How To: Assembling standard expansion module in RF Explorer WSUB1G PLUS

The RF Explorer WSUB1G PLUS includes a new, advanced set of internal electronics which enables it to fit Expansion PLUS modules, currently being developed and expected to be available before mid 2019.

The new internal expansion port is 16 pins wide in WSUB1G PLUS, whereas standard spectrum analyzer modules come with 12 pins wide connector. However, we made the new 16 pins connector fully compatible with 12 pins expansion modules, so you can easily expand your RF Explorer WSUB1G PLUS with RFEM24G or RFEMWSUB3G <standard> expansion modules.

Firmware support for expansion modules requires version 3.06, available in our download page. Please follow below instructions to assemble the expansion module in your RF Explorer WSUB1G PLUS spectrum analyzer.

You will need to order a separate top aluminum CNC cover to assemble a standard expansion into the new form factor of WSUB1G PLUS. Please check this product from SeeedStudio for more details.

ESD precautions

As you will be dealing with ESD sensitive electronic CMOS components, you should use antistatic protection to avoid any impact on the circuit. For that, it is recommended to use an Antistatic wrist strap. See below tools you will need for the upgrade.

Assemble tools small

Before following this process, be sure you upgrade the RF Explorer WSUB1G PLUS firmware with the v3.06 or latest available version from the download page. The firmware upgrade must be completed before you install the hardware Expansion Module.

Remove RF Explorer case cover

The very first step is to power off your RF Explorer and disconnect it from any external USB source or power.

RFEPlusAssembled small

Then remove the rubber protection.

RFEPlus removed rubber small

Get top and bottom cover off by removing the small screws, indicated by red arrows below. Use an appropriate Philips screwdriver of the right size to avoid damaging the screws. Remove the SMA nut as well.

TopCover Plus small

BottomCover Plus small

Note: There is no need to remove the main PCB from the front cover, we suggest not removing it; otherwise assembling it back with all button keys may be a bit difficult.

Plug the Expansion Module in

You can now get the PCB out of the box, you may optionally disconnect the lipo battery but that is not mandatory if you keep the power switch in the OFF position at all times.


The 12 pin male connector from the Expansion board must be plugged in the 12 pins marked in yellow in above image, avoiding any contact with the 4 pins marked in red. By connecting this incorrectly may damage the expansion and/or mainboard and is not covered by guarantee, so make sure the right connection and alignment is used. See more detailed picture below.


After proper connection, the alignment of the boards must look like these images below.

 Alignment detail

Alignment detail 2


  • Review very carefully your battery is not making contact with any PCB or connector anywhere.
  • The battery should have been assembled in the factory in such a way that would be in an area far from the Expansion Module contacts. However, if you see the battery in risk of contacting the PCB, connector or anything else, you must fix that before assembling the RF Explorer unit back.
  • Always proceed very carefully with the Lithium Ion battery and make sure it is not punctured, damaged or inflated in any way. A healthy battery is a flat rectangle with no signs of any deformation. If you have any doubt, please take a picture of your unit and send it to us for further help. Read this article for additional information on battery handling and care.

Assemble RF Explorer

Next step is to securely attach the back cover, top and bottom covers.

Final step is to tighten all screws up in all top, bottom and back covers.

Power the unit on, if everything is working as expected, you will see a screen detailing the base model and new module in place. Check the new module is identified as expected, below is an example but the exact screen will depend on the model installed.

The asterisk mark indicates the SMA connector associated with the module, and the [ACTIVE] signals the currently actived one.

You can use the MENU button to navigate to this screen anytime to review your configuration. To switch between the two available modules, you can use the MENU button to navigate to the FREQUENCY MENU and then cycle through the active module by clicking ENTER on the Module option at the bottom.


  • There may be minor variations in the pictures shown when compared to what you have, based on model or production batches. If you got any question, please ask in the list or by the contact form.
  • All the RF Explorer CNC job is done with sub-millimeter accuracy. It may be sometimes difficult to fit everything perfectly in place if you tighten some screws too much before having the others in place. You may need to release a bit some screws for the others to fit properly in place. Generally speaking, it is better to have all the screws in place before you tighten them up to their final position.

How To: Create Linux custom Raspberry Pi setup for RF Explorer IoT

RPI 5b

We recommend using our ready-to-go Raspbian images for your Raspberry Pi (supporting models 1, 2 and 3). We did all the hard work to have them correctly configured for RF Explorer IoT.

If you prefer or need to implement a customized OS image for Raspberry Pi, please follow below indications:

  • For Raspberry Pi models with embedded Wifi or Bluetooth (such as model 3), it is strongly recommended to disable both WiFi and Bluetooth. Otherwise they may create significant RF noise and interference with sensitive RF circuit inside the RF Explorer IoT module. Search for official documentation or see this link.
  • Raspberry Pi native UART requires some modifications to be usable by RF Explorer IoT module:
    • First, make UART available for external use. See this link.
    • Second, Increase UART clock to enable 500Kbps: modify /boot/config.txt to include a init_uart_clock=8000000 (see link)
  • If you are using the Raspberry Pi as headless device (no digital Video or Sound output) then is recommended to switch off HDMI and Sound ports. See this link and this link.
  • Install mono if you plan to use .NET libraries and examples. We recommend mono 4.0.5, this is a tested version. Depending on the distro and Raspberry version you use, you may need to build mono in the Raspberry from git sources, which takes several hours. See for more details.
  • Install python 3.5.x if you plan to use Python libraries and examples. See link

How to: FM modulation with RF Explorer Signal Generator

RF Explorer Signal Generator RFE6GEN does not directly create FM or AM modulation signals, but can be easily used to produce low rate modulation including SINAD signals using Frequency Sweep.

