FCC/HD question(s)

[cd637299]

I hope I am wording this right....I am not a techie....

Whenever there are declarations of an FM radio station for FCC purposes, like coverage area, contour, pattern, range (output), etc., does the FCC take into account HD, or the possibility of adding HD for the station, thereby adding QRM to the adjacent frequencies? or can a station just all-out *add* HD without asking the FCC?

Are/were there not a few cases where the FCC told a station that they were *not* allowed to run HD for fear of interference to existing stations on adjacent frequencies (or, heck, even co-channel)?

I just wonder how often that existing stations have logged a complaint when another station turns on the HD juice.

There are very good HD stations, and I am not against some of them; this is basically a DX question for me.

Apologies if these questions have been brought up already....just curious.

cd

 

[JohnnyElectron]

IIRC, all you have to do is tell the FCC that you have "digital' and they mark a box and list it with your license status - period.

 

[Ai4i]

Your HD ERP between 1% and 10% depends on the proximaty of first adjacencies. For example, I would guess that DC stations with first adjacencies in Baltimore and visa versa would be stuck well below 10%.
Also, a grandfathered station can only run the greater of 1% or 10% of what their contour would be if licensed today. Think AM's are all 1% max.
BTW...in the pure digital mode, the total bandwidth can be reduced to much less than what it is in the hybrid mode for both AM and FM stations.

I wonder if FM stations were digital only (an oxymoron) and ran 100% power within their traditional bandwidth, would people on these boards still have issues with it.

 

[diymedia]

BTW...in the pure digital mode, the total bandwidth can be reduced to much less than what it is in the hybrid mode for both AM and FM stations.

I wonder if FM stations were digital only (an oxymoron) and ran 100% power within their traditional bandwidth, would people on these boards still have issues with it.

True for AM, not for FM. all-digital AM-HD's spectral footprint drops from 30 kHz to 20 kHz, but the all-digital FM-HD spectral footprint remains the same. iBiquity lays it all out on a white paper you can get off their site.

 

[DaveBayArea]

Your HD ERP between 1% and 10% depends on the proximaty of first adjacencies. For example, I would guess that DC stations with first adjacencies in Baltimore and visa versa would be stuck well below 10%.

Any station can go to -14 dbc (6%) with just a notification. An increase to -10 dbc (10%) requires an STA, and you must provide a showing to the FCC that there will be no interference.

BTW...in the pure digital mode, the total bandwidth can be reduced to much less than what it is in the hybrid mode for both AM and FM stations. I wonder if FM stations were digital only (an oxymoron) and ran 100% power within their traditional bandwidth, would people on these boards still have issues with it.

If only that were really true. Unfortunately the "pure digital" mode uses twice the occupied bandwidth of analog. Check out page 7 of the NRSC standards document for HD Radio transmissions:

http://www.nrscstandards.org/SG/NRSC-5-B/1026sE.pdf

There are now efforts toward "spectrum repacking" on the television bands since the digital TV transition. If there is no redesign of the Ibiquity system to narrow the occupied bandwidth, HD will not work in digital-only mode with the present allocations. In addition, radio receivers have become much better since the present allocation rules were written, so 400 KHz channel spacing is totally possible in a single market. The problem is that there is no real incentive for the FCC to act on this, because - unlike TV - there is no possibility to auction off new spectrum.

The interference problem is very real, and realistically there is not much that operators can do about it except try to work with the offending stations.

Dave B.

 

[iyiyi]

If only that were really true. Unfortunately the "pure digital" mode uses twice the occupied bandwidth of analog. Check out page 7 of the NRSC standards document for HD Radio transmissions:

http://www.nrscstandards.org/SG/NRSC-5-B/1026sE.pdf

I made the same mistake. I downloaded NRSC-5-B and all the normative references described therein. After using the better portion of a black ink cartridge and a ream of paper... I discovered that NRSC-5-C was the version that should have been downloaded and followed. Big deal I thought as I tried to reference the normatives from NRSC-5-B (April 2008) to the NRSC-5-C (September, 2011) Broadcasting Standard.

