Build FM Transmitter Output Amplifier

[amanisdude]

Hi all!

I know this is not a circuit design forum, but would anyone here know how to build a good yet simple FM transmitter output signal amplifier from scratch? (That is, buying components and soldering them in necessary arrangement, not mining for ore, etc.) I want to build an amplifier for a simple smartphone automobile transmitter.

In terms of how I would go about doing this, this video essentially shows how I would open up the device and solder leads to it. However, instead of soldering an antenna, I would solder a coaxial lead to the homebrew amplifier, and the amplifier would output to a carefully crafted antenna. Is there a good resource which would instruct me on how to do this?

Also, just for learning's sake, how powerful would I be able to make such a transmitter without the signal becoming distorted? (I don't intend to break any laws, I'm just trying to figure out how FM signal amplifiers work.)

Thanks for any help!

-amanisdude
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[5B4AJB]

You're looking for a "linear amplifier", they are quite simple devices in essence.

Regardless of the mode (FM, AM, CW, SSB etc) a linear is a linear. It multiplies the input by a factor.

What you want to build is probably illegal, but as far as Amateur Radio Linear Amplifiers go, you might be able to find one for 4m that would work.

[amanisdude]

You're looking for a "linear amplifier", they are quite simple devices in essence.

Regardless of the mode (FM, AM, CW, SSB etc) a linear is a linear. It multiplies the input by a factor.

What you want to build is probably illegal, but as far as Amateur Radio Linear Amplifiers go, you might be able to find one for 4m that would work.

By "4m", I assume you mean 4 million dollars/sterling. J/K.

Hmm... I see. What of something like this? It seems to rely on an old vacuum tube, but the output is significantly stronger. I would assume that the old tube could just be replaced by an operational amplifier, and the input could be hooked up to a transmitter device instead of a receiver antenna, no?

Also, could a 70 MHz linear amp be ramped down and modded to work in the 88 MHz range?


-amanisdude
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[5B4AJB]

70MHz = 4m, sorry was thinking in old money again...

Valves (tubes) require several Voltages for operation, ergo, more complicated power supply - OK if you have them in the junk box, but go for solid state if building from scratch.

Google around you can find loads of circuit diagrams - http://www.seekic.com/uploadfile/ic-...4273524769.jpg

There are also loads of transistors available, to suit your power requrements...