FM transmitter 1W

[dark_soul]

Greetings, I wonder if you might advise me with an FM transmitter that I'm learning how to design, I hope you can help me , so, I explain the following:

I found a website and magazine which contains description about how to design a power amplifier, so I began to calculate the formulas of the page and the magazine, and I got different values so I decided to build both, but in neither case did well, only get a lot of noise and very little of audio input.

The first tests were done with a piece of wire approximately # 22 to make the antena, then use a coaxial cable 50 ohms, and for forming the dipole use the same cable # 22.

I hope you can help me, I attach my calculations to get an idea of what I'm doing and find my error.

For all thank you very much

 

[colin55]

You will practically no RF out of the circuit. The class C ouptut stage needs to get all its energy to turn it ON from the oscillator stage and the oscillator cannot provide this much energy.
You have no capacitor across the battery. Should be 22n to 100n

The first thing you do is remove the output stage.
Work on the oscillator stage with a simple power meter and see what it is producing.
The tank coil should be 5 - 6 turns of 0.25mm wire 2.5mm dia
The capacitor should be 5 - 22p with 22p across it.
The base resistor should be 47k. The cap to base should be 1n
The input cap should be 100n
The pick-off cap should be 47p

Do this and come back.

The power meter can be found on Talking Electronics site under one of the FM bugs. It is called power meter or LED power meter and simply consists of two diodes, a LED with 470R and 100n connected to an analogue multimeter 10v range.
You should get a very good reading and the LED should glow.
This is where you start.

 

[colin55]

I have found where you copied part of your circuit from:
**broken link removed**
The circuit has a number of mistakes. The load for the electret mic must be increased to at least 47k. The variable cap needs a 22p across it and the circuit needs a 22n across the supply rails. These will make an enourmous difference.

 

[dark_soul]

Thanks for your help, I comment, I make adjustments that you told me, including Led Power Meter and did not get more than 20 cm in the transmission, so I decided to try some other circuit and the result was the same.

I Probe also put an antenna with a cable # 22 approximately 1 meter and nothing, then a cable # 22 with 19 laps and improved only slightly.

With the LED power meter, as I haven't an analogue multimeter just I try to adjust to having more light on the LED.

I'm lost, I hope to guide me, again thank you very much for your help.

 

[colin55]

Did you put the LED Power Meter on the collector of the oscillator stage? You need class A output. Put 22k to 47k between base and 9v rail. 100R emitter resistor and connect the base of the output transistor to the collector of the oscillator via a 47p. Now fiddle with an inductor (coil) on the collector and an "output matching circuit" consisting of inductors and capacitors to match the impedance of the output transistor to the antenna.

 

[harti212]

Help???

The circuit has a number of mistakes. The load for the electret mic must be increased to at least 47k. The variable cap needs a 22p across it and the circuit needs a 22n across the supply rails. These will make an enourmous difference.

Does it mean?Are you sure that 1W power. 1 km from the coverage area?
----------------------------------------------------------------------------------------
orginal language;
Bunu mu demek istedin? 1 W Gücü olduğuna eminmisin?.Kapsama alanı 1KM mi?
Translate language: Türkçe/Turkish
Translate by google translate.

 

[harti212]

Transmitter in the picture above, the problem is how to function without the need to do?(without causing a problem?)
How do I increase transmitter power to 1 W in this?
Does my pictured electronic elements lined up correctly?Is so wrong?
Traslate by google.
Orginal Language: Turkish;
Yukardaki resimdeki verici sorun yaratmadan nasıl çalışır ? Gücünü 1W a nasıl yükseltirim.
Benim Resimimdeki elektronik elemanların yerleri doğru mu çizilmiş? yoksa yanlış mı?

 

[audioguru]

The Miniature Transmitter has a line of sight range of about 300m to a very sensitive hi-fi tuner or car radio, about 100m to a cheap Sony Walkman radio set to "distant" or cheap clock radio and a range of across a narrow street to a cheap "scanning radio" from The Dollar Store.

The RF amplifier has a power gain of only 10 to 16 times and it loads down the output level from the oscillator so it will increase the range to about double.

It is difficult to tune the transmitter to a nearby cheap radio because it overloads the input of the cheap radio which causes the signal to appear wrongly at many spots on the dial. Tune it to a high quality radio that does not become overloaded.

 

[audioguru]

There is a translation problem.
In the Miniature Transmitter you used 22nF for C3 but is should be 1nF. 22nF should be added across the supply rails which is across the battery.

The circuit must be built very small on a pcb. It will not work if you make it on a breadboard.

 

[Jackdaniel]

and you must use a battery instead of a wall-powersupply! Do it and feel the improvements

 

[harti212]

R1)47K , R2)1M , R3)100K , R4)10K , R5)100R ,R6)10K, R7)1K , C1)22nF , C2)22nF , C3)1nF ,
C4) 0-22pF ,C5) 4.7pF, L1)0.1uH ????
Does it mean?

9v is send power supply this circuit.

 

[carbonzit]

R1)47K , R2)1M , R3)100K , R4)10K , R5)100R ,R6)10K, R7)1K , C1)22nF , C2)22nF , C3)1nF ,
C4) 0-22pF ,C5) 4.7pF, L1)0.1uH ????
Does it mean?

Does it mean what? Your question makes no sense as worded.

 

[Mr RB]

I think he is asking "what does 0.1uH mean?"

 

[4pyros]

I think he is asking "what does 0.1uH mean?"

Its a coil.

 

[harti212]

Have been misunderstood.

Are you kidding, I know that its coil.

I asked if only the electronic elements is incorrect.

 

[ericgibbs]

Are you kidding, I know that its coil.

I asked if only the electronic elements is incorrect.

hi,
Its a 0.1uH [0.1microHenry or 100nanoHenry ] inductor , the value is in the correct region for around 100MHz frequency operation.

 

[4pyros]

Are you kidding, I know that its coil.

Sorry I don't understand your questions.

 

[audioguru]

The 22nF capacitor parallel with the battery is missing from your schematic and list of parts.

 

[harti212]

Which one is right?in this picture?

down or up picture?

orginal language: Turkish;
Resimdeki, hangi şema en doğrusu? Aşağıdaki resim mi? Yukarıdaki resim mi?

Translate by google.

 

[colin55]

The coil is 5 turns of 0.5mm wire on 2.5mm former, air core
The 5-22p must have 18p across it. The 22n across the battery must be very close to the power rails of the circuit. The 9v supply must be very close to the 22n.