DIY Box Reflector - sick gainz!
Posted: Tue Sep 14, 2021 3:50 am
This is not my original idea, it's my practical implementation of the Ez-10 corner reflector. It makes omnis directional like a dish would but it's less picky about conditions. You can make this thing in 15 minutes, it costs nothing and it folds for storage. I got a ~10 dBm difference in software to a faraway 2.4 GHz access point. That represents about a tenfold difference in received signal power.
Materials:
-Your favorite USB wifi adapter + USB extension cable
Recommended: $16 Terow ROW02CD AC1200M (MediaTek MT7612U) with CD driver. No CD version causes annoyances in Windows. https://smile.amazon.com/dp/B086L6TR6G/
The Terow is similar to the Alfa AWUS036ACM but 3x cheaper, lacks any accessories and has poorer construction. I own both and they're functionally almost the same. MT76 adapters are infamous for being more hassle free.
Linux: Drivers already there. Supports pentesting features on both bands. Do not try to go directly from monitor to AP mode, needs to be in managed first. This is the only quirk I can think of.
Windows: Use NetGear A6210 drivers. Few extra settings compared to the ones on MediaTek's website.
-Boxcutter
-Rectangular box, as big as you can feasibly make and use
Recommended: Used USPS 1095 priority box
Approx: 15" (L) x 12" (W) x 3-1/8"(H)
-Shipping Tape
-Aluminum Foil
Warning: Exceeding EIRP limits is generally illegal.
Warning 2: Highly directional equipment may skew Wigle data. Use good judgement.
Instructions:
1. Make two cuts into your box to chop off one of the short sides. Your box should now open like a trifold. Save this flap.
2. You will make slots and thread the cardboard flap through for structural support. Cut slots near the top of the box on the two side walls.
3. As neatly as you can, grab your reel of aluminum foil. Tape aluminum foil on the two inside side walls of the box.
4. Take off your antennas if they are removable. Make a hole and jam your adapter through, either just the USB bits (easier to get a tight fit) or the whole thing if you need to adjust antenna/reflector distance.
5. Hook the adapter to the USB extension cable.
5. Thread flap through top slots.
6. Hook antennas back up.
7. If you have a two antenna adapter, deploy them completely parallel or in a V shape, see which one works better. You can hang the adapter from flaps, use string, zip ties for tight fit if you think it's necessary. Use MacGyver skills.
Optional (?): Cover the middle panel with aluminum foil, either on the inside or the outside of the box. Try to leave no gaps but it shouldn't matter that much.
Adjustments:
-Connect to the AP and run "watch -n0 iwconfig" in Linux or equivalent stat panel. Steer your antenna towards the AP. Stop steering when bit rate, link quality and signal level look good.
Note: Also try "watch -n0 iw dev wlanX station dump" it has a lot of useful info!
-Indoors = Signals will bounce and make consistent testing difficult. If you do not have direct line of sight sometimes pointing slightly away from the AP works better.
-Beamforming may affect results
-Making the side walls bigger will improve gain with diminishing returns
-My (v1) reflector is probably incomplete since I don't have any foil in the middle. I don't know if putting it that close to the adapter causes interference, will test later.
References:
http://www.freeantennas.com/projects/Ez-10/
https://en.wikipedia.org/wiki/Corner_reflector_antenna
Edit: Added picture of a v2 I made. I did not chop off the flaps so the box is taller and I added foil to the middle section. I've slightly updated the instructions to make them simpler.
"The spacing of the rods D should not be more than 0.06 (6%) of the wavelength." -Wikipedia
I'm not sure if that instruction is properly cited but it would suggest you want continuous foil if possible with no gaps. The wavelength of 2.4 GHz is about 12 cm and 5 GHz is about 6 cm. 6% of those lengths is extraordinarily tiny.
v2 achieved best performance with the antennas deployed parallel, while v1 seemed to like the V pattern. In terms of performance both reflectors work, I didn't compare them very hard. Someone more knowledgeable should chime in.
Edit 2: Tips from an antenna design book I couldn't completely verify:
-The angle of the reflector should vaguely be 90 degrees. A more narrow corner supposedly improves gain and directivity but may require larger side walls. I experimented but couldn't come up with a good conclusion. Since this contraption is kind of flimsy I found the 90 degree angle to cause least problems.
-The antenna(s)' distance from the reflector's center should be between 25% and 75% of the intended wavelength, with a suggested value of 50%. So in theory:
2.4 GHz: antennas ~6.2455 cm from center
5 GHz: antennas ~2.998 cm from center
This does seem to matter somewhat and could explain why I found differences from arranging the antennas full parallel vs V pattern. But even if your antennas are really far away you still get some gain. I recommend sliding your USB adapter around to see what works. Try your luck getting good clearance with your MacGyver skills.
