I am curious about the size and configuration of your house. For a stationary antenna, I would believe that you might be even better served by a 6dB or 9dB antenna.
I based that on the comment from @lewis.heidrick "3db is good for 2 to 3 story small sized per floor homes." - my house is typical 1-1/2 floor 1938-ish design, around 1200sf footprint, maybe 2000sf finished including basement and upstairs. The hub is on the main floor towards the front of the house. It would be better located more centrally but I've never found the ideal place for it - finding an "obvious" place always ends with realization there's some big HVAC duct in the wall right next to it - which i haven't tested the effect of but seems like it can't be good!
I guess I thought the 3dB antenna might have better vertical coverage for the other floors, but it would be an interesting experiment to try a different type.
I do still have the VeraLite external antenna kicking around somewhere - that one just came from Amazon, and looking back to 2013, it was described as "GSM Wireless WIFI Signal Antenna 7dBi 900/1800 MHz". What would you think of giving that a try?
The home you describe is an ideal candidate for higher gain antenna (5dbi-9dbi). While the higher gain antennas do squash the signal in the vertical axis, there is still plenty of signal in the vertical axis for 2 stories.
As for your old antenna. Your old antenna is dual band and as such, the rated gain is for only one of the two frequencies. The other frequency will have lower gain. A single band antenna is usually superior to a dual-band antenna. I suggest you try a higher gain single band antenna.
Happy as I am with my current external antenna (3db) I would like to also try a 5db antenna.
Problem is you are all working with US Z-wave frequency and I am using a EU Z-wave (868 Mhz).
I got my current antenna from Aliexpress for less than 5$ and I would like to make sure my 5db antenna is of good quality.
The online stores you mentioned does not sell these 868Mhz antennas. How can I know for sure the antenna I am buying is a good one? Any things I can read in the spec to make sure I get a good quality antenna?
I'm surprised to hear you say that, I couldn't get a z-wave signal in my brick garage without a dedicated repeater between my VP and garage. My C7 doesn't have that issue at all.
No to mention my VP ran like a dog with only 20 z-wave devices and would crash if I tried to add more. Im up to 100 on my C7 and it runs pretty darn well.
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Just curious, for the HE staff to really understand if external antennas are actually helpful, I'm wondering the answers to this poll. Unfortunately, from the posts here it's hard to tell how biased the positive results are -- if only people having issues do the upgrade, we don't know if it actually makes things worse for people who already had no issues. Thinking this poll could be useful to the staff to assess whether or not adding external antennas in the next hardware revision is a good idea (cc @bcopeland )
- My Zwave worked great prior to adding an external antenna and still is after adding an external antenna
- My Zwave worked great prior to adding an external antenna and got worse after adding an external antenna
- My Zwave was having issues prior to adding an external antenna and this fixed it
- My Zwave was having issues prior to adding an external antenna and my issues persist after adding an external antenna
- I have issues, but no, I'm not soldering my hub an risking breaking it
- I have no issues and therefore I'm not willing to try this out
0 voters
Just goes to show how much my anecdotal observation is worth then! It is hard to compare though, since the mix of devices has changed over time. My Vera Plus was in the same location as the C-7 is now though and some of the communication seemed more reliable. For example, I seemed to get fewer missed devices when activating a scene. That was the only thing about it which was more reliable though - towards the end I couldn't dare trying to add any more devices, and it was always essential to have a backup before trying that anyway!
I found Vera worked great till I got to 15 devices, it was all downhill after that. 
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That has changed after two additional days. It is now up to 49.
Here's the thing - I didn't have any z-wave issues to begin with, but I had decided that my purchases going forward would be Zigbee. This antenna mod is making me re-evaluate that decision. I'm actually looking forward to zwave-LR now!
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Is this same modification possible on a C-5? I believe I wouldn't be able to see the before/after results as transparently as you all have, but am wondering if the hardware is there to do the same mod. (sorry if this has been covered and I missed it).
Yes, the C5 has the same antenna circuit board layout as the C7. The C5 board can accept the U.FL connectors.
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The longer I wait, the better it gets!!! Before external antenna, 49 (48%) devices directly connected. I'm now up to 92 (89%)!
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Did you ever get your front lamppost to join the mesh?
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Yup. Again, antenna issues. I replaced the antenna on that device with a more powerful one (just a wire) and it worked flawlessly for about a month so far. I'm really convinced that almost all of my issues are related to the antenna not being powerful enough
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I'm very comfortable with the shorthand expression "more powerful antenna" but only if one's aware that it's shorthand 
I don't want to be pedantic, but for future readers, I want to mention that antenna have nothing to do with output power. The power is created by the radio electronics, in our case, SiLab's SOC. That energy is coupled to an antenna which shapes the direction of power. It's quite common to use the exact words because a 9db antenna certainly gets presented as if it increases power by 9db 
But strictly speaking, it doesn't. It takes the energy there is and reshaping it, takes energy away from one direction (vertical) and adds it to some other direction (horizontal.)
All we do with swapping the antenna is to change the radiated shape of the RF energy. The Full Wave antenna length is 12-13 inches for US frequency (908-916mhz), which means half wave is 6-6.5 inches and quarter wave is in the 3 inch range.
Clearly the omnidirectional antenna used in this mod is in the 6 inch range while the internal pcb antenna is in the 3 inch range. Is that where the benefit is found?
I think if we tried pointing the "sharp end" of this antenna at a group of ZWave devices we'd find that in that direction, it's not so good
The built in antenna seems to have a donut shape radiation pattern, with the donut hole pointing front and rear of the Hub. The Omni antenna has a very similar donut shape radiation pattern, but with the hole pointing up/down. Additionally, one could tilt the omni ultra easily since it's built for that. Perhaps for someone's home, a 45degree tilt is ideal. The internal could conceivably do the same, but ...
"Squishing" the radiation pattern, via this mod and the 9bd antenna, so that more of the energy goes out horizontally is nearly ideal for ME with individual hubs on each floor of my home.
Anyone else notice that: "I don't want to be pedantic..." is instantly followed by being pedantic??
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Iām wondering if you could steal the 2.4 antenna from and old linksys router.?
Possibly for zigbee. But not for z-wave. You'd still to desolder the existing zigbee antenna and solder on the appropriate connector.
Is part of the benefit from getting the antenna out of the small steel box.
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It is plastic.
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I now wish the poll had yet another option:
I thought my ZWave was great prior to adding an external antenna, but now I know what great really means!
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