Sunday, July 29, 2012

Veronica 1W FM Transmitter


I Made the transmitter about a month ago and im not using it as much these days, so i will write about it after the month of building and using. I chose to build this transmitter mainly because that there were alot of discusuions about it in forums  and that the circuit for this transmitter had a PCB image attached to it  really was easy not to screw something up when desiging your own pcb design. The very first time i made this board it turned out mirrored. Because i was inexperienced i desided to start all over and get it right.

Before building it i had to find all the substitute parts for the circuit because half of the parts used on the original one doesnt seem to exist anymore.
Instead of the BC548 transistors i used BC547 . Instead of the BF494 i used BF199.  Instead of the power transistor 2N4427 i used a 2N3866.  I substituted the D1 double varicap KV1310 with a BB204  and everything is working. Sucess! Very first times i turned it on i tought it wasnt working because the LED just wouldnt work. It turned out that i was using too low voltage to make the tuning easy. On 12 volts 1 amp the LED just wouldnt light up strong enought for me to notice that im tuning. Next time i gave it 13-14 volts and you could really see the LED glowing bright, then i could tune it properly to a desired frequency. All the coils were made from 1mm copper wire formed on the required size drill bits . When touching anything it  frequency remains stable . The range i got from it wasnt very amazing, but i wasnt even pulling a watt, you need about 15 16 volts for that.

Making this cost me about 50 Litas (~15 euro) . Building it was great fun . Power transistor, varicap and BF199's had to be ordered in my local shop. The power transistor came all the way from germany!
If you do find yourself making one of these and you come across some trouble feel free to ask me here i will be happy to help you with it. I was pretty lost when i had to pick the right substitutes but here , i did it. I had it on without any antenna on 12 volts several times and the thing didint burnout or exploded. People said to me that this circuit is over-complex  and has way too much parts for such a homemade device. They might be right but when i looked for a circuit to make i found none that had a pcb image ready for me to print and make. An RF amplifier for this would be nice!

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