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ba1404 clock signal , help

G

gula

Jan 1, 1970
0
Hi guys.
I build a FM transmitter based on the ba1404 chip.
The problem arises because this chip need a 38Khz crystal for produce
a subcarrier signal for the stereo transmition, but that crystal is
hard to find. To solve it i programed a PIC16f84 to generate the 38
Khz signal and, depending of what crystal use for the PIC, i could
reproduce the 38Khz fecuency more or less exactly. (For example wuth a
PIC runing on a 4MHZ crystal a can generate a 38,4 Khz signal).
What accurate such signal have to do?

Thanks, and scuse my english.
Cheers.

Gula
 
J

Jasen Betts

Jan 1, 1970
0
Hi guys.
I build a FM transmitter based on the ba1404 chip.
The problem arises because this chip need a 38Khz crystal for produce
a subcarrier signal for the stereo transmition, but that crystal is
hard to find.

http://www.sicom.co.nz/38khz-crystal-dt38-xidp74360.html

those guys are in my home town, there may be someone handier to you as
they don't ship internationally. (not from their web site atleast)

these guys do though:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=852333;keywords=38khz
To solve it i programed a PIC16f84 to generate the 38
Khz signal and, depending of what crystal use for the PIC, i could
reproduce the 38Khz fecuency more or less exactly. (For example wuth a
PIC runing on a 4MHZ crystal a can generate a 38,4 Khz signal).
What accurate such signal have to do?

others have reported failure with that approach.

Do DDS maybe? not something I would try for reasons stated above :)

Bye.
Jasen
 
M

Mark F

Jan 1, 1970
0
Jasen said:
http://www.sicom.co.nz/38khz-crystal-dt38-xidp74360.html

those guys are in my home town, there may be someone handier to you as
they don't ship internationally. (not from their web site atleast)

these guys do though:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=852333;keywords=38khz


others have reported failure with that approach.

Do DDS maybe? not something I would try for reasons stated above :)

Bye.
Jasen
THe BA1404 is a really noisy chip, and there are so MUCH better
One device available commercially - I've now bought about a dozen
of them for friends, rellies, others, gifts etc. Great MP3 sound
quality, the Audio in jack isn't very good, but still likely better than
the ba1404

/mark


http://www.dealextreme.com/details.dx/sku.8181
 
G

gula

Jan 1, 1970
0
http://www.sicom.co.nz/38khz-crystal-dt38-xidp74360.html

those guys are in my home town, there may be someone handier to you as
they don't ship internationally. (not from their web site atleast)

these guys do though:http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=852333;keywo...


others have reported failure with that approach.

Do DDS maybe? not something I would try for reasons stated above :)

Bye.
   Jasen

Scuse me, but i don't have good english. What means DDS?
Cheers
 
J

Jasen Betts

Jan 1, 1970
0
Scuse me, but i don't have good english. What means DDS?
Cheers

"Direct digital synthesis", it's a way to get more frequency
precision than the clock provides from a computer-generated wave,

at it's most crude you could make some cycles longer than others
so that you get 38 cycles per milisecond. more advanced methods
use digital to analogue conversion to make the change appear to occur
part-way throgh a cycle.

Bye.
Jasen
 
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