Replacing the 433MHz antenna on emonBase

I’ve just received the new emonTx V.4 and emonBase kit and I’m excited to install it and explore.

I was thinking it would be nice to mount the emonBase in my (homelab) network rack. It is enclosed and metal so will most likely block the signal between the emonTx and emonBase.

It would be nice to extend the antenna on a coax to be mounted outside the rack. However, it looks like the antenna is soldered in only one place. Ideally I’d like to solder on an SMA connector to the board. Do you think it would work to split a coax and solder the braid to ground and the centre to the antenna pad? Alternatively is there an different RF daughter board I can buy that has a coaxial connector?


If you keep the connections short and clean, it should work.
(minimal length of braid and center conductor, no loose strands of either one)

Take care not to melt the dielectric when soldering.

Keep the total length of feedline as short as possible.
Signal loss increases as the length of the cable increases.

For a short run, say less than 3 meters, you can use any coax intended for RF.
i.e. don’t use cable intended for audio.

Unlike DC, RF can be affected significantly by wire/cable length and connectors.
At the frequencies used by the OEM transmitters, geting it right can be a bit tricky,
but is not impossible.

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Thank you @Bill.Thomson, perhaps we should consider a coaxial connector on the next revision.

We have been looking at this product by Adafruit which we could potentially use to replace our own mini RFM69 SPI board, it has a coaxial connector, a display among other items:, Its the high power RFM69 module, we’ve got one here to test.



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u.FL connector is an industry standard. It’s usable to 6 GHz. Good choice.

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Thanks for your feedback. I’ll get it all working before i try modding. It’s not the only thing that has to live outside the track. Unfortunately many consumer electronics like hubs nowadays have internal antennas.

I don’t know how i missed it before, but I’ve just noticed the WiFi modules for emonTx.

Am i correct in understanding with one of the WiFi modules options i can drop the need for an emonBase and run a local version of emoncms in a VM (or LXC) on my home server?

I’m not certain how the WiFi modules work from the shop. I expect you can set the target IP address for emoncms and it passes data via HTTP or MQTT. If so, then yes, this means you do not need an emonbase/emonpi with an RFM receiver.

I am working on an ESPHome component to do this, but it has stalled on my lack of C++ skills. The MQTT output works fine but I want to get the HTTP interface working as well (ESPHome Component for EmonTX (ESPx & PiPicoW)).

Where is the emonbase? You can always connect it to the TX4 via the USB especially if you do not have any other OEM kit talking via RFM.

I run emoncms on a PVE LXC. Just in the process of updating it to a new container. If you use PVE then these are really useful Proxmox Helper Scripts | Proxmox Scripts For Home Automation.

Just to close off the thread. I received the Adafruit Huzzah adaptor board this week and I’m very happy to say that I have been able to connect the EmonTxV4 to my WiFi and post data directly to a local instance of EmonCMS running in an LXC on my (Intel NUC) Proxmox server.

All the setup scripts just worked and it has been entirely painless.

Thanks for your help.

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