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Author: gecoz
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Building a poor man's quarter-wave 433MHz antenna: Introduction

gecoz

After receiving the Molex antenna sample kit that kindly posted to me over a month a go, I have been thinking how to use it (or some of the antennae), and finally take part to my very first Project14 contest. Considering that I didn't own any RF instruments, and last time I dealt with RF was at university, many many years ago, I thought my project should reflect this, and build from this starting point, i.e. starting from scratch!

 

 

It followed that the best project I could get myself absorbed in was a DIY one and, since in the last year I have been toying with LoRa, the choice was a natural consequence: build an antenna and compare its performance with a few antennae I already have (including the Molex 433MHz included in the kit).

 

So, basically, my target is to build a cheap quarter-wave antenna, using only components that most makers already have laid around somewhere in their garages labs. No previous knowledge is required to follow this project, as I will try providing all the basic information needed. Forgive me in advance if, in the process of simplifying some electromagnetism and antenna theories, something will be omitted. Feel free to add/correct me, whenever you feel necessary, any contribution is welcomed!

 

I want to stress again the majority of my measurements will have to be taken with a pinch of salt: my RF equipment is very basic and I don't have any special setting available for measuring (i.e. no anechoic chamber), so all the measurements are intended more to give a qualitative than a quantitative view. Nevertheless, I will try to be as accurate and precise as possible, and employ standard measurement techniques. Again, please feel free to chip in anytime, if you spot something wrong or know better ways to take the measurements.

 

For this project, my plan is very simple and, hopefully, straightforward, whose milestones are:

 

  • build and test the antenna
  • take measurements of the antenna and all other antennae
  • test all the antennae performance and compare results

 

To help me with the tasks, I will be using 2 TTGO ESP32 LoRa boards (RX and TX) and, for measuring some of the antennae characteristics, I will use the NanoVNA, an extra-cheap Vector Network Analyzer, capable of covering the range 50Hz-900MHz! I will be exploring this tool when dealing with measuring the antenna's parameters.

 

 

Hopefully I will be able to complete the project in time for the deadline!

 

 

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Other articles of this series:

Building a poor man’s quarter-wave 433MHz antenna: Antenna’s construction

Building a poor man’s quarter-wave 433MHz antenna: Comparing Antennae

Building a poor man’s quarter-wave 433MHz antenna: Testing the antenna with ESP32 LoRa

Anonymous
  • in reply to clem57

    Hi ,

     

    Thanks for the link.

     

    Fabio

  • Hi     , here is a web page I found with some good information.Good idea for a project BTW,

    Clem

  • in reply to shabaz

    Hi Shabaz,

     

    Thanks for the encouragement and the advice. Indeed, I have noticed how sensitive the measure is to even the slightest movement, when I tried the NanoVNA. I will have to tape everything down, including myself on the chair!

     

    Fabio

  • Hi Fabio,

     

    Best of luck! I believe you'll get good results. Don't be disillusioned if initially things seem unpredictable or varying, because often just the cables moving can be enough to make a difference : )

    If you can, keeping the coax position the same so that it doesn't move between measurements, could help. And double-checking that the connector on the other end doesn't accidentally become loose when unscrewing/screwing the opposite end.

    Also, running the calibration procedure each time you sit down to start your tests (with the calibration done on the end of that cable, with the cable at the same position it will be for your measurements).