Hi, I'm using this schme for study, it's used to transmitt audio signal to vhf band 120 Mhz FM modulation to receiver (the receiver is SDR radio in the our lab).
it's works very good, stable frequency, good voice quality, and low power consume.
but the transmittion distance is not more than 40 meter in open field. I need to amplify the R.F power output of this transmitter. but i don't know how. could you please help me?
the antenna is the audio cable itself. it's works great. long cable of about 1.5m . I also tried to use standard antenna and no better result.
pleae note that i need to use this layout, i mean i can change and remove component, but i can't change the layout of the scheme because we already maked the PCB.
note: this transmitter used for study purpose only.
Add another stage like the final that is there already, bias it a little more and increase the B+ feeding it. Using the audio wire for an antenna is not a good idea even with a choke inline. Run a third wire, or use 3 conductor cable and use one for the antenna and the other two for audio.
Peace!
K-ROCKS RadioOne
ZeroPointRadio
AM Stereo 1670
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