I noticed tonight that they really are putting out a stereo pilot tone. I haven't yet heard any program material that is obviously stereo yet.

really? I might have to listen and do some spectral analysis of their signal as I don't have any AM stereo receivers which indicate when a pilot is received.

Are you talking C-Quam analog AM Stereo? If so some of us will have to blow off the dust and plug in some old recievers...

exactly, that is what was meant analog AM stereo but the only ones I have are the Sony SRF-42 and the Accurain HD Radio receiver

Don't get your hopes up too high, guys. When I listened again, around midnight, the C-QUAM pilot tone was gone. My listening yesterday was done on a car radio using a Motorola MC13020P decoder, which needs the pilot tone to switch into stereo. I will have to try again tonight, using a Sony SRF42, just to see if any stereo material is being transmitted at all.

wow, just like the clock has been turned back 10 years KOMO STEREO 1000!

After listening to a few commercials on KOMO using the SRF42, I am pretty certain that there is NO stereo being transmitted.

hello,other stationskex,1010, etc...please resume AMStereo like komo is smart enough to do!!!!!

We have an AM stereo station still here in Edmonton, CHQT-880. It is Oldies formatted and sounds great -- yes, I still have my early 1980s Sony stereo receiver -- one of the final transistors is blown, but it works fine when you feed out of the REC OUT jacks. CHQT also feeds the local cable company with studio stereo that is fed on FM cable. We almost lost it a few months ago, but the morning Newsman still has AM stereo in his car, and convinced Engineering to replace the failing component of the AM stereo.

Most of the AM stereo stations here in southwest Washington and northern Oregon are no longer in stereo and one of them is now using IBOC but there are always skywave stations though. CHQT 880 is clobbered by KIXI down here but CKMX 1060 can be received in full stereo on a nightly basis.

I tried again a few minutes ago, and there is definitely no more stereo on AM 1000. My guess is that the times that I did detect the pilot tone, they must have been using a backup transmitter.

The answer from the horses mouth:

Brian,

Your E-mail was forwarded to me for reply.

First of all thank you for taking the time to write us with your
question, and of course for listening to KOMO AM 1000.

KOMO 1000 operated in AM stereo during the late 70's through the mid
80's, but not recently. In fact, all the AM stereo transmission
equipment was removed from service years ago.

Occasionally AM stereo capable receivers confuse night propagation, or
terrestrial noise with an AM stereo pilot tone. The result is the
stereo light on your radio may turn on, and it may attempt to decode
stereo, but KOMO is operating in mono.

If you have any additional questions, please feel free to contact me
directly.

Best Regards,

Kelly D. Alford
Vice President, Director of Engineering
Fisher Communications
kalford@fsci.com

back in 80s or 90s I listen to komo on my AM stereoreceiver, ther was muchplatform motion distortion,soundsfading up and down and back and forth.perhaps due to distance fome portland and seattlecompared with skywave distance and it fading too!!!!sounded wierd!!!I will try later tonite.will try 1010 too.

"Occasionally AM stereo capable receivers confuse night propagation, or terrestrial noise with an AM stereo pilot tone. The result is the stereo light on your radio may turn on, and it may attempt to decode stereo......"

This happens to me occasionally when I am listening to an AM station on my boombox and I have it situated near a computer, or sometimes even my satellite receiver. (If the TV set is on, AM reception turns into horizontal sync noise pretty much clear across the band!) It's just one of those weird AM things, I think. ;o)

KXL added AM Stereo in the early 90's for only one reason: Owner Les Smith's new Lexus had AM Stereo.

Boss Radio indeed.

Former KXL Chief Engineer Larry Wilson once told me that one day during Rush the stereo enhancer died and there was 40 minutes of dead air. That may have ended the stereo.

Stereo generators for both the main and backup transmitters were still in the rack as of July 2003.

> one day during Rush the stereo enhancer died and
> there was 40 minutes of dead air.

Were they doing "simulated stereo" on mono program material? I remember television stations that used to do this back then. As I understand it, simulated stereo was usually created using notch filters, sending the program material minus some band of frequencies to the left channel and sending the program material minus some different range of frequencies to the right channel. The idea was to fool the listener's brain into thinking that the sound was encircling him instead of coming from between the speakers. It sounded pretty bad.

right simulted stereo is bad. kxl did that for awhile.some beatles records have that too.yuechhhk!!!!I presume some FM stations might have done it back in 1960's??sometimes a slight delay is added to one channelwhih gives it kind of an echoey effect.butstill bad..if you switch to mono(L+R), the notch filtering is still quite noticable.sounds sort of hollow!!

