FCC Commish: Reallocate Channels 5 and 6 To LPFMers

[DToTheJ]

At a radio conference on Thursday, FCC Commissioner Mignon Clyburn suggested that the spectrum for TV channels 5 and 6 should be turned over to low-power FM stations as well as AM broadcasters and non-commercial stations.

"This spectrum is not well suited for digital transmissions," Clyburn said at the 35th annual Community Radio Conference in St.. Paul, MN. "It is time for us to take a serious look at where these services fit within the overall spectrum plan, and that Channels 5 and 6 may be a good home."

Full story:
http://www.allaccess.com/net-news/a...-mignon-clyburn-suggests-using-tv-channels-5-

 

[w9wi]

At a radio conference on Thursday, FCC Commissioner Mignon Clyburn suggested that the spectrum for TV channels 5 and 6 should be turned over to low-power FM stations as well as AM broadcasters and non-commercial stations.

"This spectrum is not well suited for digital transmissions," Clyburn said at the 35th annual Community Radio Conference in St.. Paul, MN. "It is time for us to take a serious look at where these services fit within the overall spectrum plan, and that Channels 5 and 6 may be a good home."

Interestingly, he's conflicting with his own agency's broadband plan... which calls for discouraging TV stations from leaving VHF for UHF because they want to refarm more UHF spectrum for broadband...

 

[druidhillsradio]

Interestingly, he's conflicting with his own agency's broadband plan...

Uhhhhh....It's a "she"....

 

[Tom Wells]

At a radio conference on Thursday, FCC Commissioner Mignon Clyburn suggested that the spectrum for TV channels 5 and 6 should be turned over to low-power FM stations as well as AM broadcasters and non-commercial stations.

"This spectrum is not well suited for digital transmissions," Clyburn said at the 35th annual Community Radio Conference in St.. Paul, MN. "It is time for us to take a serious look at where these services fit within the overall spectrum plan, and that Channels 5 and 6 may be a good home."

Full story:
http://www.allaccess.com/net-news/a...-mignon-clyburn-suggests-using-tv-channels-5-

It is always pleasing to hear a wise and informed opinion from this level, especially when it is a refrain I've sung for years.
Only too bad someone on the commission didn't have the leadership to tell the NAB and ibiquity this fact before such a mess was made on AM.

 

[nmoore6676]

At a radio conference on Thursday, FCC Commissioner Mignon Clyburn suggested that the spectrum for TV channels 5 and 6 should be turned over to low-power FM stations as well as AM broadcasters and non-commercial stations.

"This spectrum is not well suited for digital transmissions," Clyburn said at the 35th annual Community Radio Conference in St.. Paul, MN. "It is time for us to take a serious look at where these services fit within the overall spectrum plan, and that Channels 5 and 6 may be a good home."

Full story:
http://www.allaccess.com/net-news/a...-mignon-clyburn-suggests-using-tv-channels-5-

It is always pleasing to hear a wise and informed opinion from this level, especially when it is a refrain I've sung for years.
Only too bad someone on the commission didn't have the leadership to tell the NAB and ibiquity this fact before such a mess was made on AM.

Maybe if the Medium Wave band were to be ultimately converted to all digital with no I-hash but the present scenario is a half-fast road to the ultimate destruction of AM radio. It needs to be one (full Fidelity AM) or the other (all digital) to get significant listening.

 

[eskipper411]

Who knows, they maybe planning to move to full HD radio. That's probably why they're doing this. Just push all the LPFM's to one side of the spectrum and leave the rest to switch over to HD. So that way they're organized.

 

[Ai4i]

conflicting with...own agency's broadband plan...which calls for discouraging TV stations from leaving VHF for UHF...to refarm more UHF spectrum for broadband...

Highband VHF, or do they really want digital TV to be stuck on lowband in perpetuity?

...they maybe planning to move to full HD radio.

I would suggest any expanded broadcast band be all digital, not hybrid, as the expanded AM band was *supposed* to have been stereo.

