helps needed

[chinsoon]

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

 

[bananasiong]

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.

 

[audioguru]

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.

 

[bananasiong]

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

 

[audioguru]

If the resistor is connected from pin1 to the supply, won't the sensiticity be reduced?

Yes, you are correct, I was wrong.

You mean, without the resistor, the sinsitivity is 100mV rms, which is the amplitude of the input signal at pin3 right?

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.

Use a BJT as amplifier from a super regen before feeding in the PLL would work?

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.

 

[bananasiong]

From the datasheet (your attachment), it shows that the sensitivity is increased if the resistor is added from pin 1 to ground. I've tested this with the fo of 200 kHz, it works the same with and without the resistor. Maybe because of the minimum output of the function generator is 100 mVrms.

 

[chinsoon]

Found out Why!!!!!!!

hey, i think i found out why everything was so wierd for my superhetrodyne receiver.... my problem was that there is a tone burst signal that i measured using the oscilloscope.. but everything didnt work, even when i amplify the signal using op amp... not i know why... i suspect that the probe that is connected to my oscilloscope that is the one that picked up the signal, not my circuit.... that explains why amplification cant be done.. so the whole receiver circuit isnt working after all.....

by the way, i will reconstruct the circuit again on the PCB board...

so now i am constructing another one.. it is working, but just do not understand how it works..

this is the receiver... can someone explain how the L1 and L2 work? on the PCB board, its copper strips on it.. (attached also)...
so can i replace it with jumper wires other than using the strips? what i found out is that this will affect its frequency...

and how does that transistor Q1 and Q3 works? Q2 is an amplifier right? but just cant "see" how Q1 and Q3 is biased....

thanks

 

[chinsoon]

From the datasheet (your attachment), it shows that the sensitivity is increased if the resistor is added from pin 1 to ground. I've tested this with the fo of 200 kHz, it works the same with and without the resistor. Maybe because of the minimum output of the function generator is 100 mVrms.

bananasiong, do you mind telling me what application you are using this NE567 for?

 

[Nigel Goodwin]

hey, i think i found out why everything was so wierd for my superhetrodyne receiver.... my problem was that there is a tone burst signal that i measured using the oscilloscope.. but everything didnt work, even when i amplify the signal using op amp... not i know why... i suspect that the probe that is connected to my oscilloscope that is the one that picked up the signal, not my circuit.... that explains why amplification cant be done.. so the whole receiver circuit isnt working after all.....

by the way, i will reconstruct the circuit again on the PCB board...

so now i am constructing another one.. it is working, but just do not understand how it works..

this is the receiver... can someone explain how the L1 and L2 work? on the PCB board, its copper strips on it.. (attached also)...
so can i replace it with jumper wires other than using the strips? what i found out is that this will affect its frequency...

They are the tuning inductors (lecher lines), they need to accurately made, and stable - randomly replacing them will send the frequency anywhere!.

and how does that transistor Q1 and Q3 works? Q2 is an amplifier right? but just cant "see" how Q1 and Q3 is biased....

thanks

Q3 is a voltage regulator, a simple emitter follower. Q1 is a crude super-regenerative receiver - and is conventionally biased, just drawn on it's side.

 

[chinsoon]

They are the tuning inductors (lecher lines), they need to accurately made, and stable - randomly replacing them will send the frequency anywhere!..

so does that mean that i cant just simply replace the strip with a jumper wire. what if i want to adjust its frequency? if there is any difference from the frequency that it is suppose to be, cant the capacitor compensate?

Q3 is a voltage regulator, a simple emitter follower. Q1 is a crude super-regenerative receiver - and is conventionally biased, just drawn on it's side.

The voltage regulator part ok, but about the Q1, don really get it. what do you mean that it is conventionally biased?

 

[Nigel Goodwin]

so does that mean that i cant just simply replace the strip with a jumper wire. what if i want to adjust its frequency? if there is any difference from the frequency that it is suppose to be, cant the capacitor compensate?

The capacitor can compensate to a certain extent, but slight changes in the lecher line will produce a much larger change.

The voltage regulator part ok, but about the Q1, don really get it. what do you mean that it is conventionally biased?

Collector to +ve via a load, emitter to ground via a resistor, base biased with a potential divider - exactly as biasing should be.

 

[chinsoon]

The capacitor can compensate to a certain extent, but slight changes in the lecher line will produce a much larger change.

lets say if i want to do some modification and the PCB board needs to be changed, can i just follow the curve part of the copper strips? and the rest changed according to what i need to solder on. The curve copper line is the one that affect the frequency right?

 

[bananasiong]

L2 and the trimmer cap form the LC tank circuit.

bananasiong, do you mind telling me what application you are using this NE567 for?

I just want to learn how it works in a RF receiver.

 

[Nigel Goodwin]

lets say if i want to do some modification and the PCB board needs to be changed, can i just follow the curve part of the copper strips? and the rest changed according to what i need to solder on. The curve copper line is the one that affect the frequency right?

No, the entire track affects the frequency, in fact lecher lines are usually just straight.

 

[chinsoon]

L2 and the trimmer cap form the LC tank circuit.

is there anyway to calculate the theoretical value of the frequency of that tank circuit?

by the way, why must there be 2 curve copper lines there? what is L1 doing there?

 

[Nigel Goodwin]

is there anyway to calculate the theoretical value of the frequency of that tank circuit?

Presumably, but I've no idea what it would be.

by the way, why must there be 2 curve copper lines there? what is L1 doing there?

It's the primary of a transformer, matching the impedance of the aerial to the impedance of the tuned circuit.

 

[Laksiri]

Can I know ift's color or is it suitable if use any if more than 470khz.

 

[chinsoon]

Can I know ift's color or is it suitable if use any if more than 470khz.

i've checked the color codes online... even though i didnt get much information on it, but i am quite certain that i should use the yellow color ones.

The problem is that i found out that the measurements that i obtained is not from the circuit. Its the probe that is picking up the signal. So even when the probe is left unconnected, the oscilloscope still shows signals.....

That situation has mislead me for quite a long time, thinking that there is something wrong with the output.

 

[audioguru]

The problem is that i found out that the measurements that i obtained is not from the circuit. Its the probe that is picking up the signal. So even when the probe is left unconnected, the oscilloscope still shows signals.....

That situation has mislead me for quite a long time, thinking that there is something wrong with the output.

Your 'scope is set to be much too sensitive. The output of the 567 decoder should go from +12VDC to close to 0.5VDC when it receives a signal that it is tuned for.
The input to the 567 is a tone of 25mV or more.

 

[chinsoon]

Your 'scope is set to be much too sensitive. The output of the 567 decoder should go from +12VDC to close to 0.5VDC when it receives a signal that it is tuned for.
The input to the 567 is a tone of 25mV or more.

ya. thats what i learn from all of you.. initially i didnt know how to read the datasheet.

but now the problem is that the situation shows that the stages before the NE567 of my circuit are not picking up any signals. its the probe that is picking up those signals. so now i know the problem is not with the NE567, but is the stages before, might be the oscillator, the IFT, ZN414....

and i cant identify which one is giving the problem. the oscillator in my college lab can only show signals up to 20MHz whereas mine is using 27MHz..