Come to find out that normative 1026s rev.E was published 1/30/08. The correct normative referenced in NRSC-5-C is 1026s rev. F published 8/24/11. Many other normatives described in NRSC-5-C have also been revised and updated.

I managed to pull this Einsteinian stunt several months ago all by myself!

Therefore I advise anyone desiring to download and print these files to ensure they have the latest version of the NRSC-5-x standard first!

-

 

[DaveBayArea]

I made the same mistake. I downloaded NRSC-5-B and all the normative references described therein. After using the better portion of a black ink cartridge and a ream of paper... I discovered that NRSC-5-C was the version that should have been downloaded and followed. Big deal I thought as I tried to reference the normatives from NRSC-5-B (April 2008) to the NRSC-5-C (September, 2011) Broadcasting Standard.

Come to find out that normative 1026s rev.E was published 1/30/08. The correct normative referenced in NRSC-5-C is 1026s rev. F published 8/24/11. Many other normatives described in NRSC-5-C have also been revised and updated.

Wow. Thank you. This spec includes many things that I was wondering about - like the expansion of audio bandwidth on AM and a spec for extended hybrid mode. I'll save the legwork for anyone else and let you know that the link to the new spec is here:

http://apps.fcc.gov/ecfs/document/view;jsessionid=f32yPclFQQZw0LG3LCrLFcsJJKJQnXmpqPdvG5b0ncHlMSzjVnvV!1471562840!-321460796?id=7021898832

Unfortunately, they did not fix the occupied bandwidth problem for full digital mode in this spec either. That might not be possible without replacing all of the existing receivers, but I'm not sure. So the answer to the Original Post is that full digital on FM does not reduce interference. I don't quite know how this would work - with the majority of the RF energy being off-channel (see figure 21 on page 34 of that document). Bottom line is that the occupied bandwidth of the all-digital signal is still 400 KHz instead of 200 KHz (for analog). I suspect the present allocations would work fine in places like North Dakota. But for most populated areas an all-digital transition would mean something similar to the changes to AM radio that were made in 1941 with NARBA.

On a side note, this spec also indicates that there can be an asymmetrical sideband difference of 10 db. However our transmitter manufacturer claims that Ibiquity only allows a 4 db difference in hybrid mode. I need to pursue this further.

Thanks again, iyiyi, for providing the update.

Dave B.

 

[iyiyi]

Unfortunately, they did not fix the occupied bandwidth problem for full digital mode in this spec either. That might not be possible without replacing all of the existing receivers, but I'm not sure. So the answer to the Original Post is that full digital on FM does not reduce interference. I don't quite know how this would work - with the majority of the RF energy being off-channel (see figure 21 on page 34 of that document). Bottom line is that the occupied bandwidth of the all-digital signal is still 400 KHz instead of 200 KHz (for analog). I suspect the present allocations would work fine in places like North Dakota. But for most populated areas an all-digital transition would mean something similar to the changes to AM radio that were made in 1941 with NARBA.

On a side note, this spec also indicates that there can be an asymmetrical sideband difference of 10 db. However our transmitter manufacturer claims that Ibiquity only allows a 4 db difference in hybrid mode. I need to pursue this further.

Dave B.

They didn't address the occupied bandwidth problem because there is no problem! If iBiquity decided to reduce the digital channel from 400 to 200 kHz there would be no reason to replace any existing receivers. Both MW and VHF signals get converted to 10.7 mHz and are demodulated in the same I/Q detector. DSP algorithms are optimized for the characteristics of each band. A 50kW erp analog (radiotelephone) FM that decided to run pure digital (radiotelegraph) only at -10dBc would have a 5kW QAM constellation spanning a 400kHz spectrum. A cheap analog FM radio has a capture ratio of 3dB. This means that any interfering signal less than 50% power of the analog will be rejected as noise. Present allocations work fine with no need for NARBA type changes OR moving to North Dakota. Digital broadcasting produces clean signals. TV's 8VSB (which completely sucks in comparison to HD's ISB) has channels 29,30,31 and 32 in Boston and Providence has channel 12 and 13's antennas about 1 meter apart on the same tower. I am 15 miles from a mono, analog, class A 102.7 and 50 miles from a full class B HD hybrid on 102.5. This gives me 2 HD and 1 analog channels of yippie-kai-yay cowboy music on the 102.5 PLUS 1 channel of snooze (NPR) on 102.7 -- with no mutual interference between the two stations. Lucky me! For seconds (adjacents that is) there is an HD 94.1 10 miles and a 93.7 HD and 94.5 HD 50+ miles away on the same azimuth. Also an HD 103.7 less than 10 miles on my left and a 103.3 HD and a 104.1 HD 50+ miles straight ahead. All of them with no HD reception problems (factor in the standard distance issues).

