Some More Simple FM Transmitters

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audioguru said:
It is a highpass filter that blocks every AM radio station and CB transmitter in town.


Yes, it will be fine.
Click to expand...

Audioguru it's not that sensitive... so it can catch am radio...
atleast mine it isn't...

do you think if i lower the 10K resistor i can improve it's sensitivity?
 
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whiz115 said:
Audioguru it's not that sensitive... so it can catch am radio...
atleast mine it isn't...
Click to expand...
It is not supposed to be sensitive. It is supposed to show the output strength of your FM transmitter when it is about 1m away from the signal strength antenna. At a distance of only 1m the signal is pretty strong.

do you think if i lower the 10K resistor i can improve it's sensitivity?
Click to expand...
Try it.
 
audioguru said:
It is not supposed to be sensitive. It is supposed to show the output strength of your FM transmitter when it is about 1m away from the signal strength antenna. At a distance of only 1m the signal is pretty strong.


Try it.
Click to expand...

1m distance? if i don't tie the antennas together it doesn't do a thing!

ok i'll try lowering it...though i would prefer the circuit to light a led if it if the radiation is above a certain level... i don't know if it is possible using a darlington so i can amplify that 0.000005A and light a led.
 
If you tie the antennas together then you change the tuning of the output tuned circuit.
The voltage from the signal strength circuit is much too low to light an LED without an amplifier.
I think my circuits produced a few hundred milli-volts.
 
mkwatis said:
@audioguru
it takes how far/meters?
Click to expand...
My FM transmitter, the Mod4, has a range of over 2km to a very sensitive high quality home stereo or a good car radio over an open river valley when its 9V alkaline battery is brand new.
Its range is 300m in the open to a cheap Sony Walkman radio.
Its range is across the street to a cheap scanning FM "radio" from The Dollar Store.
 
And can you give a good antenna for this transmitter?
Included its diagram?
Im just new in this kind of stuff.. Got only a year of learning only theories of this.
 
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