ADMIN UPDATE: The following posts and dipole work by
ChemE are kept for reference. But his latest dipole updates and design files are at
this new thread.
First things first; major credit to captcha for putting out enough excellent information that I could get going on modifying his design! I very much appreciate the foundation you created since my RF skills are non-existent.
Ok, I still have some tuning and experimenting left to do on this project and Luka has asked for a 433MHz version, but I'm going to call my smaller cheaper PCBs.io antennas an
absolute unqualified success. My testing method is to place a node sending a packet every 8s at 300kbps about 50' away broadcasting at -18dbm (power level 0) with a few walls in the way and then listened for 20 packets. I sum the RSSI of those 20 packets and base my results on the average of those 20 RSSIs. Captcha has already done quite extensive work to show how his PCB antenna compares to 1/4 wave monopoles, eBay purpose built antennas, etc, so I'm being lazy and just comparing mine to his.
Captcha's average RSSI = -91.65dbm
ChemE rev2 trimmed (too far): -88.90dbm
ChemE rev2 untrimmed: -84.5dbm
I don't have a VNA nor do I plan to acquire one so based on what I can test, these little babies are more sensitive than the baseline design (no idea why that would be the case) and importantly they are dramatically cheaper which was my goal.
You can order my 915MHz version here ($4.79 for 4 copies shipped anywhere in the world):
https://PCBs.io/share/4XRDgEDIT: Added the eagle files which confusingly are named rev3 but they are the correct ones which correspond to the board I tested and you can order from PCBs.io.