No WLS IBOC, no interference on WNMB

[RadioFixerCLE]

[ WGY which runs IBOC on 810 causes no interference to neighbor WNYC on 820 Khz. The laws of physics must be different here in NY than elsewhere.

I used to be able to tune in 1080 WTIC out of Hartford on some nights. But try as I might, I have heard no IBOC hash from them at night here in Manhattan. And I do believe they're an HD now.

 

[R.F. Burns]

[ WGY which runs IBOC on 810 causes no interference to neighbor WNYC on 820 Khz. The laws of physics must be different here in NY than elsewhere.

I used to be able to tune in 1080 WTIC out of Hartford on some nights. But try as I might, I have heard no IBOC hash from them at night here in Manhattan. And I do believe they're an HD now.

Yes they are IBOC. WTIC has horrible coverage for a 50 KW station in my opinion. I believe the ground conductivity up on the mountain just outside of Hartford where their transmitter site is located must be pretty poor. Listen to WBZ and see if their sidebands are causing any interference problems, or WPHT on 1210. Other then local first adjacents here in the NYC area I notice no difference on the AM BCB than I did earlier in the year pre; the advent of nighttime Iboc. Oh, 50 KW WGY on 810 in Albany causes no reception problems in a northern suburb with WNYC AM (820), which turns off their IBOC exciter at night.You'd think considering that people claim to be hearing WOR's sidebands causing interference to their locals at distances of a thousand miles or more I'd be able to at least hear WGY's IBOC sidebands considering that I'm about 120 miles south of their transmitter site. At 810 Khz, their skywave signal is not bouncing over me by the way.

 

[RadioFixerCLE]

Hell, I still can't tell if WNYC AM 82 here in New York does IBOC at night when they drop down to 1,000 watts.

I sure can't hear any hash on the sides from them, so I dunno....maybe it's just too weak to pick up? :-\

 

[Savage]

Western New York report: all stations which used to be easily readable here and which are now clobbered by IBOC sidebands:

WGY 810 to CKLW 800
WTIC 1080 to WBAL 1090
WBZ 1030 to KDKA 1020 (especially bad)
WFAN 660 to WSM 650
WTAM 1100 to WBT 1110
WHAM 1180 to WWVA 1170

M-3 map shows soil conductivity in Hartford to be either 1 or 2. Not great, but not the worst either.

Barry McLarnon keeps an updated list of HD-AM stations and whether they use the system at night. His records (as of 11-3) show WNYC NOT using IBOC at night:

http://topazdesigns.com/iboc/station-list.html

 

[ve3jf]

[ WGY which runs IBOC on 810 causes no interference to neighbor WNYC on 820 Khz. The laws of physics must be different here in NY than elsewhere.

I used to be able to tune in 1080 WTIC out of Hartford on some nights. But try as I might, I have heard no IBOC hash from them at night here in Manhattan. And I do believe they're an HD now.

Yes they are IBOC. WTIC has horrible coverage for a 50 KW station in my opinion. I believe the ground conductivity up on the mountain just outside of Hartford where their transmitter site is located must be pretty poor. Listen to WBZ and see if their sidebands are causing any interference problems, or WPHT on 1210. Other then local first adjacents here in the NYC area I notice no difference on the AM BCB than I did earlier in the year pre; the advent of nighttime Iboc. Oh, 50 KW WGY on 810 in Albany causes no reception problems in a northern suburb with WNYC AM (820), which turns off their IBOC exciter at night.You'd think considering that people claim to be hearing WOR's sidebands causing interference to their locals at distances of a thousand miles or more I'd be able to at least hear WGY's IBOC sidebands considering that I'm about 120 miles south of their transmitter site. At 810 Khz, their skywave signal is not bouncing over me by the way.

There's no black and white as far as interference is concerned - it's all a matter of degree. WGY's skywave signal *is* "bouncing" over you to a considerable degree. At a distance of 120 miles, the elevation angle of the skywave is about 45 degrees. WGY has a tall tower (183 degree electrical height), which are relatively good at suppressing high-angle skywaves. At 45 degree elevation, the radiated signal is at least 12 dB less than it is at low angles. Take a look at this plot that shows the delivered field strength vs distance for a typical 50 kW station (WGY would fall between the two curves): http://www.topazdesigns.com/ambc/50kw-fieldstrength.png Note that these are the field strength values that are expected to be exceeded 10% of the time, as is customarily used for interference calculations.

The maximum field strength is at a distance of 400-500 km (250-310 miles), and it falls off more quickly as you approach the transmitter than if you increase the distance beyond the maximum. It's still a fat 60 dBu (1 mV/m) way out at 1300 km (about 800 miles). In your case, you're a bit off the left side of the graph, where the skywave field strength is falling off rapidly.

There are other variables too - e.g., perhaps your antenna orientation maximizes the signal from WNYC and suppresses that of WGY to some degree.

These anecdotal observations are interesting, but they don't mean a whole lot unless you can quantify the field strengths of the stations involved, and also explain any other measures you have taken to improve the reception.