Should your transmitter manufacturer and or ibiquity believe any sideband adjustment is needed, PLEASE let THEM perform any measurements and adjustments. You don't know me or owe me, but please believe me when I tell you that the best day of your life was the one BEFORE you started "tweaking" those sidebands!

-

 

[JohnnyElectron]

I can receive 1st adacents on the FM band IF and only IF I have a new HD radio with it's hyper selectivity, or an $1800 Fanfare FTA-100 tuner.
Otherwise, no 103.7 AND 103.9, even on a good day.
Likewise, there is some built-in "HD magic filter" on HD-AM that magically filters out the HD hash on 2nd adjacents on the AM band, where a regular analog tuner has the unbearable noise on AM (ie: 560 HD smotes 580 analog locally). Of course the analog audio bandwidth on the HD-AM tuner is crap, not AMAX quality to be certain.

 

[diymedia]

Should your transmitter manufacturer and or ibiquity believe any sideband adjustment is needed, PLEASE let THEM perform any measurements and adjustments. You don't know me or owe me, but please believe me when I tell you that the best day of your life was the one BEFORE you started "tweaking" those sidebands!

I hope they're getting it right now...especially since it took the NRSC till 2010 to approve an FM testing methodology that would finally "make sure stations are all measuring the performance of their IBOC systems in the same way."

 

[Darth_vader]

"Likewise, there is some built-in "magic Ibiquity filter" on MW that magically cuts the Ibiquity hash on 2nd adjacents on the MW band, where a regular analog tuner has the unbearable noise on MW (ie: 560 in Ibiquity smokes 580 in AM locally)."

This "magic Ibiquity filter" thing is also known as a "digital signal processor", and it also does an excellent job of cutting all the wideband electrical/electronic noise pollution on MW around here. That's part of the reason why they're such good DX rigs. You get to a point eventually where audio bandwidth becomes irrelevant and it comes down to just making the stations *listenable*.

 

[DaveBayArea]

They didn't address the occupied bandwidth problem because there is no problem! If iBiquity decided to reduce the digital channel from 400 to 200 kHz there would be no reason to replace any existing receivers. Both MW and VHF signals get converted to 10.7 mHz and are demodulated in the same I/Q detector. DSP algorithms are optimized for the characteristics of each band. A 50kW erp analog (radiotelephone) FM that decided to run pure digital (radiotelegraph) only at -10dBc would have a 5kW QAM constellation spanning a 400kHz spectrum. A cheap analog FM radio has a capture ratio of 3dB. This means that any interfering signal less than 50% power of the analog will be rejected as noise.

I would invite you to visit the mountains of Northern California, where our HD signal - even at -14dbc - doesn't make it six miles from our class B-1 transmitter. We're on 89.5 and instead you get analog 89.3 and 89.7 clear as a bell in some spots, then move 5 feet and you get nothing but HD noise. Nulls in mountainous terrain can be 20 db or more, so a capture ratio of 3 db is meaningless.

Present allocations work fine with no need for NARBA type changes OR moving to North Dakota. Digital broadcasting produces clean signals. TV's 8VSB (which completely sucks in comparison to HD's ISB) has channels 29,30,31 and 32 in Boston and Providence has channel 12 and 13's antennas about 1 meter apart on the same tower.

