[SOLVED] (TA2003) Fm/Am receiver

[Masood_786]

Hi All
Is there any one who experimented with TA2003 chip. I was first checking the mixer output of the chip but unable to find any output. Later i would connect mixer output with IF filter to Pin 8. I have done the following

1. Connected NE612 with 10.245Mhz crystal to get output (oscillator for 10.245 Mhz) from Pin 5. pin1 was gounded via 10k resistor and pin5 is producing the desired frequency.

2. Connected TA2003 for FM mode. Pin 14 (vcc) pin2 (gnd) pin 9 (gnd)
Pin 6 (vcc) and connected output from NE602 to FM oscillator input of
TA2003 at pin 13 and Left Pin 1 (open) and connected pin 3 (mixer output) to oscilloscope but did't get ans signal (frequency). Later i also connected Pin 1 of TA2003 to gnd via wire and later via 10k resistor but no luck.

When there in no FM RF input at Pin 1 of TA2003 then mixer should produce 0+10.245Mhz and 0-10.245Mhz and i should get fm local oscillator signal at 10.245 Mhz. This way i wanted to check that FM mixer module of IC is working fine but no luck.
Can anybody help me on this.

Masood

 

[davenn]

2. snip and connected output from NE602 to FM oscillator input of TA2003 at pin 13

now why would you do that ??? you are effectively connecting an oscillator into an oscillator. Pin 13 is for is for connecting a tuned cct (capacitor/inductor) to tune the INTERNAL oscillator. Feeding an osc. cct into there isnt going to work.

Dave

 

[Masood_786]

Thanks Dave for the reply.
The internal schematic of the TA2003 shows pin 13 as oscillator input(base of transistor) same as pin 6 of the NE602/612. The NE602/612 can be connected from external source(like 74hc4060 frequency divider) or by connecting crystal to drive the oscillator. I thought that there should be no problem if i provide external signal to drive the oscillator as in the case of Ne602/612. Maybe i am wrong but can you tell me how can i drive it's oscillator except connecting tank circuit.

Masood

 

[davenn]

from what I read of the chip ( and many other IF chips are the same) pin 13 connects an external tank cct to "the internal Osc" so changing the values of the tank cct effectively change the internal osc freq
You have to remember that the tank cct ISNT an osc its just controlling the osc's resonant freq (its an intergral part of the osc cct)
The tank cct is on the outside of the chip so that the user has some control over the freq of operation

Dave

 

[Masood_786]

Thanks Dave

From your statement

"The tank cct is on the outside of the chip so that the user has some control over the freq of operation"

I have understood that Pin 13 needs to be connected to Tank circuit only and nothing else to have some control over the frequency of operation of the internal oscillator. The chip TA2003 is for FM band so it means internal oscillator should have frequency of operation between 88-108 MHz Fm band. Am I right ?

Then how come the Chip (TA2003) mentioned at site
"http://uzzors2k.4hv.org/index.php?page=tvtuner" has been used that connects Tank circuit tuned for 28.2 MHz? (i am not able to find frequencies the chips would also work besides FM band, not mentioned in data sheet).

Masood

 

[davenn]

Thanks Dave

From your statement

"The tank cct is on the outside of the chip so that the user has some control over the freq of operation"

I have understood that Pin 13 needs to be connected to Tank circuit only and nothing else to have some control over the frequency of operation of the internal oscillator. The chip TA2003 is for FM band so it means internal oscillator should have frequency of operation between 88-108 MHz Fm band. Am I right ?

No not necessarily .... 1) the TA2003 has both AM and FM IF functions, and you are able to to use either one or both depending on your need. The chip was primarily designed for use as an IF Osc/Detector is Broadcast AM/FM receivers, say like car radios.

Then how come the Chip (TA2003) mentioned at site
"http://uzzors2k.4hv.org/index.php?page=tvtuner" has been used that connects Tank circuit tuned for 28.2 MHz? (i am not able to find frequencies the chips would also work besides FM band, not mentioned in data sheet).
Masood

Its getting used on 28.2 MHz cuz he has chosen tank cct capacitors and inductor that will tune the Osc for that freq

The input freq from the SAW filter is 38.9MHz (thats the IF output from the TV Tuner). That 38.9MHz is mixing with the 28.2 MHz osc to produce 10.7MHz IF at pin 3. It comes out of pin 3 and through a 10.7MHz filter and into Pin 8, where its amplified and and fed to the FM detector (demodulator) with the help of that 10.7MHz discriminator coil and capacitor hanging off pin 10.
Detected audio out is appearing at pin 11.

cheers
Dave

 

[Masood_786]

Thanks all guys specially Dave for guiding me, i was busy experimenting with the TA2003 for 38.9Mhz Tv reception and later for FM band radio but no luck, actually the web site i mentioned earlier in post has the circuit where Pin15 of the TA2003 is unconnected whereas in rest of the web sites the Pin15 is connected to Tank circuit(Pin15 is FM RF out), ithink it should work even if it is not connected to tank circuit. i am really confused, can any one help me out the issue is regarding Pin15 only.

 

[vfone]

Theoretically is possible to work without that tank circuit. But my guess is that it will not work because this tank is connected to Vcc, and there is possible to be an internal open collector stage. Needs at least to be replaced by a resistor connected to Vcc.

 

[Masood_786]

Thanks Dave,
it means that circuit mentioned at the web site
_-= Uzzors2k =-_ Project Site is not correct, there Pin15 of TA2003 is unconnected and i wonder how it is working as FM receiver.