More Evidence of HD-Radio Interference

[dbdigital]

This letter was written by the respected engineer Elliott Klein of Klein Broadcast Engineering, L.L.C. and sent to CGC:

"SPECTRAL "REGROWTH" (HD RADIO STYLE) IN THE DENVER FM MARKET

"Spectral regrowth is created as intermodulation products
between the IBOC carriers and the analog carrier. The resulting
spectral regrowth causes unacceptable second, third, fourth and
sometimes in extreme cases fifth adjacent channel interference....

I experienced the problem firsthand at a client's station in the
Denver market."

How he dealt with it is discussed here: http://www.bext.com/_CGC/2007/cgc800.htm

More and more HD-Radio appears to have that 'rush to market, worry about the issues later' look about it.

But here's a reply to Mr. Klein's letter:

http://earthsignals.com/add_CGC/Letters/DenverHD_resp_Klein.htm

db

 

[4dude]

I hope the FCC is flooded with complaints about this crap taking over the AM spectrum..... (Not that it will do any good)

 

[dbdigital]

As a follow up to my earlier entry, broadcast engineer Elliot Klein wrote a lengthy letter to LA Radio on the subject of HD-Radio and reception problems. I wish I could reprint the whole letter since most of you don't subscribe to LA Radio but here are a few points of interest from it:

"In an urbanized, cluttered area such as Los Angeles, Chicago (which is an ideal market for IBOC because its flat with no terrain issues) or any other urbanized metro area the IBOC HD radio coverage starts to become unreliable at a field strength of less than 90 dBu. This is five to ten times higher than needed for reliable good quality analog FM reception. My business associate, from The RF Team, Paul Strater, lives in Oswego, IL. and can see the top of the Hancock Center from his two story home. His residence is well with the 60dBu contour (1.0mV/M) let alone the protected 54dBu (0.5mV/M) contour of the class "B" stations located atop the building, the same signal strength to which most of the stations on Mt. Wilson are FCC protected. Paul Strater has told this writer numerous times he can NOT reliably receive any IBOC HD radio transmission without an outdoor antenna at his home.

I favor the idea of streaming AES/EBU audio and data (digital audio and data) on a sub-carrier of the main analog carrier. Similar to what we as broadcasters did with Muszak or leasing out an FM station's sub-carrier frequencies to a company that ran stockmarket quotes in the form of data on the subcarrier. We could now run digital audio on the old subcarriers ourselves, this would actually approximate the analog FM station's regular coverage. Additionally, this would greatly reduce the possibility of adjacent channel interference to other stations."

Sounds like he's describing FMeXtra.

"My personal opinion on IBOC HD radio is that it is a poorly conceived system and does not come close to replicating an FM station's analog coverage. If we are having noise and interference problems with the IBOC HD signals now, then just imagine what it will be like with the Ibiquity request before the FCC to allow more power for the IBOC HD radio signals."

http://www.laradio.com/

db

 

[scanman1]

I hope the FCC is flooded with complaints about this crap taking over the AM spectrum..... (Not that it will do any good)

Me too, especially since, from experience, I know you can't even get a proper lock on the Digital signals and still prefer the analog audio. 8)

 

[dbdigital]

Here is a reply from Elliott Klein in response to an engineer who disputed his claim by stating that the offending station was in full FCC compliance.

"REPLY COMMENT ON FM HD RADIO ADJACENT CHANNEL INTERFERENCE

Responding to the "Long Form Reply" to my letter posted
in CGC #800 regarding "IBOC spectral regrowth," I know what we
measured. I heard the interference before the bandpass filter
was installed. [EDIT]

Elliott Klein, Klein Broadcast Engineering, L.L.C."

http://www.bext.com/_CGC/2007/cgc801.htm

So the issue of digital noise on adjacent channels is not just a figment of some HD-Radio-hater's imagination, it is real and a problem for existing analog radios. The bandpass filter sounds like a good remedy.

db

[EDIT-post truncated because quote originates from a copyrighted source. As this citation does not follow standard guidelines for fair use, it has been cropped. Unauthorized use of copyrighted content is a violation of our terms of service. The correct URL for the quote has been provided by Radio-Info below as a courtesy.]

http://www.bext.com/_CGC/2007/cgc802.htm

 

[davideduardo]

Re: No Evidence At All of HD-Radio Interference

Here is a reply from Elliott Klein in response to an engineer who disputed his claim by stating that the offending station was in full FCC compliance.

..... (clip)

So the issue of digital noise on adjacent channels is not just a figment of some HD-Radio-hater's imagination, it is real and a problem for existing analog radios. The bandpass filter sounds like a good remedy.

You should get an award for taking things out of context and making them seem to support your conclusions when, in fact, they do not in any form or fashion.

The "problem" is not inherent in HD radio with properly designed HD exciters. However, one model by one manufacturer did not work per iBiquity and FCC specs, and the engineer of the second adjacent station spoke with the offending station's engineers and they quickly shut the defective exciter off and sent it back to the factory.

The interferred with station is KRCD 102.9 in Los Angeles. The interference was from KBIG. The HD exciter was from BE. I work for the owner of KRCD.

Properly operating, there is no second adjacent interference. And in this case, defective equpment was the issue.... the HD system is not the issue.

