New NPR power calculator available (unofficially)

[bigtom101]

I think you have to look further into it in terms of cost to implement changes. Would the existing HD equipment be able to do this or would a station have to replace everything or at least some components of their existing HD chain. If it costs anything it's not likely to happen. Also, what about all those millions (just kidding Bob) of HD receivers already out in the field? Since none of them are to my knowledge field upgradeable, are they obsoleted?

From what I understand, it is all done in the exciters software. So no need to replace any equipment to adjust the sidebands aside from upgrading the firmware. As far as the radio's go, they are compatible with asymmetrical sideband reception.

 

[Savage]

Ummm.....bigtom, there's a LITTLE more to increasing digital injection than just tweaking the exciter. It's a complex issue with variables including TX headroom, antenna and transmission line rating, and whether the station uses low-level or high-level combining in the case of a common antenna. Depends on the site and the installation.

Actually, the data shows that most FMs operating HD will need to either replace their transmitters, or possibly reject loads in the case of passive combining. There will be enormous additional power demand. And a need for more HVAC. One FM I know of, stopped running HD partly because it had TRIPLED their utility bill (and no listeners was another big reason. When the digital went off they got zero complaints.)

If antennas need replacement, the towers may need additional guying to accomodate the heavier antenna and Tx line.

In the case of tightly packed rooftop antenna farms on office buildings, there may not be any room for bigger transmitters or additional transmitters. That means, since digital and analog transmitters must be colocated, you'd be looking at a whole new site.

"Upgrading the firmware?" Absolutely not. Read RW this week. The consensus is that -14 dBc, -10 dBc, it won't matter much because few stations will make the capital expenditure to upgrade.

 

[bigtom101]

Ummm.....bigtom, there's a LITTLE more to increasing digital injection than just tweaking the exciter. It's a complex issue with variables including TX headroom, antenna and transmission line rating, and whether the station uses low-level or high-level combining in the case of a common antenna. Depends on the site and the installation.

Actually, the data shows that most FMs operating HD will need to either replace their transmitters, or possibly reject loads in the case of passive combining. There will be enormous additional power demand. And a need for more HVAC. One FM I know of, stopped running HD partly because it had TRIPLED their utility bill (and no listeners was another big reason. When the digital went off they got zero complaints.)

If antennas need replacement, the towers may need additional guying to accomodate the heavier antenna and Tx line.

In the case of tightly packed rooftop antenna farms on office buildings, there may not be any room for bigger transmitters or additional transmitters. That means, since digital and analog transmitters must be colocated, you'd be looking at a whole new site.

"Upgrading the firmware?" Absolutely not. Read RW this week. The consensus is that -14 dBc, -10 dBc, it won't matter much because few stations will make the capital expenditure to upgrade.

I know that you will need new gear and possibly a new antenna for the power increase. I thought he was talking about adjusting the sideband power levels individually - a gentlemen from Nautel was talking about that on a podcast I listen to and he mentioned iBiquity was working on a new firmware release.

I may have been born at night, but not last night Bob! LOL

 

[Savage]

I read radeo's post in the form of your quote and didn't get the context of his comments. If indeed he was talking about asymmetrical sidebands and not overall site upgrades, you are correct and I beg your pardon. Sorry, didn't mean to get pedantic.

 

[Carmine5]

So will full HD reception will be possible while mobile? That's great news if so. Up to now all I've read is that mobile ATSC would have to use a portion of the main stream (thus reducing the bits available) and that only less than SD quality would be available for mobile devices, even if it's replicating the main program in the HD stream.

I haven't read the ATSC M/H spec but do you know if it just adds "intelligent" stream data to make almost the full 19.38Mbps recievable while mobile so it doesn't have to replicate streams. If the European type DTV system was adopted the need for a mobile standard would not have been necessary, right?

Also I believe IBOC on FM does use forward error correction "The channel encoding counteracts the normal RF transmission imperfections, which can include fading, interference and atmospheric noise. Forward error correction (FEC) adds correction bits to the pretransmitted signal with bit redundancy being used to improve system resistance to errors." http://radiomagonline.com/digital_radio/eye_iboc/radio_iboc_fm_waveform/

The key application of Mobile DTV, of course, is cellphones and similar portable devices and so the default size is 416x240. It also uses MPEG4 instead of MPEG2 and is IP encapsulated and so requires a separate transport stream (although it is interwoven into the main channel DTV stream as MPEG2 packets). It does include an electronic program guide and other data. Plus H.264 is a pretty flexible codec so who knows what level of quality can be achieved with Mobile DTV in the future.

