WBZ (AM) IBOC Off!

[Tom Wells]

"Physics"? Well, if it can make 100Mhz a one meter wavelength and 1 Mhz a 100 meter wavelength; I'd sure be interested in "studying" some of that stuff! Do you know where a kid could cop a sample of this "physics"?

Why yes, it's 300m for 1 mhz, my slip. I hold to the other statements. Thnx, DGO2816.

I cannot offer any help with where to look for physics... Information is pretty widely available these days.
Integration of data is the responsibility of the student.

 

[aerie]

Does anyone know which (if any) local FM stations have opted to up the power on their digital signals? A few stations are spotty for HD where I live in Andover and I can't figure out why, since other stations from the same transmitter site come in fine. For example, I get all the stations from the Pru except WXKS-FM HD and they share the upper master antenna with WZLX, WBMX, and WMJX--all of which I get just fine. I am assuming that the HD signal comes from the same antenna as the analog signal: WXKS-FM does have a backup antenna that is at a lower height than the master antenna.

 

[mgpt6]

WKLB is probably at higher power. They were a test station for higher FM IBOC power

 

[DanStrassberg]

Thanks, Laurence. I was hoping someone who knows more than I do about DA patterns for AM would chime in on that subject.

I think that Laurence has a relatively limited understanding of the issues involved in what he has proposed. Back in the day, the only channel on which there existed two 50 kW Class I AMs operating ND at night was 1070. Back before CBA moved from Sackville to Moncton, the great-circle distance between KNX and CBA was a little less than 2900 miles Though there are now many ex-Class II AMs in the US and Canada between New Brunswick and California, many of them operating with substantial night power, CBA alone should have established KNX's NIF and vice-versa. It certainly would be interesting to know what the NIF values for these two stations were before CBA moved and all of the Class II stations were built on 1070. My guess is that neither station was "interference-free" at its 0.5 mV/m 50% skywave contour. The meaning of interference-free here was that the RSS of 10% co-channel skywaves was no greater than 25 microvolts/meter.

Other relevant frequencies are 810 (WGY is ND; KGO is not), 680 (KNBR is ND; neither WPTF nor WRKO is), and 850 (KOA is ND; neither WEEI nor any of the other ex-class IIs from the east coast to Michigan is). 640 is an interesting case. When NARBA took effect in 1941, NF was not part of Canada. Besides KFI, there was (and perhaps still is) a 10-kW ND-U station on 640 in NF. Those two stations are further apart than were KFI and CBA and the NF station on 640 was just 10 kW--not 50. My guess is that that KFI did therefore meet the criteria for NIF coverage at its 0.5 mV/m 50% skywave contour.

Stations that would share Class A channels under Laurence's plan would receive substantial co-channel and first-adjacent nighttime-skywave interference at their 0.5 mV/m 50% skywave contours. Moreover, the chances of such a radical realignment are vanishingly small because all of the other Western-Hemisphere nations now have an interest in these channels.

 

[iyiyi]

I think there were originally 40 clear channels. 15 of them were compromised. In addition to the above mentioned, I believe 1170, 1190, 1080, 1140, 1530, 1560, 1060, 1090, 1110, 1510, 1520 and 710 had two dominant 50Ks known as "Class II(2) A". Also IIRC, WABC had KOB and WBZ had KTWO on their channels but were considered "Class I A" anyway. Possibly it wasn't until the early '60s before 1030 was officially a class IA signal. I also think that KOA runs a "resistor" on their antenna at night, making them less than 50Kw, but I don't know what power KOA actually radiates at night. I may well be wrong on all of this but I feel most it is somewhere in the vicinity of the ball park.


