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Old 21st August 2012, 09:36 PM   #1
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Default Have IBOC noise on your FM? Please do this

The FCC has established an "Interference Protection and Complaint Remediation" procedure to protect the reception of analog FM signals. It is documented starting at page 10 in http://hraunfoss.fcc.gov/edocs_publi...A-10-208A1.pdf . This procedure is a bit complex, and it requires that you first contact the station that you believe is receiving the interference. The onus is on them to first try to work it out with the station supposedly creating the interference.
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Old 22nd August 2012, 05:05 PM   #2
kevinkr is offline kevinkr  United States
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Good tip.. I've pretty much given up on FM as a source of music for mostly commercial not technical reasons, but those of you who haven't this might be worth considering if your favorite station is the one being interfered with.

Something else to note is that some tuners are much better at rejecting iboc on channel and adjacent(?) sidebands than others, might want to check whether reception issues are consistent from tuner to tuner.
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Old 23rd August 2012, 03:52 PM   #3
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My problem station is KBAQ in Phoenix.

Tuners which have been noisy on KBAQ are: Updated and aligned Dynaco FM-3, McIntosh MX-130, Harman-Kardon TU 920, Sony ST-S550ES, freshly aligned Harman-Kardon Citation IIIX, Harman-Kardon Citation 14, Sherwood S3000-V.

A few tuners are quiet on KBAQ: Scott 370 and 312C, McIntosh MR-65B.

Many FM users on internet user groups report less HD-related noise from those Scott tuners, which reinforces my suspicion of HD-related noise.

Another user reports: "The Luxman 5T10 is a highly regarded tuner... just noisy on KBAQ."

There's a thread on Audiokarma: List Of Tuners That Can Properly Filter HD Radio Self Noise? at List Of Tuners That Can Properly Filter HD Radio Self Noise? - AudioKarma.org Home Audio Stereo Discussion Forums. Good luck!
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Old 23rd August 2012, 04:12 PM   #4
kevinkr is offline kevinkr  United States
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My understanding is that tuners with particularly good SCA filtering ahead of the MPX may be immune to most if not all iboc interference.. My McIntosh MR-71 in particular and Kenwood KT-8005 seem not to have issues with iboc interference..

It is possible that a carefully designed unity gain linear phase LPF filter cutting off around 65kHz and placed between the detector and MPX decoder might help.
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Old 23rd August 2012, 04:31 PM   #5
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Quote:
Originally Posted by hifigeezer View Post
The FCC has established an "Interference Protection and Complaint Remediation" procedure to protect the reception of analog FM signals. It is documented starting at page 10 in http://hraunfoss.fcc.gov/edocs_publi...A-10-208A1.pdf . This procedure is a bit complex, and it requires that you first contact the station that you believe is receiving the interference. The onus is on them to first try to work it out with the station supposedly creating the interference.
The other people on this thread seem to write about how HD radio signals interfere with the reception of the FM signal of the same station. That is, when the station you want to listen to turns on HD radio, you have to contact the station and it should then try to work it out with itself?
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Old 23rd August 2012, 04:35 PM   #6
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Please read the page at the link below on IBOC (HD radio) noise and analog FM reception. Note that at the end of the page there is a list of tuners that have post-detection filters that remove or greatly attenuate IBOC noise. It's likely not complete, but it helps you pick out the technology that is already there in certain vintage tuners...

HD Radio Self-Noise

I have invested in some vintage tuners from the list. Luckily I have some high quality FM stations nearby. You can definitely tell the difference! My latest acquisition is a Technics ST-S8 which needed some alignment. I also have a Pioneer F-99X, which is a really great little tuner. Both are nice!

-Charlie

Last edited by CharlieLaub; 23rd August 2012 at 04:41 PM.
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Old 23rd August 2012, 04:39 PM   #7
kevinkr is offline kevinkr  United States
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Actually it is both interference from the originating station and interfering side bands from the closest adjacent station that has been discussed here. The remedies (non-technical) are different of course, and note that the iboc technology discussed here is different from DAB and other European digital FM formats.

Iboc creates a lot of problems for critical listeners and the great irony is that comparatively few FM receivers currently in use in this country support it. FM and satellite radio will probably be killed off by internet radio unless I miss my guess. (Many new cars here offer internet connectivity in one guise or another)
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Old 23rd August 2012, 08:33 PM   #8
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Originally Posted by MarcelvdG View Post
The other people on this thread seem to write about how HD radio signals interfere with the reception of the FM signal of the same station. That is, when the station you want to listen to turns on HD radio, you have to contact the station and it should then try to work it out with itself?
Yes. It will be interesting to see whether the noisy station takes the blame or points the finger at the alternate channel. If they admit they are the problem, in theory the regulators should make them correct it. Stations in the USA are mostly owned by corporations but some are listener-supported. It can be hard to get the government to enforce the rules.
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