4W FM transmitter

[kelumsd1]

Hi,

I,m Kelum.

    I have really doubt in how to wind L2(RFC) in 4W FM transmitter. (http://www.electronics-lab.com/projects/rf/021/index.html). It say's "RFC (resistance 1MOhm with wrapped around her inductor of enough coils from fine isolated wire. Scratch of utmost inductor and you stick in utmost the resistance making thus a parallel L-r circuit.)". But I can't uderstand how to wind it. If any one know that, please tell me becouse I'm beginner for this.

Thank you!

[Hero999]

It's total nonsense.

It's probably been translated into English from another language using software rather than human brain.

A radio frequency choke is normally just an inductor with a high impedance at the freqency of interest, try a 4.7

[Alex Tsekenis]

That circuit is part of this kit:

http://www.smartkit.gr/details2.php?lang=2&wh=1&the1id=1&the2id=6&the3id=39&theid=39&open1=1&open2=6&open3=&thepid=206

and the text was originally in Greek. Anyway, you can have a look at the coils on that PCB, there is one on top marked RFC2 but the circuit doesn't care what the component looks like so you can use something else with a small inductance value as Hero pointed out.

In the original instructions you are required to wind a coil using thin wire around a 1MOhm resistor. Obviously inductance is not too critical.

[Hero999]

How did you know that?

Assuming what you've said is true, it's only part of the kit and is incomplete. The real kit probably has a couple of RF stages after the part shown here and possible pre-emphasis.

[Alex Tsekenis]

I used to build such kits since I was 10 back home in Greece. My first kit was this:

http://www.smartkit.gr/details2.php?lang=1&wh=1&the1id=1&the2id=6&the3id=29&theid=29&open1=1&open2=6&open3=&thepid=122

A 555 based led flasher, which didn't work due to cold solder joints (my first solder iron was a 120W pipework tool from my grandpa).

Anyways, I have built the 4-Watt kit pictured and I can still recall the schematic more or less. Such kits from SmartKit are imported in the UK by Quasar Electronics. I have seen other copies of SmartKit kits in the projects section of this site so I am not surprised.

The kit pictured had a microphone input and an amplifier around it (the T0-92 transistor). I really can't recall if any emphasis circuit was employed, I would have not recognised it back then anyway. I can check if you really need to know. I do remember that it was a pain to tune the circuit using those variable capacitors and that a stabilised 12V source was needed. I used this kit back then:

http://www.smartkit.gr/details2.php?lang=1&wh=1&the1id=1&the2id=6&the3id=32&theid=32&open1=1&open2=6&open3=&thepid=144

[audioguru]

We have two Greek 4W FM transmitter projects.

The Smart Kit one linked by Alex is the other one that also does not have pre-emphasis:
http://www.electronics-lab.com/projects/rf/001/index.html

[Alex Tsekenis]

So similar... Thanks audioguru for pointing this out.

[DAVICOM]

4 W ....400 mW :o