Author Topic: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked  (Read 33311 times)

berrall

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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

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can you post the pcb?

berrall

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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

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Picture of board with new componet plaement and values.


berrall

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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.

DiegoCCS

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Hello Berral,

Your circuit for variable power output on the Pira 5W transmitter will be very useful for me, as I would use the TX to drive an amplifier I'm developing.

I can't see the circuit image, it seems the link is invalid.
It it's not much trouble for you, can you update the images?

Many thanks adn best regards,

DiegoCCS

spielor

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I would love to see those as well!

kimsin

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berrall, these are amazingly useful mods. I believe it was very important to have an option of having a shutdown option when PLL isn’t locked. It saves the power and along with the new variable power supply, the new mods are going to make the circuit much safer and practically useful. I can’t see the images of the circuit you have provided here though. It’ll be great if you can upload these again.

pcb assembly