TVTechnology: AM IBOC Interference Dispute Sparks Debate

Leslie Stimson / 09.10.2009

AM IBOC Interference Dispute Sparks Debate

My story in the previous issue about an IBOC interference dispute between two California AMs generated much reader interest.

Midwest Television, licensee of KFMB(AM) in San Diego, submitted a second interference complaint to the commission about Kiertron, licensee of KBRT(AM), a Class D in Avalon, Calif., and has asked the agency to suspend KBRT's authority to transmit in digital. KBRT says it has reduced its digital power by 6 dB but feels the previous FCC notice to turn off its digital power isn't final.

Some commenters say KBRT should ask the FCC to let the station transmit in all-digital mode; however the commission rules governing IBOC are for a hybrid analog-digital system only. It hasn't gotten to the all-digital rules yet.

Another reader says "stations used to be held accountable with possible fines for interfering. Now they just let it go [be sold] to the highest bidder."

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Posted by: Jerry Arnold

Thu, 09-10-2009 - 7:15PM Report Comment

The FCC with their palms neatly greased by Ibiquity on a regular basis is not going to do a thing as far as IBOC goes that would in any way stop that flow of cash. FCC Rules and regulations are conveniently given a knowing wink and a nod. The ONLY hope the AM band has is IF enough AM broaders continue to refuse to clutter up the band further by implementing this science fiction.

Posted by: Anonymous

Mon, 09-14-2009 - 9:32AM Report Comment

The fact is that KBRT was on the channel all by itself for many years before KFMB moved in back in 1962 and created a ton of 5 mV overlap and interference that did not previously exist. Today, KBRT could LEGALLY fill up its spectrum to the limits specified in 73.44 with anything other than IBOC carriers and there would be no recourse for "newcomer" KFMB. Thankfully, that hasn't happened, and thankfully KBRT has been cooperative. I have it on good authority that KBRT VOLUNTARILY reduced its digital sideband power by 6 dB before the FCC ordered the reduction. I'm betting that a further voluntary reduction is in the works somewhere along the line. The IBOC issue aside, the lesson here is that when you move in and create a situation with almost complete overlap, you're going to have to expect a bunch of interference. What the heck do you expect??

Posted by: Anonymous

Thu, 09-10-2009 - 6:11PM Report Comment

Those two stations are 20kHz apart. There would be NO PROBLEM AT ALL if they both turned off their HD carriers! Heck, I hear them both just fine with my narrowband table radio. Don't tune between them, thought!

Posted by: Anonymous

Fri, 09-11-2009 - 11:29AM Report Comment

When KBRT ran C-Quam there was no interference problem on 760KHz, so I say they go back to C-Quam and have some really great sounding analog instead of harsh audio up and down the dial. If they don't want to do decent-sounding analog then they should seriously push the FCC for TV channels 5 & 6 for AM migration to all-digital FM on the low-end of the band.

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