Tom Ray said:
>>>> Incidentally, I have a home theater system that is only 2 years old. The spec on the AM section for audio bandwidth is 50Hz to 2.5kHz. I measured it. It's 10dB down at 3kHz. So those narrow band radios are out there.
>>>> iBiquity had numerous radios....old and new....for testing. There has been a great deal of research done. The conclusion is that the majority of AM radios - including new ones - are narrow band. From what I've heard, and in my experience, I believe that.
Oh yes - I know the old reference designs are going to die hard. For those of you not in the electronics industry - let me explain. Most consumer electronic items are manufactured in China by companies whose names you have probably never heard of - Darfon, Primax, etc. These companies are contracted by American companies to produce hundreds of thousands or millions of an item - on a particular schedule, at a negotiated price - inside cases designed to look "cool" by marketing types in the US. There may be performance goals. These Chinese companies have virtually NO in house electronics designers - I know - I've been to them personally. They do the work based on "reference designs" from IC makers and other sources. They are good at picking the reference design they need for the price and performance goals, and laying out PC boards quickly to fit inside the case they have to use.
My job, frankly, was to unseat those reference designs (for wireless mice in my case). IF we could prove we could save them even a penny or two, and still allow them to meet their cost and schedule, the Chinese companies would listen. Otherwise, they would stick with their old, comfortable reference design. To meet their schedule - WE did the design and even PC board layout for them. And snagged a lot of business that way.
Now - apply this to the radio makers. TI, Silabs, Sanyo, Toshiba, etc. are going into those companies with the same constraints. If the Chinese manufacturer can save money, they will - and pocket the difference. If the IC manufacturer doesn't have their act together, the Chinese will produce an old "3 IF can design" like your home theater.
It is probably inevitable, though, that the old three IF can design will go. The size reduction, cost reduction, reliability improvement will drive new and smaller radios. Reduce the size of the PC board and the number of holes drilled, you reduce the cost of raw materials, fabricating, stuffing it with components, there will be less etching chemicals to go to hazmat waste disposal. That is why you open up a large component electronic - and there is a little bitty PC board in it. The performance enhancement is the coffin nail for the old three IF can approach. I was astonished when - by simply substituting a better ceramic filter and an 8 inch ferrite bar - I made my daughter's boom box perform as well as a GE Superradio 3! The IC manufacturers are putting decades of semiconductor experience into these chips to make them undeniably the best design approach both for low cost and high performance equipment. And the saavy engineer like us can take advantage of that by simply doing some simple things to improve the performance, all it takes is a data sheet!
My brand new car radio - to replace one that shorted out the battery - Pioneer. NO AM RF components at all. All done inside the IC. And it is a HOT performer, one of the best AM radios they have made. And - WIDEBAND and simultaneously very selective! Push the button to one of a half dozen audio tapers and I get a version for speech. Or for music with various equalization. AM music stations sound great - they are out to 10 kHz easily. But the annoying 10 kHz heterodyne is filtered out inside the IC!!! Talk radio DOES sound good in wideband - so perhaps IBOC has an advantage for talk stations if it provides similar wideband experience. It must be vocal harmonics that make a difference. But wideband does not require IBOC. Merely a desire on the part of the station to do so, plus a newly designed radio capable of it. Which includes a whole lot of radios!
Like you, I have a pile of older radios around the house. The GE Superradio design is virtually unchanged from 35 years ago, except for the use of varactors and bandwidth increasing switches. Mono I get 3 to 4 kHz on some of them, 5 to 6 kHz on others. They are four IF can instead of three. Wide position I get 13 to 15 kHz, depending on the serial number and if it is an "A" or a "B". Old Radio Shack table radios - three IF cans, 3 to 4 kHz. My wife's childhood six transistor portable, 3 IF cans. Her old clock radio, 3 IF cans. Ward's Airline I got at a garage sale, 3 IF cans. GE is probably the newest thing I got with IF cans in it. But the IF can manufacturers are in China, too, vigorously cutting prices in an attempt to forestall the inevitable. And they succeed in getting new designs - the nature of the business. But they know they are losing ground rapidly, which is why they are also selling ceramic filters.
All this goes to make the point - the old narrowband AM radios are slowly on their way out. Research done based on the old 3 IF can designs is almost useless, because it is going to be increasingly hard to find them in the coming years. The IC manufacturers WILL take the market from the IF can people, who are already adapting to the inevitable. Therefore, wideband radios WILL dominate the market, it won't be for high fidelity, it will be for cost and reliability reasons. And therefore, IBOC self jamming noise WILL be a serious issue with listeners.