-

 

[Laurence Glavin]

As I did when considering how the Boston-and-vicinity FM dial would look if full-power frequencies in the city began at 92.3 a la NYC, Chicago, Los Angeles, I was doing a little surmising after spending time at Dave Gleason's web site, American Radio History. One model I looked at was WGY-AM 810 in Schenectady, NY and WHB-AM 810 in Kansas City, MO. I get the impression that WHB settled on 810 after operating on other frequencies (at least according to Wikipedia). Nowadays, we have the example of stations around here on the old lower-case clear channel outlets, such as WAGM-AM 890 and WBNW-AM 1120. It appears that if you're in the area of WAGM, it still gets some nighttime interference from WLS in Chicago, while WBNW gets adjacent-channel interference from WBBR-AM 1130, but not so much from KMOX in St. Louis. Of course, stations all over the AM dial have had to live with nighttime interference from co-channel stations that predated them. One of the most notorious instances, WCRB-AM 1330 in Waltham would operate from local sunset in the winter until 8:00 pm most nights while WPOW-AM on the same frequency was beaming a 5,000-watt signal (at least from the transmitter; its ERP was probably higher) due northeast from Staten Island, NY. During the days when WCRB-AM was a daytimer, WPOW probably came in like a local to listeners in Waltham!

 

[DanStrassberg]

WBZ had KTWO on their channels but were considered "Class I A" anyway. Possibly it wasn't until the early '60s before 1030 was officially a class IA signal. I also think that KOA runs a "resistor" on their antenna at night, making them less than 50Kw, but I don't know what power KOA actually radiates at night. I may well be wrong on all of this but I feel most it is somewhere in the vicinity of the ball park.

KTWO did not move from 1470 to 1030 until half of the Class IA channels had been "broken down" sometime in the '60s, I believe (maybe 1966, but that's a guess). WBZA apparently had no effect on WBZ's IA classification. KTWO was not the first Class IIA station; IIRC, that honor went to a Roswell NM station on 1020 whose call sign at the time was KSWS, IIRC. It is now KCKN. A curiosity regarding KTWO is that notwithstanding WBZ's sending a stronger signal toward it than any other ex-Class IA AM sends toward the co-channel ex-Class IIA, KTWO is, I believe, with the exception of KKOB, which is a special case, and KTNN, which was never a IIA, the only ex-Class IIA that uses a two-tower DA at night. All of the other ex-IIAs that run 50 kW at night and 50-kW-N stations that are comparable to ex-IIAs use at least three towers. Now, you can claim that KTWO's simple DA is a consequence of the long distance between Boston and Casper but it doesn't appear so. The distance between WABC and KKOB is about the same but WABC is ND. KTNN is 1933 miles from WFAN even though, when KTNN was allocated, WFAN (or whatever the calls were at the time) had long since dropped its DA.

 

[DanStrassberg]

One of the most notorious instances, WCRB-AM 1330 in Waltham would operate from local sunset in the winter until 8:00 pm most nights while WPOW-AM on the same frequency was beaming a 5,000-watt signal (at least from the transmitter; its ERP was probably higher) due northeast from Staten Island, NY. During the days when WCRB-AM was a daytimer, WPOW probably came in like a local to listeners in Waltham!

When WCRB (AM) went full time (with 1 kW-N), 1330 in NYC was still shared by WEVD and the old WBBR (no relation to the current WBBR 1130). Back then, the time-share had WBBR on from 3AM to 8AM and 5PM to 8PM Monday thru Friday. (Actually, the 5- to 8PM hours did not apply to Mondays because of a third shared-time station, WHAZ, Troy NY, which operated only on Monday nights.) The weekend schedules were different, and I don't remember them. Back then, WBBR transmitted from Brooklyn and WEVD from Queens. WEVD ran 5-kW-U (DA-2, I think). WEVD's night pattern was kind of a figure eight oriented more or less north to south. The skywave to Boston at night was strong but not what it later became.

WCRB used a three-tower array oriented almost exactly east-west and, at night, sent everything pretty much to the east. Later, WBBR built a new transmitter site at the northern end of Staten Island overlooking Lower New York Bay. The night signal toward Boston must have been equivalent to at least 25 kW ND and it really increased WCRB's NIF, drastically reducing the Waltham station's nighttime coverage. I believe that WBBR paid for WCRB's upgrade. (Also, by the time WCRB's upgrade was built, the station's calls had changed to WHET.) The three 200' towers were replaced by two 300' top-loaded towers that produced a cardioid night pattern oriented southwest to northeast. The taller top-loaded towers were electrically equivalent to 166 degrees, resulting in a signal that was much superior to that from the old three-tower array. WCRB's upgrade was made possible by WHAZ's change from shared-time operation to daytime operation, which did away with the need for WCRB to protect WHAZ.