Again: the issue was a defective exciter, which was not built by iBiquity. Nice try to twist the event to fit your agenda... but you are just 100% wrong on this one. Next time you make one up, try not to make up something about one of the stations I work with every day.

 

[vsa]

Re: No Evidence At All of HD-Radio Interference

Here is a reply from Elliott Klein in response to an engineer who disputed his claim by stating that the offending station was in full FCC compliance.

..... (clip)

So the issue of digital noise on adjacent channels is not just a figment of some HD-Radio-hater's imagination, it is real and a problem for existing analog radios. The bandpass filter sounds like a good remedy.

You should get an award for taking things out of context and making them seem to support your conclusions when, in fact, they do not in any form or fashion.

The "problem" is not inherent in HD radio with properly designed HD exciters. However, one model by one manufacturer did not work per iBiquity and FCC specs, and the engineer of the second adjacent station spoke with the offending station's engineers and they quickly shut the defective exciter off and sent it back to the factory.

The interferred with station is KRCD 102.9 in Los Angeles. The interference was from KBIG. The HD exciter was from BE. I work for the owner of KRCD.

Properly operating, there is no second adjacent interference. And in this case, defective equpment was the issue.... the HD system is not the issue.

Again: the issue was a defective exciter, which was not built by iBiquity. Nice try to twist the event to fit your agenda... but you are just 100% wrong on this one. Next time you make one up, try not to make up something about one of the stations I work with every day.

KRCD is at 103.9 not 102.9. KBIG is at 104.3.

 

[davideduardo]

Re: No Evidence At All of HD-Radio Interference

KRCD is at 103.9 not 102.9. KBIG is at 104.3.

Typo. 103.9 is the second adjacent to KBIG. Obviouslly, as the creator of the KRCD fomrat, and having put it on the air on 2/11/07 I do realize it is on 103.9. http://www.davidgleason.com/2006_Recuerdo.htm

The other defective BE exciter was on Jack, and was interferring with another Class A, on 93.5. It got sent back to Quincy, too.

 

[dbdigital]

Re: No Evidence At All of HD-Radio Interference

Here is a reply from Elliott Klein in response to an engineer who disputed his claim by stating that the offending station was in full FCC compliance.

..... (clip)

So the issue of digital noise on adjacent channels is not just a figment of some HD-Radio-hater's imagination, it is real and a problem for existing analog radios. The bandpass filter sounds like a good remedy.

You should get an award for taking things out of context and making them seem to support your conclusions when, in fact, they do not in any form or fashion.

The "problem" is not inherent in HD radio with properly designed HD exciters. However, one model by one manufacturer did not work per iBiquity and FCC specs, and the engineer of the second adjacent station spoke with the offending station's engineers and they quickly shut the defective exciter off and sent it back to the factory.

The interferred with station is KRCD 102.9 in Los Angeles. The interference was from KBIG. The HD exciter was from BE. I work for the owner of KRCD.

Properly operating, there is no second adjacent interference. And in this case, defective equpment was the issue.... the HD system is not the issue.

Again: the issue was a defective exciter, which was not built by iBiquity. Nice try to twist the event to fit your agenda... but you are just 100% wrong on this one. Next time you make one up, try not to make up something about one of the stations I work with every day.

The stations involved are in the Denver area not Los Angeles:

"I'm familiar with the Denver spectral regrowth case and
have even laid eyes on the filter that fixed the problem. The
Class C in Denver is Entercom's KALC "Alice" on 105.9 and the
rim-shot, KJAC, is licensed to Timnath with its transmitter site
in a canyon way up north." - Cris Alexander

If you re-read Mr. Elliott's remarks, he plainly indicates that this is a problem with the technology itself:

"Spectral regrowth is a problem with the HD technology. It
occurred in Denver and other markets."

Obviously he has seen this elsewhere and, as a respected engineer, understands the reasons underling it.

I refuse to get into a pissing contest with you and really dislike being "stalked".

db

 

[davideduardo]

Re: No Evidence At All of HD-Radio Interference

"Spectral regrowth is a problem with the HD technology. It
occurred in Denver and other markets."

I refuse to get into a pissing contest with you and really dislike being "stalked".

This issue, a repeat of the LA problem, was caused by a paarticular brand of exciter, not the technology.

 

[dbdigital]

Re: No Evidence At All of HD-Radio Interference

"Spectral regrowth is a problem with the HD technology. It
occurred in Denver and other markets."

I refuse to get into a pissing contest with you and really dislike being "stalked".

This issue, a repeat of the LA problem, was caused by a paarticular brand of exciter, not the technology.

If you disagree with Mr. Klein's conclusion then I suggest you contact him at Klein Broadcast Engineering, LLC. Look him up, he's in the book.

db

 

[davideduardo]

Re: No Evidence At All of HD-Radio Interference

If you disagree with Mr. Klein's conclusion then I suggest you contact him at Klein Broadcast Engineering, LLC. Look him up, he's in the book.

No need to. A misbehaving exciter will cause exactly the problem described. The manufacturer of the offending units is retrofitting them, and the issue is pretty much closed.

This is not unlike the problems with drifting Ampliphase transmitters on AM in the 60's... one misbehaving rig could cover 500 kHz up and down the dial.