ASUS USB-AC56, wiring, antennas, etc

This is not a “how to” at present, but I’m hoping people add to it so it will become a resource on how to for this wifi adapter.
I’ve primarily used the AR9271 chip wifi adapters on 2.4, but thought I’d try the ASUS USB-AC56.
I’ve read/searched the wiki, forum, and telegram and have questions concerning it. I’ll add a few photos I’ve found (sorry I cannot credit the sources since I didn’t record them), and a few observations (please correct if wrong), but mainly I have questions.

Antennas, I understand there are two internal, and two external (an SMA and a MS156 plug (?)).

I’ve read that when the external(s) are connected, the internals are disconnected. True/false, does it matter? Can it be run just on the internal antennas?
I’m guessing the stock antenna functions either in 5.8 or 2.4 frequencies. If I am using it for 5.8 frequency can I instead use any 5.8 antenna? Can I get a MS156 plug and hook it and the SMA up at the same time to two 5.8 antennas, as in the following photo? is that diversity then, and can I use different type antennas?

I’m not very good with electronics but can usually figure things out with a volt/ohmeter, but these antennas are beyond me. This photo shows a nice way of connecting some cables to the adapter. It looks like the cables are being soldered to the internal antenna solder points, but again using the ohmeter I can’t figure it out exactly. I’m assuming this is a valid way to connect external antennas?

Hard wiring, it looks too tricky to remove the USB totally, which is what I’ve done in the past on other adapters, so it looks like the next best thing to to partially remove some of the USB metal and solder to the inputs, along the lines of the photo. Any better way of doing this?

Cover, I’ve read somewhere, and can’t find it again that it is best to keep the cover on the adapter, for sensitivity reasons/tuning I think. I’ve seen photos of people using it with and without the cover, does it matter?

I appreciate any input, photos, corrections, etc. Please make this a how to resource for the ASUS USB-AC56.


Right now 5.8g is the only band that works correctly with openhd and this nic.

I believe both antenna (the internal and whatever you plug in) run at all times. I am basing this off, seeing changing rssi values in radiotap. But I could easily be wrong.

This card has quickly become my favorite, displacing the 036nha for me. It has good power and sensitivity. The footprint is relatively small. The 5.8g band is less crowded so less interference. Also some pi only have 2.4g internal wifi so this card does not conflict…

I would like to remove the heavy sma plug. My builds tend to be small and need to save weight. Maybe cut it off and direct solder an antenna or u.fl plug.

I think you really want the cover on. The cover prevents interference and the card is tuned with the cover… my understanding…

I hard wired the way it is in the above picture, cutting a piece of metal from the cards usb plug.
Removed from 2 Asus the plastic shell, they are working as tx in the plane, no adverse symptoms…

Why you don‘t like to use 2.4ghz Band/ carts?

For a long time I did like 2.4g with the 036nha being one of my favorites

-more interference on 2.4g
-the high power 2.4g cards seem to have a big footprint (although I do have a couple 036 cards that are in that tube format for outdoors but hard to find)
-2.4g conflicts with alot of rc transmitters and older pi internal wifi with only 2.4g
-there are more 5.8g cards to chose from and they are working great- I get good results with ac56

other than that there is no BIG reason not to use 2.4g. If you get good results with it then use it! They work great too


I’m just in the experimentation stage, but I’m finding that the 5.8 does not interfere with the GPS near as much as 2.4, that might be the big reason I switch. And I generally fly smaller planes and quadcopters, so smaller is better, however while the antennas are smaller, the AC56 is a bigger footprint than the little 2.4 card I use. Otherwise, 2.4 has worked very well for me, so no real complaints.

Not sure how much is visible, but “stripping down” AC56 is easy.
USB is very easy to unsolder - first straighten metal shield with pliers, unsolder it, then can easily unsolder remainder of USB, no hot air required.
GND, D-, D+ and VCC pins are “second” pins from left (antenna looking up) - second pad, 4, 6, 8.
Unsoldering SMA with soldering iron alone is harder probably. I used hot air gun. Internal antennas are easy with soldering iron alone, no guide required.
Now after soldering you have 2 points where antennas should be connected:
1 - where SMA middle pin was, scratch silkscreen around pad, prepare coax cable so it would look like ψ - (shield twisted from both sides, long story short - smaller losses) solder it here.
2 - cut trace after connector and DC cap (else track will work as antenna and detune everything), scratch silkscreen, prepare coax cable in the same way ( ψ) and solder it here.

Now two options - add glue to hold cables in place and cut remaining PCB parts (not needed - can save ~0.8g and some space), or add zipties and fix coax in place using PCB.
Board alone is something like 7.3g excl. coax, for air use (this in photo is for ground with limited space inside) i would cut PCB, use shorter tracks on PCB, would be below 7g for sure.


I’ve recently tried the AC56 USB cards but have only tested plugged in to USB ports (pi 3b+ for airpi and pi 4b 2gb for groundpi). I’m seeing a nasty amount of video disruption (bottom 2/3 of frame visible maybe 20% of flight). I do have the radio near a holybro telemetry 915mhz module and fs-i6ab receiver and am wondering if those radios are causing issues or if I need to break down and get rid of the usb connectors and solder to pi (powered via GPIO with 5V 3A UBEC). Any help would be much appreciated.

Get rid of the telemetry module. If it’s a quad(not much space) , try solder everything, if it’s a plane, try keeping some distance between Asus card and rest of the components (10-15cm at least). My wifi card is plugged, but far from everything.

1 Like

Thanks for the info! Will try those recommendations out. I have a quadcopter on the S500 frame so some room to move things around. Last two questions…are you running buster on the airpi/groundpi and did you change the 5ghz freq settings at all or allow auto? Just trying to control for all factors.

Was running buster air, stretch ground, at 5180mhz. Keeping stretch for old osd, but sooner or later will move to buster…

Ah, ok. I have a pi4 for the groundpi so have to run buster on it. How do I check which freq it chose (or is your 5180 a manual setting)? I’m new to openhd but comfortable with Linux, raspberry OS, etc. so maybe I just need to find some time to poke around the settings/config. Thanks for the info!

Manual selecting 5180. One day, due to some external interference (wireless communication, I guess ), I had to choose 5240mhz, but it was ok too for 15k, if I remember correctly.

So not sure that (manual freq) helped me. Even when quad and ground are within a couple feet get occasional video glitches and 2-3% lost packets. You have heat sinks on your ac56 cards? Mind sharing your settings-1.txt? I can’t quite figure out the video issues.

That’s true, me too having some occasional glitches and 2-3 packet lost. On (out of three) two AC I have a small radiator, on one I didn’t.

I tried wiring my ASUS USB-AC56 as you have where b+ red wire and b- black wire going to a 5v 3a bec and I have D+ green wire going to PP43 and D- blue wire going to PP42 on my pi3b+ but when the pi is powered on and the AC56 is connected to the bec the blue light on the AC56 doesn’t light up. Unsoldered it from the pi and plunged in another AC56 that still has the USB connector on it plugged into what would have the PP42&43 contacts and it light up. Does the one you have hardwired light up cause mine sure doesn’t. It lit up before the connector was removed btw. Thanks, Robert

If you’re referring to the early photo I posted here, that was some other type wifi card and I was just trying to indicate that removal of the USB and direct soldering could be done “along the lines” of that photo for an example. Here is a photo from telegram of someone who actually soldered to the AC56. Sorry, didn’t mean to mislead on the initial photo. There is also a schematic on telegram of the USB leads, but I wasn’t able to find it.