{"id":6424,"date":"2013-03-14T08:00:45","date_gmt":"2013-03-14T12:00:45","guid":{"rendered":"http:\/\/www.engineeringradio.us\/blog\/?p=6424"},"modified":"2023-04-08T19:58:35","modified_gmt":"2023-04-08T23:58:35","slug":"the-am-hd-all-digital-test-part-i","status":"publish","type":"post","link":"https:\/\/www.engineeringradio.us\/blog\/2013\/03\/the-am-hd-all-digital-test-part-i\/","title":{"rendered":"The AM HD all digital test, Part I"},"content":{"rendered":"\n

After reading this article in Radio World<\/a> it seems the all-digital AM testing completed last December was “nearly flawless.” This comes as no surprise considering that WBCN is owned by CBS, also an iBiquity investor.\u00a0 Could there really be another result?\u00a0 I think not.\u00a0 But let us examine the technical aspects of the WBCN test itself.<\/p>\n\n\n\n

WBCN is on 1,660 KHz in the expanded part of the AM band.\u00a0 According to the FCC database, it transmits from a single 90.7 degree tower.\u00a0 As such, the tower is likely either broad-banded already or easily modified to be.\u00a0 Also according to the FCC database, there are eight other stations licensed to 1,660 KHz, all of which transmit with a power of 1 KW at night.\u00a0 This eliminates much of the interference issues found on the rest of the AM band.\u00a0 It can be further noted, the problem with electrical noise is most prevalent below 1,000 KHz.\u00a0 There is little wonder in the nearly flawless results.<\/p>\n\n\n\n

From a technical standpoint, this is about as favorable a testing configuration as can be conceived for AM IBOC.  If AM HD radio did not work under these test conditions, then it would never work at all.  The actual data from the tests has yet to see the light of day and it may never be released.  This is likely due to the same reason the NAB will not release its technical improvement study on AM; we simply won’t understand it.<\/p>\n\n\n\n

Near the end of the article, someone (it is not exactly clear who) asks the NAB, “Why the opacity?” For which the answer given is “to get stuff done.”\u00a0 There is a fair bit of hubris in that statement.\u00a0 Is the NAB now the technology decider for the rest of us?\u00a0 I think not.\u00a0 Shutting out everyone but a very select few rightly causes suspicion, something that the Radio World article acknowledges.<\/p>\n\n\n\n

Accurate, real-world testing involves more than using one technically favorable test subject.\u00a0 In fact, the tests should be run in the most technically challenged environment to present meaningful data points in real-world conditions.\u00a0 Stations like a six-tower directional on 580 KHz, a 190-degree tower with a folded unipole on 810 KHz, or pretty much any class C AM station at night time.\u00a0 These types of tests will represent at least a few of the existing antenna systems and stations.\u00a0 Will that happen?\u00a0 It depends on whether the FCC will hold somebody’s feet to the fire and demand meaningful testing.<\/p>\n\n\n\n

Much ink has already been spilled by various trade publications debating the future of AM broadcasting.\u00a0 Most take the position that there are several technical issues that make AM broadcasting problematic if not downright untenable.\u00a0 There are indeed some technical issues with AM when compared with FM or IP-based audio distribution.\u00a0 There are also several ways that AM broadcasting is superior to both FM and IP-based audio distribution.\u00a0 The truth is that AM broadcasting’s issues are complex and involve technical, regulatory, and operational considerations.<\/p>\n\n\n\n

These can be broken down as follows:<\/p>\n\n\n\n