Thanks for proving my point. A re-allocation of the FM band would allow 400 KHz spacing in the same market, as there is 6 MHz spacing in the same market on television (see my earlier post). 6 MHz is the occupied bandwidth of TV and 400 KHz is the occupied bandwidth of an HD signal.

I am 15 miles from a mono, analog, class A 102.7 and 50 miles from a full class B HD hybrid on 102.5. This gives me 2 HD and 1 analog channels of yippie-kai-yay cowboy music on the 102.5 PLUS 1 channel of snooze (NPR) on 102.7 -- with no mutual interference between the two stations. Lucky me! For seconds (adjacents that is) there is an HD 94.1 10 miles and a 93.7 HD and 94.5 HD 50+ miles away on the same azimuth. Also an HD 103.7 less than 10 miles on my left and a 103.3 HD and a 104.1 HD 50+ miles straight ahead. All of them with no HD reception problems (factor in the standard distance issues).

You don't mention whether the class B hybrid is running -20 or -14 dbc, but it's obvious that you're not receiving the upper HD sideband of 102.5 if you're receiving analog on 102.7. If there was a 102.3 in your area I suspect you would not receive HD from 102.7. That is the case here, only it is complicated because both 89.3 and 89.5 are running HD at -14 dbc. I would invite you to listen to actual radio reception under HD interference conditions. Here is an example of 89.3 interfering with 89.5:

http://www.youtube.com/watch?v=yLTWihy5zvc

Not to be outdone, here's an example of 89.5 interfering with 89.3 (complete with an EAS test):

http://www.youtube.com/watch?v=I8LSIPe2ZnA

As you can see, HD Radio has compromised the reception of these two stations for about 1/2 million potential listeners.

Should your transmitter manufacturer and or ibiquity believe any sideband adjustment is needed, PLEASE let THEM perform any measurements and adjustments. You don't know me or owe me, but please believe me when I tell you that the best day of your life was the one BEFORE you started "tweaking" those sidebands!

Wouldn't consider it.

Dave B.

 

[iyiyi]

They didn't address the occupied bandwidth problem because there is no problem! If iBiquity decided to reduce the digital channel from 400 to 200 kHz there would be no reason to replace any existing receivers. Both MW and VHF signals get converted to 10.7 mHz and are demodulated in the same I/Q detector. DSP algorithms are optimized for the characteristics of each band. A 50kW erp analog (radiotelephone) FM that decided to run pure digital (radiotelegraph) only at -10dBc would have a 5kW QAM constellation spanning a 400kHz spectrum. A cheap analog FM radio has a capture ratio of 3dB. This means that any interfering signal less than 50% power of the analog will be rejected as noise.

I would invite you to visit the mountains of Northern California, where our HD signal - even at -14dbc - doesn't make it six miles from our class B-1 transmitter. We're on 89.5 and instead you get analog 89.3 and 89.7 clear as a bell in some spots, then move 5 feet and you get nothing but HD noise. Nulls in mountainous terrain can be 20 db or more, so a capture ratio of 3 db is meaningless.

Present allocations work fine with no need for NARBA type changes OR moving to North Dakota. Digital broadcasting produces clean signals. TV's 8VSB (which completely sucks in comparison to HD's ISB) has channels 29,30,31 and 32 in Boston and Providence has channel 12 and 13's antennas about 1 meter apart on the same tower.

Thanks for proving my point. A re-allocation of the FM band would allow 400 KHz spacing in the same market, as there is 6 MHz spacing in the same market on television (see my earlier post). 6 MHz is the occupied bandwidth of TV and 400 KHz is the occupied bandwidth of an HD signal.

I am 15 miles from a mono, analog, class A 102.7 and 50 miles from a full class B HD hybrid on 102.5. This gives me 2 HD and 1 analog channels of yippie-kai-yay cowboy music on the 102.5 PLUS 1 channel of snooze (NPR) on 102.7 -- with no mutual interference between the two stations. Lucky me! For seconds (adjacents that is) there is an HD 94.1 10 miles and a 93.7 HD and 94.5 HD 50+ miles away on the same azimuth. Also an HD 103.7 less than 10 miles on my left and a 103.3 HD and a 104.1 HD 50+ miles straight ahead. All of them with no HD reception problems (factor in the standard distance issues).