For a FM modulation of 1KHz tone typically used for SINAD, proceed as follows:

  • Select the Start Frequency the value you need (e.g. 2.000000GHz)
  • Select the Stop Frequency the FM deviation you need. For instance for a 5KHz deviation, set exactly 5KHz above (e.g. 2.000005Ghz)
  • Select the Frequency Step same value as FM deviation (e.g. 5KHz)
  • Select the Step Delay. For a 1KHz tone, you need 1ms delay, therefore define Step Delay:00.001
  • Select RF power you need and start transmission using Frequency Sweep operational mode.

With this technique the highest rate tone generated is 1KHz (which correspond to 1ms step delay). With a 2ms step delay, frequency tone is 500Hz, etc.

How to: SNA Measuring RF Filter response

Using Network Analyzer functionality

RF Explorer Signal Generator enables advanced Network Analyzer functionality (SNA) when a RF Explorer Spectrum Analyzer is connected to the same computer. This is an advanced feature, used to identify Insertion Loss/Gain vs Frequency to fully identify S21/S12 scalar response of a 2-port RF device. These include filters, amplifiers, terminated couplers, etc.

In this self contained, 5 minutes tutorial video, you can learn how to measure frequency response of a 2-port RF device such as band pass filter. The same process can be used to measure any other RF device.

What you will learn:

  • How to measure response of a band pass filter, including all RF connections required and RF Explorer for Windows
  • The same process can be used to measure any 2-port RF device.

What you need:

  1. RF Explorer Spectrum Analyzer model for the frequency required for test
  2. RF Explorer Signal Generator RFE6GEN
  3. Quality RF cables
  4. SMA wrench (8mm or 5/16")
  5. Device Under Test (DUT)- in this case we will use a 1675MHz BPF

Video Best viewed in HD 1920x1080 full screen


  • Normalization: This is standard SNA requirement to rule out any cable, connector or environmental imperfection. The application will properly measure the response of your setup and will consider that 0dB response in order to refer any measurement to it.
  • DUT: Device Under Test. It is the standard term to refer to the RF device being tested. The DUT can be an amplifier, a filter, etc. Any DUT will require the same steps and can be considered a 2-port black box.
  • SMA Gender: SMA connectors (as most RF connectors) can be male or female. Male is the one with a center pin connector, and female is the one with center hole connector. The gender of the RF Explorer units is standard SMA female, whereas DUT can be any gender. In order to connect RF Explorer Signal Generator on the input of the DUT, and RF Explorer Spectrum Analyzer to the output of the DUT, you need quality cables and connectors. The higher the frequency, the more critical is selecting quality cables, adapters and connectors. We suggest quality 6GHZ semi-rigid cables we offer from SeeedStudio and other distributors (click on images below for more details). You may also need a Female-Female adapter as pictured below when normalizing a DUT response that is Male-Male gender. Warning: Using low quality, long cables may significantly reduce repeatability and resolution of your measurement.

Procedure summarized

  1. Select the START / STOP frequencies to sweep, and the number of steps. The more steps you use, the longer the sweep will take. Recommended values are from 50 - 200 steps for a good compromise of speed and resolution.

  1. Select power: By default you should select -30dBm in the CW power value, that is good for most testing. However, if you are using an attenuated line for normalization and test (e.g. attenuator is in series for some reason, or using a Directional Coupler for reflection / SWR) then increase to -10dBm or more. On the other hand, if the normalization connection is amplified (e.g. with mixer or amplifier of some sort) then decrease to -40dBm. As a general rule, you should select a power level that feeds the Analyzer input port at -25 to -35dBm ideally, as that is the best compromise between high power to reduce environmental noise and still being in the linear range of the analyzer.
  2. First step is normalizing the setup response. To proceed with normalization, you need to use the exact same cables, connectors, adapters and everything you will use with the DUT, except the DUT itself. Sometimes you may need an adapter to plugin both cable ends if the DUT is Male-Male, use a suggested adapter above in that case. Click on [Normalize SNA] and wait a few seconds for the tool to alert on the normalization step is done. The RF Explorer Spectrum Analyzer unit will show TRACKING in clear text and no other functionality is available while SNA is working.
  3. Once normalization step is done, you can now connect the DUT and click on [Start SNA] for continuous tracking sweep. Screen will be updated with SNA results every few seconds.
  4. Important: Do not change START/STOP/STEPS configuration or otherwise you would need to Normalize again. Normalization is valid for a specific setup and needs to be done again if modified. For instance selecting a different number of steps or frequency range or power, will immediate clear normalization data and Start SNA button will be disabled to force a new normalization.
  5. Click on [Stop SNA] to stop tracking anytime.