The big break for the station, which by then had become WRCA, was when what had been WBBR (and later WPOW and WNYM) moved its transmitter site to the site of the 970 station (now, itself using the WNYM calls) in Hackensack NJ. Hackensack is largely northwest of New York City's five boroughs, so WPOW's pattern could be designed to send most energy to the southeast, drastically reducing the skywave toward Boston and almost certainly reducing WRCA's NIF to a value lower than it had ever been in the history of the Waltham station.

 

[4CX1000A]

But the iBiquity system is not the only digital-audio transmission system that has been demonstrated on the AM band. Unfortunately, I can't remember the name of the European digital audio transmission system that has been demoed on the MW band. However, somebody is sure to remind me.

Digital Radio Mondiale. It is superior to HD Radio in that it can use skywave propagation, making it suitable for use on the shortwave bands.

 

[fybush]

Later, WBBR built a new transmitter site at the northern end of Staten Island overlooking Lower New York Bay.

WBBR never transmitted from Brooklyn, though the studios moved there in 1931. It was always a Staten Island station, at least in transmitter location. (Indeed, it was a Staten Island license even before the Witnesses bought it.) The site was at 1111 Woodrow Road in Stapleton, almost to the southern tip of the island, and it was inland, overlooking nothing much in particular. It became a three-tower directional in 1946, 5 kW-U, and by the time WEVD became WNYM in the early 1980s, both halves of 1330 were using the Staten Island transmitter site. The move from Staten Island to Hackensack happened in 1989, I think.

 

[necrat123]

For example, I get all the stations from the Pru except WXKS-FM HD and they share the upper master antenna with WZLX, WBMX, and WMJX--all of which I get just fine. I am assuming that the HD signal comes from the same antenna as the analog signal: WXKS-FM does have a backup antenna that is at a lower height than the master antenna.

WGBH-FM, WKLB, WAAF all run at high level* IBOC. This list is accurate as of 11/7/2011, and based on the FCC's digital notifications only.
I've measured WGBH-FM's and WKLB's on a spectrum analyzer and they are indeed running higher levels.

WAQY in Springfield, MA is running high level IBOC too.

Yes, WZLX, WBMX, WMJX , and WXKS all use the upper antenna, but for analog only. The digitals for WZLX, WBMX, and WXKS are done using single bay ERI antennas on a short tower, on one corner of the building. WMJX's digital is combined into the 4 bay lower master FM, which also has WBOS, WTKK and WROR analog/digitals into it.

(* By High Level, I mean more power than the nominal -20db standard.)

 

[chrish]

When WCRB 1330 was a three tower array they were 5KW-DA-2 and stayed as such when they ripped down the old array and put up the two new 300' towers
with the top loading.

 

[aaronread]

Digital Radio Mondiale. It is superior to HD Radio in that it can use skywave propagation, making it suitable for use on the shortwave bands.

Ummm...you can receive IBOC AM via skywave, too...I've listened to WBZ (AM) and WTIC (AM) in areas near Rochester NY in digital on my HD Radio in my car.

DRM isn't really all that superior to HD Radio for AM. Both have the same problem of putting signal into adjacent channels. Both have problems with the digital coverage area being markedly smaller than the analog (as far as listeners are concerned). The only really nice advantage is that DRM works across a much greater range of MW frequencies than HD Radio does. But that's irrelevant for modern radio listening.

I would opine that most of DRM's advantages stem mostly from the fact that it's noticeably newer technology than HD Radio is. The first HD Radio test transmissions were in 1992, nearly four years before anyone even started really working conceptually on DRM.

Please note, just because I don't think DRM technology is better (or at least "not much better") than HD Radio, doesn't mean I think HD Radio for AM is "good."