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Simple FM transmitter

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#21
This thread talks about an FM transmitter.
You have a receiver problem that should be in its own thread.

Phone your radio station and ask them to boost their power so that your cheap or defective radio can pick them up without cutting out. Good luck.

haha, no no i have a tuner so i can listen to my ipod in the car. it plugs into a cigarette lighter and i sync the frequency so it'll play out of the car speakers. but it'll cut out at times, sometimes causing me to surf for another channel that i can set it to.
 

killivolt

Well-Known Member
#23
haha, no no i have a tuner so i can listen to my ipod in the car. it plugs into a cigarette lighter and i sync the frequency so it'll play out of the car speakers. but it'll cut out at times, sometimes causing me to surf for another channel that i can set it to.
I like what guru is saying. It may well be a connection problem.
Either on the Ground to antenna or pole connection or just a poor receiver.




kv
 
#24
May i know how far the signal can be transmitted?
Not sure about this one, but silicon chip did one of a similar design that was sold in a kit form at one of the local electronic kit retailers here in Aust. I think it was in their Nov 89 issue. It ran off 2 X 1.5V batteries, and the output coil was actually etched into the PCB rather than wound. It got a range of about 100m from memory, and fitted into a match box, complete with batteries.

I hooked one up to a 9V battery, and it was good for 500m, and that's only the point at which I turned the car around and went home again. :)
 

mvs sarma

Well-Known Member
#25
Not sure about this one, but silicon chip did one of a similar design that was sold in a kit form at one of the local electronic kit retailers here in Aust. I think it was in their Nov 89 issue. It ran off 2 X 1.5V batteries, and the output coil was actually etched into the PCB rather than wound. It got a range of about 100m from memory, and fitted into a match box, complete with batteries.

I hooked one up to a 9V battery, and it was good for 500m, and that's only the point at which I turned the car around and went home again. :)
The Mod4 version of AG is much refined Mono and perhaps far superior in performance compared to Nov89 SC design.

If you wanted Stereo, perhaps Micromitter of silicon chip is the best and One "AN920" has suggested specific mods for improving unwanted Noisy tone comming at higher end of audio. you may implement that. Once you want Mono, i feel MOD4 is superior by any means.
 

audioguru

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#28
There are some AM transmitter circuits on the internet. I entered AM Transmitter Circuit in Google and got pages of circuits. 129,000 links.
 

audioguru

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#31
Can anyone provide me a circuit for a TV Transmitter which can radiate the signal to a distance of 3 to 5 Kilo meter either in VHF or UHF.
It is illegal to operate an uncertified TV transmitter.

It is illegal to operate a certified TV transmitter without a licence.

In the USA this month, analog TV transmissions from TV stations will cease.
 

Mike_2545

Super Moderator
#32
Actually, they moved the transition from analog to digital to between March 14 and June 12.

I guess not enough people got a government coupon or something.
 
Last edited:
#33
please identify the importance of coil length

what's if I changed the inductor from which the antena rises changed in length could this affect the frequency.
THANKS
MEDSOL
 

audioguru

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#34
what's if I changed the inductor from which the antena rises changed in length could this affect the frequency.
THANKS
MEDSOL
Guess what determines the frequency of the very simple FM oscillator?
1) The length, diameter, turns spacing, wire size and number of turns of the coil.
2) The inductance of the traces of the circuit board layout.
3) The capacitance of the trimmer capacitor, the capacitance of C6, and the capacitance of the transistor.
4) The supply voltage (because it affects the capacitance of the transistor).
5) The capacitance of the circuit board layout.
6) The distance to the antenna of anything conductive that affects the capacitance of the tuned circuit.
7) The distance of anything conductive near the circuit board.
8) Maybe more things that I forgot about.
 
#36
hello
could u plz help me to understand this cct
i am realy have a great problems in dealing with cct for coomunications
could you also estimate the range (distance) for this cct
 
#37
hello
could you plz help me to understand this cct
i have a realy great problem in dealing with communication cct.s
could u alsi estimate the range ( in distance) for this cct and how
 

audioguru

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#38
The very simple circuit uses an audio preamp transistor and an RF oscillator transistor.
Its output power is low so that buildings, trees and hills block its signal.
Its range might be 500m in the open to a very sensitive home stereo FM tuner or car radio, about 150m to a cheap Sony Walkman portable radio and across the street to a cheap "scanning" radio from The Dollar Store.
Its range decreases as the battery runs down.
 
#39
I cant still post threads so im posting this here........I built a fm transmitter.....the circuit says it goes up to 400m...well i get a very clear "triiiiiiiiiiiiiiiii" sound from the radio when i connect it to the power supply...its definetely working but when i speak from my mike there is no sound.I used a mike i got a from a very old telephone. The circuit says to use an electret one. Is this affecting my transmitter???...other wise it has got a good range..i can get that sound for about 30m (still didnt check properly) Also i want to build a good antenna for this ...pls help me
(here's the link : ="http://www.uoguelph.ca/~antoon/circ/fmt1.htm"
 

audioguru

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Most Helpful Member
#40
That is the poorly designed circuit that I fixed then I improved it.
Of course it needs an electret microphone. You don't even know which type of microphone you have.
The transmitter's audio preamp transistor is not biased properly so it is saturated when the 9V battery is brand new and it is cutoff when the battery is used a little.
 
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