The Southern Ontario/WNY Radio-TV Forum / Some AM Stereo Noodling

**Posted by Fitz** January 29, 2025 11:10 pm

Fiddling around with my AM stereo Transmitter and recorded a partially scoped air check from Kome FM, San Jose ( 1979) have not uploaded this particular segment to the site. I took the feed directly from the reel to reel player ( recorded at 3.75 IPS). Note that Happening Ten Years Time Ago/Yardbirds was not recorded or released in true stereo and sadly they play the long version of Bluebird by Buffalo Springfield which does not have the great Banjo solo at the end. Also maybe the only time a rock FM station plays Led Zep and Hermans Hermits.

I think I have reduced the hum that I got on previous tests but there is still some ( what can you do it's AM) and of course tape hiss.

KOME FM AM Stereo

Last edited by Fitz (January 29, 2025 11:10 pm)

**Posted by Big8Newsie** January 30, 2025 7:31 am

CKLW went AM Stereo in 1982. Here’s a series of reports on the switch. https://m.soundcloud.com/terry-scott-980453183/cklw-goes-am-stereo-sept-1982

Last edited by Big8Newsie (January 30, 2025 7:31 am)

**Posted by Plate Voltage** February 3, 2025 6:23 pm

Big8Newsie wrote:
CKLW went AM Stereo in 1982. Here’s a series of reports on the switch. https://m.soundcloud.com/terry-scott-980453183/cklw-goes-am-stereo-sept-1982

I just listened to that clip now. It's very interesting and one of the things that caught my attention were the mentions made of adapters that would allow AM stereo to be received on existing AM-FM Stereo radios. Were such adapters ever made and brought to market? I hadn't heard of such a thing until I played that clip and definitely never seen one.

I'm guessing the least obtrusive way to do this would be to have an AM stereo tuner that would then transmit an FM stereo signal that the existing AM/FM stereo receiver could be tuned in, much the same way FM transmitters for MP3 players and Bluetooth devices work with car radios these days.

**Posted by RadioActive** February 3, 2025 6:39 pm

I never got to hear actual AM stereo in its brief existence. I was told by those who did that it sounded pretty good, but its fate was much like HD Radio seems to be - no one knows it's there, so it's eventually not going to be a factor. Wish I could have experienced the real thing over an actual radio.

Not that there wasn't a brief burst of publicity for the new technology. Here's a CFRB ad from 1990. Notice the "AM Stereo" at the bottom of the logo. (Also notice that the station once had a hefty sports department.)

**Posted by Fitz** February 3, 2025 10:49 pm

Plate Voltage wrote:
Big8Newsie wrote:
CKLW went AM Stereo in 1982. Here’s a series of reports on the switch. https://m.soundcloud.com/terry-scott-980453183/cklw-goes-am-stereo-sept-1982
I just listened to that clip now. It's very interesting and one of the things that caught my attention were the mentions made of adapters that would allow AM stereo to be received on existing AM-FM Stereo radios. Were such adapters ever made and brought to market? I hadn't heard of such a thing until I played that clip and definitely never seen one.

I'm guessing the least obtrusive way to do this would be to have an AM stereo tuner that would then transmit an FM stereo signal that the existing AM/FM stereo receiver could be tuned in, much the same way FM transmitters for MP3 players and Bluetooth devices work with car radios these days.

I wondered the same thing about the adapters. Never saw one either.

**Posted by darcyh** February 3, 2025 10:57 pm

My father in law had a dodge product form the early 80's. It came with an AM stereo receiver. In London I was pleasantly surprised how good CJBK and CKSL both sounded. Good frequency response (for AM) and great channel separation.

**Posted by tvguy** February 4, 2025 8:16 am

I bought an AM stereo tuner. Radio Shack offered an AM Stereo tuner which could be connected to an amp. Stereo separation was very good. I recall hearing something on CFTR or CHUM-AM which had great instrumentation (separation) on the left and right channels. I rented a chrysler product, possibly in Calgary for a drive to BC, and the AM stereo was surprisingly good, as darcyh observed. If I recall correctly there were two “standards” the Kahn and C-Quam. C-Quam was the system that went into Chrysler products.. Didn’t one of the Toronto stations adopt Kahn, whereas the others went with the other technology - C-Quam. My Radio Shack only decoded one of the two systems. If you wikepedia AM stereo there's a good photo of the Radio Shack "Realistic" tuner that I owned.

Last edited by tvguy (February 4, 2025 8:20 am)

**Posted by Fitz** February 4, 2025 9:01 am

There were actually 4 systems. Magnavox also had one and I can't recall the 4th. My receiver I think could decode more than one system. My transmitter uses C-Quam.

Here's something I found on You Tube where the Realistic tuner was used to pick up AM stereo:

**Posted by tvguy** February 4, 2025 9:26 am

**Posted by RadioActive** February 4, 2025 9:54 am

And all the different systems was one of the reasons this never caught on. It's a shame they couldn't agree on a single standard or we might have AM stereo still with us today.

From 1983:

**Posted by tvguy** February 4, 2025 11:58 am

Here is the tech info for the Radio Shack Tandy TM-152 which I owned. It was only Motorola C-QUAM compatible.

https://steampoweredradio.com/pdf/radio%20shack/radio%20shack%20realistic%20tm-152%20am%20stereo%20tuner.pdf

**Posted by Skywave** February 4, 2025 12:13 pm

I had a Dodge Caravan which came with AM stereo as standard equipment. It was actually reasonably impressive, although the high frequencies were truncated above 10 kHz to avoid adjacent channel nighttime interference.
The FCC, in its wisdom, refused to specify a single standard after a lot of industry testing, and instead said that it would be a "marketplace decision". They had originally anointed the Magnavox design, but there were howls of protest that the analysis was flawed. That left Kahn, C-Quam and Harris as the competing systems. GM, Ford and Chrysler adopted C-Quam, and Harris decided to pull out and back C-Quam. It wasn't until four years later that Mexico and Canada declared C-Quam as the standard, as if it made any difference by then.

**Posted by Forward Power** February 4, 2025 12:29 pm

Last time I tuned in AM stereo must have been about 2003, when I was about to graduate from the radio broadcasting program at Belleville's Loyalist College. One of the hosts on Loyalist's campus station, CJLX, was also a car salesperson, and one evening when she was driving me home, she was borrowing a Chrysler PT Cruiser which had AM stereo capability. At that time, the city's CJBQ was still running AM stereo; we tuned it in, and it sounded quite good - I had done my internship a month prior at Quinte Broadcasting, and discovered that 'BQ was then using a pair of Texar Audio Prism processors, one each for the left and right channels. I don't remember if the monitor feed in the CJBQ on-air studio was stereo OTA or from the processors.