What LC tank circuit is needed for a 318 MHz remote control 9 DIP switch for a garage door controller transmitter opener using the PT2262 IC?

Question

I want to use the PT2262 remote control encoder to create a garage door remote. This is just for fun. (I realize I can get a universal controller 318 MHz 9-DIP switch remote for about $16.)

I was first uncertain on how to integrate the 9-DIP switch. The datasheet's first application diagram has eight bits or four switches:

The address pins seem to be left open in these middle two circuits because they are intended to be used with a DIP switch.

I have not found anything that describes how to start to design the circuit for DIP switches. But I assume to just add on like the fourth circuit did from the first circuit. Besides connecting pins 8 and 7, pins 6, 5 and 4 would be connected.

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Might that work? See the last schematic. I'm confused about these two:

1. For the LC tank circuit in the upper right, what design will work? fr = 1/(2π√LC)

• 318 MHz = fr

• C = 25 pF (or 30pF?)

• L = 10 nH

2. I'm also uncertain where the tactile switch to turn it on should go. It seems the middle two schematics from the datasheet suggest it should be either connected between ground and pin 14 (nTE)...

...or between 12 V and Vcc:

Edit

Related

• https://www.electronics-lab.com/project/4-channel-rf-remote-controller/
• http://graznik.de/posts/reverse-engineering-remote-control-power-sockets-info-gathering/

Answer 1

In RF applications you can calculate what frequency will resonate a tank circuit but almost never will the physical circuit work spot on, and when going up in frequency it becomes worse and worse. At UHF and beyond even LC tanks don't look obvious or are not used (stubs and resonant transmission lines are more common. Anyway, there is always some tuning or iteration involved beacuse of the parasitics of the components and PCB. The circuit itself looks simple but there is no obvious flaw in it. I'd make a prototype and try if at least the RF oscillator works (you can use an inexpensive SDR receiver to find the frequency), then try to trim it to the correct frequency and test it for stability within its applicable use case (expected voltage variations, temperature variations, component tolerances).