To do this, just log into YT via the WiFi admin interface at SSID GL-MT300N-V2-* (or something similar) at its factory default IP address 192.168.8.1. On a ...
KiwiSDR
Example KiwiSDR USB Single cable Connection to a Wireless Router
Kiwi 192.168.7.2 USB-micro
Jumper @R168
YT
PoUSB
USB-A 192.168.7.1 assigned to tether(USB)
USB-micro, power ONLY Jumper +5VDC
10.0.0.144 received from Local WiFi DHCP
Admin over GL.iNet WiFi
Port Forward (NAT) connects IP:8073
Access over Local WiFi
Kiwi accessible as 10.0.0.144:8073
WiFi to local subnet
Firewall:Port Forwards:192.168.7.2:8073
Here's what I think it takes to make a portable Kiwi System work better. This includes hardware mods to allow powering a YT ("Yellow Thing") wireless router over its single data connection from the Kiwi as well as YT set-up to access the Kiwi. Doing this can remove wired-LAN and power supply common mode current paths that raise the KiwiSDR's noise floor.
Hardware mods:
On the Kiwi, pads for the missing R168 are to be found on the BBG above P9, pins 1&2 here:
Either solder in a zero ohm 0603 SMD part or jumper with a bare wire. This connects the Kiwi system 5V, conditioned by filtering at the Kiwi's barrel power connector, to both USB-A (Host) and USB-micro (Client) connectors on the Kiwi's BeagleBones board. This supply then connects via a single USB-A <++>USB-micro cable and can supply power for the router, thus avoiding an additional power supply path and potential noise current loop. On YT the two USB connector 5V lines have adjacent pads, USB-A 5V below the USBmicro(power) 5 in the photo, that can be accessed and tied together:
I've actually used both a Schottky diodes across these pads as well as the jumper present in the picture above. This diode is 'backwards' across the IC that provides 5V for the USB connector. It appears that shorting it rather than using a diode is OK.
The PoUSB system has run for extended periods with no issue and so far no local noise/ingress at all. The Kiwi can be powered from a SMPS 5V Buck converter with no evidence of the switching frequency anywere in the Kiwi.
With this arrangement for the first time an isolation transformer at the Kiwi SMA makes no imiprovement and also for the first time I can actually short the SMA shield (Kiwi PCB ground plane at the SMA) to the Kiwi enclosure with no effect visible at HF.
Since getting the PoUSB to work I've discovered that the GPS QRM at 1575 MHz is lower but still present. It seems that without big LAN&PS CM noise current sources generally the KiwiSDR is better behaved. I find that a GPS antenna mounted right on the cover of the Kiwi works if I ground the SMAs directly to the aluminum enclosure. This is something I wasn't able to do previously as it added a loop that LAN/PS CM coupled into.
These latter results seem to me important, certainly for portable operation and may indicate things are more under control than they were. It may also be worthwhile to use PoUSB to help avoid problems on stationary systems and not only the portable system for which PoUSB was originally intended.
Software mods:
The Kiwi seems to always assign 192.168.7.2/30 to it's client USB port. Other than waiting for it to become available after power up nothing needs to be done. The YT discovers it OK once it has come up and YT seems to assign its own USB interface as a result, at least sometimes. I think the Kiwi must bo providing DHCP for this to occur.
Beyond this physical and power and port conficuration, all that is required is to create a port forward for the Kiwi so that YT can present that port to the outside world as though it were coming from itself. To do this, just log into YT via the WiFi admin interface at SSID GL-MT300N-V2-* (or something similar) at its factory default IP address 192.168.8.1. On a new YT the password is "goodlife" or maybe "Goodlife", I've changed mine but it says in the instructions which it is. It might be a good idea to update the YT firmware at this point. Once in and updated, go to the "Firewall" tab and map the Kiwi's ports to YT by setting up the tethering interface.
Assign a static rather than DHCP address to YT's USB(Tethering) port. It comes from the factory set to DHCP and should be changed it to static, 192.168.7.1 to match the hard coded network that the Kiwi demands and remove thenecessity for DHCP from the Kiwi. Both YT and Kiwi USB will then have static addresses..
Set YT's USB port to static as 192.168.8.1 under :More Settings: Advanced: Network:Interfaces:Tethering:Edit
and give it the static address and a subnet mask. It only communicates with the Kiwi but 255.255.255.0 is an OK mask.
Here's an example that works:
YT should now both have connection to a booted-up Kiwi and should pass that on to the outside world. To get a WiFi connection to the outside, you'll need to have scanned for your home WiFi network, entered the password and connected. This should give you a picture on YT's main page of this form (in this example the WiFi network is SSID "Corridor"):
The above is showing the Tethering/USB connection to the Kiwi, the Wifi connection to the local Wifi network and in this case the connection to the administration WiFi connection shown under WLAN Clients.
Using the IP address found for the home WiFi network, 10.0.0.162 in this example, the Kiwi should be accessible via Wifi as 10.0.0.162:8073 assuming the default Kiwi port of 8073 was set up on the Kiwi administration page was mapped with no change as shown above.
You will need to have previously provided an administrative password to the Kiwi since if you don't if you try to get to Kiwi admin via something like 10.0.0.162:8073/admin as you normally would it will complain that you aren't on its 192.168.7.x USB subnet and won't let you in. If you have reason to want to SSH directly into the Kiwi/BBG I suppse you'll have to add an additional port forward or else temporrily use wired LAN to connect to the Kiwi.
I think that adding this single-cable PoUSB connection may be pretty worthwhile for portable Kiwi systems. With no connections to the router (YT) there is no longer a CM current ingress path from LAN/PS lines, through the Kiwi and out the antenna or even PS-to-LAN current through the Kiwi ground plane. I think this is why I'm no longer seeing network of any SMPS noise when powering the Kiwi from a 12V via a 5V buck converter switching at ~960 kHz. Even CM current from the antenna coax has nowhere to go so the Kiwi doesn't see any QRM now. The system can function by powering through YT's micro-USB power input instead of the Kiwi's barrel but this would be a bad idea since it would add a noise current path from the external power supply.
There is still an issue of the Kiwi leaking internal 1575 MHz QRM and causing problems with KiwiGPS use. But since the other CM current paths are mitigated it is now finally possible to short the Antenna and GPS SMAs on the KiwiSDR to the Kiwi enclosure, I used aluminum HVAC tape to test this, and so to have the Kiwi's GPS antenna sit directly on top of the enclosure. Previously there was so much QRM that the KiwiGPS couldn't acquire good satellite signals.
There is no doubt still much to learn here but hopefully others of you will try this and add to our collective knowledge.
Glenn N6GN
24 Feb 2021
Writer LibreOffice 6.4