I used a USB mouse pcb and replaced the scroll wheel encoder with a rotary encoder with no detents, inserted it in a box preserving all the functions of the original mouse (3 buttons + cursor pointer). It installs as a second USB mouse.

I added a switch to enable the pointer motion, this prevents the cursor from moving from its position when you turn the knob or keep the box in your hands.
If you just want a knob without the other functions of the mouse the assembly will be just a ten minutes work.

Here is the box:




This is the list of the parts that i used; they are very common parts that can be found on Ebay or Aliexpress. Copy the URL of the images and paste in Google search by image to find the sellers

mouse-usb  box_small

knob_small encoder_small


The box internal size is mm. 96 x 56 x 21

The mouse size is mm 96×55 so its lower part fits perfectly inside the box, you just have to cut and reduce the height of the two sides. This is very helpfull because there is no adjustment to make to fit the pcb inside the box, just put some glue on the four pins that hold the pcb in position and a couple of drops between the base of the mouse and the bottom of the box

The knob is 45mm diameter, but that’s the diameter of the lower rim, the upper part is 37 mm.

The pushbutton is 12 x 12 x 7; i used chinese B6000 glue to fix them on the cover, just small drops on the black plastic pins at the four corners. I have inserted the wood spacer that you see in the picture to support the switches just in case the glue was not enough. The 4th switch sits on the support of the scroll wheel.

The encoder is the most important part, it’s type EC16 with no detents. the ones i purchased are hard to rotate but this can be fixed opening  (very easily) and removing the grease and the o-ring. It will spin like a whirligig!

The total cost of the parts purchased from China was about 4$ but it was calculated considering the cost of single pieces sold in lots of 5 to 10. The delivery time was from 30 to 60 days

Here is the pcb before the modification:


The wireless version coming soon!


Added weight to the knob using lead for hunting. The weight passed from 22gr. to 50 gr.
Filled up with glue and covered with a plastic cap.
The knob turn very easy and fast with one finger, i use it all the time when scrolling up&down web pages and pdf as well.

weighted_knob weighted_knob2

Installed Pluralinput on my Windows 7 pc to have two indipendent cursors.
The functions of the second mouse can be customized a little


Now i can leave the knob’s cursor on a digit of the frequency counter and do other things with the normal mouse like changing operating mode, selecting a memory, jumping to another portion of the band displayed.
The knob will work indipendently even if SDR# is not the active window; SDR# window can be partially overlapped by another window as far as the cursor will stay on SDR# window . I can have two windows side by side and keep on tuning the SDR while i use the browser. Unfortunatly we cannot lock the cursor on a specific window but at least it will be ready in position when we go back to the SDR# window.

There is another Windows software called Eithermouse supposed to do the same thing but it doesn’t seem to work correctly.

Linux users could check Multi-pointer X

This is probably the maximum that can be done without having specific driver that lock the second mouse cursor to SDR# and assign customized functions to the keys. Other existing solutions to take control of the SDR# program involve the use of a microcontroller like Arduino and a spedific plugin, but this basic project is nothing like that, it started only to replace the scroll wheel with a knob using common ultracheap parts.


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