Guide: Aeotec Z-Wave Stick - Adding an External Antenna

[jmone (Nathan)]

My house is all concrete and double brick and my Z-Wave reception was unreliable at best. Dotting a bunch of repeaters seemed to help but it was still not great. I found the biggest impact was the location and positioning of the Z-Wave Controller as it’s reception is unfortunately not that great. I struggled to balance a location with good reception with the practicability of where to put the PC/Controller.

I did not have these issues when testing a Fibaro Home Center 2 all-in-one soln, as it has an external antenna… but I’d chosen to go with OH so that HW was out.

So I got a 2nd Z-Wave Stick and set about modifying it to see if I could boost it’s reception so I could then have more location options. Here is what I did:

• Popped off the plastic cover of the Z-Wave stick

• Carefully scraped back the top layer to expose the copper of the internal antenna near “L7”. This is where I will then solder the centre pin of the shown SMA Connector.

• Cut the internal antenna where shown (it looks like a 1/4 wave) so it is “disconnected”
  

  

• Put a blob of solder on the exposed copper first then when heated it back up while positioning the centre pin into this. It’s bit fiddly but to to bad

• Soldered a bit of wire from Ground to a Leg of the SMA Connector
  

  

• On the reverse side of my mod, I used 2 part epoxy to glue the connector to the main board of the Z-Wave Stick so that movement will not (hopefully) crack the solder joints.
  

  

• The rest is more cosmetic. I needed to clip a bit out of the plastic covers to give clearance to the SMA Connector but once that was done it did “click” into place, but I then also wrapped that end of the Controller with some clear tape to hold it together.
  

  

• And finally, all I needed to do was attach an Antenna of the correct wavelength and test it out! In this case I got what looks like a full wavelength antenna, but given the Controller now has a SMA Connector, it could be any suitable one.
  

  

Thanks
Nathan

[jmone (Nathan)]

An here is the difference it made:

• With an Antenna, the Z-Wave controller now communicated directly with twice as many devices as before (see row 1)
  

  

• Running Pings from the controller was better (less “Missing” and lower "Max Poll, ms) as highlighted.
  

  

• There was no change with this mod when doing a Network Health check, both got the same results.
  

  

From an anecdotal POV, the Z-Wave network is now reliable. I still have an “amber” issue and long ping times for Node13 that is a fibaro wall dimmer at the far end of the house, embedded in a concrete wall with a metal wall boxs that faces away from all my other devices… but it seems to work just fine.

[jmone (Nathan)]

Finally, here is the Map in openHAB

[Bruce_Osborne]

Good write-up! This could also be a solution for some older homes.

One building I needed to cover with Wi-Fi was an old stone building with plaster & (metal?) lath walls. We ended up putting an AP in every room to get good coverage. Your solution might not work there, but it should be an improvement. especially with repeater nodes.

[jmone (Nathan)]

I should also mention that I’ve tried a bunch of powered Z-Wave devices as “repeaters”. The best by far are the Aeotec Light Bulbs. You tend to have them in the open, they have an exposed 1/4 wave Antenna and they can punch through walls. I’m pretty underwhelmed with the Aeotec dedicated “repeaters”. The Aeotec Gen 5 power plugs seem a bit better then then smaller Gen 6 ones.

[Bruce_Osborne]

Just curious. What Z-Wave region? Choices vary depending on region.
For instance, Zooz devices are pretty good and they help with OH support, but US/Canada only.

[jmone (Nathan)]

Australia - so 921.4 MHz

[aspork42 (James O'Gorman)]

What apps are you using for diagnostics? I might do the same mod…

[jmone (Nathan)]

Welcome to the forum James! I used:

• Aeon Z-Stick Back up tool : to backup / restore the image between sticks
• Silabs Z-Wave PC Controller : for the Map and Ping (as well as re-discovery etc)
• Aeon IMA Tool - for the health check (PC Controller also has a more complicated version this but it never seemed to end for me)

[Burzin_Sumariwalla]

Hi,

Nice writeup and solution. Does adding/modifying an antenna change its certifications? Granted, given the scenario, the modification here seems unlikely to cause interference for others. I’m just curious.

Regards,
Burzin

[jmone (Nathan)]

I don’t “think” so as it does not change either the frequency or power, just a better Antenna.

I should mention that you need to get an Antenna that covers the correct frequency range for your Z-Wave stick or you will get worse reception (most 900MHz Antenna should be a good match for most Z-Wave regions). You can’t just bung on one from the back of your old WiFi AP and expect it to work.

[chris (Chris Jackson)]

Yes, it will affect certifications, and is probably technically illegal (although probably not something you’d ever be hauled up for).

The reason is it changes the power. Power is not just defined as the amount of power coming out of the chip, but the amount of power transmitted - this includes antenna gain and is normally defined as EIRP. An antenna like this has considerably more gain than the original antenna with which the certification was performed, so the effective power is now a lot higher.

This may therefore interfere with other devices in the band, and may also cause out of band interference if the antenna matching is poor (which is likely given that you haven’t performed any matching). Also the long earth wire is likely to contribute to this - you really should look for an earth right next to the RF output as this wire will effectively be part of the transmission network which will further mismatch the system.

Should you care - It’s up to you . I’ve done similar tings myself in the past so it’s not something I personally get too worried about, but it is useful for people to understand in case neighbours complain, or you have issues with other devices in your own house.

[jmone (Nathan)]

Thanks Chris - good to get more insight on how this all works. I’m pleased with the results so far and have not noticed any other interference issues (and the nearest neighbour is 50m away). Good call on the long earth wire, I based my mod off this mod where it grounded to the earth trace in the main board but my soldering skills are poor (well my welding skills are even worse!) and I could not work out exactly how it was done.

[jmone (Nathan)]

FYI - This is an antenna I used - 915MHz ISM band dipole omnidirectional antenna, which was the closest match I could find for Australian Z-Wave ( 919.8 / 921.4 MHz)
Frequency 902 ~ 928MHz
Peak Gain (bent) 2.5dBi
Peak Gain (straight) 2.4dBi
Average Gain (bent) -1.0dBi
Average Gain (straight) -0.9dBi
Efficiency (bent) 81%
Efficiency (straight) 82%
Impedance 50Ω
VSWR < 1.9 : 1
Polarization Linear
Radiation Pattern Omnidirectional
Input Power 10 W

[Bruce_Osborne]

It would change its ERP (effective radiated power) so it would in fact affect the certification and likely be illegal.

For reference I have a US FCC RF license.

[Bruce_Osborne]

The gain, if different than the internal antenna, would affect certification. If your antenna is higher gain it is likely illegal.

[jmone (Nathan)]

I’ll take the chance… Here is the Oz Spec for this spectrum:

Table A-1: Australian arrangements in the 900 MHz band
Item Class Frequency
(MHz)
Max EIRP Additional Notes Reference
20 All (any)
transmitters
915-928 3 mW No conditions Radiocommunications (Low
Interference Potential
43 RFID 918-926 1 W No conditions Devices) Class Licence 2015
45 RFID 920-926 4 W 1. Must comply with ISO/IEC standard;
2. Limit on emission below 917.75 MHz;
3. Limit on emissions above 926 MHz;
4. Must only be used where 1 W is not sufficient.
54 Frequency
hopping
915-928 1 W Minimum number of hopping channels
58 Digital Modulation 915-928 1 W Power Spectral density limit

[sdda (Sven)]

Slightly off-topic but where can I get the software?
I’ve never seen it before an I really need to get my Z-Wave network fixed or replaced.

EDIT
Sorry, scratch that. I just saw that this question was already asked. Shame on me.