 

[pianoplayer88key]

Aas for TV 5-6... Besides just putting LPFMs there.... what about moving many of the smaller AMs there, including the graveyarders, and leaving AM mostly for the clears, and regionals that would have a 250-400 mile or so daytime 1mV/m groundwave coverage radius or so? Also I would like to see some LPAMs, as well - maybe limit them to 50 watts with a 1/8-wave antenna, and protection similar to class C is today (or possibly a bit less protected - maybe somewhere between TIS and class C protection). Also I would think we could do 3rd-adjacents to full power local AMs, 2nd adjacents to higher level LPAMs, and possibly first adjacents (as long as they're not diplexing) with the weaker (10-watt, 50-meter antenna licensed and 1-watt (measured at antenna input terminal), 25-meter antenna (not counting transmission line or ground lead) part 15) LPAMs. I would mostly put them above 1200kHz (but not exclusively), with 25-50 watt allocations sometimes available on lower frequencies where the higher ones are saturated. Also we could leave some higher powered AMs in the top of the band (above 1500kHz or so) to take advantage of the near-shortwave-like skywave. Also I would do away with IBOC on AM... but what about opening some of the HF spectrum for digital? Isn't that done in some countries?

 

[TheBigA]

Aas for TV 5-6... Besides just putting LPFMs there.... what about moving many of the smaller AMs there, including the graveyarders, and leaving AM mostly for the clears, and regionals that would have a 250-400 mile or so daytime 1mV/m groundwave coverage radius or so?

All that makes way too much sense. That's why it won't happen.

In the case of Clyburn, she is simply reiterating the views of the MMTC (Minority Media Telecommunications Council) report from a couple months ago. She is only one commissioner. She might be able to sway Copps on this one. But no one else will support her, especially the Chairman. He isn't giving away spectrum space to anyone, including minorities or NCEs.

 

[Ai4i]

Forget this nonsense about "except for the clears and big signal regionals". All the AMs simulcast on their new VHF channels for a few years and then vacate the one megahertz band forever. WFAN would be more competative as a B1 or B2 on the Empire than with the signal they now enjoy and in this digital world, you certainly don't use analog FM.

 

[Tom Wells]

Forget this nonsense about "except for the clears and big signal regionals". All the AMs simulcast on their new VHF channels for a few years and then vacate the one megahertz band forever. WFAN would be more competative as a B1 or B2 on the Empire than with the signal they now enjoy and in this digital world, you certainly don't use analog FM.

Clearly, there are differing views on what radio ought to be able to do.

One should be able to tune in WFAN in, ohh, say Harrisburg Pa, and listen all the way, driving back to NY.
Or the other way.
I now have a commute where I drive from a point 7 miles from downtown Chicago to about 25 miles NW of the city.
The towers are visible (line-of-sight) the whole way, and I get plenty-o-multipath the whole way.
The 50 kw clear AMs sound good for 200 miles, then there's the cancellation area, and good again from 250 out to whatever.
Reduction in service area will hurt more people overall than the improvement in audio for the local (stationary) listeners.
Mobile listeners will enjoy the switch to FM in the local area, but many fringe listeners will lose services.

These things are trade-offs.
If AM MW is vacated, it would be a huge loss to rural residents. As MW truly is optimized for analog, and digital dosn't work reliably
there, what good proposals are there to take advantage of the characteristics of MW?

Are you ready to give it up to those who still recognize the value and make the best use of skywave?

 

[pianoplayer88key]

