When adding an extension to my house, I began looking for a reliable, high throughput Wi-Fi solution. One of the options was to deliver Wi-Fi over coax, using coaxial cables to send Wi-Fi frequencies directly between my router and a cable outlet. I expected I would need low loss LMR cabling at 50 Ohms to cover the distance, but it turned out that several products allow me to make use of standard RG-6 cabling at 75 Ohms, which most homeowners already have in their walls. This approach has a number of pros and cons described below, but appears to be a promising solution for inexpensively improving Wi-Fi coverage in many homes, particularly for cord cutters.
Pros and Cons
Wi-Fi over coax claims to offer several advantages versus Wi-Fi meshed repeaters and distributed access points. One is that the signal avoids obstructions like concrete and drywall, losing only a fraction of its strength when reaching distant rooms. Another is that a single SSID can be broadcast throughout the home without handing off devices to different access points. Unlike Power over Ethernet access points, it's not necessary to run Cat5e through walls so that APs connect to a gateway switch, plus the electricity is drawn passively from the router itself. And unlike meshes or other repeaters, throughput isn't halved, nor are hidden nodes of interference created between the access points.
One apparent disadvantage of Wi-Fi over coax is that the router being used needs to have at least one detachable RP-SMA antenna, although many of the routers offered by Asus, Netgear, TP-Link and others meet this requirement. Secondly, there may be a trade-off between using Wi-Fi on a cable and using other signals, such as cable TV. Dualcomm sells a Wi-Fi over coax kit with diplexers that support TV and cable modem frequencies from 5 to 860 MHz, but unfortunately limits Wi-Fi to 2.4 GHz. However, several products sold by Coaxifi allow for Wi-Fi from 2.4 to 5.875 GHz, with relatively easy installation even in a home with a cable modem (either connecting the router directly to ‘home run’ cabling, or placing the router in another room). These include special antennas with F connectors to screw directly onto a standard cable outlet, as shown below.
|Dual band antenna with F connector for cable outlets|
I didn't find a legitimate review online of any Wi-Fi over coax product that described RSSI or MCS index results based on sustained Internet traffic, and am not a fan of reviews that list results by arbitrary locations ("living room," "office," etc.) as though all homes are built the same. My testing below is based on placing TP-Link's 4 antenna Archer C3150 router in a Motorola shielding box (below) within an 8 inch concrete enclosure connected to various lengths of RG-6 cable, to prevent signal leakage over the air during Wi-Fi over coax tests. The products tested include the Coaxifi “StraightShot” with a single antenna as well as a 2 way splitter, and the “McFly” 4 way splitter which is billed as a whole home solution. Testing the router’s over the air results made use of all 4 of the C3150's antennas, versus 1 antenna for each Coaxifi test. In each test series, channel 36 (5,180 MHz) at an 80 MHz width was set on the C3150 with band-steering disabled, using a Google Pixel as the receiver. Lengths of 25, 100 and 125 feet of RG-6 cable were used for comparison with 10, 20 and 30 feet of Wi-Fi over the air. A gigabit Internet connection was tested 3 times per test series, with the maximum throughout result taken.
|Router on battery power in shielding box before testing|
One of the reservations I had about Wi-Fi over coax was the lack of MIMO support in rooms where only one connector was available in a cable outlet, figuring that throughput would be notably lower than a 4x4 MIMO router would otherwise support. Surprisingly, this turned out to be a red herring, since the Coaxifi kits consistently outperformed the C3150 at distances of 20 feet or more. As the test results show, Coaxifi over as much as 125 feet of RG-6 would reliably hit 256-QAM 5/6 modulation and 310 Mbps of throughput at 5 GHz (at an RSSI of -44 dBm), while the router's 4x4 SU-MIMO performance 20 feet and 2 walls away fell to 16-QAM 1/2 modulation and 284 Mbps of throughput at 5 GHz (at an RSSI of -59 dBm). In terms of the corresponding link rates, that's a difference between 866.7 Mbps and 520 Mbps in Coaxifi's favor, with 1 stream outperforming 4 spatial streams. So even with a router like the C3150 that delivers up to 968 milliwattsof power, typical attenuation in a 3 bedroom home could be severe enough to give Coaxifi an edge over using the router alone. Since some homes have dual gang cable outlets, it might also be possible to use Coaxifi in a 2x2 MIMO configuration, which did improve throughput in the tests.
Very little signal appears to be lost with Coaxifi’s kits. In fact, the 5 GHz RSSI over 125 feet of RG-6 was 32 times stronger (in nanowatts, 39.8 nW versus 1.3 nW) than the RSSI from the over-the-air tests just 20 feet away from the router. Naturally, the RSSI gets lower the farther one's device is from the antenna in either configuration, but staying above the 'danger zone' of -65 to -67 dBm for reliable packet delivery was not a problem.
Results were mostly consistent between Coaxifi products, with a few interesting differences. In the 100 foot test series, the 4 way splitter slightly outperformed the StraightShot 2 way splitter (292 Mbps versus 285 Mbps, respectively). This could be due to the low insertion loss (<0.6 dB per port, per the manufacturer) and smaller SMA connectors on the splitter, given that F connectors are lossier and cable assemblies add their own unique loss characteristics. Comparing the 2 way Coaxifi splitter in a 2x2 MIMO configuration (connecting two antenna ports) at 25 feet versus the single port StraightShot at 125 feet, the throughput difference was only 43 Mbps (353 Mbps compared to 310 Mbps) at 5 GHz.
|Rear view of router when connected to StraightShot adapter|
Based on the results, Coaxifi could be a simple, inexpensive way to improve both Wi-Fi coverage and throughput, particularly if you have devices that are 20 feet or more from your router. (Looking back, this is close to the manufacturer's claim of delivering more coverage over 100 feet of cable than Wi-Fi alone can deliver over 25 feet.) It's also a good way of putting extra cable outlets to use around the house. The 4 way splitter might work best with more powerful routers and is also handy for packet capture with a USB adapter, while the StraightShot signal and 2 way splitter should deliver plenty of signal strength with low powered routers. I actually ran out of RG-6 cable testing Coaxifi, but since these products can deliver 256-QAM even at 125 feet, they clearly can carry Wi-Fi signals even farther, whether on longer RG-6 runs, with LMR cable, or with a signal amplifier. The concepts behind Wi-Fi over coax may not be as intuitive as other plug and play hardware, but when you consider that Wi-Fi mesh kits costing upwards of $300 have no guarantees of working, paying around ten times less to solve your coverage issues seems sensible.