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No IBOC on 1200, 1330, 1600

D

DanStrassberg

When the new Newton AM triplex at 750 Saw Mill Brook Pkwy was built, all three stations' facilities supposedly included everything necessary at the transmitter end to allow broadcasting in AM-band IBOC. For sure, WKOX's studios, if not those of WRCA and WUNR, are IBOC compatible (which I think simply means stereo capable, but may also suggest that proper equalization/audio-compression equipment has been installed). We know that the WKOX studios (in Medford, I believe) have what it takes for IBOC because WKOX and WXKS (AM) are a 100% simulcast and WKOX runs IBOC 24/7.

I figured that once all three stations had received licenses to cover (it happened in late May), we'd be hearing that insufferable AM-band IBOC hiss on 1190, 1210, 1320, 1340, 1590, and 1610. I don't miss the hiss but you may be able to catch it only on 1190 when WHAM's skywave comes in here. I've heard nothing that I could identify as IBOC hiss on the other five frequencies, however. I can think of several reasons why this might be so, but does anyone know the real reason?

Although both CCU (WKOX) and Beasley (WRCA) have been ardent and vocal promoters of IBOC (including the AM-band variety), I don't think Champion (WUNR) has a taken a position on IBOC. OTOH, AFAIK. WUNR did install the necessary transmitter-site equipment because of an agreement that there would be "parity" between WRCA's and WUNR's facilities (whatever that means).

Did any of the three companies purchase iBiquity licenses to transmit IBOC? These licenses are expensive and, considering the financial problems of both of the national companies (CCU and Beasley), maybe the iBiquity licenses became victims of the recession.

Maybe the stations are waiting to turn on IBOC until the end of the 1-year period that began when licenses to cover were granted. During this period, the licensees are rquired to satisfy all reasonable complaints of interference to radio reception within the stations' 1V/m "blanketing" contours.

Maybe the studio equipment is lacking--this could be a problem even for WKOX because, even though its studios themselves are IBOC capable, the audio link from Medford to Newton may not meet IBOC requirements.
 
Perhaps they realize that IBOC is a complete and utter waste of time and money especially on AM? I live approximately 8 miles from WTAG's transmitters and not once have I gotten a lock on them with my dust laden Sony XDR-F1HD, even with a C Crane Twin Dipole antenna which cost more than the Sony. I do however get their sideband hash all over 570 and 590 and to a lessor degree 560 and 600 on all my radios. They run Ihash only days, however they did test it a few months back at night and the wide swath of hashy noise was unbelievable. WBZ sounded like krap with artificial sounding highs akin to nails on a chalkboard between frequent drop outs when I tried it with the C Crane, with the stock Sony loop antenna, it doesn't come in at all. Let's just hope that these stations have enough sense to not use it, the AM band is full of IBOC hash here in central MA already, especially from that triumverate of noise: WBZ, KDKA and WINS.
 
All other things being equal, Dan, the more complex an AM array, the more opportunity for IBOC difficulties. A major contributor to self-interference from IBOC is common-point nonlinearity. Also critical networks in the phasor and deep nulls frequently give trouble. A serious degree of self-interference can result from poor pattern bandwidth; e.g., when the carrier amplitude rapidly decreases in relation to the sidebands which happens while listening in cars moving through various nulls and lobes. The most pronounced adverse affects are experienced close in to the transmitter site.

Considering that these are high-power installations using a lot of antiresonating networks for the triplexing, plus the number of towers suggests deep nulls, I can forsee the potential for plenty of problems with IBOC.

HD-AM requires a picture-perfect load to work properly. We all know how common THAT is in AM directional systems - even modern ones. ::)
 
I can't imagine the programming on any of the three stations would sound any better in "crystal clear digital sound."
 
I can't imagine the programming on any of the three stations would sound any better in "crystal clear digital sound."
 
Savage said:
HD-AM requires a picture-perfect load to work properly. We all know how common THAT is in AM directional systems - even modern ones. ::)
Click to expand...

Even though each of the five patterns (two each for WKOX and WRCA. one for WUNR) uses some or all of the same five towers, if I'm not mistaken, each of the three companies engaged a different consulting engineering firm to design its antennna system. If I'm right about that, coordination among the designers must have been quite an interesting challenge. Nevertheless, each of the arrays is supposed to be broadbanded. I think the meaning of broadbanded is that the driving-point impedance is supposed to be flat over the IBOC bandwidth (15 kHz on either side of the carrier frequency, I believe), the amplitude response is supposed to be flat over that bandwidth (just HOW flat, I don't know), and the phase is supposed to be linear vs frequency over that same bandwidth. Sounds like quite a challenge. I tried to visit the site yesterday but I could not find it. It would be interesting to know whether each station has a separate ATU building at each tower it uses. That would mean that three towers have three ATU buildings and two towers would have two ATU buildings. I wonder if that's how it was done.
 