Yes... and a view I have is that the higher frequencies (VHF, UHF), at least broadcasting, should be for services that don't need ultrawide coverage - where line-of-sight coverage is sufficient, for example. The lower frequencies should mostly be used when greater coverage area is desired - SW and MW (at least above 1400kHz or so) for the skywave, and MW and maybe LW for the groundwave over-the-horizon coverage. (I'd also allow small, low-budget MW stations as well, like I said in my previous post.)
As for big signal regionals, and clears... I personally might like to see places where you could drive on the highway cross country and listen to one station all day (assuming you're passing by the town where their transmitter is located at around noon or 1pm or so)... that's one idea of what I mean by wide-ranging groundwave coverage, basically. Actually, though, you'd have your choice of 2 or 3 stations, none of which are owned by the same company... and if you add the possibility of tuning into a second station as the first is fading out (because you were already going away from their transmitter), you would have quite a few more choices, as well. (This is assuming you're in a rural area, like west Texas, for example. To use that location as an example, an AM station might be based in, say, Midland, TX, and have groundwave service from El Paso to Dallas or so, assuming an omnidirectional antenna (maybe something that would almost cover the entire state of Texas, if the transmitter is centrally located), and a signal that unless you're in a noisy area, is still fairly listenable at the fringes - maybe something like indicating 30-36dBu or so on the Tecsun PL-310 or 380 for example.)
Also... I was thinking of one possible use for the wide-coverage AMs. Hey hasn't BBC (or whoever) sometimes synchronized multiple transmitters on the same frequency in Europe, with overlapping signals and the same programming? Would something like that work here, and put some of the nationally syndicated network programming (Rush, Dr. Laura, ESPN, Radio Disney, etc) on those? (I'm thinking have the transmitters spaced a few hundred miles or so, depending on the dial position and ground conductivity. Also I'd allow higher transmitter power than 50kW for those stations, and I'd require them to at least have half-wave antennas over a ground plane, or possibly the same type of antenna (a Franklin - two stacked 1/2-wave antennas) that 1530 KFBK uses.)

 

[Ai4i]

One area where power levels should be upped has got to be Alaska.

If channels five and six become part of an expanded radio service, I can see owners of TV stations which had been on those channels and who just a few years back upgraded to circular polarized antennæ and then abandoned them to go digital on UHF, ;D smiling ;D (if the hardware is still in place)

 

[pianoplayer88key]

I agree Alaska should get a power increase.
If a FM or TV was atop a 2000-foot tower on Mt McKinley's summit with 100kW for the FM or 5 MW for the UHF TV (don't remember the VHF TV limit but I think it's between those figures), how far might their coverage radius go? Is a 200 plus mile radius possible without having to rely on tropo or e-skip? I can often hear a couple Santa Barbara FM stations here in El Cajon near San Diego, about 200 miles away.
Also, assuming a fairly low dial position (below 800 kHz), either a half-wave antenna over a ground plane or two stacked half-wave elements (like KFBK uses), and taking into account the poor ground conductivity in Alaska, what power level, assuming a geographically centrally located transmitter, would be sufficient to blanket the entire state with at least a 1mV/m or so groundwave signal? Or would longwave broadcasting be better for covering a wide area like that while at least somewhat avoiding the variablity caused by skywave?

 

[rfry]

...Also, assuming a fairly low dial position (below 800 kHz), either a half-wave antenna over a ground plane or two stacked half-wave elements (like KFBK uses), and taking into account the poor ground conductivity in Alaska, what power level, assuming a geographically centrally located transmitter, would be sufficient to blanket the entire state with at least a 1mV/m or so groundwave signal?

For some perspective on that answer, below are calculations I posted earlier this month on a broadcast list server. The conductivity I used is higher than in Alaska, where according to a web reference I just read it ranges from 0.5 to 5 mS/m. So the contour distances for this super-power AM station in Alaska will not be as great as shown below.

Frequency = 700 kHz
Applied Power = 2,000 kW
Radiator = Single 195-degree monopole with 2 ohms of r-f ground loss
Radiation (IDF) at 1 mile = 11,180.3 mV/m
Earth Conductivity = 8.0 mS/m

Results:
Contour level Distance to contour

10.000 mV/m 113.2 miles

5.000 mV/m 146.9 miles

2.500 mV/m 186.3 miles

1.000 mV/m 245.1 miles

//

 

[pianoplayer88key]

...Also, assuming a fairly low dial position (below 800 kHz), either a half-wave antenna over a ground plane or two stacked half-wave elements (like KFBK uses), and taking into account the poor ground conductivity in Alaska, what power level, assuming a geographically centrally located transmitter, would be sufficient to blanket the entire state with at least a 1mV/m or so groundwave signal?

