Rich asked for justification for AM Stereo on Part 15 radio. To which I say, Why Not? I do it because I think its cool, and it doesn't cost any more to do it.
There were two systems in the 80's that the Radio station owners could use for AM Stereo. The C-Quam by Motorola and another one which I don't have as much info about. However Radio manufacturers started to push the Motorola standard in the later 90's in cars. I've heard C-quam a while ago and all I could say was Wow. But most stations were mostly talk Radio so that was one reason AM Stereo failed. Plus during the implementing of C-Quam many Radio manufacturers that had Radio's that could receive FM Stereo did little to nothing to improve AM in fact it was the opposite as their receivers were pure T garbage. With the right filtration AM could sound as good as FM this I've heard with a Grundig 450 Radio. With the right processing AM can sound good however you just need enough power to push through the noise. C Quam is a different way of modulation as well and with their system it did seem to filter some of the noise associated with regular AM. With the NAB's revitalization efforts along with others AM could be just as usable as FM. However there has to be phases to the fix of the problem. HD AM does not even sound as good as C Quam, and this is why I feel some tried to put a halt to any real attempt to use analog C-Quam. Think IBOC and HD FM that was being pushed hard until the mid 2007 ish era. Now people really don't talk too much about HD Radio as their disappointment in the quality they expected stopped that. Will the new campaign for C-quam do the same? Maybe not so much because you can still listen to the AM station without the ability to use C-Quam. You just don't get the high fidelity of C-Quam AM.
As far as the use of AM Stereo for part 15 this is all part of Station8's AM Initiative for part 15. Just as I wanted to start an FM Initiative. In fact he was really big into me testing his antenna, being a part of a part 15 group that is for the better of Radio programming. His initiative his a few phases. If you attend the ALPB meetings you'd know by his participation in the meetings as well as the ALPB site. I've been given a chance to be a part of this via a donated transmitter. Granted I'm a huge FM fan. At first I myself did not believe AM had any chance to get listeners. The C-quam initiative which the NAB is indeed involved in will not only help part 15 stations but licensed stations. However for some reason the American people take a lot of time to get used to any new technology that does come out. Video Laser Disc was one. As soon as people did start to buy the players after 10 years along came DvD's. The smart thing that Pioneer and many manufacturers did when they made the new combo players that played DvD's was to play the Laser Disc's as well. Then came Blue Ray which could also play DvD's. At least the C-Qualm system does not leave the old Radio's alienated because you still can listen to the station. And when you do decide to buy a C-Quam system you'll get the benefits of improved sound. I think this will also help us.
As for FM in the mean time while we wait for the C-Quam Radio's to hit every store is important as we need to be able to help improve Radio for the better of all mankind. Hobby Radio does have a nice touch to get more people interested in buying and using Radio's. As I've explained during the first phase of my FM Initiative. 87.7 and 87.9 is a HUGE part of the initiative because first off it allows people who use car transmitters to be on their own FM channel that won't jam anyone else. Second it allows hobby Radio operators to entertain a small group of people within ¼ mile. It will be shown to the NAB and others when Station8's antenna is ready for the mass production line that hobby Radio can be in the same band and yet not cause harm. The FCC made the rules for antenna length and ground and did not say that you can't have a high gain antenna. This IS a HIGH GAIN antenna. We got what we wanted without breaking any FCC rules which is hard to believe. We have struggled for years with that one, but we circled the fence until we found a weakness and for lack of a better word exploited it I guess only to a certain extent. When this is put to light I can't see why we can't get 87.7 and 87.9 Mhz. Again this is detrimental to the FM initiative. Mr. Station owner complained about MrBruce because he was using 87.9 Mhz. They only cut their own throats because many part 15ers are not like me and go off air after 6PM to check as to rather or not a temperature inversion is moving into their area. So again a big mistake on Mr. station owner's behalf. When the AM initiative goes through all of these folks may wish they did let the FM initiative go through. Why? Because now part 15 has more than 200 times the range that I was asking for in the initiative. Remember I was only asking for ¼ to 1 mile at best to a Car Radio. Sometimes its best to give a little because nature will take its course. I'm not saying this in meanness, only to present the nature of what just took place. The analogy is sort of like what happened what happened to New Orleans. They tried to plug a few flood holes and turned a blind eye to the real issue. The Antenna will be the Flood. The FM Initiative I tried to start was the least of their worries. And its all without breaking a single rule once again. Its just how you play the game. Its a game of cat and mouse. I'm sure once the antenna is made that someone somewhere will cry foul. But I thik its wrong to cry foul because someone used 87.9 Mhz while trying to not cause any interference to those who pay big fee's to be on the air. That is all I'm saying and I'm not trying to start any wars. I'm just being factual in all of this.
Well folks, I own a Radio Shack Realistic TM-152 AM-AM STEREO receiver, it's designed to be hooked up to an external amplifier, since it does not contain it's own built in final audio amplifer stage.
I also have a Chris Cuff C-Quam AM STEREO transmitter, built by Chris Cuff.
Feeding a stereo sound track into the transmitter via the RCA Left/Right audio input jacks, the resulting audio quality is superb, in a blind test, you can not tell the difference from FM stereo verus AM stereo!
Now, it is unfortunate, that Chris Cuff built this transmitter as a device that only carries the transmitted signal a few feet away from the 10 foot antenna wire. He built it like a wireless system with very limited range, perhaps with the intent of passing the audio program material to a near by AM radio receiver. Built as it is, the output stage can not produce an RF carrier that could reach outside your own home.
So it is not capable of reaching a possible next door neighbor's house, built the way it was built. It also does not have enough RF power output to drive any possible external RF power amplifier to allow a signal strength anywhere near what the FCC would allow. This transmitter has the high output modification already built into it and it still can not transmit more than several useful feet from the antenna.
Station8 is waiting for me to take and supply photos of the transmitter's circuit board from various angles, so he can put together a manual for it complete with photos. His future plans are to redesign the output stage with Chris Cuff's permission, to extend the range to a more usable signal beyond one's own property.
My opinion on the audio quality I have witnessed from other AM STEREO broadcasters that I have received on my TM-152 receiver is that I could not tell the difference from FM stereo, versus AM stereo in a blind comparison.
The only downfall with my TM-152 is that it does not have, without a slight circuit modification and an external A/B switch, both WB and NB AM capabilities.
Bruce.