Improved antenna for 433 MHz units and sensors

Hello all DIY builders who keep developers on their toes!

Upon request, I thought I would show here how I rebuilt my HomeyPro (early) 2023 to get better reception, but allso transmission for devices using 433 MHz.

I have thrown away most of my old 433 units, but I wanted to be able to continue using some of them, among other, my 8 temp/hygro sensors (Telldus). Only one or two of the sensors could be detected (in my 1879 3 story stone house) unless they were right next to the Homey, with new batteries.
This my old Tellstick ZNet Lite v2 had no problem with… Slight disappointment about Homey there.

With some basic knowledge of soldering and fine mechanics skills, I think most people can do the same thing as I have below, but I only take responsibility for my own mistakes! Similar guides already exist for the HP 2019 so I’ve just used other people’s experiences.

The following tools have been used:
I started by locating the four screws on the underside and using the scalpel to expose the Tx10 screws.

On the circuit board, Athom has been kind enough to write out which antennas do what. You can also see that during the development stage they probably used miniature contacts for external antennas, which they no longer use in series production, but the traces remain.

Where these miniature contacts sat, I made a cut in the connection so I could splice in my shielded connection to the new external antenna. I drilled a hole (where nothing critical sat) for the passage of the cable.
Since I couldn’t wait for delivery from websites, I used recycled material from an old laptop (the antenna cable) and the connector (SMA Male) from my old Telldus Tellstick Net, which has done its job.
I actually also tested its white antenna (connection: RP SMA with 5 DBI gain) that was on the Tellstick with the same good results as the black one in the pictures below with a 1 meter cable (10 DBI gain) and with a loose RP SMA connector at the end. Be sure to order antenna and cable with the right male/female connector! (I didn’t)
Try to get as short and little exposed parts of the antenna (without shield) as possible at the PCB and the contact, see pics.

The mounting of the SMA Male connector on the circuit board was done with super epoxy, solder the cable first! But of course it could also have been attached/screwed to the cover instead.

Below you can see the cover with a drilled hole for the connector and the new external antenna.

When I connected the power, it didn’t take many minutes before all my 433 MHz sensors popped up one by one, even though most of them are on water heaters etc. in the basement two floors down. Despite all the quirks in the choice of parts, 433 MHz now works like a charm!
This was in September 2023, now I will do the same on the Zigbee antenna!

Just a tip, you absolutely do not need to use the same gadgets as in this guide. Pay attention that the SMA connectors and antennas can be bought in both male and female so you get parts that fit each other. For my upcoming Zigbee antenna I will use the opposite M/F so they can’t be mixed.

Since I live in Sweden, I buy a lot of stuff from local distributors, for example
Better antenna with cable for Tellstick ZNet/Net/Duo (433Mhz) - StyraHem
but they are also available on Amazon, Alibaba or whatever you prefer.

Now, have fun with your DIY build and please, don’t cut yourself!

Greetings / Göran


Nice write-up on this.

I wonder, the solder pad next to where you cut the trace. The one with solder on it, it might be that removing the solder there would disconnect the onboard antenna.

Haha, you could absolutely be right OH2TH! It matches how a miniature connector works where the external antenna disconnects the internal one when the PCB connector is “activated” with a male connector. Will check this when I open the HP for the next rebuild (Zigbee).

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Nice guide Goran, thank you.
Just wonder if you have had time to get the Zigbee mod done.
I am about to go on, just not sure where best place to pick up the GND as my multimeter shows me a continuity in between the zigbee antennas circuit and all other grounds.

Thank you very much. I have 40 KAKU switches around the house controlling different zigbee lights and scenes, and I was desperate how weak the 433 reception was. I had to be very creative with Homey positioning an had to replace some switches or use them only directly paired to few KAKU relays I also have. I was realy thinking about throwing all switches out and using some zigbee ones instead (not reasonably priced or environmentaly friendly solution), but after doing your mod, everything works like it used to do with my retired KAKU gateway, even better. (my soldering experience is very limited, but desperate situations need desperate solutions, so I tried anyways ;))


Hello Jan. Very nice to hear that someone benefited from the guide.
Thanks also to Athom for giving us the opportunity for this forum where we can share these experiences. I myself still feel like a beginner with my Hoemey Pro. Greetings Göran