Studying AM stereo has been both a technical and electornic education and information presented here is the product of that and if I seem partial to ISB and linear synchronous detection it's because that I am. I feel that these two issues are the most important for good stereo and mono reception during adverse conditions like nighttime interference, multipath and skywave reception. The current adopted system addresses neither of these issues direcly but instead uses other approaches that are at best second rate. For DX listening nothing beats synchronous detection for extracting a signal out of a high noise enviornment and ISB filters can be used to choose either the upper or lower sidebaed to deal with interference and/or multipath problems.

I first got into AM-Stereo in the mid to late 80's when I bought the book "AM Stereo & TV Stereo New Sound Dimensions" by Stan prentiss and later I purchased a Realistic TM-152 tuner on clearance for ~$10. Not satisfied with the narrow banwidth 4.5KHz sound quality I obtained wider filters, added 10KHz notch filters, added synchronous detection and post detection equilization to boost the higher frequencies. I was able to get high quality sound out of the MC13020 chip especially in synchronous mode. Looking at the newer chips it does not appear that some will easily lend themselves to synchronous conversion and others not at all. Although the MC13020 chip does have its flaws it's the easiest to get synchronous detection out of.

I lost interest a while after my favorite station switched formats and later turned off their C-QuAM® AM Stereo. There was another station that broadcasted in the Kahn ISB system that would trigger the chip's pilot tone circuit. Decoding Kahn ISB with C-QuAM® gave a strange phasing effect for the lack of phase shift filters but the chip actually preformed better during noisy conditions on ISB than it did on a C-QuAM® broadcast. This station later turned off their AM-Stereo also. The only two stations left are Spanish ones listed as Kahn and the other one as Harris in the Stan Prentiss book. They only light the light but I hear no separation. The last station I get that has any separation is ~250 miles away from me that played old time country music and catered to truckers. Their commercials got so bad that you would hear three to four songs per hour and other spots in stereo and after September they switched to an all talk call in format. There seems to be an extreme drought around here of AM Stereo broadcasts and what a waste for all those exciters sitting on shelves collecting dust. I eventually lost interest and found computers and only recently have I found the online AM Stereo community, and I though I was the only one out there.

Most of this information is stuff I've dug out of my archives and only recently have I reassembled it and put it on the web. If some of the information seems dated its because it probably is but I want to share what I have and in time hope to bring it up to date. I have done signal analysis and have constructed some of the circuits. The others are variations of the ones I did build. Some tweaking may be required though depending on the particular application. My technical view may be different on certain issues but is just my prespective. My descriptions may or may not be completely accurate but should provide good ideas. This is presented for information purposes only so enjoy at your risk ;-).