You don't mention whether the class B hybrid is running -20 or -14 dbc, but it's obvious that you're not receiving the upper HD sideband of 102.5 if you're receiving analog on 102.7. If there was a 102.3 in your area I suspect you would not receive HD from 102.7. That is the case here, only it is complicated because both 89.3 and 89.5 are running HD at -14 dbc. I would invite you to listen to actual radio reception under HD interference conditions. Here is an example of 89.3 interfering with 89.5:

http://www.youtube.com/watch?v=yLTWihy5zvc

Not to be outdone, here's an example of 89.5 interfering with 89.3 (complete with an EAS test):

http://www.youtube.com/watch?v=I8LSIPe2ZnA

As you can see, HD Radio has compromised the reception of these two stations for about 1/2 million potential listeners.

Should your transmitter manufacturer and or ibiquity believe any sideband adjustment is needed, PLEASE let THEM perform any measurements and adjustments. You don't know me or owe me, but please believe me when I tell you that the best day of your life was the one BEFORE you started "tweaking" those sidebands!

Wouldn't consider it.

Dave B.

Just watched your vids. I would like to see the KQEI route replicated with the 89.5 HD switched off for an A-B test. 89.5 is the lion with 89.3 directional and pumping around 1/16 of it's 3.3kw toward 89.5. Vids could be more informative if the drives also featured both the 89.3 and 89.5 signals for comparison on each drive. I believe that the Auburn video featured a drive up 49 from Cool on to I-80 East. Auburn appears to be roughly equidistant between 89.3 and 89.5. Let's give 89.3 a -10dBc HD signal of 330w (because I'm too dumb to figure 4%). 89.3's DA maybe sends 20 watts of IBOC around 25 miles Auburn's way. 89.5 has a 1.75kw signal about 25 miles away and 1/2+ mile higher in altitude than Auburn. The drive up 49 clearly shows that the Laws of Physics have decreed a radio shadow for 89.5 in this area. I suggest that you contact the engineer of 89.3. Each of you drive your own routes of concern for your respective stations and video your findings. At a convenient time for all parties, one station can kill HD while the other engineer drives his routes sans HD QRM and vice versa. Now both stations have a handle on how much HD is actually affecting each other.

As you state in your 1st paragraph, nulls in mountainous terrain can be 20 dB or more. No argument here! I would say that rt 49 south of Auburn is close to that! 89.5 is unable to get a 3 dB leg up on a 20 watt QAM signal 25 miles away. I hazard a guess that if 89.3 killed it's HD, the ride up rt 49 into Auburn would be just as choppy for 89.5. The 5 foot HD kill you describe is the exact dimensions for multipath interference and the 89.3 and 89.7 "clear as a bell" are the points where those signals are 3 dB more than the 89.5 HD signal. The 89.5 HD signal is still there, it is masked by the FM detector.

Local signals are -14 dBc AFAIK. When they were -20 dBc it was madness trying for any HD at all. 89.7 Boston has the best HD and it seems like 103.3, 94.5 and 102.5 are the other out of market stations packing some HD juice. 89.7 is the only signal that you can reliably drive with - even as close as 35 to 40 miles to Boston. WBZ 1030 AM is the out of market station with the best HD signal of AM or FM.

I never thought about 102.7 knocking out 102.5's upper sideband but you are correct! I was wracking my brain trying to find a 1st adjacent signal of sufficient amplitude to test and it was right there grinning at me all this time. Thanks! FWIW, 102.7's strong local signal seems to have no adverse effect on 102.5's out of market HD signal.

I downloaded your station program guide. Wow! Quite the art of radio! You people should be VERY proud!

