Originally Posted by dzl_
Did you do a post or write-up on your setup and thought process anywhere. This is an area I would enjoy learning more about (Both the Antennas you chose as well as the DC router).
Nope, not yet, but I'll try to summarize here. Maybe some info you're not so interested in, but it serves as background for our use-case, which informed our decisions on routers / antennas / etc.
Wife absolutely has to have internet access for work. I'm more flexible but it would be nice. Also, we wish to boondock as much as possible, the remoterer the betterer, which means access via cellular data plans (mainly), and/or public wifi (secondarily). So for the best signal, we need at least one antenna on the roof (outside the faraday cage we call a bus) for cell, and at least one for wifi.
Why do I say "at least"? Because many towers/modems/routers now support mimo, which can benefit from multiple independent streams of data, utilizing multiple antennas. Mimo's the reason many home routers now have multiple antennas.
Why didn't I say "more than one"? Because some antenna designs offer mimo capabilities in a single unit... multiple antenna elements, fed by multiple leads, but all through the same penetration.
In our case, we chose to go with two separate antennas wifi (2x2) and two more antennas for cell (2x2). Why? In part, because it's my understanding that mimo should/might/maybe work better with physical separation between elements. Also, 2 good high-gain antennas work out to about the same cost as one combined unit. And 2 antennas exactly the same offer a measure of redundant back-up should one get damaged/fail. And finally, having multiple antenna mounts allows me some flexibility to changing things up, adding another radio, whatever.
Mimo isn't necessary - you don't need more than one antenna to complete a connection to a cell tower, nor more than one to access public wifi, but if implemented on both ends can greatly increase data rates, which may make the difference between being able to work from the woodside office of our dreams vs a Walmart parking lot.
So now we have two omnidirectional antennas on the roof for cell data (2x2 mimo), and 2 omnis on the roof for public wifi access (2x2 mimo). That's great if we have line of sight to even a fairly distant cell tower. But what if we're in a depression and have to get up over a hillside, buildings, or treelines? What if the nearest cell-tower is so distanct that even with clear line-of-site it isnt enough?
A booster (amplifier) might solve problem #2, but it won't help much w/ #1.
A directional antenna on a mast would potentially solve both.
So our 'plan B' is just that. A directional antenna (2x2 mimo... 2 elements, one vertically polarized, the other horizontally polarized), a mast, and low-loss coax jumpers (likely LMR400). Erect the mast/antenna, remove the two cell antennas from the roof, connect one end of the jumpers to were they used to be, connect the other ends to the directional antenna, and point it at the distant tower.
Plan C: If that still isn't enough, maybe then a booster might come into play. But I'm not buying a booster until I see this as a likely scenario. The booster would go between the router and one of the cell antennas, so I simply make sure I have a power circuit necessary to power the booster available where I'd need it if I did, as well as the space to mount it. But I seriously doubt I ever will, so I also make sure to buy something I can use that circuit for, like a DC-powered beer-bottle opener.
Plan D: Public wifi. That's already met with what we did above, preferably combined with a router that's capable of wifi-as-wan functionality. Pretty much just what it sounds like... all your connected devices go through your router just as they always would, no individual connections with the public wifi source need to be made.
So now if we can't connect in the boonies, we can drive a little closer to civilization and work in the starbuck's parking lot (and of course we'll buy enough coffee to cover the bandwidth we use - that's a given
) Or an RV park. Or a bar. Whatever.
Some boonies might only have access to one provider, though. Verizon is likely the best bet, but it would be nice to have another provider to fill the voids. It would be even nicer if you could combine the bandwidth between the two where both are accessible for higher data rates. So we want our modem/router to have that capability if possible.
Speaking of which, since we're interested in boondocking, power is an issue. Not only does a 12v DC router avoid conversion innefficiencies, it may allow the inverter to go into sleep mode (or be powered off) where if we were using your average consumer/commercial modem/router powered by an A/C wall-wart, that wouldn't be the case. Plus hardware designed for transit applications is hardned against the rigors of the mobile environment...
