Friday, December 03, 2010

FCC proposal on TV spectrum refarming

edited by w9wi 2010-12-03 1041 to add the title I forgot the first time!)

OK, I've had some time to read the FCC proposals on further refarming of TV spectrum. The way I read it (don't guarantee I've got it right)

The link:

The highlights:

- No specific channels are targeted for refarming. They propose to make all UHF channels co-primary between TV and new land mobile services. Any channel surrendered by a TV station would be available for land mobile. Land mobile would protect existing TV facilities, but new TV stations would protect land mobile.

- Stations would be encouraged to voluntarily share their channel with another station(s). Nobody would be required to channel-share. Stations that volunteer would receive a cut of the revenue when surrendered channels are auctioned.

- FCC envisions two HD streams could be broadcast over a single channel. More than two SD streams could be transmitted. They mention some stations fear sharing would result in poor HD picture quality; an inability to add subchannels; and/or the inability to implement mobile DTV.

1.Channel splits would not necessarily be 50/50. Stations might agree to some other split.

2.Stations would be individually responsible for things such as EAS, indecency, children's educational programming, etc..

3.The FCC does NOT propose to allow the addition of new stations, not currently authorized, to a shared channel.

4.They ask about sharing between commercial and non-commercial stations. Should a non-commercial station, on a channel reserved for non-commercial operation, be allowed to offer half of its channel to a commercial station?

5.They also ask whether LPTVs should be allowed to share channels, either with each other (IMHO they already are!) or with full power stations.
(the idea of sharing a channel between a LPTV and a full-power station brings up some interesting issues. To the best of my knowledge it is not possible to split an ATSC channel among more than one transmitter – if two or more stations share a channel, they must share the same transmitter. It is not possible to split the power levels either. You can't operate WIIW-LP's half of channel 14 at 15kw while operating WHTN-TV's half at 500kw. So if a LPTV shares with a full-power (FP) station, either the LPTV becomes a FP station or the FP station limits its power to LP levels...

Not sure what the FCC is thinking here.

At one point they write “...we do not envision that channel sharing, from a technological perspective would entail a fixed split of the six-megahertz channel into two three-megahertz blocks.” It is simply not possible to split a six-megahertz channel into two three-megahertz blocks if you expect an ATSC receiver to decode either block! Then again, at another point in the document, they do suggest they understand how the channel could be split...)


6.The Commission is insistent that no station volunteering to share a channel would lose any must-carry rights on cable/satellite. They're also insistent that no new must-carry rights be created.

- The FCC understands there are serious problems with VHF. They wish to discourage stations from moving from VHF to UHF.

- To that end, they have determined that VHF reception on indoor antennas is a problem.

- Both an outside engineering firm and the FCC's own staff measured a variety of available indoor antennas. They found the gain on UHF channels ranged from -6dBd to +21dBd. On VHF-high, only 30% of antennas tested had more than 0dBd of gain; some were as low as -25dBd. They didn't even bother to test these antennas on VHF-low! (many of them were marked on the package as not working on VHF-low.)

- The FCC considered VHF power increases of up to ten times. (which could allow as much as 1600kw ERP on VHF-high. I believe there may be an existing analog station in Kuwait operating at this kind of power level, but with a VERY directional antenna.)

- Engineers felt a power increase won't make much difference. They suggest a reduction of spurious emissions from consumer devices is necessary.

- The FCC said, quote:“While it would be desirable to reduce that noise, the rules limiting spurious emissions from unintentional radiators have been crafted to provide protection of licensed services while allowing production of economically viable devices.”

- In other words, they're willing to allow consumer electronic devices to interfere with OTA TV reception in order to keep device prices low. (though realistically, imposing new limits on spurious radiation would do nothing about devices already in the field)

- FCC proposes to increase power anyway. In Zone I, a four-fold power increase would be permitted for VHF stations. (from 10kw maximum to 40kw on VHF-low, from 30kw to 120kw on VHF-high.) No change is proposed from the 45/160kw figures in Zones II and III.

- There will be no change in interference protection requirements. Which in practice probably means few if any power increases will be possible...

- They also propose to impose mandatory antenna performance requirements. The All Channel Receiver Act (which required TVs to receive UHF from 1964 on) gives them the authority.

- Compliance would be required with ANSI/CEA standard 2032-A, “Indoor TV Receiving Antenna Performance Standard”. This establishes a minimum gain of -12dBd for VHF low, -8dBd for all higher channels. Among other things, it also establishes overload susceptibility standards for amplified antennas.

IMHO...

- Many stations will not be interested in spectrum sharing.

- Some smaller stations will be interested. For example, I can see Sinclair merging their Milwaukee stations WVTV and WCGV into a single station, comprising two program streams on the RF channel 18 transmitter. Or, Nashville-area stations WJFB (two SD home-shopping streams) and WHTN (two SD religious streams) merging into a single transmitter, transmitting four SD streams on RF channel 44.

- I can also see this happening in smaller markets. Maybe in Fort Wayne, WISE-TV (RF-18, NBC) merging with WPTA-TV (RF-24, ABC) into a single transmitter, transmitting two HD streams on RF channel 18.

- The technological attempts to encourage stations to stay on VHF are pointless. Engineers have already indicated power increases won't help. (and those increases are limited to a fraction of the country, and will probably be nearly impossible to implement due to interference concerns)

- The antenna performance requirements are a very good idea. Unfortunately, they're too late. Millions of viewers have already purchased antennas that simply do not work on VHF.

- PSIP remapping will ensure any spectrum sharing will be invisible to viewers. (beyond the need to rescan) WHTN and WJFB may both be transmitting on RF channel 44, but they'll continue to be channels 39-1 and 66-1 respectively as far as viewers are concerned.

- I think we'll hear more about LPTV before this proceeding is complete. I don't think they thought out that paragraph very well.

--

Doug Smith W9WI
Pleasant View, TN EM66

4 comments:

Anonymous said...

Please note that the listed ERPs for the UHF stations [shown on page 30 of the PDF link to the FCC's 10-196] are WRONG. What is shown is a repeat of the ERPs for low band VHF stations.

Doug Smith said...

It's coming up as page 34 when I pull it up but yes, it does look like they reprinted part of the low-VHF table instead of the UHF table.

Judging from the rest of the text, I would presume they intend no change in the UHF table from current figures.

Anonymous said...

What are the current figures for UHF?

Doug Smith said...

That would help... Copied from FCC regulation 73.622:

Maximum Allowable ERP and Antenna Height for DTV Stations on Channels 14-
59, All Zones
------------------------------------------------------------------------
Antenna HAAT (meters) ERP (kW)
------------------------------------------------------------------------
610........................................................ 316
580........................................................ 350
550........................................................ 400
520........................................................ 460
490........................................................ 540
460........................................................ 630
425........................................................ 750
395........................................................ 900
365........................................................ 1000
------------------------------------------------------------------------