-

 

[DaveBayArea]

Just watched your vids. I would like to see the KQEI route replicated with the 89.5 HD switched off for an A-B test. 89.5 is the lion with 89.3 directional and pumping around 1/16 of it's 3.3kw toward 89.5. Vids could be more informative if the drives also featured both the 89.3 and 89.5 signals for comparison on each drive. I believe that the Auburn video featured a drive up 49 from Cool on to I-80 East. Auburn appears to be roughly equidistant between 89.3 and 89.5. Let's give 89.3 a -10dBc HD signal of 330w (because I'm too dumb to figure 4%). 89.3's DA maybe sends 20 watts of IBOC around 25 miles Auburn's way. 89.5 has a 1.75kw signal about 25 miles away and 1/2+ mile higher in altitude than Auburn. The drive up 49 clearly shows that the Laws of Physics have decreed a radio shadow for 89.5 in this area. I suggest that you contact the engineer of 89.3. Each of you drive your own routes of concern for your respective stations and video your findings. At a convenient time for all parties, one station can kill HD while the other engineer drives his routes sans HD QRM and vice versa. Now both stations have a handle on how much HD is actually affecting each other.

I have been in contact with them, and we're both stuck between a rock and a hard place. We would like to continue using HD, and it actually works OK for KQEI because their 89.1 sideband has no interference. It works for us too, going East on 80 and 20. Maybe 5 listeners per week in those areas if that, though. When we both were -20 dbc there were only slight interference problems, but of course HD didn't work. Testing in different areas by shutting off and turning on the HD isn't really practical, but there are co-located translators on interference-free channels at each of our transmitter sites we can use for testing, and of course a spectrum analyzer shows the actual signal strength. There is a bit of a shadow in Auburn, but way more of a shadow in the American River Valley and down toward Coloma and Placerville. Yet KVMR booms into those communities, even though the signal is about 15 db less than it is in Auburn.

You bring up something I never thought of, however. I always assumed that KQEI's DA was calibrated and working correctly. That is worth double-checking.

As you state in your 1st paragraph, nulls in mountainous terrain can be 20 dB or more. No argument here! I would say that rt 49 south of Auburn is close to that! 89.5 is unable to get a 3 dB leg up on a 20 watt QAM signal 25 miles away. I hazard a guess that if 89.3 killed it's HD, the ride up rt 49 into Auburn would be just as choppy for 89.5. The 5 foot HD kill you describe is the exact dimensions for multipath interference and the 89.3 and 89.7 "clear as a bell" are the points where those signals are 3 dB more than the 89.5 HD signal. The 89.5 HD signal is still there, it is masked by the FM detector.

You're absolutely correct. It's a manifestation of what I was saying earlier - that an FM station's occupied bandwidth with HD must now be considered to be 400 KHz. If the other two stations were on 89.1 and 89.9 there would be no issue with either our HD propagation or reception of any of the stations. The Longley-Rice maps provide a further insight. I posted KMVR's and KQEI's here:

http://davencin.members.sonic.net/FCCStuff/KVMR_Real_Coverage.JPG
http://davencin.members.sonic.net/FCCStuff/KQEI_Real_Coverage.JPG

As you can see, KQEI is way stronger than KVMR in Auburn, even though Auburn is within KVMR's "FCC Protected Contour". It is also the largest city in our market and a big source of revenue. Needless to say, this is a big problem. Ironically, the 105.7 translator (240 watts from the same site) has a clean signal throughout Auburn, where KVMR is very spotty due to the interference. We have quite a bit of support from Sacramento, but the signal isn't that clean down there either.

Local signals are -14 dBc AFAIK. When they were -20 dBc it was madness trying for any HD at all. 89.7 Boston has the best HD and it seems like 103.3, 94.5 and 102.5 are the other out of market stations packing some HD juice. 89.7 is the only signal that you can reliably drive with - even as close as 35 to 40 miles to Boston. WBZ 1030 AM is the out of market station with the best HD signal of AM or FM.

I never thought about 102.7 knocking out 102.5's upper sideband but you are correct! I was wracking my brain trying to find a 1st adjacent signal of sufficient amplitude to test and it was right there grinning at me all this time. Thanks! FWIW, 102.7's strong local signal seems to have no adverse effect on 102.5's out of market HD signal.

