HD Radio Carrier Interference

[pioneernut]

I noticed the other day that scanning on a digital tuner that it stopped one channel above every station that broadcasts in HD radio. Example, a radio station at 97.1 would cause the scanning to stop at both 97.1(actual station) and 97.3(loud static), but not at 96.9. I noticed this on about 6 stations in the area that I heard are broadcasting in HD radio, the other stations that don't broadcast in HD didn't cause this problem. Has anyone else noticed this or heard about problems like this? I'm thinking the side carrier for the HD broadcast is causing the tuner to stop on the adjacent channel. I'm wondering if anyone else has any thoughts on this.

Thanks
- Mike

 

[pilotprose]

Let me see if I can shed some light on this. From what I have heard, stations that broadcast in HD have the same thing going for them that the "old" stereo stations do. That is, there are adjacent stations next to your "real" stations. In the older FM band, these were used for such things as, Muzak, educational and audiance specific topics, like listening to doctor's reports. You could not pick these up without a "tuned RF receiver" that was available as an add on. Electronis Illustrated did an article on this eons ago for those people that wanted Muzak in their homes!?!?!?!?! Well, HD is doing something similar and I think your unit is picking up the adjacent carrier and locking onto it. This would serve the same purpose as the older FM units did. In fact, there is a current commerical on the radio, FM, that expounds on this. I forgot what content they said is there, but it is there. Advertisers want all the available air space they can get, so nothing goes untocuhed. Hummmm, wonder where Muzak fits into all of this? I'll ask my wife, she is from Stepford...

 

[Vinyl Rules!]

Kill HD Radio Now, While It's Still on Life-Support!

I noticed the other day that scanning on a digital tuner that it stopped one channel above every station that broadcasts in HD radio. Example, a radio station at 97.1 would cause the scanning to stop at both 97.1(actual station) and 97.3(loud static), but not at 96.9. I noticed this on about 6 stations in the area that I heard are broadcasting in HD radio, the other stations that don't broadcast in HD didn't cause this problem. Has anyone else noticed this or heard about problems like this? I'm thinking the side carrier for the HD broadcast is causing the tuner to stop on the adjacent channel. I'm wondering if anyone else has any thoughts on this.

Thanks
- Mike

There has been extensive discussion of this in the Yahoo FM Tuner Group. You can get to them via their home page at www.fmtunerinfo.com

Most people in the FM Tuner Group are vehemently opposed to HD Radio because it (a) HD Radio sounds terrible (it utilizes a lossy codec running at about 96Kbs), even worse than MP3; and (b) Most HD Radio installations end up causing the exact problems you have described.

To briefly rehash what's been learned:

(1) Go to http://users.tns.net/~bb/hdrsn.htm for a technical explanation and graph of what you are now experiencing with HD Radio.

(2) Most stations don't engineer the HD Radio install properly and their signal ends up "bleeding" over into the adjacents on either side. Sometimes it affects one side more than the other. So a station at 97.1 could make stations at 96.9 and 97.3 virtually unlistenable.

(3) There have been a handful HD Radio stations that have done a proper engineering installation and these seem to be only the HD Radio stations in the Chicago area according to one of the posters in the FM Tuner Group. It is expensive and time-consuming to install the HD Radio broadcasting equipment so that it does NOT affect the adjacent channels.

This is likely due to most FM stations firing their own station engineers years ago and contracting out their engineering needs to just a once-a-week visit.

(4) There are some tuners that are immune to HD Radio adjacent channel interference and some of them have been discussed in postings in the FM Tuner Group as well as in the site URL in (1) above.

(5) The potential for this interference problem with HD Radio was raised with the FCC during the licensing process HD Radio went through at the FCC, but the FCC chose to ignore it.

I don't know the politics driving HD Radio, but I can say that Congress, while continuing to slash the budget allocated to the Corporation for Public Broadcasting managed to find and allocate funding that would permit ANY public radio to add HD Radio to their existing station and not pay a penny for the equipment - Congress managed to find funds to pay for any HD Radio equipment a public radio station wanted to install.

