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Author Topic: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked  (Read 47833 times)

berrall

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Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« on: May 05, 2012, 05:32:39 am »
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.

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travoltas

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #1 on: May 10, 2012, 07:19:45 pm »
can you post the pcb?
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berrall

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #2 on: May 10, 2012, 09:31:56 pm »
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


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berrall

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #3 on: May 10, 2012, 10:04:01 pm »
Picture of board with new componet plaement and values.

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berrall

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #4 on: May 10, 2012, 10:20:46 pm »
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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DiegoCCS

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #5 on: September 14, 2012, 08:33:15 pm »
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
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spielor

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #6 on: August 08, 2013, 12:33:29 pm »
I would love to see those as well!
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kimsin

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #7 on: November 11, 2014, 10:11:21 pm »
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
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RIGMO

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #8 on: December 08, 2022, 11:03:01 pm »
Quote from: berrall on May 05, 2012, 05:32:39 am
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.


Pleas contact me
Can you again post ?
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RIGMO

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #9 on: December 09, 2022, 12:06:28 am »
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johnis

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #10 on: December 09, 2022, 07:00:02 pm »
can you ost the schematic of the modifications or the new pcb layouts?
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RIGMO

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #11 on: December 13, 2022, 01:14:18 pm »
any backup?
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RIGMO

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #12 on: December 31, 2022, 12:13:55 am »

soon
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RIGMO

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #13 on: December 31, 2022, 11:21:36 pm »
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RIGMO

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Re: Pira Cz 5W FM Transmitter Mod for Varible Power and RF shutdown when not locked
« Reply #14 on: April 14, 2023, 04:59:30 pm »

Quote
the Jan Kolar "Pira" effort works reasonably well, though its performance is almost entirely determined by the construction of the inter-stage coupling transformer and the careful alignment of the output stage trimmer capacitor.  It also has the (minor) inconvenience of using an obsolete PLL IC (which will be difficult to find in future) and the firmware forces a "re-tune" every half-hour, which can put small noise bursts on the carrier. 


 Is this caused by not connecting pin 4 (MCLR, RA5, Vpp) to 5V through the 10k resistor?
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