KQEI has the same thing up here. They come in fine digital, because their 89.1 carriers have no interference. We're actually working on an idea to run asymmetrical sidebands - which is why I was at first interested in the new spec of 10 db. Both Nautel and Harris have options in their menu for a 4 db difference - but no more. Of course we need special approval to actually run it.

I downloaded your station program guide. Wow! Quite the art of radio! You people should be VERY proud!

A truly active and vibrant community radio station with lots of local support. I have to say that I'm quite proud to be here. Just wait 'till festival season when the live broadcasts start. Here's a story I wrote about that:

http://www.thebdr.net/articles/audio/codecs/RI-ZIPOne.pdf

I'm hopeful that we can resolve our problems before Summer.

Dave B.

 

[iyiyi]

The #1 Problem this situation currently suffers is: Nobody has their ducks in a row. Only way to get ducks in a row is to lead them. The best way to lead them in this case is with a Plan. Can't devise a Plan unless you can define the problem in a clear, concise manner.

There are 2 first adjacent FMs both running HD and operating on and about hostile (to VHF radio!) terrain in the foothills+ of the Sierra Nevada Mountains. 89.3 is a 3.3 kw Class A in the lowlands with a DA theoretically protecting 89.5, a Class B1 located 1,200 meters up in the hills with an ERP of 1.75 kw. The 2 stations are roughly 100 km apart. There is an approximate 10 mile swath of real estate running to the NNW from south of Folsom - Placerville, through Hidden Valley, Beale AFB and out to Palermo and beyond. This swath is effectively a radio shadow for 89.5 created by a steep rise in terrain through those areas. 89.3 complicates things because the steep rise brings a huge signal increase because the territory is now eye level and more to the 89.3 tower. 89.3's upper HD sideband does a pretty good job of "wooshing" 89.5's terrain compromised analog signal within that swath. There are other areas where 89.3's analog signal is compromised likewise by 89.5's lower HD sideband. This is the "Problem" as I currently understand things.

I suggest that the "Problem" be further defined. I would drive the three worst areas affected by 89.3. The Auburn one showing how 89.5 is affected in stop and go morning traffic on 49 is excellent. The 89.3 being affected by 89.5 is excellent. It shows how the signal is adversely affected while driving over some distance. Also three drives of 89.5's worst effects on 89.3 is helpful. It is best if each drive is repeated with the other frequency for reference. Maps sketching each route so those unfamiliar with your region can understand where the QRM is can be very helpful. Those Longley-Rice maps very helpful! Using co-located translators or other 0.5 assed schemes is a non-sequitur. There is no real way to solve this with anything other than hand to hand 89.3/89.5 participation! Both stations possess an intelligent and knowledgeable audience that is aware of attempts being made to mitigate interference. The occasional announcement that "testing may temporarily interrupt HD programming this week" should suffice. Kill HD on both signals. Drive the analogs. Next day activate HD on one frequency. Drive both signals. Day after, kill that HD and activate HD on the other frequency. Drive both signals. You already know how both HD signals behave. Check and see if 89.3 is using the same DA antenna as the analog. They may well have installed another antenna for the HD either on the same tower or even a different tower. This 89.3/89.5 is a very fixable problem, regardless of cause, once you can determine the exact source.

I drove the 102.5 (WKLB) HD signal again (I'm well beyond their 54 dBu). There is a mono 102.7 (WRNI) local and I discovered a 102.3 in stereo (WMOS). I stopped the car and was able to get a clear 102.3 in analog stereo, 102.5 HD1 and HD2 and clear 102.7 at the same time. The RBDS also functioned OK on 102.5. Also I discovered that listening to the HD2 signal allowed me to concentrate on driving (audio drops out with HD loss) and compare 102.5 to the other Boston HD FMs. It performed equal or better than it's peers. WGBH 89.7 must be running -10dBc. They come in too good, even on HD3, better than any other Boston FMs.

-

 

[iyiyi]

The quick and dirty fix here is for KQEI to swap frequencies with KZCA. KZCA has a CP and 89.1. KQED (I) has coin and also has problems with 89.3. Sweet. Simple. Speedy.

