With IBOC turned loose, I'm going to take a different tack on some of this and focus on the actual bandwidth. There is a requirement that stations' signals fit within a clearly defined mask. I wonder how many are truly in compliance 24/7/365? If the antenna system changes such as with wet ground, that may alter things. Further, I would be willing to bet that many just barely fit the mask - or may not even be in complete compliance. If that is the case, then if a station is found to be interfering, the victim may have an administrative recourse. I would hope that Bob Savage considers this.
Next week one of my clients is to have it's yearly RF occupied bandwidth and spurious signal tests done. I'll query the fellow who does this about what he's found, and just what equipment and methods are required to make a case against an offender. This house of cards may have a rather well-hidden vulnerability. This needs to be examined more closely. In the past, several types of modulation monitors were built to ensure compliance with the rules. Perhaps some enterprising company will create a similar product to monitor occupied bandwidth of IBOC. I suppose the best way to test it would be to use a device like the SDR-IQ and record a part of the spectrum surrounding the assigned frequency. In that recording, drop carrier for a few seconds and do an A/B comparison to see what vanishes. The change of patterns at sunrise/sunset may provide just that opportunity, though shorter. Have any of you with a local IBOC station and a SDR-IQ or other radio equipped with a spectrum display looked at this? My SDR-14 has not arrived yet. Depending on the intensity of the anti-IBOC crowd, this could get interesting. I think much more can be done beyond a barrage of letters that will be ignored. And, all that is being done is a passive measurement to see if a station is complying with the rules. No different than looking at their monitoring points. Speaking of which, I have never seen IBOC referenced to antenna pattern monitoring points. I wonder if they are affected by the addition of the IBOC signals? If they are increased beyond limits, then that's another problem. The most commonly used field intensity meter isn't so narrowband that it would totally reject +/- 10KHz signals. And, the precise positioning of a null will be slightly different on those adjacent frequencies due to a differing phase shift. Yet another issue.. OK, I'm about six or eight months in advance of my self-imposed one per month IBOC posts.. I'll shut up now. Craig Healy Providence, RI ... Sent at 8:16AM EDT. _______________________________________________ IRCA mailing list [email protected] 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: [email protected]
