Some More Simple FM Transmitters - Page 10 - Electronic Circuits Projects Diagrams Free

audioguru · 28th May 2009, 01:00 AM

Quote:

Originally Posted by Tails

Hi. (Sorry for the late reply). So, any transistor that has the same specifications as the 2N2222 will work fine right?

Yes or like the other transistors mentioned.

EmmKay · 22nd June 2009, 06:33 AM

@audioguru,
thank you for your circuit. I am in the process of the completing the build today and my query related to the tuning of the transmitter. Can you please enlighten me as to what should be the tunning sequence as to VC1, VC2.

I plan to use it to transmit a 16Hz blip to a distance of 1.2KM as a status check of a mechanical device. No elec. interference is around and line of sighht is available for installation Do you forsee any problems with that!. FM would be below 89.9 or above 104 to 108 as these freq. are not used in the desert where it will be used.

Thank you again for any input that you or any of the others may have on this.

audioguru · 24th June 2009, 08:28 PM

You have too many posts about the FM transmitter. First you must fix its wrong transistor voltages.

Q2 is the FM oscillator and it must be tuned to the frequency you want to use. Q3 is the RF amplifier that has very broad tuning. it is tuned for a peak at the frequency you are using.

The range is far to a very sensitive high quality FM radio. If the radio is cheap and poor quality then the range is only across a street.

The audio response at 16Hz is poor.

whiz115 · 23rd July 2009, 10:45 PM

Quote:

Originally Posted by audioguru

Of course the output of the 5V regulator should be 5V, even when it is loaded.

I tried tuning my FM transmitter with my Sony Walkman FM radio. The radio was badly overloaded and the signal was all over the dial, even when I switched the Local-Distant antenna attenuator to Local.

I made a field strength circuit:

the diode does half wave rectification the 1nF does smothing and the 100K must be the output impedance...

but why you need the 22-100pF capacitor and the 10K resistor to the diode?
also can the diode be a BAT41?

audioguru · 24th July 2009, 01:18 AM

Quote:

Originally Posted by whiz115

why you need the 22-100pF capacitor and the 10K resistor to the diode?

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

Quote:

can the diode be a BAT41?

Yes, it will be fine.

whiz115 · 24th July 2009, 02:20 AM

Quote:

Originally Posted by audioguru

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

Yes, it will be fine.

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?

audioguru · 24th July 2009, 02:33 AM

Quote:

Originally Posted by whiz115

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

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.

Quote:

do you think if i lower the 10K resistor i can improve it's sensitivity?

Try it.

whiz115 · 24th July 2009, 02:43 AM

Quote:

Originally Posted by audioguru

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.

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.

audioguru · 24th July 2009, 03:30 AM

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 · 11th September 2009, 12:32 AM

@audioguru
it takes how far/meters?

audioguru · 17th September 2009, 11:31 PM

Quote:

Originally Posted by mkwatis

@audioguru
it takes how far/meters?

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.

ladybliss · 15th October 2009, 07:42 AM

Can you give me some specifications of this transmitter?..

ladybliss · 15th October 2009, 07:43 AM

Quote:

Originally Posted by ladybliss

Can you give me some specifications of this transmitter?..

ladybliss · 15th October 2009, 07:45 AM

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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22nd June 2009, 06:33 AM	#137
EmmKay	@audioguru, thank you for your circuit. I am in the process of the completing the build today and my query related to the tuning of the transmitter. Can you please enlighten me as to what should be the tunning sequence as to VC1, VC2. I plan to use it to transmit a 16Hz blip to a distance of 1.2KM as a status check of a mechanical device. No elec. interference is around and line of sighht is available for installation Do you forsee any problems with that!. FM would be below 89.9 or above 104 to 108 as these freq. are not used in the desert where it will be used. Thank you again for any input that you or any of the others may have on this.

24th June 2009, 08:28 PM	#138
audioguru	You have too many posts about the FM transmitter. First you must fix its wrong transistor voltages. Q2 is the FM oscillator and it must be tuned to the frequency you want to use. Q3 is the RF amplifier that has very broad tuning. it is tuned for a peak at the frequency you are using. The range is far to a very sensitive high quality FM radio. If the radio is cheap and poor quality then the range is only across a street. The audio response at 16Hz is poor. __________________ Uncle $crooge

24th July 2009, 03:30 AM	#144
audioguru	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. __________________ Uncle $crooge

11th September 2009, 12:32 AM	#145
mkwatis	@audioguru it takes how far/meters?

15th October 2009, 07:42 AM	#147
ladybliss	Can you give me some specifications of this transmitter?..

15th October 2009, 07:45 AM	#149
ladybliss	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.