The link above is a one-hour air check taped in March of 1984 using a Sony SRF-A100 AM stereo radio at my home in La Canada. It was the 4pm hour. I was unable to determine the day of the week. It has been converted to an MP3 at 192kbps. Any broadband connection should have no trouble streaming it.

I have three hours. I chose this one because of the dramatic stereo trip provided by the first three songs.

The first thing you will hear is the end of a newscast by Gillian Harris followed by a KRLA “in stereo” ID. The first song is the Stones Satisfaction (to quote Humble Harve) “in magnificent mono!” Remember, its 1984, and it is all vinyl all the time. Oldies often were dubbed from mono 45-rpm records because that was what was available. The second song is a rather forgettable song by Ray Parker Junior, “The Other Woman,” which is in stereo. Not great stereo, but stereo. Then the irony, the oldest song in the set is Bobby Vinton’s “Devil or Angel,” and it is in super wide stereo!

So, at least stick with it for the first three records to experience the stereo. Go ahead and crank the balance left or right to see how good the separation really is. I can tell you it measured 30 db when we proofed it. That is better than a really good vinyl pickup cartridge, and was limited by the Continental transmitter’s ipm (and actually a little iam too),not the stereo system (C-Quam did no better on that transmitter). If you stick it out to the end, the “The Witch Queen of New Orleans” has some fun stereo effects.

The (boring) technical details

The recording was made at my home in La Canada, which is about 14 ½ miles from the (then) KRLA transmitter site in South El Monte. My recollection is there was close to 100mv/M of 1110khz at my house. The transmitter has moved since then so I cannot easily verify this. It was made 2-track stereo 7-1/2 ips from a Sony SRF-A100 radio which contained a true Kahn stereo decoder.

The transmitter was a Continental 317-C2 running 50 KW. The stereo exciter was the first-generation Kahn exciter (STR-77). Regrettably we never got to try the second-generation (STR-84) unit, which among other improvements provided a way to place the processing downstream of the phase shift networks. This was a much better design than the original.

The audio processing was Gregg Labs (5 band) set to what I would call moderately aggressive processing.

There was a 12.5 khz brick wall filter at the output of the audio console to reduce splatter issues to second-adjacent XEPRS. There was also a sharp notch at 8khz to remove any trace of the 8khz tertiary tones that were being used for “cartamation.” These in my experience were inaudible to the ear./p>

The cartridge (“cart”) tape players were ITC criterion series (old) which we upgraded to stereo and added a matrix system (Eventide “monstermat”) which eliminated the stereo summing issues these old machines had at the sacrifice of a little signal to noise ratio. Obviously there was a similar system in the recording chain, which was an ITC series 99 unit.

Since this was 1984, CDs and other digital media were not around yet, so the music was always transferred from vinyl records. The stereo dubs were done using a Stanton 680EE pickup. The quality of the vinyl records varied quite a bit. You may notice occasional needle “ticks” on some of them. The format had a heavy oldies mix, which often meant an old well-worn 45rpm record was the only available copy, and these were often monaural.

Technical apologies

These reel-to reel tapes spent 32 years in a box in my garage. They survived pretty well, but there was a good deal of lubricant shedding. I had to run the tapes through twice, cleaning the heads and guides each time. That cleaned things up well enough to transfer to digital. Fortunately, none of them were “squealers.”

The continental was a modern transmitter, but it was a Dougherty design. The FCC has never had a requirement for intermodulation distortion measurements on transmitters; only harmonic distortion measurements are required. When I have measured these on my own, I have found that they typically have about 6 percent IMD. No audiophile would consider that hi-fi! It is most noticeable on complex music with lots of parts playing at once.

The directional antenna (both day and night patterns) was not broad banded the way today’s antennas are if a station is using the digital stereo system. In fact, the day antenna was quite restrictive. It is remarkable the high frequencies survived as well as they did!

