AM stereo lives!!

[cd637299]

How about C-Quam AM stereo over shortwave? A clever shortwave pirate broadcaster has been experimenting with this using a home-brew C-Quam exciter. Here's a wideband sample that I recorded off the air with the SDR on 6920 kHz. The C-Quam was decoded with a free software program called Sodira:

6920 khz X-FM C-QUAM STEREO 0238-0246 UTC 18NO12.mp3

Enjoy

Quite interesting. You must be right in the proper-DX-zone for this station.

Do you remember NDXE, the ambitious SW project in the early 1980s? They were based in Opelika AL, and their intent was to broadcast in stereo (Kahn maybe?)---but I think I was told by one of the main NDXE folk over the phone that you'd have to get 2 SW receivers, tune one just over freq, the other just below.

Of course NDXE never came to be.

cd

 

[kilokat7]

How about C-Quam AM stereo over shortwave? A clever shortwave pirate broadcaster has been experimenting with this using a home-brew C-Quam exciter. Here's a wideband sample that I recorded off the air with the SDR on 6920 kHz. The C-Quam was decoded with a free software program called Sodira:

6920 khz X-FM C-QUAM STEREO 0238-0246 UTC 18NO12.mp3

Enjoy

Quite interesting. You must be right in the proper-DX-zone for this station.

Do you remember NDXE, the ambitious SW project in the early 1980s? They were based in Opelika AL, and their intent was to broadcast in stereo (Kahn maybe?)---but I think I was told by one of the main NDXE folk over the phone that you'd have to get 2 SW receivers, tune one just over freq, the other just below.

Of course NDXE never came to be.

cd

Sounds like double sideband with suppressed carrier. The shortwave station mentioned above has also experimented with this stereo mode. I caught just a minute or two of his broadcast using this mode on shortwave but it was enough to allow me to experiment with the SDR software to simulate exactly what you describe using two radios tuned to each sideband for the stereo effect. I accomplished the same thing in the software environment by feeding the lower sideband to the left audio channel and the upper sideband to the right audio channel. The result is here:

http://www.youtube.com/watch?v=br6WwDFVc4A

Unfortunately there's some audio dropouts on this video caused by my setup, but you get the idea. I think it's great to see people experimenting with these modes again.

I haven't heard of NDXE before but I'm off to go read about it - thanks!

 

[dxer2_2000]

update: if anyone wanted copies of my AM stereo recordings of 2CA, I'd send them on DVD discs as the audio files are bigger than 1GB each (24Bit/96khz wav) - so a CD wouldn't even hold one file!

(see previous posts about contrib to postage etc)
dxer2_2000

 

[boombox]

I did the same thing until I was able to finally get my AM Stereo Walkman. This was when I was still living in New Jersey.

And what I did was take my two portable receivers and send them through the auxiliary connection to my big stereo system and listened through the headphones.

WFIL and WNBC sounded great.

Once I got my AM Stereo Walkman, I noticed the two different settings of 'A' and 'B' depending what station you were listening to.

I forget what 'A' was called but I remember 'B' was called "Kahn Hazeltine' because WNBC and WFIL seemed to use that mode.

You could hear a stereo sound with either setting but it seemed more spread out from left to right on those particular stations in B mode.

WLS, which came in at night, sounded better in the 'A' mode.

I'm guessing the A setting would have been Harris / Motorola.

For a while in the early 1980's local station KOMO 1000 ran in stereo, using the Kahn method (KOMO was an MOR station at the time, MOR being the early version of AC). I would tune one radio to the left of center, the other one to the right, and it was definitely stereo. This was before AM stereo radios were available.

 

[romer979fm]

from boombox - "I'm guessing the A setting would have been Harris / Motorola."

I dug up my OLD Sony SRF A-100...and you're correct

"A" is labeled HARRIS / MAGNAVOX / MOTOROLA COMPATIBLE
"B" is labeled KAHN / HAZELTINE

 

[MarioMania]

What's more commen Motorola or Kahn?

 

[cd637299]

What's more commen Motorola or Kahn?

Motorola (C-Quam) became the standard for AM Stereo, but way too late. In the 80s there were 5 companies competing for the right to be the "only" format for AM Stereo. It may have been 1990 or so where Motorola was crowned king.

I'd say that during the competition, there were more Motorola-compatible AM Stereo stations than the others. Maybe that influenced the FCC decision.

In Australia, where our OP lives, Motorola was the standard from the start; someone feel free to correct me.

cd

 

[spt87]

I think Motorola got a big boost when GM started putting their system in a lot of their cars as did Chrysler. Ford and Toyota did too but I thinked they lagged a bit.

I don't believe any system besides C-Quam was ever available from the factory in any cars. There were several multi-system radios in the aftermarket (I still have a Sony model).

For that matter, I've never heard of a Kahn only, Magnavox only, etc. receiver. Seems receivers either were Motorola C-Quam only or were multi-system.

 

[mimo]

C-QUAM was also the standard in Canada, and they were declared the standard by the mid 80's, as most stations adopted it. That may have influenced auto manufacturers in North America to install it. The vast majority of AM stations in Canada went stereo. In some cities you couldn't even find a station that was not in stereo on AM.

 

[KenoGuy]

Kahn-Hazeltine was probably the better system, as it did not suffer from the "platform motion" phenomenom at night like Motorola C-QUAM (the other systems were compatible with C-QUAM, and hence didn't have their own switch position).

In this area WMAQ 670 was the only one who used the Kahn system, and was the best sounding of the lot. It was also the only system that worked with 2 detuned radios, as the stereo info actually rode on opposite sidebands.

At the height of AM Stereo implementation in the Chicago / Milwaukee area, there was stereo on 540, 560, 620, 670, 720, 780, 820, 850, 890, 920, 1250, 1290, 1340, 1390, 1510, 1530, and 1640.

Now there is 890.

 

[pianoplayer88key]

I suspect part of the platform motion is caused by the co-channel interfering carriers not being synchronized to the exact same frequency. When my SRF-42 was functioning properly, I remember at night hearing rhythmic stereo field swaps on some frequencies where two or more stations were audible simultaneously. Listening to the same frequency on a mono radio revealed a beat on the carrier at the same rate.
One thing I did like about that SRF-42 was its ability to maintain stereo separation even on extremely faint signals with maybe 1 or 2 dB S/N. Assuming there were no interfering signals, co- or adjacent-channel, I could listen to stereo on a weak signal that some larger radios couldn't detect the carrier at all. (It did have a problem with splatter, even 2nd-adjacents - at home 1110 KDIS was tough to get by 1130 KSDO.) Also the platform motion does have an advantage - aids station identification on graveyard channels.

How well would the Kahn system deal with offset-carrier co-channel interference, and still maintain faint-signal stereo reception?

 

[AMradiofan]

Given what seems like a resurgence in the broadcasting of AM stereo in the USA, it would be fun to have stereo AM stations check in here as well.

We did it quite some time ago to provide a stereo stream when we added "streaming" and for the "fun" of it! It's gotten much talk for us in the USA and overseas. Many comments we get say that the listener had no idea AM could sound this good!

Some "buzz" (no pun intended) of bigger stations returning to it is making for interesting watching as IBOC gets shut down more and more... and the more stations implementing CQUAM with quality, the more voices AM has saying, "leave AM alone" to those who would have us move or go digital.

Properly programmed, properly processed, (two easy things to do with attention to detail) AM stereo can be quite good, and for locals with ONLY an AM, going stereo and adding a stream will really add to the audience! It sure did for us! www.i1430.com/listen.html