move their transmitters to not so market central locations because of corporate disputes with large tower companies.
But that's not the norm, and most who repacked came out a winner. Especially on the back end equipment end.

Sometime I will compile a list , only in the markets that it matters, of who left T Band and who went.

 

[RFI-EMI-GUY]

Have there been any indications as a result of Chan 14 repack, that the 462/467 MHz band is suffering any Out Of Band Emissions from DTV? What are the prescribed limits dBc or absolute value dBm of OOBE from Chan 14?

 

[Reelfishguy]

This is from FCC Rules and Regulations Part 73--

73.687



(3) TV broadcast stations operating on Channel 14 and Channel 69 must take special precautions to avoid interference to adjacent spectrum land mobile radio service facilities. Where a TV station is authorized and operating prior to the authorization and operation of the land mobile facility, a Channel 14 station must attenuate its emissions within the frequency range 467 to 470 MHz and a Channel 69 station must attenuate its emissions within the frequency range 806 to 809 MHz if necessary to permit reasonable use of the adjacent frequencies by land mobile licensees.

(4) The requirements listed below apply to permittees authorized to construct a new station on TV Channel 14 or TV Channel 69, and to licensees authorized to change the channel of an existing station to Channel 14 or to Channel 69, to increase effective radiated power (ERP) (including any change in directional antenna characteristics that results in an increase in ERP in any direction), or to change the transmitting location of an existing station.

(i) For the purposes of this paragraph, a protected land mobile facility is a receiver that is intended to receive transmissions from licensed land mobile stations within the frequency band below 470 MHz (as relates to Channel 14) or above 806 MHz (as relates to Channel 69), and is associated with one or more land mobile stations for which a license has been issued by the Commission, or a proper application has been received by the Commission prior to the date of the filing of the TV construction permit application. However, a land mobile facility will not be protected if it is proposed in an application that is denied or dismissed and that action is no longer subject to Commission review. Further, if the land mobile station is not operating when the TV facility commences operation and it does not commence operation within the time permitted by its authorization in accordance with part 90 of this chapter, it will not be protected.

(ii) A TV permittee must take steps before construction to identify potential interference to normal land mobile operation that could be caused by TV emissions outside the authorized channel, land mobile receiver desensitization or intermodulation. It must install filters and take other precautions as necessary, and submit evidence that no interference is being caused before it will be permitted to transmit programming on the new facilities pursuant to the provisions of §73.1615 or §73.1620 of this part. A TV permittee must reduce its emissions within the land mobile channel of a protected land mobile facility that is receiving interference caused by the TV emission producing a vertically polarized signal and a field strength in excess of 17 dBu at the land mobile receiver site on the land mobile frequency. The TV emission should be measured with equipment set to a 30 kHz measurement bandwidth including the entire applicable land mobile channel. A TV permittee must correct a desensitization problem if its occurrence can be directly linked to the start of the TV operation and the land mobile station is using facilities with typical desensitization rejection characteristics. A TV permittee must identify the source of an intermodulation product that is generated when the TV operation commences. If the intermodulation source is under its control, the TV permittee must correct the problem. If the intermodulation source is beyond the TV permittee's control, it must cooperate in the resolution of the problem and should provide whatever technical assistance it can.

 

[gmclam]

This is from FCC Rules and Regulations Part 73--

Funny how that excerpt is discussing requirements for stations on channel 69 since that is no longer used for television. It would seem that needs to be changed to channel 36. But with "co-use" of the T-band, there must be something more specific for that.

 

[RFI-EMI-GUY]

" 73.687

Further, if the land mobile station is not operating when the TV facility commences operation and it does not commence operation within the time permitted by its authorization in accordance with part 90 of this chapter, it will not be protected."

This is problematic for GMRS stations as they are no longer licensed by location. Proving incumbency is difficult because there is no longer a database of repeater locations. The TV station could deny responsibility and it will be necessary for the GMRS licenseee to prove they were in operation beforehand.

 

[RFI-EMI-GUY]

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.

Those items are simply going to start corroding again and slowly raise the UHF Part 90, Part 95 noise floor once again. What were they thinking??

 

[rr60]

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.

So here it is some relief. Perhaps half a loaf at best. The repack left old tropo problems intact and created new ones such as CH19 interference to PS in New Jersey not heard before as stations moved onto it during early 2020.

Congress repeals T-Band auction as part of massive funding bill with COVID-19 relief - Urgent Comms

Public-safety and business-industrial licensees with LMR systems on T-Band spectrum would be able to continue operating those networks, thanks to a scheduled auction of the airwaves being repealed as part of the massive federal funding legislation passed yesterday by Congress. This reported $1.4...

urgentcomm.com