For some perspective on that answer, below are calculations I posted earlier this month on a broadcast list server. The conductivity I used is higher than in Alaska, where according to a web reference I just read it ranges from 0.5 to 5 mS/m. So the contour distances for this super-power AM station in Alaska will not be as great as shown below.

Frequency = 700 kHz
Applied Power = 2,000 kW
Radiator = Single 195-degree monopole with 2 ohms of r-f ground loss
Radiation (IDF) at 1 mile = 11,180.3 mV/m
Earth Conductivity = 8.0 mS/m

Results:
Contour level Distance to contour

10.000 mV/m 113.2 miles

5.000 mV/m 146.9 miles

2.500 mV/m 186.3 miles

1.000 mV/m 245.1 miles

//

Ok, R. Fry, now you've got me curious...

What would a best-case and worst-case scenario be like for coverage contours?
Best-case scenario would be a 50kW transmitter on 540kHz with a ground conductivity of 30 mS/m (I'm also curious about seawater performance (5,000 mS/m), center fed into two stacked half-wave elements. (KFBK uses that type of antenna without a ground radial system, but at a much higher frequency.)
Worst-case would be 250 watts on 1600kHz, ground conductivity 0.5mS/m, 45° or so antenna without a ground plane.
In addition to the 1 mile, 10, 5, 2.5, 1mV/m contours, what would the distances be at the maximum permissible contour (as specified in FCC 1.1310 - 614 V/m), and at a contour where the signal would be at about a 1dB SNR on the PL-310 (assuming no interference from other stations, and assuming the RSSI is still 15dBu when the SNR is up to about 18dB), and 1.5dB above average atmospheric noise?

Also, what difference does various factors, like frequency, ground conductivity, power, etc, make? (Assume the antenna will be the same electrical height in all cases.) Example comparisons would be 540 kHz vs. 1600 (or 1700) kHz frequency, 0.5 mS/m vs 30 & 5,000 mS/m ground conductivity, 250W vs 50kW transmitter power. For the comparisons, what would be the difference in distance for the same field strength, or difference in field strength at the same distance? As an example, I'm guessing that if you take 1kW on 1000kHz and the 1mV/m goes 50 miles, then if you have 10kW the 1mV/m would go 100 miles... but what would the contour at 50 miles be with 10kW?
Or another way to put the question of how much difference do the various factors work.... How much do you have to change ground conductivity, frequency, or transmitter power to A - double (or half) the distance to a particular field strength contour, or B - double (or increase 10x) the field strength at a particular distance?

Also, how do you make those calculations? I haven't had much luck on the FCC's website, and using my browser's "view source" function on their Figure 8 calculator page comes up empty.

 

[rfry]

Ok, R. Fry, now you've got me curious...What would a best-case and worst-case scenario be like for coverage contours? ... Also, how do you make those calculations?

Estimates of this can be made using the FCC charts of groundwave field vs. distance that may be downloaded at http://www.fcc.gov/mb/audio/73184.html .

These FCC charts are normalized for an inverse distance field (IDF) of 100 mV/m at 1 km. To use them for other values of IDF, first find the value of the field shown on the chart for the given frequency, path length and conductivity, then multiply it by the quotient of the new IDF/100.

Example problem: What is the groundwave field at 100 km over a path of 8 mS/m conductivity when 1 kW on 740 kHz is radiated by a single, 90-degree monopole using an r-f ground consisting of 120 each, 1/4-wave buried radials?

Solution: First, find the IDF at 1 km for that transmit system configuration using the calculator at http://www.fcc.gov/mb/audio/bickel/figure8.html . In this case the IDF is about 306 mV/m.

Next, find the field value corresponding to the distance and conductivity shown on the appropriate FCC chart - which in this case is about 0.2 mV/m.

Multiplying 0.2 mV/m by 306/100 yields ~0.6 mV/m. Answer

The commercial software available to make these calculations is quite expensive. But you can answer many of your own questions at no cost by using the techniques given above.

RF

 

[w9wi]

If a FM or TV was atop a 2000-foot tower on Mt McKinley's summit with 100kW for the FM or 5 MW for the UHF TV (don't remember the VHF TV limit but I think it's between those figures), how far might their coverage radius go? Is a 200 plus mile radius possible without having to rely on tropo or e-skip? I can often hear a couple Santa Barbara FM stations here in El Cajon near San Diego, about 200 miles away.