I assumed HD Radio has some form of error correction scheme. But if the 2nd band is just a duplication of information as a safety why not get rid of it, beef up the error correction on one band and reduce the overall size of the signal?

c5

 

[RadeoEngineer]

I read radeo's post in the form of your quote and didn't get the context of his comments. If indeed he was talking about asymmetrical sidebands and not overall site upgrades, you are correct and I beg your pardon. Sorry, didn't mean to get pedantic.

I should have quoted the post to which I was responding. I was referring to asymmetrical side bands. There's no question site upgrades will be required (and expensive) for increased digital power. I fortunately don't know enough about it (having never been saddled with an HD) to have an understanding of the asymmetrical side band question.

 

[Len14043]

Thanks for posting the link. The important number to keep in mind is the "D/U Ratio" in the second to last column in the second box. This represents digital-to-analog interference to each adjacent channel neighbor from the upper or lower IBOC sideband of the station under study. In reality, this is co-channel interference and cannot be eliminated through improvements in receiver selectivity.

For many years, FCC allocation standards have been based on a 20 dB co-channel D/U ratio, so a value less than 20 should be considered problematic. And if that number is low enough to be negative, expect a disaster.

For some examples of severe interference, here are several stations in the Northeast:

WKTU (which transmits from the Empire State Building); look at the effect on WPRB and WNNJ. There's plenty of population in those interference zones.

WDAS, Philadelphia vs WIOV

WUSL, Philadelphia vs WAWZ

But for that matter, WAWZ vs WUSL. (Hope they both remember Luke 6:31)

WENJ vs WPEN-FM

WAEB-FM vs WPPZ

WJFK (near Washington) vs WWMX and WWEG. Ugly!

Of course, grandfathered stations will also cause a lot of trouble. Check WTSS, Buffalo vs WLGZ, WVOR, and WNAE-FM.

Or, WNTQ, Syracuse vs WCIZ in Watertown. I also wonder about the impact on Canadian stations which apparently aren't taken into account here.

After studying some contour maps and looking at January 29, 2010 FCC order concerning their methodology in determining the allowable digital power of the IBOC candidate station, I realized that the D/U ratio is the analog-to-analog ratio between the candidate and first adjacent stations, and not the digital-to-analog interference as you indicated. The D/U ratio for the digital-to-analog, i.e. co-channel interference equals the D/U ratio in the NPR calculator minus the allowable digital power. That means the digital power of the candidate station is at least 20 db below the 60 db analog contour of the adjacent station in most cases. The analog power of WJFK, probably the worst case scenario, is 70.9 db at the 60 db analog contour of their lower first adjacent WWMX, and 74.7 db at the upper first adjacent WWEG. The NPR calculator allows both digital sidebands of WJFK -14db below their analog power. This means the lower digital sideband of WJFK would be 56.9 db at the 60 db analog contour of WWMX, and 60.7 db at the 60 db analog contour of WWEG. Admittedly, the examples you cite in the Northeast are still problematic, but the digital interference at the 60 db contour of adjacent stations will be minimal to non-existent in most cases. See the excerpt from the FCC order below (red font), and you will see that it is identical to the latest NPR calculator. Please correct me if I am wrong.

A licensee desiring FM Digital ERP in excess of -14 dBc is required to calculate the station’s analog F(50,10) field strength at all points on the protected 60 dBu F(50,50) contour of a potentially affected first-adjacent channel analog FM station. This calculation must be done using the station’s licensed analog facilities and the standard FCC contour prediction methodology. Once the most restrictive analog F(50,10) field strength of the proponent station has been determined, the licensee will use the following table to determine the proponent station’s maximum permissible FM Digital ERP:

Proponent Analog F(50,10) Field Strength at Protected Analog 60 dBu F(50,50) Contour Maximum Permissible FM Digital ERP
51.2 dBµ and above -14 dBc
50.7 dBµ - 51.1 dBµ -13 dBc
50.3 dBµ - 50.6 dBµ -12 dBc
49.6 dBµ - 50.2 dBµ -11 dBc
49.5 dBµ or less -10 dBc

The maximum permissible FM Digital ERP levels shown in this chart were calculated using the procedure in Appendix J of the AICCS Project Study and the formula set forth therein. In situations in which the simplified method above is not applicable due to unusual terrain, environmental or technical considerations, or when it produces anomalous FM Digital ERP results, the Bureau will accept applications for FM Digital ERP in excess of -14 dBc. These applications must include a detailed showing containing a complete explanation of the prediction methodology used as well as data, maps and sample calculations. The Bureau will evaluate these applications on a case-by-case basis.

