and i was applying the decoupled audio signal to the base of Q1 and the values for C1, C2 and L were 1n , 10n , and 50uH respectively to get about 700 KHz carrier frequency. i could see the AM signal clearly displayed on the oscilloscope , but when i tried to receive it in a radio i could not hear the audio signal sound unless i touch the antenna with my hand , when i do touch the antenna i hear a very clear and loud voice and it has a high range . when i leave the antenna i cant hear anything .
Is there anything i can do to handle that problem ?
the antenna i use is one from an old radio and i connected it to about 30 cm of wire directly to the emitter of Q1
To transmit at this low frequency you need a long antenna and a good earth connection. For shorter antenna's you need a loading coil to compensate. Without this you will not transmit further than your bench.
as said in the last row it does not need an antenna or using just 30 cm will increase the range . does this imply that the output signal power in this circuit is larger than that of my circuit ? what do u expect the range of this circuit be ?
Every Circuit uses DC power input to increase the power of AC signal
Here the second ckt uses a 9V supply and considerable dissipation by the resistors is not of great impact and so The power of the second Transmitter Ckt is higher than the previous one which uses just a 6V DC margin for amplification and enhancement
oh sorry i forgot to say that i used 9V battery instead of 6 V in my circuit and i got around 6v p-p in the oscillator output. may be it has something to do with the resistors ?
actually the audio signal i used was amplified in a first stage CE amplifier and the decoupled output was applied to Q1 base hence it's also a multistage amplifier . i wonder if the problem is related to the position of the tank circuit or to the oscillator type .. ?