I agree that it was unlikely to be a form over function decision. First because frankly, 90% of people have this thing buried on a shelf/cabinet/rack never to be seen by most people. That said, I think I saw @bravenel mention somewhere on this thread that they've at least considered adding an external antenna down the road, so in some ways we're also doing a little free R&D for them. If I'm remembering incorrectly I'm sure he'll reply so I realize I made that up 
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Have you guys actually seen a Hubitat Hub... and compared it to other RF-centric devices???? The Hubitat Hub is beautiful, while other RF devices actually have prominent antennas. While I do not know, I "posit" that form was absolutely given weight over function.
It’s not that hard to add inconspicuous antenna ports, most cellular wifi models have them.
The 2 white cables coming out of my 4G backup service are to an external antenna.
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One other thing to mention, if you'd prefer to stuff this hub in your faraday cage of a rack, external antenna with leads to the outside of your rack make this a viable option.
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I use the same backup modem with my setup. It's fantastic. It's to the left of the ups. I get about 85 MB/s with it. I'm about a block away from the cell phone tower.
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Nice! I’m getting between 2 and 4 bars, depending on which way the wind is blowing. 
I live in a hilly area and without my external antenna I was lucky to get 1 bar.
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I've completed this mod, following @lewis.heidrick to the letter. I had more trouble with the soldering than I anticipated. I didn't get a picture, but the stock antenna leads on my C-7 looked like they had been soldered in by a 5 year old with two left hands. I had to remove A LOT of solder from the board after removing the leads, before I could get anywhere close to a successful placement of the new u.fl connectors. So depending on your particular unit, if you have zero soldering experience, I certainly wouldn't make this your first go. I do have experience and a nice solder station thankfully, and perhaps it would've been better handled by someone with more experience than I. In any case, I would evaluate your situation carefully before jumping in with the soldering iron. With that said, my results have been very positive. I've never had "trouble" with my z-wave mesh, but as I've expanded it, I have started to notice small issues at the edges like on/off delays, missed devices in groups, etc. I have lots of repeaters, but I could tell there was beginning to be a strain on the signal paths to some devices. Before the mod, I had 30 devices directly connected to the hub, and 48 hours after the mod, that number is up to 39. All devices that are still connecting through repeaters have at least one less hop than they did before. There are a number of devices that were connecting at 40kbps before that are now connecting at 100kbps. There is also a significant reduction in RTT for a number of devices, that you can see in the pics below. Overall, this is a pretty significant improvement. I can literally feel the difference in a number of devices as far as reaction time to commands, and that is backed up by the data below. Your mileage may vary of course. For reference, my home is 3 stories and my hub is located centrally on the middle level. I've included a picture of the finished installation and before and after screenshots of the Hubitat Z-Wave Mesh Details app.
Before external antenna installation:
After external antenna installation:
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I noticed after doing this mod that I was able to reduce my overall device count quite a bit. Before the mod, I kept adding devices solely for the purpose of strengthening my mesh in more distant areas. I've now gotten rid of most of those no real purpose plug in repeaters. I still keep one around to send me notifications when the power goes out, but my box of shame has turned into a cabinet of shame. At least I have spares now.
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I came across this on several hubs actually. Seems like it's more common on the newer C7's than on the older ones before they started reinforcing the USB connector. They don't use leaded solder either which takes more heat to remove.
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Before I jump into this I have a few questions. I have 4 C7 hubs, 3 are in a small house on two different floors. I moved over from ST a few years ago then the C7 was new and had a very difficult time as the technical problems were being resolved with the C7. I had a Wave network issue that couldn't be solved with repeaters, switches etc, so I just threw hubs at the problem. It has been woking fine, most of the devices connect directly. I've been toying with the idea of consolidating a few of the hubs and came across this thread. How should I approach consolidation, do the antenna upgrade first, or just start moving devices to one hub then do this?
you have to power the hub down to do the mod.. which is my way of pointing out you can disable 50% of the house (after consolidating) of 33% before. I'd go with Antenna then consolidate. 
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I have my parts ordered and will be doing the mod most likely this evening.
While reading through the thread I had a thought. 99% of my issues are on the ZWave side, though that radio is 900mhz. Zigbee up at 2.4 seems to have no problems reaching everywhere just fine with nearly zero delay. Makes me wonder if there is something inherently wrong with the design of the inbuilt zwave antenna, as it should perform better than zigbee?
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This hasn’t been my experience. Zigbee on SmartThings and then HE has always been much faster and more reliable than z-wave. It seems like any z-wave device that isn’t directly connected to the hub is near unacceptable in response time compared to Zigbee devices. Even directly connected devices installed in the same room as the hub have a lag compared to Zigbee devices on the other side of the house. I have chalked it up to z-wave having slower transmission speed and it doesn’t seem to route as efficiently as Zigbee.
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I agree route selection and fallback behaviors seem really inconsistent at times..
I do think it's gotten a bit better after the HE and radio firmware updates released earlier last year though.
@wogfun let us know how it goes! I am looking at maybe doing this as well.
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Top speed for ZWave is 100kbs, with 40k and 9.6k as historical speeds that are still supported. Zigbee, on the other hand, has always been 250kbs. You can get 2.5x more packets onto a Zigbee network, theoretically. Or said the other direction, Latency is 2.5x lower.
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I'd go with this ordering too, though for me partly a matter of paranoia about my soldering skills - if it didn't work out I'd only have destroyed 33% of the system rather than 50-100% of it! As it happened I only have one hub, the antenna upgrade went fine, and I'm very happy with the result.
Another argument for upgrading first and consolidating second - the consolidating will probably go a lot easier on a hub which already has the upgraded antenna.
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That would explain a lot of things including why Zigbee doesn't seem to get as congested as Z-Wave.. a lot more room to fall.
You would think that with Z-Wave even 9.6k would be enough for quick switching etc as long as you don't have too many devices.. unfortunately protocol and routing issues seem to get in the way... This also seems to hamper the longer theoretical distance allowed by the lower frequency. Maybe this is one of the reasons why LR is no hop.
9.6k is fast enough BUT it consumes 10x the frame space. Thus you can only do X on/off's per unit of time. 40k is 4X and 100k is 10X in the same unit of time. In a way, it has more to do with what's being prevented than the successful data rate.
Naturally, a single controller can't hit theoretical packet per second (pps) rates. That means there's a reasonable quantity of 'dead air' that allows parallel operations. It's this reason that convinced me that 3 ZWave meshes are my solution.
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That makes sense.. nice info thanks.
I really liked running my hubs by location but right now have a multi-hub config by device type - zigbee and z-wave. I guess I could always add another "Z-Wave" C-7 though... 
I have, as I have documented a couple of times, 3 hubs that have a radio enabled in my production set of 4 hubs. One hub has both Zigbee and ZWave, the other two are ZWave only. I don't have enough Zigbee to be worth the price of another array of repeaters. For MY sanity, I have very specific areas of the house that get assigned to a specific hub. If I ever have reason to check a device, I don't want to take a tour through my hubs to find it.
My most recent purchase, a C-7 was intended to replace one of the C-5's and I did start at the front of the house, migrating devices. But one day that ground to a halt and I've simply left it as is. So that new hub is now known as "Front" in my head and I'm ok with the results.
I got a pair of Lifx bulbs as a result of its native support and I've got a WLED string of individually addressable string of lights ready to add... those conveniently go on my only hub that has zero radios enabled. since they are WiFi.
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