---
title: "RF"
url: "https://nearfieldnotes.com/families/rf/"
site: "Near Field Notes"
---

# RF

Notes for when a radio’s range comes up short.

## Notes

- [Antenna ground](https://nearfieldnotes.com/notes/antenna-ground/): How much ground does a 2.4 GHz PCB antenna need? About 40 mm behind the antenna. With 10 mm, 22% of the power gets out, and a perfect matching network only lifts that to 43%.
- [Trace or U.FL jumper](https://nearfieldnotes.com/notes/ufl-jumper/): When does a U.FL jumper beat a trace to the antenna? Past about 2.0 cm at 5.5 GHz on a common 4-layer board. Over 10 cm there, a trace delivers 60% of the radio’s power and a coax jumper between two U.FL connectors 83%. On a 2-layer board at 915 MHz, the trace wins up to 13.3 cm.

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Source: https://nearfieldnotes.com/families/rf/