In quiet moments, like when the DJ is talking, you may notice a little 120 hz hum in the background. I can only conclude this was from the wall wart that was powering the Sony receiver. I guess I should have switched to batteries. Sorry about that! Just know that it wasn’t on KRLA’s air like that!

Enjoy a little bit of LA radio history!

AM Stereo: what went wrong

This is an opinion piece, but I speak as someone who was deeply involved with AM stereo. You may be surprised at the truth.

First, I listened to the first AM stereo broadcasts back in the late 50’s. Kahn had placed the system on the air on a border station, XEAK 690. It was not legal to use the system in the USA. At that time, you heard the stereo by side-band tuning: Since the Kahn system transmits the left channel on the lower side-band, and the right on the upper side-band, this was fairly easy to do, but it worked best with identical radios. Also, John Q. Public wasn’t likely to consider this acceptable. But my point is that AM stereo was ready by the 60’s.

FM means “forget money” was the cry of FM broadcasters in the 50’s, and once again, the FCC meddled in something they should not have. They chose to give stereo to FM and not give it to AM. This may well have sealed AM stereo’s fate way before the system wars began; more on this a bit later.

When AM stereo was coming on the scene in the 80’s there were competing systems offered by Magnavox, Kahn, Belar (RCA-Sansui), and Harris. I’m not discussing the technologies here. If you are curious, on my files page is a paper I did on the AM stereo wars. Ultimately the FCC chose the Magnavox system. Kahn and Motorola cried foul and under pressure mainly from Motorola, the FCC abandoned its decision in favor of the marketplace. This cowardly act by the commission placed a second nail into the AM stereo coffin.

Those of you who know me know that I was a strong advocate for the Kahn system. I believed (and still do) that it was the technically best approach for AM stereo. But, I also think that the FCC’s decision for Magnavox was correct. The reason I think this is that Magnavox was the only system advocated by a company that was a major consumer electronics firm. (Motorola abandoned that market in the late 50’s as did many others like RCA). Had the FCC stuck to their guns, I believe we would have had AM stereo walkmans, boom boxes and other receivers available at K-Marts all over America where we needed them. We would have at least had a fighting chance, maybe.

What I’m about to talk about I wasn’t aware of back then, but talking to others who knew Leonard Kahn, I have concluded that the FCC doomed the broadcast industry to be in the crossfire between Leonard Kahn and Norm Parker of Motorola. They hated each other. It was a real blood feud. Looking back, I suspect had it not been for Norm’s hatred of Leonard, Motorola might not have even bothered with AM stereo. But Norm was committed to win at any cost, even lying to the broadcasters about “all the receivers” that would be available with their system. This turned out to be either a flat out lie, or a fantasy. Motorola loves to attack people for patent infringement, and they made a lot of enemies in the consumer electronics field. The manufacturers who were “on board” only did limited runs and then stopped. One manufacturer had only made 50 units, yet that receiver was proudly displayed in the Motorola Booth at the NAB convention. Anyone who tried to purchase one found that it was impossible. Dealers weren’t carrying them, and sales people had no awareness of AM stereo. The much-anticipated Delco radios which were supposed to be in GM vehicles never got there, because GM had no commitment to them. They were sold as a “dealer option,” meaning that the radio would only be in a vehicle if the dealer ordered it specifically. Of course station managers and chief engineers often ordered it with the vehicle or after the fact and had it installed later. The only manufacturer I know of who put them in many vehicles was Toyota. But they got into the game late, and it ultimately fizzled. It probably would have anyway.

Broadcasters were seduced by empty promises. Norm and Leonard are both dead and buried. There is a lesson here for those who will learn it.

But that wasn’t what really killed AM stereo. What killed AM stereo was actually that first decision by the FCC to give stereo to FM first. I remember the day that I was in the lobby of KRLA proudly pointing out the new stereo speakers to one of the women who worked in the office, and she said “I’ve heard stereo before.” I remember the sinking feeling this gave me. Stereo’s market window was from about 1964 to 1975. Stereo wasn’t interesting any more, and was no longer even a selling point in consumer electronics. It was just too late.

Chris Hays