>>Hiss behind the audio... Yes, does happen. Some stations have a more correct setup that others. The digital sidebands are sometimes less confined to the correct bandwidths. For example, the 550 station had extra sidebands at 27kHz either side of the 550 spot. While it was within the FCC requirements, they were still there. The upper and lower sidebands are supposed to be phased. One is -90° and the other is +90°. That puts them at 180° and they null out in the analog band. If the antenna system isn't perfectly flat on the load across the whole spectrum, then some digital hiss would be heard as the null isn't as exact. <<
It isn't just hiss behind the audio either, as in the case of KFBK 1530. There becomes a echo hum behind with the hiss. I used to listen to KFBK at night years ago, but not any longer as the noise drives me nuts. It is very irritating to listen to. KFI has the noise too, but it isn;t as irritating as it is and not as loud. The KFBK's noise often sounds like a train behind their signal with a whoosing sound. Now on KCBS 740 is now bad. KEX can be noisy too, so I never listen to them. KEX is worse at night once the skip takes ahold of their signal. KSL isn't to bad. Some are and some aren't. >>And night skip does affect it, if there's a signal from an adjacent IBOC station. WBZ-1030 is 30+ miles from Providence. KDKA-1020 IBOC interferes with them at night. It affected one of my clients receiving EAS at night. I had to use one of the large ferrite loops set to null KDKA to fix that.<< I think there is a lot more IBOC in the East than here. The NW has not gone with it as much on AM. I think as I type this we only have a handfull of stations in the NW. The ones I know run is 24/7 are Tacoma/Seattle/Olympia/Everett 850/1250/1340/1380 Portland 1190/1330/1640 >>Other than a noninductive resistor load, there really is no flat transmit load anywhere. Antennas are different loads across a frequency band, some worse than others. That's probably the main reason why some stations are worse than others, and some don't run it at night. There is a limitation requirement for spurious signals. It's not expected to be zero, but under a specific value depending how far off the center frequency it is. Ever notice a second or third adjacent station has some noise? Happens on FM as well. I have a local 93.3 with IBOC. When they run that, I cannot hear a 92.7 station about 40 miles away.<< I have noticed IBOC hiss on frequencies there doesn't see to be a station adjacent at night, especially off the Eastern beverage. However, I know that the IBOC hiss can travel and if I do a bit a searching, I find some 5 KWer running IBOC in the Midwent or East on an adjacent that I probably am hearing. Too bad I cannot get the signal itself. A nice new catch. hi. >Given the quick addition of internet access in new vehicles, IBOC will probably be overrun by streaming audio. My personal guesstimate is that when the streams are accessable by a significant percentage of people, even transmitters may be less important. Think of the change from horses to automobiles a hundred years ago...<< I agree with you on that, I think that is coming. Especially in parts of the country where electric rates are climbing. Is the 50KW transmitter worth the cost to keep it running? The question is, will we be around by then to take advantage of the cleaner radio dial? It seems many of these stations are reluctant to drop the IBOC, even though there is no adantage of keeping it especially on AM. IBOC radios have never been big sellers, even for FM. Patrick Patrick Martin Seaside OR KGED QSL Manager _______________________________________________ IRCA mailing list IRCA@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: irca@hard-core-dx.com