I have a schematic attached of a fm antenna booster and I tried the bias shown as a test with a transistor and the transistor's output is about 1/10 of a volt from collector to ground. I am powering it with three volts and when I add a 10K resistor from the base of the transistor to ground I found that I was able to achieve 1/2 the supply voltage of 3V which was about 1.4V at the collector to ground. I used a 560 ohm resistor from collector to positive instead of 1K since the circuit call for 12V and I want to use 3V. With the circuit as it is, I think the 27K base bias resistor is too low and it has to be much higher because the output is about 1/10 of a volt measured from collector to ground. If and when I assemble the whole circuit as shown in the schematic, would R1 alone of 27K overload the transistor and prevent RF amplification of the FM signal? Is the bias wrong as shown with only R1 and I should use the 10K from base to ground? The output voltage should be at 1/2 the supply voltage of quiescent right? I want to build the circuit to boost the fm antenna signal for my Walkman via the headphone jack connection since the headphone wire is used as an fm antenna. I think I know how to isolate the amplified signal using RF chokes and capacitors.

 

There is something wrong with your circuit. If the collector voltage was 0.1V and the base bias comes from the collector, then 0.1V is not enough to turn on the transistor at all.

 

If and when I assemble the whole circuit as shown in the schematic, would R1 alone of 27K overload the transistor and prevent RF amplification of the FM signal?

I think you know the answer.

Is the bias wrong as shown with only R1 and I should use the 10K from base to ground? The output voltage should be at 1/2 the supply voltage of quiescent right?

Yes, that will give you the widest operating range without destruction of the input signal. There are many ways to accomplish the proper biasing. I think the 10K is good solution but there are experts around here that may tell us a better approach.

 

There is something wrong with your circuit. If the collector voltage was 0.1V and the base bias comes from the collector, then 0.1V is not enough to turn on the transistor at all.

You're right, I failed to mention that I biased the transistor from the positive supply voltage

 

You're right, I failed to mention that I biased the transistor from the positive supply voltage

So what happens if the 27k is connected to the collector as per diagram?

 

So what happens if the 27k is connected to the collector as per diagram?

With 330 ohm used for R2+R3 and R1=33K the output at the collector is about 1.6V with a 3V power supply. With 2.2K used for R2 + R3 and 33K used for R1, the output at the collector is ,7V with a 3V power supply. I guess I have to use the 330 ohm collector resistor for R2 + R3 and use a 22K resistor in series with a 10K pot for the bias resistor R! if I want to use two AA batteries for 3V to power the completed circuit--that's my best guess.

 

I followed the schematic and the circuit seems to work at 3 volts with R3=330 ohm and R2=100 ohm because I tried it on my Walkman and clarity of weak signals seems to be better but I am not sure and I feel it has to do with my mental illness. Maybe the physical result of my test memory is not being deleted when I undo a connection like from the headphone common to a jumper cable as the antenna. The circuit did not amplify with the input of the RF amp connected to the common of the headphones but worked when the RF input was connected to a jumper cable as the antenna. Attached is a schematic showing the inductor to block RF between both commons of the Walkman and headphones.

 

I don't know if you are able to see the schematic I made with paint. If not, I will upload it again. Can you detect how the mental illness is operating according to my explanation?

 

I can see the images fine but cannot comment on the rest.