I will leave you to speculate on the political implications of this. :scratch2:

(6) Because so many stations have done such a poor job of installing their HD Radio equipment, Ibiquity Corporation, the inventor and owner of HD Radio, has now petitioned the FCC to allow them to change the HD Radio specs, that, if approved by the FCC, would result in even MORE interference with the adjacent channels.

(7) Some urban stations whose Arbitron ratings are being hurt by suburban stations adjacent to them are purposely letting their HD Radio station bleed over into their competitor's spectrum in an effort to cause their competitor to lose listeners. No station will of course admit to this practice, but it has been discussed at length in the Radio Industry's professional trade journals.

(8) IMHO, the best thing you can do if you are affected by this problem is to file a formal complaint with the FCC reporting the station causing the problem. Click on this URL to file a complaint with the FCC: http://tinyurl.com/fpg3z

Be sure to copy the offending station on their complaint. Anytime a listener files a complaint about a broadcaster with the FCC it becomes a big deal, particularly if the complaint involves poor engineering by the FM station. The FCC keeps a list of all complaints filed against all Radio and TV stations and the stations must periodically renew their broadcast licenses with the FCC.

Complaints can become a deal-breaker, particularly if another business group is trying to gain control of the frequency that is up for renewal, so most radio stations are very sensitive to having a listener go to the trouble of actually filing a formal complaint with the FCC.

And if you feel the offending station is purposely trying to "jam" a competitor on an adjacent channel, be sure to mention this as well in your complaint.

HD Radio is still in its infancy and will be on life-support for at least 2 or 3 years as there are no radios to buy. Most stations that implement HD Radio don't even have a monitor to listen to and monitor their HD Radio broadcasts! If every FM station that converts to HD Radio gets 50 to 100 (or more) complaints filed against them, this WILL BE NOTICED at the FCC and it would be a big help in killing off HD Radio.

 

[pioneernut]

Thanks for the excellent explanation. I'm glad I'm not the only one who's noticed it. I think I'll have to go the route of getting a list of offending stations and try filling a complaint. FM radio would be fine, if they just played something worthwhile and quite firing djs and reformating good stations.

Thanks for the info,
Mike

 

[Vinyl Rules!]

Question About Your Pioneer F-91

Mike,

I noticed you list a Pioneer F-91 as your tuner.

In the FM Tuner Group, the Pioneer F-9, F-90 and F-99 have all been listed as being unaffected by HD Radio noise from adjacent channels. This is because all 3 of these tuners have excellent adjacent-channel selectivity so this makes them good tuners to use in an area whrere there are HD Radio stations broadcasting and you want to listen to a station that's adjacent to one.

The F-91 is an unusual design from Pioneer and rather unique: It's IF selectivity is changed on the fly by the tuner depending upon the amount of noise it detects from adjacent channels. On paper, this is a great idea as wide IF settings tend to sound better than narrow IF settings.

You noted your tuner, when in the scan mode, would sometimes stop next to the HD Radio station in your area and I'm guessing this is because there was enough signal bleed from the station to an adjacent channel to "trick" your tuner into stopping on the HD Radio noise bleeding into the adjacent channel.

I have two specific questions about your F-91:

(1) Are there any stations next to the HD Radio station that's causing your problem, and if there are stations, can you hear them OK, or is there noise in the background from the adjacent HD Radio station?

and

(2) How does your F-91 sound on the HD Radio station when you listen to it? I'm curious: When you tune to the frequency of a station broadcasting an HD Radio signal, some tuners with wide selectivity will pick up noise from the HD Radio sidebands which can sound like a hissy or crackling sound that is faintly in the background on the analog signal you are listening to.

I've not seen a posting anywhere noting how the F-91 performs in this kind of situation and I'm curious because the F-91's design is rather unusual with it's "sliding" selectivity that is automatically adjusted by the tuner.