modifying the transmitter

This 4-channel A/V transmitter is declared 700mW, however only 280 mW gives on Channel 4  (1200MHz),is very popular in  FPV, looks very nice, smooth finish unlike the other on eBay.
My idea is to control the widest possible range of frequencies

BLT81 Transitor it is final stage,probably this can give 500mW at 900MHz as transmitter of DPCAV , adjusting the variable capacitor could get 350 mW on 1200 MHz

My idea is to modify the transmitter with the least possible damage

With a soldering iron and some skill is possible to separate the case components of the transmitter to access the controller chip.
I was very surprised that this transmitter is of Racewood

The microcontroller has no part number, perhaps a PIC12C508 as I saw a photo posted (RCGROUPS) a Racewood Tx

Here microntroller and Dip SW remove out, pin out to PLL TSA5520, the microcontroler check always PLL locked,if PLL unlocked, send  serial bits again. My control program aims to do the same, but expanding the range of frequencies to synthesize.

This graph shows the frequency versus the voltage on the varicap diode, the lowest frequency of 1040 MHz the PLL takes a while to locked, in the frequency of 1270 mhz never locked.

Changing the value of the inductance (L printed) of the oscillating circuit of the VCO is possible to synthesize more frequencies up or down.

Like most of these transmitters use the PLL TSA5520,control program should be able to handle frequencies from 900 MHz to 1300 MHz.

You must remove the pull-up 10K(103 marking) resistor on GPIO.4 (pin 3)

Frecuency Programing by IR Port  and Sony TV Remote control

The TFMS5400 device is a IR sensor module, this module is very large and not within the container the transmitter, the solution is to mount it outside and secure with hot glue

you just have to remove the original microcontroller  and replaces with PIC12F629, remove the resistor 10k smd  and connect the module sensor IR


The hex file for PIC12F629 here , Caution !!! it is only for PLL TSA5520.
To start the LED one blink when sending data, you have a minute to adjust the frequency.
The LED will remain lit when you press the "OK" button on the TV remote control Sony, indicating ready for adjustment. If press "OK" again then exit adjust mode (LED off).
Pressing the 4 digits of the desired frequency, the LED flashes between digit and digit, Wait until the LED is on for the next digit press.
If you want to 1280 MHz then push "1", "2", "8", "0" on TV remote control Sony.
If you want to 980 MHz then push "0", "9", "8", "0" on TV remote control Sony.

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