General Category    (This section is not monitored) > FM Transmitters, RF Amplifiers

Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked

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berrall:
Made a small modification to the circuit to provide varible power from 10mw to 5-7watts. The same circuit also provides RF shutdown when the PLL is unlocked from pin 1 of PIC16F627A.

New componets as below.

Q5 - BC547
R24 - 1K
R25 - 100K Multiturn Cermet Trimpot

I have also modified the board layout to accomodate the additional parts.

travoltas:
can you post the pcb?

berrall:
Mirrored artwork for double sided PCB. On the artwork are also trimmers for the MPX and RDS input - these are 50k mutliturn cermet and a fan connector with 500R cermet trimmer for speed control by the 2SC1971 transistor.

Top artwork



Bottom artwork

berrall:
Picture of board with new componet plaement and values.

berrall:
The board was created with Press 'n' peel toner transfer and ironed on both sides. Worked well.

Note RF out only comes up once the PLL LED is lit on the board - this takes anything upto 60 seconds.

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