I have never heard of notch filtering being used on stereo talk stations up to this point. Back when KNX 1070 from Los Angeles was running stereo it did not sound like any sort of pseudo stereo effect was being used and only the ads and jingles were in stereo. The fact that the radio was falsing is no surprise either it is possible for two carriers 25 Hz apart to create a heterodyne which can be confused by AM stereo decoders for a pilot tone under skywave conditions and sometimes even with groundwave reception too.

The third time that I encountered the "stereo pilot tone" on KOMO, I strongly started to suspect falsing. That time, the stereo indicator would come on when KOMO was fading out, and the indicator would go out when the signal was stable. I'm glad that we had the good fortune of getting an official answer on this thread.

KXL still has a great AM signal.

Lots of talkers and lots of cars. Turning the legacy AM Stereo on, given it's not a huge expense, could bring a nice bang for the buck.

If the audio chain is mono, big deal. The stereo capable radios will just open up. Talk, even that produced at a strict 5Khz, sounds better, crisper than it does with the narrow roll off.

I've noted that difference on my GE III. It's pretty nice overall.

Most AM Stereo capable car radios do not open up too wide. They won't hit the 10K, but they will do 6-8. That puts the aggressive roll off in a much better place for voice.

(won't sound pinched an as nasal)

Since they've local programming, they can call the shots on that, meaning Lars will sound just great in those cars.

Given KEX is HD, and the number of AM Stereo cars is highly likely to be higher than the number of HD capable cars, at this point in time, they could test the waters and see if overall audio quality is actually gonna impact them in a positive way.

At the least, that's a good test run to judge the merits of potential audio upgrades.

If the audio chain happens to be stereo capable, the local programs could pack a nice punch! The bumpers would improve, but so could segments with guests!

I'm working in the Detroit-area long-term, and some CBS Radio stations here are transitioning to HD Radio on both the AM and FM bands. They are pushing dealers who sell digital home and car radios as part of their promotion.

I like the local dealer angle. Really it's about some numbers right now, and the local value add is always good to see.

To clarify my above post, I'm largely ok with where AM HD is at right now. The stuff I've been able to hear has transitioned past the quality of better web streams. Longer term, given that continues and stations can get along, it's all good.

Where I was really headed was bang for the buck, and to see if quality makes any real difference. Lighting up the older AM Stereo rigs will make a difference. On talk, it's a nice one actually!

Take that and it's something to talk about and differentiate with. Always good to have those things.

There is always the, "If you think this is good, just wait!" kind of thing too. Framed properly, right outta the gate, the idea that AM is "On the move", combined with some greater diversity in programming forms, depending on modulation scheme used, market, topology, proximity to other AM's, etc... could get more people sampling and that's important.

Nobody that's younger tunes AM. IMHO, it makes sense to leverage everything at this point in time, just for that "on the move" perception, if nothing else. Plus, AM is largely about cars. Your board driver or passenger is one of the better shots at getting somebody to tune the dial. Why not stand out then, where possible?

It could be possible that your radio was receiving the phase modulated digital carriers from WMVP (the former WCFL) 1000kHz in Chicago who is listed as broadcasting IBOC.

AM stereo tuners have been observed to have their pilot lights lit by IBOC.

Kd7yuf says:

"it is possible for two carriers 25 Hz apart to create a heterodyne which can be confused by AM stereo decoders"

I looked on the FCC site for a while and could not find a spec for AM frequency tolerance... are they allowed to be that far off? I could not find an answer.

New Harris AM transmitter specs are about 2 parts per million... and can be much better with external reference (such as gps)

As I understood it, the frequency tolerance for AM broadcast stations is +/- 20 Hz. However, gauging by ear, it seems that many stations today operate under much tighter frequency tolerances.

twhat I recall on kxl was the simulated fakebstereo on everything(news,talk,sports and commercials,and jingles,but at some point they resumed real true stereo which lasted until the stereo was completely shut offperhaps year or more later,plus at some point in the sequence oftkxlevents of time back thenthe kxltreble was all filtered out(sounded like a telephone,which sounded even worse than the"fake stereo"(Kent would know about that,I think that was the second time I raised that as an issue?first time was when970 crusin oldiesdid thatseveretreble filteringpreviously

HD exciters have a GPS reference for the carrier frequency.

Is GPS used simply because it is technically feasible to do this today, or does IBOC absolutely need this tight a frequency tolerance to work? Or, is the idea that someday stations will run synchronized booster transmitters to fill in coverage holes?

A proper time clock reference is needed to help match the analog diversity delay to the digital audio. Just like in any digital audio a stable time sync is needed.

With half the system at a transmitter site and the other half at a studio and the digital audio being delivered in packet form as a UDP stream then GPS becomes the only universally available standard reference.

Billboise says:

"HD exciters have a GPS reference for the carrier frequency."

And they also provide a GPS derived frequency reference output so that the analog transmitter can synchronized.