Enter Peplink. Their Pepwave line of cellular mobile modem routers includes models with the features previously described... the allowance for multiple SIM cards to support multiple providers, wifi-as-wan functionality, sma/r-sma connections for attaching multiple exterior antennas, mimo (different 'levels' of mimo depending on the network category and - correspondingly - price of the thing), mil-spec construction, 12VDC input voltage (we have a 12v house system, I haven't researched 24V but they probably have that option?), the ability to combine multiple providers for higher data throughput, and a whole bunch more features which would be useful.
All this said - to summarize our system now that you know something about the logic driving our decision:
Pepwave MAX BR1 MK2 Cellular Router
(They have a 5G model available now, but it's much more coin. Maybe once 5G becomes more popular. For now not worth it for us).
2 x Pulse Larsen panel-mount phantom-series 2.4g/5g wifi antennas w/ n-female base
(can't remember the part # but if you'd like it let me know. Pulse makes great quality antennas and pretty much all I use for anything. Mouser electronics is a great source)
2 x Pulse Larsen panel-mount 4G-LTE / 5G cellular phantom-style antennas w/ n-female base
(same I just said for the wifi antennas)
A flat plate to mount each someway on/above the roofline. The antennas we used need a ground-plane... basically a plate of metal upon which to mount them that acts as the other 'half' of the antenna... but the size of the ground-plane shrinks as frequency increases, and at the high frequencies we're talking here, the ground plane doesn't have to extend more than a few inches or less past the edges of the (very small) antenna itself).
Coax to connect the antennas to the router. Here's where loss comes into the equation, and here's where you either make or break your system. The higher the frequency, the higher the loss. And both the cell & wifi frequencies we're talking are pretty high (especially the public wifi on 5ghz) . In general terms, the larger the diameter of the coax, and/or the shorter the run, the lower the loss. But some coax is significantly better than others. The Times Microwave LMR series is the only thing I use for anything in this frequency range. It comes in a variety of diameters.
How much loss you can accept is kind of a judgement call. Every 3db is halving your signal, so to me, I'd hope to be aiming for 1.5db loss or less if I can at the highest supported frequency. The antennas have something like 3-8 dbi gain (just going off memory here), plus there's the gain of them being mounted outside on the roof as opposed to a device inside the bus, so you can stand some loss in the line and still be ahead of the game making all this a worthwhile pursuit. But if it got to 3, or 6, or 9... you might be better off just sitting on your nature's head from your phone.
Taking my setup as an example, if I mount the modem/router directly under the roof-line in the rear cap area, and coax from the centerline of the bus over to an edge (I'm planning on mounting a solar panel directly over this area in the back, with the 4 antennas mounted near the corners), the minimum run of coax required I've measured out to be ~7 feet. So I add 2 more to that for a fudge factor, then another foot because 10 sounds better than 9. I want 1.5dB or less loss in 10 feet of coax at my highest frequency... let's say 5Ghz (high-band wifi). If I use the Times Microwave Calculator
, I find 10' of LMR-240 ultraflex at 5000Mhz (5ghz) (I'd go with ultraflex versions due to the decreased bend radius & flexibility required in most mobile installs) gives me 2.4dB insertion loss. Not what I wanted, but maybe I could live with it? The antenna gain is more, so it's still better than me sitting on my roof with my cell-phone using Starbuck's 5ghz wifi (not even sure if they have 5ghz wifi lol). Your call may be different than mine. But I'm a performance junkie. So I need to go bigger w/ the cable, or shorter with the run. Here the limiting factor is pretty much the sma / r-sma antenna jacks on the router. Anything bigger than LMR240 (same size as RG-8X) coax and I don't even think they make sma connectors (could be wrong though). Plus bigger cable means bigger cable glands, higher price, less utility. So maybe the easiest way is to move the antennas inboard. Can I do it in 5'? Measure again, yes I can. 5' of LMR240-UF at 5000Mhz is 1.4dB. That's well below the antenna gain, which means maybe I'm sitting in one Starbuck's parking lot, using the 5Ghz wifi of another Starbucks one block away? Why? BECAUSE I CAN!!!
And don't even talk to me about 2.4ghz now. I own that frequency.
Was this so much more than you asked for? Was this rambling stream-of-consiousness response even human-readable? A help or a hindrance, I'm not sure. But if you have questions shoot me a PM and we'll chat on the phone