AM HD TURNOFF PACE ACCELERATES

[Tom Wells]

Why do some of these station's IBOC go off for a few days and then come back on?

NO one knows!   ( Officially )

Possible and quite plausible reasons:

1. Encoding has failed and all hissing is in vain. It can actually hiss uselessly for days with no decode possible.
KFUO ? the Lutheran college in St Louis had this and *sparkles* beyond the hiss to about 60 khz each side.  Reboot did not help....they turned it off for quite a while.

2. Encoder hardware has failed and waiting on repair/replacement/upgrades.
3. Antenna system  bandwidth/spectral regrowth issues, and being worked on as part of upgrades to AM HD, each step reducing
    to some degree the intrusiveness of the hiss as perceived to local listeners (step 1) and less splat on 2nd adjacents,
    (step 2).
 4 No one noticed it was off.  ( It is sad but some radios are so crippled by design that you can't hear anything above 3 khz. )
 5.Live sports broadcast, "forgot" to turn back on/wouldn't boot.
 

[DavidEduardo]

Why do some of these station's IBOC go off for a few days and then come back on?

Most stations don't have backup HD equipment. Between the economy, uncertainty about HD's benefits and insecurity about whether the hardware will be signficantly changed or altered there are quite a few reasons why stations won't have backups any time soon. 

[Savage]

Tom: you forgot:

6.  Got to the Tx site but forgot to stop to get change, so couldn't pump more quarters into the HD exciter - no pay, no play

7.  Barometric pressure was too high on an alternate Thursday for the HD to work

8.  Couldn't get out to Tx to reboot Decepticon because had to fix GM's DirecTV system at home

9.  Engineering pickup truck needed oil change

10.  I just hate that #@!!xx** thing

[JohnnyElectron]

11: iBiquity hasn't sent me the parts I need to fix the exciter since I can't buy them myself!

12: Software upgrade didn't work last time, so I left it off - 24/7; no more AM IBOC for one of 2 stations.

13: AM Stereo worked, didn't piss-off the 2nd adjacents and we had a nice signal, (125%+ peaks /-100% neg peaks) was (is) plenty, who needs 140%+ anyhow?  And there were millions of Chrysler Minivans and GM's with AM stereo radios.  The hardware penatration of AM stereo in 1990 was equal to what XM/Sirius has now.
 

[klutch00]

11: iBiquity hasn't sent me the parts I need to fix the exciter since I can't buy them myself!

12: Software upgrade didn't work last time, so I left it off - 24/7; no more AM IBOC for one of 2 stations.

13: AM Stereo worked, didn't piss-off the 2nd adjacents and we had a nice signal, (125%+ peaks /-100% neg peaks) was (is) plenty, who needs 140%+ anyhow?  And there were millions of Chrysler Minivans and GM's with AM stereo radios.  The hardware penatration of AM stereo in 1990 was equal to what XM/Sirius has now.

I think it's high time that someone bring back AMAX Stereo. Wasn't that supposed to be a high-quality transmission standard?

[TVradioguru]

I think it's high time that someone bring back AMAX Stereo. Wasn't that supposed to be a high-quality transmission standard?

Years ago I received an earphone demonstration of AMAX AM stereo at NAB.  They weren't very pleased with my response to listening.  To me as compared with FM stereo, it was very unimpressive.  There was a high pitch tone or squeal above the music and talk.  I had very good hearing back in the day, and that tone would drive me, and most female listeners to change the station.  AM is in a rough situation to begin with.  Bringing back old failed technologies in the hope that radio manufacturers will adopt it is wasting the Internet bandwidth and effort to type it.

[satech]

Years ago I received an earphone demonstration of AMAX AM stereo at NAB.  They weren't very pleased with my response to listening.  To me as compared with FM stereo, it was very unimpressive.  There was a high pitch tone or squeal above the music and talk.  I had very good hearing back in the day, and that tone would drive me, and most female listeners to change the station.

That was probably the 10 kHz adjacent carrier whistle.  These days DSP based receivers can filter this out much more effectively than analog filtering ever could, while still preserving wideband audio response.  Unfortunately most DSP receivers are excessively narrowband on AM, probably because iBiquity convinced the manufacturers that a 5 kHz audio brickwall would soon become mandatory for all AM transmission in the USA.

[JohnnyElectron]

Two things in the electronics world have changed drastically since then: the ability to put AM stations carrier frequency 'dead-on' by using GPS, etc...and all DSP radios that can kill the 10KHz adjacents (in fact, the DSP radios can even kill the IBOC buzz on the 1st & 2nd adjacents!)  The 3rd gen AMAX chips and DSP also eliminates the AM Stereo 'platform motion' that Kahn was so opposed to. 
If iBiquity wouldn't sue me, I'd convert their exciters to transmit C-Quam -and- a barebones AM station ID for HD displays!
 

[HadYourPhil]

AM Stereo sounds dynamite on a good radio like the mid-2000's Dodge Intrepid radio, for example. No whistle, etc.

[klutch00]

Years ago I received an earphone demonstration of AMAX AM stereo at NAB.  They weren't very pleased with my response to listening.  To me as compared with FM stereo, it was very unimpressive.  There was a high pitch tone or squeal above the music and talk.  I had very good hearing back in the day, and that tone would drive me, and most female listeners to change the station.

That was probably the 10 kHz adjacent carrier whistle.  These days DSP based receivers can filter this out much more effectively than analog filtering ever could, while still preserving wideband audio response.  Unfortunately most DSP receivers are excessively narrowband on AM, probably because iBiquity convinced the manufacturers that a 5 kHz audio brickwall would soon become mandatory for all AM transmission in the USA.

OK so AMAX may or may not be the solution. Either way couldn't a high-quality analog transmission standard be implemented?