 

[R.F. Burns]

Western New York report: all stations which used to be easily readable here and which are now clobbered by IBOC sidebands:

WGY 810 to CKLW 800 - In NYC I can hear both but WNYC's analogue sidebands interfere with WGY both day & night. WNYC is analogue at night. They diplex from the WMCA site in the Meadowlands. There was a fire there last year if memory serves. I was told by the then WMCA chief that WNYC wouldn't be doing IBOC again. WNYC said otherwise and they are back running IBOC until sunset. It may have something to do with bandwidth at night through the diplexer.


WTIC 1080 to WBAL 1090 - No interference north of NYC. Although the HD light flashes on my IBOC radios, I can not hear any sideband interference here.

WBZ 1030 to KDKA 1020 (especially bad) - WBZ same as WTIC, and I can still hear WHO on 1040 when WEPN's sidebands aren't blasting me away and propagation is just right. No problem hearing KDKA in NY either. WBZ causes no interference here.

WFAN 660 to WSM 650 - WSM was almost impossible since the early 8-'s when WNBC finally cleaned their audio and took out all of the frequency limiting (They used to sound like a 3 K non eq telco loop with no sidebands prior to the arival of Bob Pitman in the 80's) If I want to hear WSM I listen on the internet. WSM's analogue signal has always only been a DX catch here in NYC. WTAM 1100 to WBT 1110 - Has WBT turned on their nighttime HD? I recently talked with their chief and he explained that they were having trouble due to their old transmission facility. They are however now running a DX 50. That said, in NYC both WBT and WTAM are as clean as they were last year.


WHAM 1180 to WWVA 1170 - No HD interference. Both are clean here in NY. We must be missing somehtig down here. I guess this will all be settled soon by the FCC. Other than the fcat that I can no longer listen to first adjacents on WFAN, WOR, & WCBS, nothing has changed in NY on the AM band.

 

[R.F. Burns]

Western New York report: all stations which used to be easily readable here and which are now clobbered by IBOC sidebands:

WGY 810 to CKLW 800 - In NYC I can hear both but WNYC's analogue sidebands interfere with WGY both day & night. WNYC is analogue at night. They diplex from the WMCA site in the Meadowlands. There was a fire there last year if memory serves. I was told by the then WMCA chief that WNYC wouldn't be doing IBOC again. WNYC said otherwise and they are back running IBOC until sunset. It may have something to do with bandwidth at night through the diplexer.


WTIC 1080 to WBAL 1090 - No interference north of NYC. Although the HD light flashes on my IBOC radios, I can not hear any sideband interference here.

WBZ 1030 to KDKA 1020 (especially bad) - WBZ same as WTIC, and I can still hear WHO on 1040 when WEPN's sidebands aren't blasting me away and propagation is just right. No problem hearing KDKA in NY either. WBZ causes no interference here.

WFAN 660 to WSM 650 - WSM was almost impossible since the early 8-'s when WNBC finally cleaned their audio and took out all of the frequency limiting (They used to sound like a 3 K non eq telco loop with no sidebands prior to the arival of Bob Pitman in the 80's) If I want to hear WSM I listen on the internet. WSM's analogue signal has always only been a DX catch here in NYC. WTAM 1100 to WBT 1110 - Has WBT turned on their nighttime HD? I recently talked with their chief and he explained that they were having trouble due to their old transmission facility. They are however now running a DX 50. That said, in NYC both WBT and WTAM are as clean as they were last year.


WHAM 1180 to WWVA 1170 - No HD interference. Both are clean here in NY. We must be missing somehtig down here. I guess this will all be settled soon by the FCC. Other than the fcat that I can no longer listen to first adjacents on WFAN, WOR, & WCBS, nothing has changed in NY on the AM band.

 

[PhilJSmith67]

Last night I heard a rising and falling hash on WLS that I have never heard before. It turns out that Newsradio 880 was booming into Illinois, strong enough to show the WCBS HD on my Sangean HDR-1 display several times when I tuned to 880.

I am 19 miles away from WLS -- close enough that back when WLS was running IBOC, WCBS was totally obliterated, as was a Canadian station on 900. The Sangean's loop antenna is "mildly" directional but not enough to totally null-out the weak WCBS hash in the background on WLS.

It doesn't surprise me at all that IBOC on WLS was causing such trouble for WNMB!

19 miles is definitely within the NIF contour for Chicago's AM 89. I wonder what their engineer would say if you told him what you experienced...... 8)

It amazes me that a NYC station operating IBOC at all of 500 watts or so is causing such strong interference to a radio station which is over 1,000 miles away. I'm 25 miles from the city and I can't hear any of the out of town IBOC stations on any of my analog radios and none of them cause any interference to the locals here in NYC. WBZ runs Iboc and yet I have no trouble with KDKA or even WHO (if I can null out WEPNs splash) WGY which runs IBOC on 810 causes no interference to neighbor WNYC on 820 Khz. The laws of physics must be different here in NY than elsewhere.I can no longer DX WSM, but it has been barely audible for 30 years or more with local WFAN next door. As far as IDing distant IBOC stations, my best has been WPHT from Philadelphia once, but so far with the included loops I can not receive any IBOC stations after dark and none of them have increased the interference I hear at my house.