 

[Play Freebird]

The analog power of WJFK, probably the worst case scenario, is 70.9 db at the 60 db analog contour of their lower first adjacent WWMX, and 74.7 db at the upper first adjacent WWEG. The NPR calculator allows both digital sidebands of WJFK -14db below their analog power. This means the lower digital sideband of WJFK would be 56.9 db at the 60 db analog contour of WWMX, and 60.7 db at the 60 db analog contour of WWEG.

So it's quite clear that both WWMX and WWEG (which are both Class B stations) will be subject to a 6 dB increase in digital interference from WJFK well within their protected 54 dBu contours. What's in it for them?

 

[Len14043]

So it's quite clear that both WWMX and WWEG (which are both Class B stations) will be subject to a 6 dB increase in digital interference from WJFK well within their protected 54 dBu contours. What's in it for them?

Initially, WWMX and WWEG will suffer a 6 dB increase in digital interference from WJFK. But those 2 stations will be ideal candidates for filing a complaint with the FCC. If they can prove interference exists within their protected contour, WJFK will be forced to lower their digital power in 3 db increments, i.e. to -17 db and -20 db if necessary. It should be noted that those 3 stations already receive substantial analog interference well within their protected contours.

 

[Play Freebird]

Initially, WWMX and WWEG will suffer a 6 dB increase in digital interference from WJFK. But those 2 stations will be ideal candidates for filing a complaint with the FCC. If they can prove interference exists within their protected contour, WJFK will be forced to lower their digital power in 3 db increments, i.e. to -17 db and -20 db if necessary. It should be noted that those 3 stations already receive substantial analog interference well within their protected contours.

I see WWMX (like WJFK) is a CBS property, so I expect they'll go right ahead and inflict damage upon themselves, as they've done with WBZ and KDKA.

However, WWEG doesn't operate an HD transmitter and probably has no immediate plans to do so. The people in charge over there should keep a close ear on this problem (especially along the I-270 corridor), try to document it with audio recordings, spectrum analyzer shots, etc., and prepare for a costly legal battle.

Although these short-spaced stations have large areas of predicted first-adjacent interference (based on a D/U ratio of 6 dB), keep in mind that modern receivers are much more selective than they were in mid-'40s when adjacent-channel protections were established by the FCC. Receiver designers have been steadily improving performance in this area for decades - for example, the Sony XDR-F1HD tuner has an astounding first-adjacent selectivity figure of over 80 dB, and the typical car radio with ceramic filters is better than 20-30 dB. So even though the contour overlap looks pretty bad on paper, many people have been able to receive an acceptable signal, which is what really matters.

The big problem with first-adjacent digital-to-analog interference is that it's actually co-channel, so improved receiver filtering offers no solution. In order to discriminate between the desired and undesired signals, a listener would need a directional receive antenna, but obviously this isn't practical to install on a vehicle.

 

[Len14043]

Assuming FM IBOC gains traction, WJFK will never be a good candidate for the system. Even if they run at -14db and are not forced to reduce their digital power down to -20 due to complaints from WWMX and WWEG, -14 db will be ineffective due to the analog co-channel interference from those stations. As I stated before, FM IBOC will work great for the large majority of the FM stations at -10 db. If WJFK and a handful of other stations want to run IBOC, perhaps they could apply for a frequency change, if that is possible in their location. Question: Does the situation with WJFK comply with FCC rules for spacing, or did they accept the allocation with the understanding they will have to accept interference?

 

[Play Freebird]

Assuming FM IBOC gains traction, WJFK will never be a good candidate for the system. Even if they run at -14db and are not forced to reduce their digital power down to -20 due to complaints from WWMX and WWEG, -14 db will be ineffective due to the analog co-channel interference from those stations. As I stated before, FM IBOC will work great for the large majority of the FM stations at -10 db. If WJFK and a handful of other stations want to run IBOC, perhaps they could apply for a frequency change, if that is possible in their location. Question: Does the situation with WJFK comply with FCC rules for spacing, or did they accept the allocation with the understanding they will have to accept interference?

