AM tuners (with digital readouts) seek stations in increments of either 10khz or 9khz depending on where the radio is used. A friend of mine bought a radio in with him from another country and to his chagrin realised that it only tunes in 10khz increments when this country is a 9khz country.
My supposition s that there’s likely to be only one or two manufacturers of these tuner circuits supplying the world market, and that every tuner can in fact accommodate both systems, the question is how to switch between the two modes.
There is no good answer without info about the model of tuner.
You’re probably correct in that the same basic circuitry is used in all countries but how easy or possible it is to switch depends on the model. If he’s lucky, there may be a jumper or switch on the circuit board or if it’s a sophisticated thing with menus etc then it may be in the “setup” menu. Failing that, he’s probably out of luck. There may simply be two versions of the tuner chip, one for the Americas and one for the rest of the world.
The good news is these frequencies are common to both schemes
As an aside Australia uses an increment of 9 too and I thought everyone did. I recently saw a movie where a radio was shown tuned to, say 730, and I thought it was a goof, that you can’t get that. Guess I was wrong in some parts of the world.
There are more than one or two manufacturers out there, though it’s really more like a handful and not a huge number. Tuner chips like the one in your friend’s radio are programmable, and are meant to be attached to a microcontroller. Your friend’s radio probably consists of a simple tuner chip, a microncontroller which controls everything including processing what buttons you press and managing the digital display, and probably includes a single chip amplifier as well. Unlike the old days when circuits were fairly complex, you’ve basically got three ICs and a handful of support components.
In order to change the frequency increments, you’d have to reprogram the microcontroller. This is probably simple if you’ve got the source code for the microcontroller’s firmware, but it’s not something an end user can easily change.
If the radio is designed to be used in multiple countries, you may find that there’s a jumper on the circuit board or something like that which allows it to change modes, but it’s probably more likely that they would just stick a different program into the microcontroller depending on which country they intend to sell it in.
Because radios like that are a pain in the butt to tune. Radio stations are required to be centered on certain frequencies. You can much more easily run up and down the dial if your tuner only hits those frequencies.
Digital tuners are easier to use and always lock on to the center of where the station is supposed to be (which generally is where it sounds best). With that convenience you lose some flexibility.
Because AM channels have a 10 KHz bandwidth. Why would you want to tune to 981 KHz if the station is broadcasting at 980KHz?
To the OP, most digital tuners that aren’t meant to travel abroad are controlled by the LM7001 PLL chip (PDF). The available step frequencies of 1, 5, 9, 10, 25, 50, and 100 kHz are determined by the onboard reference crystal and peripheral circuitry. I’ve never seen a tuner that could switch by way of fiddling with jumpers, but will admin that I haven’t worked on many international tuners either. Your average tuner is not going to have the option to switch because that would increase manufacturing costs.
I think it’s still 10 KHz in ITU region 2 which is basically the Americas.
Everyone was 10 KHz originally. I remember when New Zealand changed. I think it was in the 1980’s. Australia probably changed at the same time. 1ZB in Auckland changed from 1070 to 1080 several years earlier presumably so they could be certain of keeping the the nice round number when everyone else changed a few years later.