Can someone suggest me chips for reciving and transmitting a fm radio between 30-80Mhz.
actually I thing one PLL chip that can work on 85-90Mhz will be fine to me.
I don't know what do you want to transmit. In case of mono audio signal I suggest you the TDA7000 Philips radio receiver. You have to use it with external 30..80 MHz RC or XTAL oscillator for fixed freq. If jou wants to tune it, then use RC OSC with varicap diodes. For transmitter use a simple RC oscilator, wich can be modulated with varicaps in FM. If you need I can send you a schematics.
30..80 MHz RC or XTAL oscillator for fixed freq. If jou wants to tune it, then use RC OSC with varicap diodes. For transmitter use a simple RC oscilator, wich can be modulated with varicaps in FM. If you need I can send you a schematics.
Can someone suggest me chips for reciving and transmitting a fm radio between 30-80Mhz.
actually I thing one PLL chip that can work on 85-90Mhz will be fine to me.
Thanks for helpping.
In all datasheets delta f = 75Khz when fm=1Khz. and if I need delta f for example 10 or 5 Khz for fm=1khz, how can I choose it????
You want narrow band and not wide band. According to the datasheet you can disable the stereo part with a switch. I think if you limit the deviation (there is a pot on the diagram to set this) to 10-15kHz you should be able to receive it OK on a narrow band receiver.
It looks like the output will be low from this chip. About -7dBm. I think you will need some amplifier to get any distance further than about 20' from it.
and here is the link of where i got the plans: **broken link removed**
i didnt think that the TDA7000 was all that great of a receiver. the stations that i got w/ it also came in on a clock radio just as good. maybe i just wasnt building it right, i dont know. i am still looking for a very sensitive FM radio for my FM bug that i built.
I built a tda7000 kit available at my local store. The selectivity is excellent as it is a full super het design. MOving the capacitor 1/2 of a degree caused the station to shift.
It was too selective, in other words!!! Sensitivity on the other hand was down compared to my good' ol sony walkman. especially in the lower frequencies for some reason.
wut kind of capacitor were u using pike? i used a 2-18 pf cap and i was able to hone in on a certain frequency quite nicely. if i'd used a 0-3 pf cap, i would get an even smaller deviation.
I know thats a huge range right there. It still doesn't cover the whole fm band though. Only about 3/4 of it. If I Wanna move it up I have to unwind the ferrite slug in the coil.
I wouldn't worry about it, I doubt it's got any low impedance matching inside the chip - it's probably only specified at 75 ohm because that's what's used for FM radio aerials.
Doing some matching may not be a bad idea as can be seen from the plots. Without matching the there's quite a bit of loss and bad return loss.
With matching the input loss is 4dB less and the return loss very reasonable in the passband. Also the added selectivity will make a difference in performance.
Doing some matching may not be a bad idea as can be seen from the plots. Without matching the there's quite a bit of loss and bad return loss.
With matching the input loss is 4dB less and the return loss very reasonable in the passband. Also the added selectivity will make a difference in performance.
How did you arrive at the circuits and plots?, there's no suggestion in the TDA7000 datasheet that the input impedance is 75 ohms? - which is what I suggested in my pervious post.
The internal block diagram shows it has a balanced input, with a 700 ohm resistor from each input to a 1.4V reference. The second input is simply grounded via a capacitor in the application note.