I've seen an alert under my question:
“Please clarify your specific problem or add additional details to highlight exactly what you need. “
Maybe this is due to the fact that I'm not very good to express myself in English, I'm sorry; I'm also a novice about these subjects: so, again, I apologize for my mistakes with the language and for my schematic. So, considering my exposed limits, I underline the part of my question where I stated “However I have some exact questions about” with a list of four question about the problem which I encountered: I asked If i correctly designed the amplification stage and if there is a better way to amplify the output of the oscillator.
Thank you all for your kind understanding.
I start by saying that I'm doing my “experiments” in a building located in a rural location and that, however, local laws allows to use low power rf transmitters.
Well: since I need to transmit an FM signal to a distance of about 30 feet inside such building, and the output signal have to pass through the walls, due to the fact that I don't have the space for a longer antenna, I was thinking to implement an amplifier stage on the output of the transmitter. The following image shows the full schematic:
Where the amp stage is still not present, and on the base of Q1 there will be a female jack where to inject the audio signal.
By a search on internet I've found that there are many similar circuits where the amp stage, most of the time is made using a “common emitter” transistor instead of a “emitter follower”, but some of them (few), however, rely on the emitter follower. I choosed the emitter follower configuration because I figured out that the emitter follower has a lower gain (usually almost equal to the input) and so for avoiding to exceed with the output power. I calculated the values of R4, R5 and R6 looking at the BFR36 datasheet and then I've found an online calculator where I inserted these values to get the values of these resistors.
However I have some exact questions about:
1) Is the emitter follower shown in my schematic, correctly designed? I have some doubts about the resistor R4 (maybe the value is too much great?)
2) Are R6 and R5 really necessary, or I can just leave R6 and get rid of R5?
3) Will be able, the amp stage showed in my schematic, to boost however the output signal in terms of strength and distance? I mean: is possible to estimate the power boost which I will get?
4) Can someone suggest me some improvements to the amp stage of my circuit or suggest me a different approach, maybe using a common emitter configuration?