The crystal oscillator in the transmitter makes a very accurate frequency but it is a rough square-wave full of harmonics that cause interference. The tank filters out the harmonics.

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Uncle $crooge

 

and take only the fundamental, 27 MHz? The tank will oscillate itself, won't it?

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Superman returns..

 

The tank is in an RF amplifier, it is not part of the crystal oscillator.

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Uncle $crooge

 

hi there...

after so many time trying i still cant get the circuit working. I've tried many ways such as using op amp, connect the relay directly to the NE567 and so on.

But i found many problems. First, the voltage to my ZN414. It is stated on the datasheet that the voltage to the ZN414 is only 1.1 to 1.3V. but when i measured the voltage, the input voltage is about 8V. and the 8V comes from the IFT. any idea why?

and when i turn on the transmitter, with my receiver off, there is also responds, which is the tone burst waveform. and i tried to amplify the voltage using op amp but the input voltage is somehow BIGGER than the output voltage.

Any idea why?

 

You've connected the transformer the wrong way, and probably blown the chip?.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Em.. there is such possibility. I mean i cant find any information or the way to connect the IFT. So i did it based on the circuit diagram. It shows that the input side has 2 pins and the output side has 3 (something like a center tap) so i followed accordingly. is that wrong?

By the way. is there any possibility that this circuit will not work. As in i got this from a website that did not state that it is tested. So my lecturer is questioning whether is this the issue or not.

 

Why not check where the wondings connect with a meter?.

It looks to be a simple enough circuit?, assuming your lecturer knows anything about electronics he should know it looks pretty viable.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Hi,
For the LM567 PLL, is it the demodulated signal goes into the input pin?
Then RC at pin 5 and 6 tune to the modulating frequency by 1/(1.1RC)?
The maximum input signal to pin 3 is only 200 mV?
When the input frequency and the tuned frequency are match, the transistor at the output is turned on right?
I'm not quite sure about that even I've read the datasheet.

Thanks.

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Superman returns..

 

Hi,
According to the datasheet, the maximum frequency, fo is 500 kHz, but the minimum is not stated. I've tried with 5 kHz, but it doesn't work as expected. The output seems to be oscillating. When I change the fo to 200 kHz, then it works. Pin 8 goes low when the variable resistor is tuned to match the input frequency.
From the datasheet as well, the maximum input voltage is 200 mVrms. Is it going to be damaged if the input signal is higher? Up to 2 Vpp?

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Superman returns..

 

Well, I am not using the LM567. I used the NE567, where some of the specs are different.

for the range of the frequency within its detection, maybe you can refer to the datasheet of the NE567. I am not sure whether is that what you are looking for, but there definitely states that the range of frequency is 0.01Hz to 500KHz

http://www.x-robotics.com/downloads/...67_SE567_2.pdf

but the 2Vpp, generally i think this IC is used in communication circuits only right?( i mean i see that from the list of application on the datasheet.). so i wont be expecting something like 2Vpp to come out from the receiver circuit.(CORRECT ME IF I AM WRONG).

by the way, how did you connect your LM567? that day audioguru has shown me the connection, but i don really understand. the one side of my relay is connected to the +Vcc and the other connected to pin8. it gives me and impression that when the relay is on, the current is flowing into tone decoder through pin8... current flowing into output pin???? very blur on this.

 

By the way, any one knows the reason of amplification using op amp that will lead to the input greater than the output??? I have tried amplifying the signal using op amp. but i do not know why the output becomes smaller than the input. I have tried op amp 741 but it doesnt seem to be working.

And anyone knows explanation on super regenerative receiver. Basically I have called it an off for the superhet receiver since its very troublesome and sensitive plus not working. So now i found a circuit which is the super regenerative circuit that will suit my application as well. (the way i see the components i have bought, its much simpler and easier to handle compared to the ones in the superhet receiver.) Just want to know the main concept of it. Any websites or tutorials would be helpful.

Thanks

 

Yes, one side of the relay is connected to the + supply and the other side connected to pin 8. It is because pin 8 is the collector of a transistor. See the attachment, we turn on the relay in this way, right? If the relay isn't being switched, I think pin 3 is not getting any signal that matches the fo, not sure.

Attached Images

Relay.GIF (2.1 KB, 12 views)

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Superman returns..

 

The LM567 is exactly the same as the NE567.
Their datasheet shows pin 7 as the ground pin that Chinsoon didn't connect.

If pin 1 has a 130k resistor to the positive supply then the input sensitivity is 20mV to 25mV RMS. Without this resistor then 100mV RMS is a normal input but is probably not availabe from a super-regen radio without an amplifier.

The datasheets show a relay coil and protection diode connected from pin 8 to the positive supply and up to 100mA is available.

Attached Images

NE567.PNG (40.8 KB, 10 views)

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Uncle $crooge

 

If the resistor is connected from pin1 to the supply, won't the sensiticity be reduced? You mean, without the resistor, the sinsitivity is 100mV rms, which is the amplitude of the input signal at pin3 right?
Use a BJT as amplifier from a super regen before feeding in the PLL would work?

Thanks

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Superman returns..

 

Yes, you are correct, I was wrong.

Actually, the sensitivity is reduced with the resistor from pin 1 to the positive supply and the sensitivity is 20mV to 25mV RMS. So without the resistor then the sensitivity is higher. then a lower input signal will trigger it.
The datasheet shows a 100mV input signal.

Yes, it is easy to overdrive a transistor then it will have a distorted output.
I don't know if the sensitivity of the 567 IC is reduced if the input is distorted.

Attached Images

NE567.PNG (4.2 KB, 7 views)

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Uncle $crooge