# RF Design / Calculations - 433.92MHz, PCB antenna, values of capacitors

#### abomin3v3l

Joined Nov 8, 2016
2
Hi.
I'm doing a RF remote control project using a PCB with microcontroller and with simple onboard antenna layout as transmitter and a 433.92MHz receiver RWS-371F-6 model. Here is the datasheet of the receiver: https://www.es.co.th/Schemetic/PDF/RWS-371F-6.PDF <=Link will download a pdf file (Moderator)

I don't have knowledge about RF design, just electronics and MCU programming. I'm using manchester encoding/decoding @ 1000bps to improve the communication distance from receptor board to the transmitter. 'RF-TX' is a 0V~5V signal.
The circuit of RF was copied from a board of a garage door opener, but I included my own microcontroller to the PCB schematic and I have some prototypes of the board. The values of resistors (150 Ohms, 47K, 47 Ohms) was also copied from the garage opener transmitter board. Here I am showing the layout of my board and the values/part number of the components. I've mounted a few pF capacitor combination values (0805) for C2/C3. I have a capacitor sample book with many values on pF range, many values from 1 to 22pF. The communication TX/RX is working correctly, but I want to check if I can increase the distance range by using adequate values for C2/C3. Currently I'm using both as 1pF.

At the receptor, I'm using coil loaded antenna with 1/4 of wavelength, the same of the picture, tomorrow I will try a straight rigid wire of 1/2 of wavelength.

Well, as said, my doubt is around the correct values of C2/C3, can somebody who understand of RF desing calculate them easily? Or does this generate a kind of service that I have to contract a RF designer to calculate them to me?

Regards.

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#### sghioto

Joined Dec 31, 2017
3,315
I want to check if I can increase the distance range by using adequate values for C2/C3.
How much range are you getting now?
SG

#### simozz

Joined Jul 23, 2017
125
More distance range implies more output power, and depending on the law restrictions in your country, you might or might not can exceed a certain tranmission power.

Probably these values of capacitors are set to match the impedance of the antenna.