Penulis Topik: Encoder Stereo BA1404  (Dibaca 21724 kali)

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Offline STL

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Encoder Stereo BA1404
« pada: Pebruari 01, 2010, 08:21:20 PM »


THE MARCONIST

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Re:Encoder Stereo BA1404
« Jawab #2 pada: Pebruari 01, 2010, 09:19:22 PM »
Thank You Bro ....

 8)

Offline dxdiag

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Re:Encoder Stereo BA1404
« Jawab #3 pada: Maret 23, 2010, 12:01:10 AM »
I Love BA1404  ;D

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Re:Encoder Stereo BA1404
« Jawab #4 pada: Maret 23, 2010, 04:39:43 AM »

The BA1404 chip, for what it is, and how very little it cost, is an amazing chip! But, it does have some flaws. For an experiment, I took an FM10a, and hooked the output of it to a Spectrum analyzer.

At first glance of the output signal (with the analyzer set with 5 log, 100 kHz. Bandwidth i.f., 3 msec. scan time/cm, 1 MHz. scan width/cm, and adjusted to fit crt.),

I nearly fell off my bench!   :o

The signal looked awful. It looked as though it was something from a horror movie. I was amazed that it sounded that good coming across my Stereo receiver. The sides of the signal were engrossed with 19 and 38 kHz Harmonics extending out 1.5 MHz. either side of the center frequency.
 
NOTE: The BA1404 does not give the ability to filter the 38 kHz Signal externally.

This is a good reason why you need a spectrum analyzer! Can you imagine amplifying this 10 mw signal, to 15 watts! And at 100 watts.....

Geeze...

Don? even want to know what it would look like.  :(

I thought to myself, "well lets try something!"  :D


I disabled the 38 khz. xtal. ...The signal looked great at this point. I reconnected the 38 khz. ...Back to where it was originally. I disconnected the mod. input to the chip.

OOOOPS! Here's one major flaw.

With no mpx input, the signal should have looked as though it had no 38 khz. xtal connected. But instead, it still had it going to it. I thought to myself, "Mmmmmm, either there was a feedback loop inside the chip (witch there should not be), or the 38 khz. oscillator was getting into the rf amp internally, and therefore passing it to the output stage.

Since i only have a block diagram of the chip, i cannot say absolutely what is happening, but, i would suppose it would be the latter.

The crystal oscillator is too close to the rf amp stage inside the chip, and therefore "bleeding" (for lack of a better word) into it. So, to prove my theory (which i love to do), i used two BA1404 chips. I used one as a stereo mpx output, and the other one as the rf amp.

I fed the mpx output of one chip into the mpx input of the other chip.

After I made a few modifications with grounds (because i ran into oscillation problems with it), the signal improved greatly, by at least 50%.

I could now at this point, disconnect the mpx input, to the second chip, and it would be as clean as with no 38 khz. signal connected to it.

The second major flaw is: Because there is no filtering to be had with the 38 khz. signal, it is passed on to the next stages of the circuit, causing the mpx output to be engorged with harmonics. This makes up for most of the rest of the output signal problems. Not much that can be done about that, since where it needs to be filtered, is inside the chip.

This chip apparently, was not intended to be used at more than 50 to 100 mw. total output. Mmmmmm... that would mean that, the makers of the chip would have known about these short comings.

Wow! ..... That means there are no flaws!  

Also, a glance at the spec sheet on the BA1404, says that 1.25 volts is typical to run this chip. So, I took the (3) 1N914 glass type diodes out of it, and replaced them with (2) ECG125 rectifier type diodes.
My voltage now was at 1.31 volts. Not only did it reduce the noise factors to zilch, but also greatly improved the stability of the output frequency to +/- 2 khz. after warm up time of 5 minutes. < (this depends on temperature stability inside the room of course.)  And, with little or no apparent loss of output power. Seems to run a lot better at that voltage. Mmmmm.... lower voltage, lower consumption, less heat, more efficient. Don't know why everyone is using 2.5 volts.

By the way, the stability before the 1.31 volt mod. was +/- 75 khz.
(Shhhhh.... i'm being nice about it!)

For a "mono fm" (with no 38 khz. crystal input, or disabled), I have no complaints against the chip.

More could be said about the BA1404, but i'll leave it at this.

Like I said, for a $2 chip, not too bad for what it is.

If ROHM would improve the chip, to where it has independent level adjustments for internal gains, external filtering and such, and "sheild" the 38 khz. oscillator internally (if that can be done),
then i would think they would have a good chip on their hands.

