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New feature for HD AM : Added Buzz to audio

T

Tom Wells

I wasn't going to bring this up, but now that there's 2 stations with this effect, I must.
WSCR AM 670 and WGRB AM 1390 now both have a buzzy rasp that follows modulation, stopping and starting along wih modulation. This is new, and in addition to the "normal" sideband hissing. It is exactly the same regardless of
center or side tuning, and must be very annoying to the listeners. Sounds like a torn speaker cone or worse.
WBBM 780 shows no signs of such a buzz, or WTMJ 620. None on 1690, either. Oh, and WMVP 1000 seems to have quit HD for good. Anyone else heard this new "issue"?
 
I wouldn't pretend to know about these two specific cases. But with two other cases where I've had the "opportunity" to A-B monitor an AM with the IBOC switched on and off in real time, I've heard a distinct loss of clarity when the digital kicks on. It sounds like about a 6 dB drop in apparent loudness accompanied by a mushy, indistinct kind of distortion - which I would guess is a form of increased intermod. I also noted a high-frequency whine on WBZ with IBOC on which goes away instantly when the IBOC is switched off.

One supposes that all the sideband digital data is somehow bleeding into and mucking up the analog modulation envelope. I know that there has been a history of IBOC causing PA module failures in high-power Harris transmitters, so the modulation mode-mix can't be doing good things with the mod circuitry.

Anyone know of any recent "updates" to the IBOC firmware? Could Tom's symptoms be coming from a late-summer drop in ground conductivity with a shift in the antenna load at the common point?
 
The radios in my grandparents' two 1996 Chrysler LHSes (the higher-end factory-stock radios of that year, build-in tape/CD players and CQAM stereo on mediumwave) have the same problem Tom describes when tuned to KEX. (I know PDX has at least two others transmitting IBAC channels, but I haven't really paid attention to them.)

With speech (KEX is a mostly right-wing political talker) it is especially noticeable, particularly on sharp sounds (like the "S"es in the phrase "sharp sounds", for example.) It kind of reminds me of listening to the audio on some of the old all-analogue "Laser Vision" discs, when the CX noise reduction kicks in, remember those? ;o)

I don't remember the particular model of the radio (I will post it here when I find out) but its MW section is wide enough that the IBAC noise on KEX is quite audible when listening in a quiet environment. Oh yeah, and then there's KKAD, which doesn't run IBAC (yet) but still clobbers pretty much everything on the east half of the dial......
 
I'm hearing this on any radio used, but only one the two stations listed.
The 6 db effective loudness decrease, mushiness and hiss are the standard-issue noise, which is the same in this case.
This sounds like old-fashioned parasitic oscillation triggered by the audio.
I have heard such noises freqently over the years before HD if a station had a RF leakage back into the audio, or some failed caps which no longer supressed the oscillation. If there were no audio, the buzz would stop. In fact, in this
case there seems to be a threshold for the audio at which the added noise is stopping and starting.
 
I too have noticed the drop in loudness, and the 'hiss' and the analog AM tuner I'm using has a nice 6KHz I.F. filter installed.

Regarding the HD (AM) radio, I get a 'time bomb' ticking sound from using the AUX input OR when using the headphone output to record HD AM (to try to show others how it sounds - so NOT a good 'feature').
Anybody else get this timebomb electronic audio ticking sound on the Directed Electronics tabletop HD radio when using the headphone jack or AUX input??
 
Maybe the "time bomb" EFX is built into the HD firmware by iBiquity to remind you to send in your annual royalty check!

30 days prior to the due date, it starts ticking over the air. The ticking gets faster and faster as the expiration date approaches - and on the fateful day, a digital (artifact-laden) alarm clock goes off, and the Decepticon shuts down! :D
 
By the way, is there anybody "home" at Directed Electronics (DICE) in regards to their HD radios? My DICE automotive converter has died, but I could get no tech support from DICE. Now I'm trying to find out about a firmware fix (maybe) for the DICE desktop radio timebomb ticker, and I'll be damned if I can talk to a real person at Directed Electronics about their HD radio issues.
Anybody got an inside contact at DICE, or do I have to mail my HD radios to Strubble with some treats from my dog (post digestive tract)?
 
JohnnyElectron said:
By the way, is there anybody "home" at Directed Electronics (DICE) in regards to their HD radios? My DICE automotive converter has died, but I could get no tech support from DICE. Now I'm trying to find out about a firmware fix (maybe) for the DICE desktop radio timebomb ticker, and I'll be damned if I can talk to a real person at Directed Electronics about their HD radio issues.
Anybody got an inside contact at DICE, or do I have to mail my HD radios to Strubble with some treats from my dog (post digestive tract)?
Click to expand...

The probably only sold three and don't care very much about it. :D
 
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