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

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

Fred27 — Sun, 26 Jan 2020 19:51:32 GMT

The nanoVNA is an incredible piece of equipment for the price, isn't it? I've heard it has some limitations when the frequency goes up, but I found it did an excellent job at 14.56MHz for an NFC antenna. It looks like it's good for sub-1GHz stuff too.

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

shabaz — Tue, 14 Jan 2020 13:36:47 GMT

Hi Fabio,

Very interesting experiments!

The measurements can also be affected by the long cable, so if you wish to isolate that (i.e. since that cable does not form part of the antenna when deployed), ferrite cores can be placed around the cable.

For example for use up to 1GHz, I used this one: Wurth 74270061Wurth 74270061 but the hole is too small for the SMA connector to go through, so it is only suitable for self-assembled cables. Otherwise, any typical clip-on ferrite for RFI suppression can be used, but they're slightly more expensive (ideally a few ferrites are used, to increase the impedance).

Also as you know measurement will also be affected by the final intended enclosure too (discussed in the Cypress Antenna PDF doc example from that doc below for a different antenna and frequency).

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

jc2048 — Tue, 14 Jan 2020 09:51:59 GMT

You've made a nice antenna there. Building it on the connector socket, in the way that you have, makes for a good, near seamless match to the cable.

According to this document, the Molex antenna is designed to be stuck to a PC or ABS surface. You're operating it in free air without the dielectric alongside, so it's a bit of an unfair test.

https://www.molex.com/pdm_docs/as/2042870100-AS.pdf