-

 

[Ai4i]

WGBH 89.7 must be running -10dBc. They come in too good, even on HD3, better than any other Boston FMs.

No can do, 'GBH is a grandfathered class B, and as such can only run the greater of (used to be) 1% or 10% of what their signal would be if licensed as a new station. However, their grandfathered status does have the advantage of keeping other stations, including first adjacents, at bay.

 

[DaveBayArea]

The quick and dirty fix here is for KQEI to swap frequencies with KZCA. KZCA has a CP and 89.1. KQED (I) has coin and also has problems with 89.3. Sweet. Simple. Speedy.

That in and of itself doesn't work because of KXPR on 88.9. But there are a few scenarios where a number of stations could move around and wind up getting rid of interference. The two problems are:

1. We need to protect stations in Reno/Carson City/etc. Even though their signals non-existent on the West side of the Sierras.

2. 2nd adjacent channel spacing requirements. They're meaningless really. I don't know of a situation where I can't park at a transmitter site and tune a 2nd adjacent station.

I appreciate your insight and the comment about getting ducks in a row, that approach has sort of been taken. The "testing" really occurred between us when we were both at -20 dbc. The interference zone around KQEI was mostly in a rural area North of Sacramento. I wasn't at KVMR when the power increases occurred, but we received upwards of 300 complaints from listeners who said they can no longer receive our signal. I believe the best compromise if we choose to continue to try to run at elevated power would be asymmetrical sidebands. Time will tell.

Dave B.

 

[iyiyi]

The quick and dirty fix here is for KQEI to swap frequencies with KZCA. KZCA has a CP and 89.1. KQED (I) has coin and also has problems with 89.3. Sweet. Simple. Speedy.

That in and of itself doesn't work because of KXPR on 88.9. But there are a few scenarios where a number of stations could move around and wind up getting rid of interference. The two problems are:

1. We need to protect stations in Reno/Carson City/etc. Even though their signals non-existent on the West side of the Sierras.

2. 2nd adjacent channel spacing requirements. They're meaningless really. I don't know of a situation where I can't park at a transmitter site and tune a 2nd adjacent station.

I appreciate your insight and the comment about getting ducks in a row, that approach has sort of been taken. The "testing" really occurred between us when we were both at -20 dbc. The interference zone around KQEI was mostly in a rural area North of Sacramento. I wasn't at KVMR when the power increases occurred, but we received upwards of 300 complaints from listeners who said they can no longer receive our signal. I believe the best compromise if we choose to continue to try to run at elevated power would be asymmetrical sidebands. Time will tell.

Dave B.

Sorry for the 89.1 idea. I'd say "That's what happens when you spend a few hours trying to juggle a bunch of maps and data tables" - but everyone knows that is whole lot of...

You have a legitimate situation here. I am very interested in how iBiquity is going to assist two stations; both WANTING to run HD, solve this. If they won't support their own product...

89.3 has the onus of protecting 89.5. The Longley - Rice maps indicate to me that 89.3 places more city grade signal within 89.5's 60 dBu contour than they do in Rio Linda! Any real Plan here must cost 89.5 little to nothing both in coin and coverage!

You are definitely on the right course for getting your ducks lined up. Maps, interference videos... Things like that add quacks in your favor when it is time to make your point. The "other guy" has to scramble to make his point when you do your homework properly. It is better to trip over pearls like my "89.1 brainstorm" now rather than realize you goofed in the middle of any serious dealings in 89.5's behalf later on!

-

 

[KB1OKL]

WGBH 89.7 must be running -10dBc. They come in too good, even on HD3, better than any other Boston FMs.

No can do, 'GBH is a grandfathered class B, and as such can only run the greater of (used to be) 1% or 10% of what their signal would be if licensed as a new station. However, their grandfathered status does have the advantage of keeping other stations, including first adjacents, at bay.

WGBH is also the only station that was reliable and sounded good on my IBOC radio, they run rings around other Boston FM's as far as reception goes including analog reception.