Converting a jap import car radio

"jdm" <

** Don't all you kiwis know about these:

........ Phil

Hi Phil,

Yes I know about band expanders but I don't want to use one.

I just downloaded the DPX-440 manual from the Kenwood USA website at

It says the FM frequency range is 87.9 - 107.9MHz in 200kHz steps and doesn't mention anything about the 76 - 90MHz band. This is very strange...

Bob

"Bob Parker"

** Wake up, Bob - the OP has the Japanese version.

" Jap Import " = kiwi jargon for a vehicle that comes ( second hand ) direct from Japan to NZ.

Never heard about how hard it is to get a vehicle re- registered in Japan that is over 4 years old ??

Most are sent to the wreckers.

....... Phil

You're right - I wasn't paying much attention. Yeah, I've been told about the Japanese flogging their hardly-used cars to NZ and other places. Kenwood don't have the most user-friendly websites. The only one I found where I could easily download the manual was the US one. I sorta expected that there might be a tiny switch on the back or similar to change FM frequency bands, but I can't see anything in the .pdf manual.

Bob

"Bob Parker"

** Such a switch cannot do the job that is needed.

A band up shift of nearly 20 MHz requires the RF stages to be retuned - likely with different coils and cap values.

Merely re programming the local oscillator frequencies on the PPL is not enough.

...... Phil

I'm the first to admit that I'm not familiar with car entertainment systems. I just didn't think it made much sense to have two different versions of the same unit built to cover different FM bands with exactly the same model number, unless it was the same unit with some kind of electronic band switching like maybe PIN diode switching of the front-end tuning components. Like I said, I'm ignorant about what's out there in car systems these days.

Thanks Bob,

I did not try the US site, I just tried the Japanese site.

Hopefully this will be able to be converted, I remember as an apprentice converting a lot of home stereos for a chain store, they imported them with the wrong band, I just had to move a diode and everything was fine.

Thanks

After thinking for a few moments, I seemed to remember that microcontroller-controlled receivers have varactor tuning of the front end as well as a PLL for frequency control. The micro just needs to be told which band to use, via a menu option, diode, link or a switch. I looked around but couldn't find a schematic. I hope you can do better. :-)

Bob

"Bob Parker"

** Varactor tuning is not so simple.

It has to cover both RF and local oscillator tuning ranges, which must track each other quite closely in an FM receiver - as the operating band is only

250 kHz wide.

Typically requires a DC control voltage of 2 to 30 volts to cover the 88 -

108 MHz band.

** That is a BIG assumption in relation to Japanese, local model, car radios.

No need for those radios to have band compatibility built in.

....... Phil

"jdm"

** Were the Nips sooooo dumb they made 240 volt home stereos with the WRONG FM band ??

....... Phil

I thought (being from an RF background), that most of the selectivity in a receiver is in the IF not the front end, and as long as the front end's selective enough to reject image frequencies, there's no real problem?

My point is that it seems ridiculous for there to be two variants of the same receiver covering different band segments, with *exactly* the same model number ... not even a suffix to indicate which is which ... unless that same unit can handle both band segments by being told which one to use.

Bob

** You thought wrong.

Good RF pre-selection is essential for any high performance AM or FM broadcast receiver.

The same does not apply to narrow band, two-way radio systems which you may well be thinking of.

** You have no reason to make that assumption either.

The 76-90 MHz version is sold only in Japan.

....... Phil

So what you're saying is that they manufacture two quite different versions of the same unit, and give them identical type numbers so there's no way of telling them apart? I'm only asking because I don't recall seeing that happen before...

Bob

** Don't be stupid.

You have not seen the Jap version nor it's manual to say any such thing.

Being sold ONLY in Japan suggests the unit will be marked and the manual written in Japanese characters.

........ Phil

I was simply asking a question not making a statement, because I don't remember seeing anything like that before. I'm trying to learn something from your experience ... which is what newsgroups are supposed to be about.

Bob

"Bob Parker"

** That Q contained an unwarranted assumption that was all yours.

....... Phil

It's over 10 years since I got out of doing repairs full time, but now I remember that Yamaha and others do have different variants of the same model with the same type number, for different markets. I withdraw some of my earlier comments. :-)

Bob

"Bob Parker"

** If you were doing instrument amp repairs - you would have come across the very popular " Roland JC120 " combo amp ( JC = Jazz-Chorus).

Been in production since 1975s and still available with virtually unchanged appearance.

See:

Internally, there are at least 10 distinct versions of the JC120, each with its own schematic.

Only way to know which schem to order is by the serial number on the particular amp.

Naturally, guitar players falsely imagine they are all just the same.

Just what Roland wants them to think.

...... Phil