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FM radio - digital tuner

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2005-2006 » Archive through 01 September, 2005 » FM radio - digital tuner « Previous Next »

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Epithumia
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Username: Epithumia

Post Number: 24
Registered: 07-2005

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Posted on Tuesday, 23 August, 2005 - 05:01 pm:   Edit Post Delete Post Print Post

Hi guys,

I'm thinking of building an FM radio for a bedside alarm clock.

(Why? Because I'm fed up with the simplistic alarms on commercial radio-alarms and think I can design something better.)

Now I'm not a radio expert, but I've found a couple of FM chips (e.g. Philips TDA7010T) which would do quite nicely. However, as usual they involve a tuning capacitor, and I'd rather do without the mechanical problems of fitting that control.

I wondered how difficult it would be to build an FM radio with the tuning controlled by a PIC (since the PIC will already have a user-interface).

Presumably I'd either need something like a varicap diode to replace the tuning capacitor (never used one before), or alternatively some as-yet unidentified FM radio chip with direct digital control.

Does anyone have any pointers?

Thanks.
The price of getting what you want is getting what you once wanted.
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Magnum4
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Username: Magnum4

Post Number: 94
Registered: 04-2005


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Posted on Tuesday, 23 August, 2005 - 10:35 pm:   Edit Post Delete Post Print Post

Hi.
This any help?
http://www.willas-array.com/prod/products/directory/pdf/toshiba/AU_0001.PDF
Regards,
Jim
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Terrym
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Username: Terrym

Post Number: 24
Registered: 05-2005

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Posted on Wednesday, 24 August, 2005 - 02:49 am:   Edit Post Delete Post Print Post

If I remember correctly, the TDA7010 has an inbuilt varicap for tuning and also features an auto tune feature.
TM
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Epithumia
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Username: Epithumia

Post Number: 25
Registered: 07-2005

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Posted on Wednesday, 24 August, 2005 - 08:53 am:   Edit Post Delete Post Print Post

Thanks Jim. I'll check out the Toshiba parts.

Sorry Terry, but I rechecked the TDA7010 data and see no mention of built-in tuning:

http://www.farnell.com/datasheets/43867.pdf
The price of getting what you want is getting what you once wanted.
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Terrym
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Username: Terrym

Post Number: 25
Registered: 05-2005

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Posted on Thursday, 25 August, 2005 - 02:23 am:   Edit Post Delete Post Print Post

Hmmm, will dig out and recheck the info I have here. Maybe the grey matter is confusing it with another chip. Cheers
TM
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Terrym
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Username: Terrym

Post Number: 27
Registered: 05-2005

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Posted on Thursday, 25 August, 2005 - 03:09 am:   Edit Post Delete Post Print Post

Just checked the Philips site, the TDA7010T does have an internal VCO for tuning, but I can't find the info re Autotuning at the moment (really must clean up around here again). If you want to use the TDA7000, Philips application note AN192 gives complete details, including varicap tuning. Possibly may be applicable to the TDA7010 as well.A Google search for "tda7010t" and "application note" throws up a few sites with useful info as well.
TM
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Epithumia
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Username: Epithumia

Post Number: 26
Registered: 07-2005

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Posted on Thursday, 25 August, 2005 - 08:47 am:   Edit Post Delete Post Print Post

The application note looks helpful. Thanks Terry. :-)
The price of getting what you want is getting what you once wanted.
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Steerpike
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Username: Steerpike

Post Number: 39
Registered: 05-2005


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Posted on Thursday, 25 August, 2005 - 02:40 pm:   Edit Post Delete Post Print Post

Microchip's application DS40160A concerns a voltage synthesized tuning system for FM radios, with scan & station memory.
( i thought I posted this yesterday? But it hasn't appeared. Curiouser & curiouser )
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Epithumia
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Username: Epithumia

Post Number: 27
Registered: 07-2005

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Posted on Thursday, 25 August, 2005 - 02:59 pm:   Edit Post Delete Post Print Post

Thanks, but are you sure about the document number?

I searched Microchip's site without success. I also googled (sometimes google finds Microchip documents which Microchip's own search misses!) and found a document DS40160A about replacing a mechanical timer.
The price of getting what you want is getting what you once wanted.
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Mike_b
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Username: Mike_b

Post Number: 38
Registered: 05-2005

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Posted on Thursday, 25 August, 2005 - 04:08 pm:   Edit Post Delete Post Print Post

I fitted varicap tuning to a cct by Raymond Haigh (6 months back perhaps). I got his pcb to save time. It used TDA7000 and I noted very much improved selection with varicap.

Yes - My mind floated to the same ideas too, but alas no further. Keep voltages well stbalised as a few mV can give you tuning errors.
Cheers

mb
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Steerpike
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Username: Steerpike

Post Number: 41
Registered: 05-2005


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Posted on Friday, 26 August, 2005 - 04:33 pm:   Edit Post Delete Post Print Post

DS40160 is the footer on the printout I have. The file name is 6_008.pdf
DD6008 seems to be a more correct reference after searching the web, but I can't actually find a download site.
If yoi message me your email addr, I'll mail you the PDF file.

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