Have you ever actually tuned an AM radio at night and examined the signal levels from various skywave and local stations? I suspect that iBiquity had not, otherwise there would be no HD-AM. Here's a rundown of some stations I am getting right this moment, about 40 miles south of Chicago, on a Panasonic RF-2600 analog receiver. I limited the list from 530 through 900 kHz, and have dialed back the RF Gain so that my local powerhouses just barely peg the needle, otherwise nearly all these stations I am about to list would. Meter reading {0 to 10} in braces.

560 WIND Chicago {8}
610 WDAF Kansas City {4}
650 WSM Nashvile {8}
660 WFAN New York {5}
670 WSCR Chicago {9}
700 WLW Cincinnati {7}
710 hash from WLW+WGN with WOR underneath {8}
720 WGN Chicago {10}
740 CHWO Toronto {7}
750 WSB Atlanta {3}
760 WJR Detroit {4}
770 WABC New York with hash from WBBM {7}
780 WBBM Chicago with hash from ? {9}
800 hash from WGY with CKLW Windsor underneath {3}
810 WGY Schenectady with hash {5}
820 WBAP Fort Worth-Dallas with hash {6}
830 WCCO Minneapolis-St. Paul with heavy hash {5}
840 WHAS Louisville with hash {8}
850 hash from WHAS with KOA Denver underneath {4}
860 CJBC Toronto {8}
870 WWL New Orleans with hash from ? {6}
880 WCBS New York {7}
890 WLS Chicago {10}
900 CHML Hamilton + unID station {4}

Wow. Isn't it amazing that a station 400 miles away (WSM) from me could register the SAME strength as a local 5,000 watt station (WIND) only 17 miles away? Or, how about a station 750 miles away (WCBS) just a few ticks shy of a 50,000 watt flamethrower 19 miles away? This is NOT a fluke. It happens regularly.

Now, let me clarify another thing. I never said the hash I was hearing on WLS was "strong." In fact, I specifically said "weak WCBS hash" in my prior post. I don't know how any confusion crept in there. My post was simply an observation, that I noticed the distinct hash on a local station where I never expected to hear a trace of it. Don't even get me started on my other locals such as WBBM (35 miles away), which gets considerably more hash than I will probably ever hear on WLS.

I did mention that WCBS was "booming in" that night. Compared to tonight's reception level, I would not have been surprised if Newsradio 880 would have hit a 9 on the Panasonic's meter. It was VERY strong, the strongest I had heard WCBS in years. WABC and WOR were also audible through the hash from my local stations that night.

As for the digital vs. analog noise issue, a 500W OFDM signal is INDEED capable of tearing into a much "stronger" analog signal. It doesn't take a whole lot of comparative power from an interfering signal to throw noise into the background on an analog AM station. Heck, I can sometimes hear Cuban stations in the background of my other local blowtorches, and that's analog-vs.-analog from 1,500 miles away.

 

[ve3jf]

As for the digital vs. analog noise issue, a 500W OFDM signal is INDEED capable of tearing into a much "stronger" analog signal. It doesn't take a whole lot of comparative power from an interfering signal to throw noise into the background on an analog AM station. Heck, I can sometimes hear Cuban stations in the background of my other local blowtorches, and that's analog-vs.-analog from 1,500 miles away.

Just one further note: assuming you're talking about a 50 kW station, you're underestimating the digital power. For reference, see http://topazdesigns.com/iboc/AM-IBOC-Parameters.html where the digital power levels for each digital sideband of a 50 kW station are tabulated. Even if you ignore the lesser contribution of the secondary sideband and only consider the primary digital sideband, the power dumped into a 1st adjacent channel is 1256 Watts.

In addition, OFDM signals are very efficient interference generators compared to analog AM signals. They are essentially broadband noise jammers. In terms of its potential to cause interference, the OFDM signal is as potent as an AM signal having at least 6 dB higher power. That means a 50 kW IBOC station is dropping the approximate equivalent of a 5 kW AM station on each of its 1st adjacent channels.

This is a really, really bad idea.

 

[dumber than a box of hair]

The sad thing is, an increase in the power level of the digital signal may be necessary in order to get decent HD coverage. After all, EVERYONE is reporting poorer digital than analog coverage, and reports of signals that don't cover the city limits, let alone the entire metro are common. Is a solution REALLY possible on the AM side?

The unfortunate stick that comes with that carrot is that the cases of adjacent-channel interference will only get worse if the digital carrier levels are raised. The AM band, even without HD, already resembles a shouting match, especially at night...and raising the HD carrier levels just makes the shouting louder. It doesn't improve the intelligibility.