It would also be great, if they would incorporate a PLL inside too!  ;)
Till next time, ......  "Always Learning"


Offline VPDX

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Re: Encoder Stereo BA1404
« Jawab #5 pada: April 02, 2010, 05:27:48 PM »
Misah ngak ntu audio.............
I LOVE ELEKTRONIKA

Offline dxdiag

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Re: Encoder Stereo BA1404
« Jawab #6 pada: April 02, 2010, 06:07:19 PM »
Misah ngak ntu audio.............
misah banget bro ari, hasil suaranya juga jernih pokoknya kualitas gak diragukan lagi. bikinnya juga gak ruwet. klu mau datang ke mojokerto tersedia tu IC BA1404 seharga Rp 9000 klu di gentegkali surabaya harganya Rp 15000, untuk kristalnya pake 38Kz harganya Rp 10000 komponen lain murah2 tu, aku bikin tuh stereo encoder abisnya nggak sampe 30Rb

Offline purwanto-amm

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Re: Encoder Stereo BA1404
« Jawab #7 pada: April 02, 2010, 08:11:53 PM »
misah banget bro ari, hasil suaranya juga jernih pokoknya kualitas gak diragukan lagi. bikinnya juga gak ruwet. klu mau datang ke mojokerto tersedia tu IC BA1404 seharga Rp 9000 klu di gentegkali surabaya harganya Rp 15000, untuk kristalnya pake 38Kz harganya Rp 10000 komponen lain murah2 tu, aku bikin tuh stereo encoder abisnya nggak sampe 30Rb

BA1404 di Bandung hargana Rp7.500, Cristal 38Khz nya Rp2.500 ......
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Offline STL

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Re:Encoder Stereo BA1404
« Jawab #8 pada: April 10, 2010, 06:34:28 PM »

Hello ....  all

Encoder Stereo  of  ...SPI  ....  PCB   have or not !   
Thank you

   STL

Offline lutfi

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Re:Encoder Stereo BA1404
« Jawab #9 pada: April 11, 2010, 01:16:21 AM »
kristalnya bisa di ganti pake MCU ! klo aga susah nyari 38000Hz
Meonggg

Offline dxdiag

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Re:Encoder Stereo BA1404
« Jawab #10 pada: April 11, 2010, 07:16:50 AM »
kristalnya bisa di ganti pake MCU ! klo aga susah nyari 38000Hz
MCU tuh apaan? Kalau MCK Q tau  ;D

Offline ndroe

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Re:Encoder Stereo BA1404
« Jawab #11 pada: Juni 05, 2010, 12:52:39 PM »
maaf bila salah ya...maklum new be juga neh
mcu kalo ndak salah mikro kontroller ya macam atmel 89c51 atau 89c52, pic18f64,cy371 dll...bener ndak mass
pernah mbuat nih encoder...suaranya oke misah banget cuma ada suara seperti suara tikus walau ndak terlalu ketara....cuitttttt...apa karena kurang rangkaian filter untuk 19khznya....
88,1 ..FM Ra' Ajeg

Offline lutfi

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Re:Encoder Stereo BA1404
« Jawab #12 pada: Juli 05, 2010, 12:12:18 AM »
maaf bila salah ya...maklum new be juga neh
mcu kalo ndak salah mikro kontroller ya macam atmel 89c51 atau 89c52, pic18f64,cy371 dll...bener ndak mass
pernah mbuat nih encoder...suaranya oke misah banget cuma ada suara seperti suara tikus walau ndak terlalu ketara....cuitttttt...apa karena kurang rangkaian filter untuk 19khznya....

betul om mikrokontroler...... untuk mendapatkan hasil yg lebih baik pergunakanlah jenis AVR seperti keluarga ATtiny, ATmega, AT90sxx ...... frequency clock yg dihasilkan sangat stabil & presisi ! 
Meonggg

Offline Eko Pur

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Re:Encoder Stereo BA1404
« Jawab #13 pada: Agustus 11, 2010, 05:09:56 PM »
wah mohon bantuan buat para master aku nyari2 keliling kota ga dapet IC + Cristalnya.ada yang bisa  bantu ga ya.......? ;D ;D ;D

Offline aji wahyu

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Re:Encoder Stereo BA1404
« Jawab #14 pada: Agustus 11, 2010, 09:23:37 PM »
wah mohon bantuan buat para master aku nyari2 keliling kota ga dapet IC + Cristalnya.ada yang bisa  bantu ga ya.......? ;D ;D ;D
Kristal'y emg  jrang yg jual mas,q nyari dari daerah wonosobo-purwokerto g da tuh yg jual gituan..

 


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