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Thanks for the clarification and links.
I think i'll buy myself the nanovna with the attenuators. Probably for my low power application i would not need necessarily an attenuator, i tried to estimate the output power by connecting dummy loads, and with 50 Ohm load the power across the resistor...
Thanks for the reply. I didn't consider the material and also the high frequency. I'm doing a lot of trial and error but I'm learning lots of things, also with the help of this forum and all the answers i received. I'll check the methods for measuring impedance with different approaches without...
Thank you. I've seen that video just yesterday and it was clear, also the smith chart, probably i'm loosing too much power just on the impedances not matched.
I tried do build a Unun with a toroid, i wanted a 9:1 unun but i choose the wires too big and got only 7 wounds, and i connected it as...
Thank you for the reply Dana. I should make a more reliable buffer with higher input impedance, yes it is always tradeoffs.
I've tried to put the audio in the base of emitter follower but when i did that, the output of the emitter follower just collapsed to 0V, while if i leave the circuit as...
Thanks for the reply. I've read the files you shared with me and i'm starting to understand the concepts of impedance matching and the related efficiency in power transfer. I think the best thing i may do is buying a NanoVna for example, in order to exactly measure the antenna impedance and the...
Thank you for your help Dana. My goal for output power is actually the maximum i can do with general purpose transistors that cannot handle much power. I just want to push the range a little farther (just some meters)with what i have. I think the max i can do is with bjt's which handles maximum...
Thank you Dana. Can you explain me what does it mean for the bias to be not flexible?
I tried the buffer+push pull amplifier but something wasn't working as expected, probably i have to spend more time studying that type of amplifier.
Do you think that, in order to keep the circuit simpler, even...
Thanks for the replies. Now i added the buffer stage with an emitter follower and on the output i get the same sine wave as the input. Now i would like to amplify the power given by this signal to drive the antenna. I'm trying to do it with a push pull amplifier, but first, i need to bias it in...
Thank you for your reply Brad. I understand what you are saying. So, in order to be able to draw more current, especially if i want to do just one stage, like only the colpitts oscillator modulated on the supply side by an audio signal, i can adjust the resistors.
If starting from this point, i...
I changed the values of inductance and capacitance for the Lc tank. Now i am using ~100 uH inductor and 2x470 pF capacitors. This gave me a resonant frequency of about 1-1.2 Mhz.The output voltage from the Colpitts jumped up to a 9 volt peak to peak sine wave. Just by doing this i increased a...
Thank you Dana for your answer. I've read about antenna impedance matching. In my case i'm using a simple wire as an Antenna that is long about 262 cm, that i keep high in the room, sticked to the ceiling. From what i understood i need to know what is the impedance of the antenna, that is not...
I changed the capacitors to 100 nf ceramic ones and the output voltage increased a little bit. The sinewave amplitude was about 3 volts peak to peak. I connected the output to a bjt emitter follower configuration in order to buffer it. If i understood better, in order to get more range now, do I...
Thank you Brian for your reply. I didn't take into account the optimal range, I didn't know. Can you suggest me how to find what is the better combination for a given frequency? As Dana said, i'll change the capacitors with ceramic ones. As you suggested, i'll try to take the output on the emitter.
Thank you for your reply Dana. I confirm that i am using standard Aluminum Capacitors, i will change them with some ceramic capacitors, even if they are of much lower capacitance. Thank you for the pdf book, i'll read it to understand better the principles.
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