Here is a schematic diagram of the radio end of my remote control station:


Remote Station Overview (G4IRN)

…and here is the control end:

Control Station Overview (G4IRN)


I recently purchased a ‘value for money’ serial-port to WiFi adapter unit direct from China to remote control my Expert amplifier via the 9-way serial port.

Model: USR-WIFI232-602


Cost: (delivered to UK, including tax which was bundled into the price): GBP41.90 (US$62)


Expert plus WiFi Adapter


Installation and Operation – Initial Set-Up:

When starting the RS232 to WiFi converter for the first time, it acts as a WiFi Access Point (AP) –  connect your local PC to the WiFi network it creates (USR-WIFI232-602_D7AC in my case).

With your browser, connect to the default IP address and use the default user-ID and password to access the management screen: (ID=admin PW=admin) – check the manual in case it’s changed.

On the unit’s management panel, the ONLY things that need changing are in the first section of the ‘Quick Configure’ screen :

* ‘AP mode’ to ‘STA mode’

* AP SSID: select your local WiFi.

The encryption type and security mode should change to whatever you have in use on your local WiFi network.

* Then type in the Network Key.

Select the ‘Device Management’ menu option. Change the management panel userID and password at this point if you wish and then reboot the RS232 to WiFi unit.

On re-start the unit will come up connected to your local network (provided you set the parameters correctly!).

If your local WiFi access point is DHCP it will have issued a new IP address to the RS232 to WiFi unit.

Log onto your WiFi access point and look at ‘attached devices’ – you should see the RS232 to iFi connected and you can ascertain the IP address. Go to your web browser and type that web address – you should connect to the RS232 to WiFi unit’s management screen.

Installation and Operation – Fix the local IP address

Configure your WiFi router such that the the RS232-WiFi adapter will always be allocated the same IP address. Different routers do this in different ways, a screen shot of mine is below.

Allocation of an IP address to the adapter

Entry #3 is the entry (in my case) that assigns to the unique MAC address of the adapter. You can choose another IP address, just make sure it’s in the correct range for your router.

I then defined a ‘service’ for the adapter and allocated a port to it, per the screen shot below:

Allocation of a firewall port to the adapter

The port I selected was the ‘out of the box’ port, number 8899 – other values are available.

I then set port forwarding so that when I access this port from my public IP address, it gets maps to the local, ‘private’ IP address.

Port forwarding

Installation and Operation – Connect to your amplifier

At this point, you can connect a cable between the adapter and the 9-way D-type socket on the amplifier – CHECK THE PIN CONNECTIONS IN THE MANUAL !!

Installation and Operation – Fire up VCOM on your local PC

Install the software provided by Expert: “KTerm_232”

Install the software provided by USR: something similar to “[USR-VCOM] Setup Software”.

The VCOM is software provided by the manufacturer creates virtual serial ports and can be pointed to the IP address (local or remote) of your serial-port adapter. When I have it running with the Expert-supplied remote-control software, the combination of both programs (local control) looks like this:

Local amplifier control via WiFi

Remote access

You need to know the ‘public IP’ address for your router. (Try

Input this IP address, along with your port number, into the VCOM software at the control end of the remote link. Be aware that public IP addresses can sometimes change – the Remote-Rig units provide a mapping from your IP address to a ‘web address’ – if you’re using RRC-1258 units then substitute the public IP address for the DNS name and port number e.g.

“” or suchlike.


Suggestions to improve this article are welcomed.

John Warburton G4IRN

15 May 2015