Chicago's ESPN Radio AM 1000 Shuts Off the Noise!

[Play Freebird]

There's no question in my mind that IBOC carriers have a detrimental effect on analog audio quality of the host AM station. 

Our station, like WHAM, is an affiliate of Fox News Radio, so it's easy to make informal A/B comparisons during newscasts. Since WHAM's audio is delayed several seconds, this allows the same "snippet" of programming to be evaluated.   I've listened on several receivers in areas where our measured field strength is somewhat less than WHAM's.  Our audio not only exhibits a pleasing increase in frequency response, but it's louder -- and this difference is easily noticed with network-grade voice material. 

On the factory radio in my pickup truck, there's an obvious and annoying hiss behind all of the IBOC AM stations.  I've also noticed this problem in VWs with the "Monsoon" premium audio system and I'm sure there are many others.   Even a narrow-IF receiver with lopsided passband response will be subject to increased noise because the tertiary digital carriers (within 5 kHz of the analog carrier) won't completely cancel out.

With regard to decreased skywave coverage, keep in mind that the AGC circuit in most receivers uses the analog carrier as a reference to set its gain. So during selective fading of the carrier, the gain in the RF stages will increase, bringing up the level of any background noise, including the IBOC sidebands.

[KB1OKL]

I live approx 40 miles due W of WBZ, it used to come in very well here, in fact it was one of the blowtorches that you could count on to always pin S meters. It is now barely receivable here most of the time. My father USED to listen to it at night while waiting to fall asleep, he recently asked me if there was something wrong his radio. This is a guy (non dXer) who used to brag about being able to receive WBZ in NC at night when he was in the service. Markie, you're doing a heck of a job.
I hear a constant hiss across WBZ as I tune across it and it's audio is now terrible as are all the other stations that use a 5 KHz filter, they sound like you are listening to a speaker with a pillow on top of it plus they're usually very distorted. AM radio used to sound great. Great decision to cut the highs like that, it makes IBOC sound different when it actually locks in for a few seconds here, little deception on ibiquities part?

[cyberdad]

RE: WLW reception in Chicago area.  Yesterday early p.m., 25 miles NW of WGN's stick, ten year old standard issue GM car radio.  There was WLW...faint, but audible.  Pretty much same as its always been going back to the '60s.

Next week, I have a business trip that pretty much takes me around Lake Erie.  Cleveland, Buffalo, Toronto, Kitchener-Waterloo, and Detroit-Windsor.  I expect WLW to be audible daytime in most, if not all, of these places, (Toronto may be an exception).  I'll post if otherwise.

[rbrucecarter5]

But in terms of reduced range, I just don't see it.

As far as Ibiquity getting the system to work properly, I don't believe that possible. As I stated in other posts, if digital is something we should strive for on the AM band, it should be a system where analog and digital are either on separate bands, or on different parts of the AM band.

This is really interesting.  So far, though, those who say there is no reduced range and those who say there is - have been talking about different stations.  So there may be something that the stations are doing differently that caused the coverage to decrease dramatically.  I can confirm that WBZ is degraded at night, though.  Local 700's in Dallas and Houston give me fits with WLW, but WGN and the other Chicagos that carry IBOC seem to be degraded compared to their signals before IBOC.  I am too far away for daytime tests on Chicago unless I can find a really quiet RF environment, even then I don't have any "before" observations.  Some listeners have independently confirmed my observations on KLIF and WBAP.  So station engineering is definitely a suspect in this discrepancy.

I have long been an advocate for putting all IBOC on a portion of the AM band - perhaps 1210 to 1490 - allowing all the power they want with absolutely no protection outside their COL.  And revert the rest of the band to the way it used to be.

[Len14043]

I have long been an advocate for putting all IBOC on a portion of the AM band - perhaps 1210 to 1490 - allowing all the power they want with absolutely no protection outside their COL.  And revert the rest of the band to the way it used to be.

