Didn't know about Mouser and quite frankly forgot all about Digikey 
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Hi Guys, RF Engineer here and judging by some of the comments, not the only one. I'd like to add a few things that may help.
Generally speaking, and I mean generally, changing to a higher gain external antenna will certainly help but also what's happening with this mod is also a change in the stock antenna polarization, ie physical position. This will change the radiation pattern of the antenna and its coverage area, or âfootprintâ. Iâm sure this is obvious to everyone but just to make sure, similar to changing the spray pattern on the nozzle on the end of your garden hose, changing the orientation of the antenna changes the area it covers. Positioning an antenna flat will have it TX/RX more up/down while standing straight up will change it to a more horizontal side to side pattern, again generally speaking in reference to zero gain Âź wave antenna.
Anybody here old enough to remember rabbit ears for your TV? While this was a receive only application, you moved the antennas around for best reception (re-polarization).
The antenna placement in the hub is a generic compromise. The hub comes with feet so logic indicates it sets flat and if done so the hubs antenna will be biased in a up/down configuration (polarization), good for multi-story situations. But this may work just fine in your single story situation.
So, adding an external antenna is a clever idea. But to a lesser degree, if you want to try something for free and no disassembly required, you may achieve better horizontal range by re-orienting the hubs internal antenna by simply placing the hub on its side and monitoring a few days for results. Or put it on its tail and monitor a few days for results and so on. Maybe with the hub setting flat, rotating it 90 degrees will help. Everybodyâs situation is unique so what works for some may not for others. YMMV. In my case, I found the best results by standing the hub on its tail.
Or, go ahead and take it apart and peel the antenna from the plastic cover and use a popsicle stick to stand it straight up. You wonât have the gain but you wonât have the shielding from the motherboard either. And itâs free as well.
And donât forget about the devices the hub communicates with and their antenna orientation as well. Ideally we would want to add external antennas to them but letâs be realistic here. In my case, I use mostly Zigbee with Sonoff devices. The Sonoff BASICBZR3 smart switch lays flat and has the antenna built into the circuit board traces. I have found better signal quality with it on its side or standing up in some cases. The ZBMINI has a lousy antenna so they seem to work best with the lettering on the cover facing back towards the hub.
The point here is this is RF. You canât touch it, taste it, feel it, hear it or see it, but itâs there and itâs using the most unreliable medium to pass intelligence⌠air. Anything you can do to help it, do it. Just speaking from personal fiddling around and letting my routing table tell me whatâs best.
On a side note, you can also source 2.4Ghz antennas from the drone FPV market.
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Thatâs actually the way mine are sitting, although I did it mainly to play with the airflow âŚ
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I found this vertical stand on Thingiverse and am going to give it a shot.
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I tried the hub on its side but it didn't make an appreciable difference. The 5db external antenna works well for me. Even a 9 db antenna would probably work, but I have some devices in the attic for water detection in the AC pans and some switches and outlets. We have 15 to 20 ft ceilings and the 9db antenna might squish the radiation pattern too much.
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The internal pattern should be similar to...
with the peach colored line being front to back internal to the hub. Placing the hub on its side would do this:
But hanging it on the wall with the cables flowing downward, would change it to something like:
I think that placing it on its side rotates the antenna along its axis.. effectively doing nothing much, it's still a 'vertical' radiation pattern. Hanging it on the wall, makes it a 'horizontal' radiation pattern.
If you have this external antenna, the rubber ducky style, then it can rotate. I think you'd want to aim the pointy end to where there are no devices 
When it's pointing straight up (or down) it's got a horizontal radiation pattern. point it 'left or right' and its got the radiation pattern of the Hub unmodified.. meaning 'vertical'.
You could try to balance the Hub 'on its nose' -- LED light down. which would be similar to hanging it on a wall.
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That's what I'm intending to try. My secondary only manages cloud integrations so itâs just on its side. The stand turned out great tho!
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I ran a repair after changing the orientation and I now have only 3 z-wave devices connecting at 9.6kbps (it used to be double that) - most are now connected at 100kpbs and a few at 40kbps.
My house is 2 storey with the Hubs roughly in the centre of the top floor.
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While my parts are coming I deciced to try the orientation. Did the @dJOS mounting and within 5 minutes I lost 3 100K devices to 9.6 and they are only 3 meters away.
Guess that ones out 
I'll try a 90 rotation and give it another test.
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Im finding some things better and some things worse. RF, so much fun! 
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Everything got better with the externals for me.
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I think I might go down that route too.
If you need some help or have any questions, I've done 38 of them so far, just ask.
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Iâve got very good soldering skills and the right tools (including a reflow oven), but sourcing the antennas in Australia is the main issue.
I get most of my components from digikey so Iâd be grateful if you could point to the right antennas and connectors from their parts catalogue.
Holy Schmoly! Once again, thank you very very much!
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The key thing to look for is the standard frequency for your region and if you can find a full wave or half wave antenna. Full wave better than half wave, half wave better than quarter wave. Next the db to get depends on your house but 5db is probably the best choice for most.
Z-Wave Australia
AS/NZS 4268 919.8 MHz, 921.4 MHz
ZigBee is pretty standard around the world using the 2.4GHz band. Part number: IN24-5RD-RSMA
2 U.FL connectors
2 U.FL to sma or rp-sma pigtail. RP just means reverse polarity, a different looking connector that screws into the antenna. If you get an RP-SMA antenna you'll need the rp-sma pigtail.
I'll look on digikey.au and see if I can find something.
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Thank you, much appreciated.
I didn't find any on spec quality zwave antennas. Ideally you'd want one with a 920 center channel, but a LoRa antenna might cover those frequencies since it's center channel is 915.
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No worries, I might see if RS or E14 have anything that meets those specs.