5MW for UHF TV was the old analog limit. It's 1MW for digital. Low VHF was 100kw (now 45) and high VHF was 316kw (now 160).

My best guess is that a 2,000-foot tower atop Mt. McKinley would be 3,824m HAAT. That greatly exceeds the 1600m figure that's all the higher the FCC's propagation curves go.

At 1,600m, a 100kw FM would have an interference-protected coverage contour of just shy of 116km. (around 75 miles) Within the existing rules, the height limit for a 100kw FM would be 600m, which would yield a protected coverage contour of 92km, around 55 miles. I tried to interpolate the curves for a HAAT of about 3,800m, and I get a protected contour of roughly 140km, about 85 miles or so.

The California coast is well known for tropospheric refraction. Santa Barbara<=>San Diego is due to local meteorological characteristics that don't exist in Alaska. (or much of anywhere else)

I agree Alaska should get a power increase.

I suspect few if any stations would want it!

- Electricity is pretty expensive up there (as is transport of equipment), I would think it would be VERY expensive to operate a high-powered station in Alaska.

- You can already serve Anchorage and suburbs just fine with the existing power levels. Increasing power would add just about nobody to your coverage area. (and thus, just about nothing to your revenues)

 

[LibertyNT]

wow it would only take 200,000 watts to Cover Alaska.
If We Had The Mexican Rules we could do it! (or most of the World Rules of Radio)

 

[pianoplayer88key]

Really? Only 200kW? I don't think so.
A few posts up, R. Fry said that on 700 kHz, with a 195° radiator and 2 ohms RF ground loss (what type of ground plane would that be, R. Fry?) and a conductivity of 8.0mS/m, the 1mV/m contour would be about 245 miles away. As far as I know, the conductivity over much of Alaska is considerably worse than that. Sure, 1mV/m would probably be a good enough signal in a rural area like Alaska to be fairly comfortable to listen to... but I'm wondering what it would take to cover the ENTIRE state with a groundwave signal. A 245 mile radius may cover a portion of the interior of Alaska, but the entire state (Attu Island on the far west Aleuitan Islands, near Nome for the farthest west mainland portion, Barrow for the farthest north, and the southeast tip of the panhandle) is MUCH larger than that!
Assuming a ground conductivity of 2.0mS/m (I'm taking what I guess to be an average), frequency of 540kHz, and an antenna consisting of a center-fed full-wave dipole (two stacked half-wave elements) (similar to what KFBK Sacramento uses)... how much power would it take to get a 0.75mV/m (assuming that would still be a fairly comfortable (20-30dB SNR) signal to listen to in a rural area on most portable radios) groundwave signal over the ENTIRE state? I'm thinking the transmitter would probably be located somewhere in or near the southern part of Denali Park.

Also, another ? for R. Fry. How does a 180° radiator over 120 evenly-spaced half-wave buried ground radials compare/contrast with two stacked 180° elements (total length 360°), center-fed, without a ground radial system? (An example of the stacked elements would be KFBK's Franklin antenna system.) Is the radiation pattern, efficiency, etc. similar or much different? Also how much different is the cost of building such an antenna system, taking into account the cost of the ground radials and the land (and labor) to put it up, and/or the cost of the 360° tall tower?
Also is it possible to build a self-supporting Franklin antenna? (One reason I could see for doing this is when land is at a premium and you don't have room for ground radials or guy wires, and want the most efficient antenna system possible.)

Also... I know the FCC doesn't use longwave for broadcasting in the USA, like other places do... but I wonder if longwave, due to the much slower groundwave attenuation, may be possible in Alaska? For example, if you erect a Franklin antenna on 153kHz and put it near the center of Alaska, what would it take to cover the entire state? As for FM/TV... if you erected such an antenna (center-fed stacked 180° radials (total 360°) for 153kHz) on the summit of Mt McKinley, then put FM and TV antennas up top... how far would their signals go until they become unusable, assuming they use the current maximum legal power?