I brought a similar proposal up several months ago along the same lines. Set aside a portion of the band to be used in the all-digital mode and eliminate the current hybrid system. I suggested using 1500 khz and up, although any frequency range set aside would be far better than the hybrid system currently in use. The stations that currently occupy the future digital band could take advantage of a liberal policy to vacate those frequencies. I'm not sure about the spacing, but if the digital stations could be separated by 2 channels, that would be great. If, for instance, WOAI wanted to go digital, they could have an all-digital feed on the digital portion of the band and remain at 1200 khz for the analog service, preferably using 5 khz bandwidth to keep the band somewhat cleaner. Although they would occupy 2 channels, that would be better than the 5 channels taken up by the current hybrid system.  If the all-digital took off, the digital portion portion of the band could be expanded while the analog portion is retired through attrition.  While this proposal would work in nearly all of the areas, it would difficult to implement in large metro areas such as NYC-unless 2 channel spacing could be used. But the current systems is also problematic in crowded areas.  Another possibility would be to use the longwave band for the all-digital feeds.

[Len14043]

RE: WLW reception in Chicago area.  Yesterday early p.m., 25 miles NW of WGN's stick, ten year old standard issue GM car radio.  There was WLW...faint, but audible.  Pretty much same as its always been going back to the '60s.

Next week, I have a business trip that pretty much takes me around Lake Erie.  Cleveland, Buffalo, Toronto, Kitchener-Waterloo, and Detroit-Windsor.  I expect WLW to be audible daytime in most, if not all, of these places, (Toronto may be an exception).  I'll post if otherwise.

WLW may be difficult near the Buffalo area during the day due to CJRN at 710 kHZ in Niagara Falls. I have received them in Milwaukee and the Quad Cities during the day.

[KB1OKL]

Another possibility would be to use the longwave band for the all-digital feeds.

I'm sure the European LW stations would appreciate the noise. LW goes a long way.

[BRNout]

I had rarely heard hiss on the analog signal from IBOC. The reduction in frequency response can be heard on a full range audio system, but not on your average radio. And again, I do not see any degradation in the range of the stations - none!

Len, I'm sorry but I have to disagree with you 100%.  The analog signal on a station running IBOC may still have the same strength, but the audio sounds a bit muddy when compared with it's non-IBOC audio.  I am sure it's because of the way that they have to compress that audio into a narrower bandwidth to accommodate the HD sidebands.  However, the difference is quite audible on all but the cheapest of radios - you just have to compare the "bright" sound of a local non-HD signal (in Chicago, WGN) versus the "dull" sound of its HD counterpart (in Chicago, WBBM).  Not only that, but a wideband radio (like my Superradio 3) will mix the hash in with the audio resulting in a crappy sound.  At my house, it does this with WBBM and WLS (during the day) and the effect is very annoying. 

The geographic range of a given station may not change from an engineering standpoint; however, the duller sound will render it's relative volume (and listenability) lower on the fringe of its range.  That's probably why you see complaints about the likes of WBZ seeming to have less range.  It's because of the flat audio - the station sounds weaker, even if its not. 

[Savage]

All of which statements are mostly true - but the analog signal actually IS weaker.  In the AM flavor of IBOC a portion of the spectral energy previously committed to the analog signal, is now being occupied by the COFDM digital carriers.  It's a zero-sum RF game.  Plus I'm convinced that the digital carriers are doing some kind of nasty intermod thing with the analog carrier, because on all stations operating HD-AM I also note a loss of clarity.

The HD apologists insisted that because the digital power is .01 of the analog that the RF loss would not be detectable by the typical listener.  This comes from the same engineering alchemists who claim that "there is no co- or adjacent-channel interference" and "nobody will notice the analog passband being reduced to 5 kHz because all today's radios are so crappy."  (None of which are actually true.)

Winston Churchill said it: "In today's world we must have a lot of engineers.  Yet we do not want to live in a world of engineers."  At least as regards HD Radio, once again: The Last Lion was SO correct.

[cyberdad]

WLW daytime reception report for today.  (Standard-issue 2009 GM rental car radio)

Gary:  Check
South Bend: Check
Toledo:  Check (tripped the "scan" button)
Cleveland:  Check
Erie, PA:  Check (with some CJRN splatter)