Materials:
-Your favorite USB wifi adapter + USB extension cable
Recommended: $16 Terow ROW02CD AC1200M (MediaTek MT7612U) with CD driver. No CD version causes annoyances in Windows. https://smile.amazon.com/dp/B086L6TR6G/
The Terow is similar to the Alfa AWUS036ACM but 3x cheaper, lacks any accessories and has poorer construction. I own both and they're functionally almost the same. MT76 adapters are infamous for being more hassle free.
Linux: Drivers already there. Supports pentesting features on both bands. Do not try to go directly from monitor to AP mode, needs to be in managed first. This is the only quirk I can think of.
Windows: Use NetGear A6210 drivers. Few extra settings compared to the ones on MediaTek's website.
-Boxcutter
-Rectangular box, as big as you can feasibly make and use
Recommended: Used USPS 1095 priority box
Approx: 15" (L) x 12" (W) x 3-1/8"(H)
-Shipping Tape
-Aluminum Foil
Warning: Exceeding EIRP limits is generally illegal.
Warning 2: Highly directional equipment may skew Wigle data. Use good judgement.
Instructions:
1. Make two cuts into your box to chop off one of the short sides. Your box should now open like a trifold. Save this flap.
2. You will make slots and thread the cardboard flap through for structural support. Cut slots near the top of the box on the two side walls.
3. As neatly as you can, grab your reel of aluminum foil. Tape aluminum foil on the two inside side walls of the box.
4. Take off your antennas if they are removable. Make a hole and jam your adapter through, either just the USB bits (easier to get a tight fit) or the whole thing if you need to adjust antenna/reflector distance.
5. Hook the adapter to the USB extension cable.
5. Thread flap through top slots.
6. Hook antennas back up.
7. If you have a two antenna adapter, deploy them completely parallel or in a V shape, see which one works better. You can hang the adapter from flaps, use string, zip ties for tight fit if you think it's necessary. Use MacGyver skills.
Optional (?): Cover the middle panel with aluminum foil, either on the inside or the outside of the box. Try to leave no gaps but it shouldn't matter that much.
Adjustments:
-Connect to the AP and run "watch -n0 iwconfig" in Linux or equivalent stat panel. Steer your antenna towards the AP. Stop steering when bit rate, link quality and signal level look good.
Note: Also try "watch -n0 iw dev wlanX station dump" it has a lot of useful info!
-Indoors = Signals will bounce and make consistent testing difficult. If you do not have direct line of sight sometimes pointing slightly away from the AP works better.
-Beamforming may affect results
-Making the side walls bigger will improve gain with diminishing returns
-My (v1) reflector is probably incomplete since I don't have any foil in the middle. I don't know if putting it that close to the adapter causes interference, will test later.
References:
http://www.freeantennas.com/projects/Ez-10/
https://en.wikipedia.org/wiki/Corner_reflector_antenna
Edit: Added picture of a v2 I made. I did not chop off the flaps so the box is taller and I added foil to the middle section. I've slightly updated the instructions to make them simpler.
"The spacing of the rods D should not be more than 0.06 (6%) of the wavelength." -Wikipedia
I'm not sure if that instruction is properly cited but it would suggest you want continuous foil if possible with no gaps. The wavelength of 2.4 GHz is about 12 cm and 5 GHz is about 6 cm. 6% of those lengths is extraordinarily tiny.
v2 achieved best performance with the antennas deployed parallel, while v1 seemed to like the V pattern. In terms of performance both reflectors work, I didn't compare them very hard. Someone more knowledgeable should chime in.
Edit 2: Tips from an antenna design book I couldn't completely verify:
-The angle of the reflector should vaguely be 90 degrees. A more narrow corner supposedly improves gain and directivity but may require larger side walls. I experimented but couldn't come up with a good conclusion. Since this contraption is kind of flimsy I found the 90 degree angle to cause least problems.
-The antenna(s)' distance from the reflector's center should be between 25% and 75% of the intended wavelength, with a suggested value of 50%. So in theory:
2.4 GHz: antennas ~6.2455 cm from center
5 GHz: antennas ~2.998 cm from center
This does seem to matter somewhat and could explain why I found differences from arranging the antennas full parallel vs V pattern. But even if your antennas are really far away you still get some gain. I recommend sliding your USB adapter around to see what works. Try your luck getting good clearance with your MacGyver skills.