I couldn't see the towers at all in the Google Maps photo, but I could see two and probably three of the five in Google Earth. I could not see the other two, but I did see the five ATU buildings. However, I could not see the transmitter building, which I know is on the north side of the property. Another curiosity: If you look at the site plat in any of the three applications, you will see that the ground system for the northeast tower is supposed to extend right to the property line to the north and east of that tower. The distance is somewhat more than 1/4 wavelength at 1200. The ground radials are extended there to compensate for truncation of the ground systems of some of the other towers where they intersect the property line. Well, to the north and east of the base of the northeast tower, there are trees almost right up to the property line. Unless I misunderstand the photo, there is no way there could be ground radials of any appreciable length extending to the north and east of the northeast tower. If I were an abuttor of the northeast corner of the property, I would like it that way and I would have put up a squawk about having those trees cut down. But if I owned one of the radio stations, I would not be happy about the loss in antenna efficiency from the elimination of the ground radials I was counting on.
 
Interesting. And as we all know when it comes to AM DAs, "design" is one issue while what you wind up with once the system is built and "walked in" can be quite another - even with today's CAD in AM arrays.

We've all been through the process of "walking in" a new directional system. Getting the monitor points all in with enough comfort-margin to keep the array from wandering out of parameters with weather changes, etc., can be quite a challenge - and you often have to do some common-point twiddling to get the final load where the transmitter likes it. (If the site is indeed "ground-system challenged" or if there are nearby reflecting structures which can fill out monitor points, the job of getting the system to perform "per design" gets frustrating.)

If the consultant doesn't take the time to carefully equalize all the RF lines, the array's characteristics can remain quite tricky once it's built and operating in the field.

Multiply all those concerns times the number of facilities using the site (three in this case) times the number of patterns (five, as friend Dan has observed.) Now toss IBOC's very demanding specs into the mix. It's not hard to imagine why HD isn't on the air - at least yet - from this site.
 
aerie said:
I can't imagine the programming on any of the three stations would sound any better in "crystal clear digital sound."
Click to expand...

I have an HD receiver, and the "Rumba" Spanish music format on 1430 WXKS (AM), which is an HD simulcast of 1200 WKOX, actually does sound a lot better on HD because the stations that have their analog audio EQ'ed for HD all roll off their highs at under 5k on their analog, making for very muddy music fidelity.
 
Eli Polonsky said:
aerie said:
I can't imagine the programming on any of the three stations would sound any better in "crystal clear digital sound."
Click to expand...

I have an HD receiver, and the "Rumba" Spanish music format on 1430 WXKS (AM), which is an HD simulcast of 1200 WKOX, actually does sound a lot better on HD because the stations that have their analog audio EQ'ed for HD all roll off their highs at under 5k on their analog, making for very muddy music fidelity.
Click to expand...

Although this may not be the case (someone here with more technicial expertise than me help me out) some would say that rolling off the highs may have been done on purpose to make IBOC's grating artificial highs stand out more dramatically.
 
KB1OKL said:
Although this may not be the case (someone here with more technicial expertise than me help me out) some would say that rolling off the highs may have been done on purpose to make IBOC's grating artificial highs stand out more dramatically.
Click to expand...

That may be the result, and iBiquity et al may regard the result as favorable to their cause, but I don't think it was what motivated the land-line telephone-quality high-end roll-off of the analog audio on AM stations that run IBOC. The system just wouldn't work with wider analog-audio bandwidth.
 
HD in both the AM and FM flavors is a zero-sum game. The more channel designated for digital, the less room there is for analog, and vice versa. It's a juggling act with digital robustness, analog quality, self and adjacent channel interference all benefiting proportionally to compromises in the other factors. I would personally make the case it causes ALL factors to suffer at an unacceptable level.

Locally a Crawford 6-tower DA has reduced analog bandwidth to 4.5 kHz so they can offer HD wonderfulness (daytime-only, of course) to its 7 digital listeners. And it's the only station in the market programming music on AM....try to explain THAT one. (While making sense, that is.)

HD-FM has 96 kbps to play with on the digital side. If the station only programs an HD-1 main channel it gets the whole 96. But hang HD-2 and HD-3 subs, and the main channel can get ratcheted down to 32 kbps. Chopping up the 96 in various ways have prompted complaints that the main channel doesn't sound as good as the HD-2 sub in some cases.

Choose your poison. HD offers plenty, and a wide variety of kinds, for everyone.
 
Eli Polonsky said:
The sounder for the "Traffic On The 3's" on WBZ sounds much cooler in HD stereo too. ;D
Click to expand...

I have never heard a more artificial sounding station that WBZ in glorious IBOC, it's like listening to someone scratch their nails on a black board.
 
KB1OKL said:
Eli Polonsky said:
The sounder for the "Traffic On The 3's" on WBZ sounds much cooler in HD stereo too. ;D
Click to expand...

I have never heard a more artificial sounding station that WBZ in glorious IBOC, it's like listening to someone scratch their nails on a black board.
Click to expand...

Are you kidding? Artificial sounding? You mean it doesn't sound like radio used to?

I think it sounds great. Sounds like the announcer is right in the room with me. And the ID is pretty cool in HD too.
 
Don Juan said:
KB1OKL said:
Eli Polonsky said:
The sounder for the "Traffic On The 3's" on WBZ sounds much cooler in HD stereo too. ;D
Click to expand...

I have never heard a more artificial sounding station that WBZ in glorious IBOC, it's like listening to someone scratch their nails on a black board.
Click to expand...

Are you kidding? Artificial sounding? You mean it doesn't sound like radio used to?

I think it sounds great. Sounds like the announcer is right in the room with me. And the ID is pretty cool in HD too.
Click to expand...


AM HD is to radio what Mobil on the Run is to shopping.
 
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