I've changed some value of the capacitors, since I couldn't get them at my place.
C2, 24pF-->22pF
C4, 2.7nF-->2.2nF
250uF-->220uF
Will these affect the operation of the circuit?
And what's the puspose of center tapping L1 with C2?
I've changed some value of the capacitors, since I couldn't get them at my place.
C2, 24pF-->22pF
C4, 2.7nF-->2.2nF
250uF-->220uF
Will these affect the operation of the circuit?
It creates a Colpitts oscillator which is the most important part of a super-regenerative radio.
Read the article that came with your schematic or see many articles about super-regenerative radios in Google.
The tuning capacitor, C3, has three leads. Only the outer two leads are used; the middle lead of C3 is not connected. Arrange L1 fairly close to C3, but keep it away from where your hand will be.
L2, the RF choke should not be near a ground. The same is true for L1. Capacitance to ground will disturb the feedback.
Hi,
I've done this circuit finally. But it doesn't work
I'm using 6 turns coil.
I'm using 9 volts Energizer rechargeable battery (7.x volts measured)
I'm using the unused resistor pin as the center tap for the coil.
I've tuned both the trimmer capacitor and the volume control, but they gave the same result, no sound at all.
is it the problem of the bf256 transistor? Is there any transistor can be used beside this?
From Google, I found that the pins representative for bf256 are different.
Some showed the pin: Gate, Source and Drain
but some gave me: Drain, Source and Gate
The manufacturers of the BF256 got the pins mixed up. It is easy to use an ohm-meter to find the gate. The gate is the anode of a diode to the source and to the drain. It is difficult to measure which pin is the source or the drain.
The voltage at the source should be a couple of volts DC.
Try a different numbered FET.
Yes, I found that too. #1 definately wrong. But I've tried both #2 and #3.
The website said that, if the circuit is not working (no sound exactly), I may need to change R4 to 20K (up to 50K). Besides 2N4416, J310 and MPF102 are recomended. Hopefully I can find either.
The voltage across R4 (after changing to 33K) is 0V (I'm using analog voltmeter, the battery is 7 volts measured). And, I could't find 2N4416, J310 and MPF102. They have only replacement for them:
2N4416-->BF256
MPF102-->BF245B
Hi,
Now I can hear some buzzy sound. I was using enamel coated wire as jumper! That's why they were not functioning and I couldn't hear anything! I've measured the voltage across R4, it is around 3 volts with analog multimeter. With the FET's pin is GSD. I've tuned the trimmer capacitor, but I can hear only buzzy sound.
Hi,
An antenna is now connected to the drain, almost 30cm long. When I tune the trimmer capacitor, within 10 degree I think, I hear some noise (like when you plugging in the audio jack). For the rest, I can hear only buzzy.
I think I have to change my component placement...
By touching a 22k resistor across the existing 33k resistor, you instantly change their total value to only 13.2k to see if it helps with the lower resistance.
No, there is no FM station in my state. Most of the FM stations in Malaysia are located more than 100km from where I'm staying.
I do not think it is pointless to construct such a radio - if the point is to learn. It is not a replacement for a good design that has been well constructed and the performance will be poor at best. ...