Comments on: The lesser of two evils http://www.engineeringradio.us/blog/2009/10/the-lesser-of-two-evils/ When I was 10, I caught the radio bug, it appears to be terminal Thu, 09 Sep 2010 01:18:14 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: admin http://www.engineeringradio.us/blog/2009/10/the-lesser-of-two-evils/comment-page-1/#comment-1515 admin Wed, 25 Aug 2010 19:42:16 +0000 http://www.engineeringradio.us/blog/?p=397#comment-1515 John, the information I used for this article came from the NPR labs December 2009 report. It states: "IBOC OFDM subcarriers are transmitted in two frequency bands that extend (for mode P3: Primary Main and two Extended Partitions) from 114 kHz to 198 kHz above and below the host FM channel center frequency." Granted, this is the worst case scenario, with three separate audio programs being transmitted in HD. One can only assume that would happen, and is happening, especially with public radio stations. I rounded up from 396 KHz to 400 KHz. Further, I understand your statement on the ODFM subcarriers and modulation. Increasing the noise floor, which is what HD radio does, makes analog receivers less sensitive. Additionally, with the hilly terrain in these parts, it is completely conceivable that within a 54 dBu contour, terrain shadowing will create areas of low signal strength. If those areas have a better line of sight to an adjacent channel IBOC station, the radio will cut out in ways that it didn't do before. Thus creating a perception of poor FM radio performance with the listeners. I can only assume you meant to continue your comment, so please do. I invite views counter to my own. John, the information I used for this article came from the NPR labs December 2009 report. It states:

“IBOC OFDM subcarriers are transmitted in two frequency bands that extend (for mode P3: Primary Main and two Extended Partitions) from 114 kHz to 198 kHz above and below the host FM channel center frequency.”

Granted, this is the worst case scenario, with three separate audio programs being transmitted in HD. One can only assume that would happen, and is happening, especially with public radio stations. I rounded up from 396 KHz to 400 KHz.

Further, I understand your statement on the ODFM subcarriers and modulation. Increasing the noise floor, which is what HD radio does, makes analog receivers less sensitive. Additionally, with the hilly terrain in these parts, it is completely conceivable that within a 54 dBu contour, terrain shadowing will create areas of low signal strength. If those areas have a better line of sight to an adjacent channel IBOC station, the radio will cut out in ways that it didn’t do before. Thus creating a perception of poor FM radio performance with the listeners.

I can only assume you meant to continue your comment, so please do. I invite views counter to my own.

]]> By: John Welstein http://www.engineeringradio.us/blog/2009/10/the-lesser-of-two-evils/comment-page-1/#comment-1511 John Welstein Wed, 25 Aug 2010 11:13:01 +0000 http://www.engineeringradio.us/blog/?p=397#comment-1511 A few exaggerations in your article: Standard IBOC actually takes up 138 kHz of bandwidth total, that is 69 kHz on each side, and each of the sub-carriers are at least 45dB down (so for a 16 kW station each sub-carrier is less than 0.5 watt), it's only when you sum all the sub-carriers' powers that you get a total of 1% power. Each sub-carrier is only 0.4 kHz wide, so for this example of a distant first adjacent 16 kW station (at 300m), only 19 watts of that is co-channel with the 0 to 15kHz of the desired station 0.2 MHz away. If this is class B for both desired and undesired stations, they would be located at least 100 km away even if shortspaced, and normally 169 km to comply with FCC spacing. Now tell me that a 19 watt co-channel station (with white noise audio) at these distances is a serious threat to listeners within your 54 dBu contour. Granted that during trop, this may sometimes be receivable, but co-channel trope with analog audio is far more objectionable. There are 10 A few exaggerations in your article: Standard IBOC actually takes up 138 kHz of bandwidth total, that is 69 kHz on each side, and each of the sub-carriers are at least 45dB down (so for a 16 kW station each sub-carrier is less than 0.5 watt), it’s only when you sum all the sub-carriers’ powers that you get a total of 1% power. Each sub-carrier is only 0.4 kHz wide, so for this example of a distant first adjacent 16 kW station (at 300m), only 19 watts of that is co-channel with the 0 to 15kHz of the desired station 0.2 MHz away. If this is class B for both desired and undesired stations, they would be located at least 100 km away even if shortspaced, and normally 169 km to comply with FCC spacing. Now tell me that a 19 watt co-channel station (with white noise audio) at these distances is a serious threat to listeners within your 54 dBu contour. Granted that during trop, this may sometimes be receivable, but co-channel trope with analog audio is far more objectionable.

There are 10

]]> By: admin http://www.engineeringradio.us/blog/2009/10/the-lesser-of-two-evils/comment-page-1/#comment-178 admin Fri, 11 Dec 2009 13:47:26 +0000 http://www.engineeringradio.us/blog/?p=397#comment-178 <em>NPR and PBS should not receive taxpayer funding</em> Truer words have not been spoken. Perhaps somebody should write a petition to move IBOC to the 76-88 MHz band. NPR and PBS should not receive taxpayer funding

Truer words have not been spoken.

Perhaps somebody should write a petition to move IBOC to the 76-88 MHz band.

]]> By: J. Aegerter http://www.engineeringradio.us/blog/2009/10/the-lesser-of-two-evils/comment-page-1/#comment-167 J. Aegerter Wed, 09 Dec 2009 19:38:03 +0000 http://www.engineeringradio.us/blog/?p=397#comment-167 It would be impossible for me to disagree. NPR and PBS should not receive taxpayer funding in my opinion as they always seem to come up with self-serving ideas. The local affiliates have their auctions and "bake sales" and can live without federal funding! America is broke and near bankruptcy. The LPFMs have more to contribute and I have always believed; "the more the merrier" when it comes to domestic broadcasting. With the advent of new Digital TV broadcasting, recently there has been a proposal to collapse the standard 6 MHz. TV channels to conserve bandwidth; while the AM band is now full of man-made noise from IBOC, and the FM band is heading in the same direction. If digital broadcasting is so great, then why not re-allocate 76-88 MHz. for Digital-only broadcasting, and see how this flies? It would be impossible for me to disagree. NPR and PBS should not receive taxpayer funding in my opinion as they always seem to come up with self-serving ideas. The local affiliates have their auctions and “bake sales” and can live without federal funding! America is broke and near bankruptcy. The LPFMs have more to contribute and I have always believed; “the more the merrier” when it comes to domestic broadcasting.
With the advent of new Digital TV broadcasting, recently there has been a proposal to collapse the standard 6 MHz. TV channels to conserve bandwidth; while the AM band is now full of man-made noise from IBOC, and the FM band is heading in the same direction. If digital broadcasting is so great, then why not re-allocate 76-88 MHz. for Digital-only broadcasting, and see how this flies?

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