The reason so many FM stations along the Northeast Corridor are short-spaced has to do with changes in FCC allocation policies over the years.

Until the early '60s, Class B stations between Washington and Boston were limited to 20 kW at 500 ft HAAT, protected to the 60 dBu contour, and could be dropped in fairly easily. Standards were rather flexible because the FCC wanted to encourage the growth of FM. Then, around 1964, the 73.207 table of distance separations was adopted, the Class B power limit was increased to 50 kW, and protection of new stations was increased to a radius of 40 miles, which corresponds roughly to 54 dB. However, existing licensees were also allowed to negotiate mutual agreements with their neighbors for facility increases up to 50 kW, which led to the short-spacing situation we have today.

Note that the new IBOC rule no longer protects Class B stations to 54 dBu. All stations, regardless of class, will receive protection to the 60 dBu based on an assumption of uniform terrain. This is a radical departure from the attitude the FCC (and NAB) held just ten years ago.

 

[Len14043]

Freebird, the 60 dBu contour will be used to simplify the process for determining maximum digital power. But if a station files a complaint alleging interference, the remediation procedures will take the actual protected contours into account. See paragraph 18 of the FCC order below:


18. The Agreement specifies that FM station eligibility for digital ERP increases beyond 6 dB is based upon protection of an analog station’s 60 dBµ contour. We recognize that the Commission’s Rules specify different protected contours for Class A, C3, C2, C1, C0 and C FM stations (60 dBµ) than for Class B1 FM stations (57 dBµ) and Class B FM stations (54 dBµ) in the non-reserved band. However, for the limited purpose of determining maximum permissible FM Digital ERP greater than -14 dBc, we will base all predictions of maximum permissible FM Digital ERP on calculations at the potentially affected analog FM station’s 60 dBµ contour. However, the mitigation and remediation procedures set forth below will apply to all instances of alleged interference within the protected service contours of potentially affected stations.

 

[Savage]

Sooper Doopir. And the "remediation procedures" set forth are almost word-for-word lifted from the earlier R&O involving IBOC AM. Remediation procedures which, despite scores of credible complaints, have NEVER been employed, frequently, occasionally or even once.

I've got a steak dinner here for the first verifiable case where the FCC actually enforces remediation against an interfering HD-FM station. (This does NOT include "negotiated" resolutions.)

 

[samb15]

Once again, we have another STUPID decision that ignores reality. As it is, FM stations are overprotected for 2nd and 3rd adjacent channels and underprotected for co-channels and first adjacents.

In the real world, many listeners and stations have enjoyed "local" radio beyond these contours, only to have it taken away by band crowding. Now it gets worse, many of the strong local Class B FM's we enjoy will become unlistenable in the car as they battle with HD-data from distant stations.

Broadcasters should try to be VERY aggressive in making interference complaints for anyplace in their protected contours. Only with a flood of cases will the FCC slam the brakes on this improperly devised set of rules.

As for previously-mentioned WJFK-FM they should just sign off, fold up their tower and go home if this is adopted. As it is they cover only about half of the market because of fist-adjacent interference on both sides.

 

[Len14043]

Once again, we have another STUPID decision that ignores reality. As it is, FM stations are overprotected for 2nd and 3rd adjacent channels and underprotected for co-channels and first adjacents.

Broadcasters should try to be VERY aggressive in making interference complaints for anyplace in their protected contours. Only with a flood of cases will the FCC slam the brakes on this improperly devised set of rules.

As for previously-mentioned WJFK-FM they should just sign off, fold up their tower and go home if this is adopted. As it is they cover only about half of the market because of fist-adjacent interference on both sides.

I agree broadcasters should be aggressive in making interference complaints within their protected contours, only if the areas which contain digital interference are already not plagued with analog interference. If the case of WJFK, if they allege digital interference within their protected contour, in the same geographical area where analog interference already occurs, the complaint should be summarily dismissed. The interference mediation procedures should not accord a station addition protections which it currently doesn't enjoy.

 

[audioguy]

The interference mediation procedures should not accord a station addition protections which it currently doesn't enjoy.

Like that would ever happen! As others have pointed out, the FCC has shown little interest in acting on ANY interference complaints to date. I would not expect this policy to change on a going forward basis.