Howdy,
Well I just did an intro and seeing as this is an automotive radio I figured I should drop it in this forum. Please don't hesitate to move it if this is incorrect.
The problem stems from a JDM car I own and its radio. The FM band over in Japan only does 76 to 90 Mhz. Now I know I can get an inline band expander but that doesn't do it for me. I'd like to fix it right.
The Q is if I may, how is a FM frequency range 'limited' as this one is? Is this in the chip or is there some external component(s) that could be adjusted or swapped out to truly increase / shift the band range to North American 87 - 108 Mhz?
It's a '95 Honda and the radio is made by 'Gathers'. FM stereo. I don't care about the AM side of things at all.
Sure hope someone could point me in some direction so I can improve my electronics understanding and perhaps fix this thing.
Thanks kindly,
Gord
Well I just did an intro and seeing as this is an automotive radio I figured I should drop it in this forum. Please don't hesitate to move it if this is incorrect.
The problem stems from a JDM car I own and its radio. The FM band over in Japan only does 76 to 90 Mhz. Now I know I can get an inline band expander but that doesn't do it for me. I'd like to fix it right.
The Q is if I may, how is a FM frequency range 'limited' as this one is? Is this in the chip or is there some external component(s) that could be adjusted or swapped out to truly increase / shift the band range to North American 87 - 108 Mhz?
It's a '95 Honda and the radio is made by 'Gathers'. FM stereo. I don't care about the AM side of things at all.
Sure hope someone could point me in some direction so I can improve my electronics understanding and perhaps fix this thing.
Thanks kindly,
Gord
Typically, front part of the fm radio, tuner, uses varactors, which is diod with capacitance. Capacitance or capacity of varactor is voltage dependant, so changing the voltage will tune to the desired frequency. This allows memory presets as well. And many other features.
However, every fm tuner front end, at least the good ones, is using set of these, which have matching curves. So each resonance circuit is aligned across the whole range of fm tuner.
One could raise the voltage used to varactors, or use different set of varactors. In any case one must know what's he doing. Plus have extensive set of expensive instruments to align the fm tuner front end. Its impossible without knowledge and instruments.
Good luck!
However, every fm tuner front end, at least the good ones, is using set of these, which have matching curves. So each resonance circuit is aligned across the whole range of fm tuner.
One could raise the voltage used to varactors, or use different set of varactors. In any case one must know what's he doing. Plus have extensive set of expensive instruments to align the fm tuner front end. Its impossible without knowledge and instruments.
Good luck!
Post #3 is likely correct in the mechanics but I would think (could be wrong) that the tuning would be determined by the programming of the microcontrollers. There is likely one on the main board and another on the tuner board. If this is true, replacing the controller ICs (if they're available for other markets) may be the only way to do what you want to do.
Will the display be able to display frequencies over 100MHz?
Will the display be able to display frequencies over 100MHz?
If you're lucky there's a sub menu or resistors/diode jumpers inside the radio.
Something similar to this:
YO3HJV: ICOM IC-7300 MARS/CAP Extended TX modification
Something similar to this:
YO3HJV: ICOM IC-7300 MARS/CAP Extended TX modification
In very modern car radios it is usually just firmware that sets the band, the fixed LC filters on the board are so broad they pass both the Japan and the European and the US bands. I wouldn't have a clue how an end user could change the firmware settings, though. Besides, in a radio from 1995, you would probably have to retune some narrowband filters and change the firmware settings as well.
Thanks thus far, Gents.
It's a very curious radio - car model specific actually so no '1 DIN' or '2 DIN' radio could ever fit without sawing an inch or two off each side.
Some owners in Japan have made consoles to house 1 & 2 DIN radios but they look...well, they look really hack.
This is stock and to note, the car was never designed to be anywhere in the world other than Japan:
Note the size of the cassette door vs. the whole width. I measured the actual radio chassis at 5 inches and the balance is just overhanging plastic to match the curve of the console.
Perry, excellent point regarding the display, thank you. I honestly don't know but I can check it out - and I guess that would be a bit of a deciding factor for sure.
It is completely electronic - the tuning that is. There's no knobs even though in the picture there appears to be a knob (there are two), they're actually just push-button toggle switches.
Okay, I'll dig inside a little more and see what I can see. Are you guys okay if I took some pictures of the boards? I'm feeling that the frequency range is set by the IC and that sure would be neat if all it needed was to swap out for one that could handle the wider range. Display permitting!
Thanks everyone - much appreciated.
Gord
It's a very curious radio - car model specific actually so no '1 DIN' or '2 DIN' radio could ever fit without sawing an inch or two off each side.
Some owners in Japan have made consoles to house 1 & 2 DIN radios but they look...well, they look really hack. This is stock and to note, the car was never designed to be anywhere in the world other than Japan:
Note the size of the cassette door vs. the whole width. I measured the actual radio chassis at 5 inches and the balance is just overhanging plastic to match the curve of the console.
Perry, excellent point regarding the display, thank you. I honestly don't know but I can check it out - and I guess that would be a bit of a deciding factor for sure.
It is completely electronic - the tuning that is. There's no knobs even though in the picture there appears to be a knob (there are two), they're actually just push-button toggle switches.
Okay, I'll dig inside a little more and see what I can see. Are you guys okay if I took some pictures of the boards? I'm feeling that the frequency range is set by the IC and that sure would be neat if all it needed was to swap out for one that could handle the wider range. Display permitting!
Thanks everyone - much appreciated.
Gord
Attachments
Display should be good to go!
Hi everyone,
Here's a picture of the display board and as they are using the clock display to handle the frequency too, well, at least there are enough segments to handle the task.
I wouldn't know how to make the thing go but maybe it would just go on its own if and when it hit 100.1+ ? So first to solve the range!
Gord
Hi everyone,
Here's a picture of the display board and as they are using the clock display to handle the frequency too, well, at least there are enough segments to handle the task.
I wouldn't know how to make the thing go but maybe it would just go on its own if and when it hit 100.1+ ? So first to solve the range!
Gord
Attachments
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