I use the MFJ-9200 radio for my Morse code and shortwave listening activities. Actually, it is a MFJ-9240, since I have a 40m module installed.
The original tuning knob is, in my experience, not that comfortable, since its diameter (D) and height (H) are both very small. There is, however, space on the unit for a larger knob, both in D and H dimensions.
Recently I bought four new knobs of varying D and H to try.
I felt improvements with all of them, but went with the 1.31"D .87"H knob. The larger D and H, especially the H, made tuning feel a lot better.
One issue to keep in mind, that you don't have to worry about with the original knob since it is so short and designed for this radio, is to make sure to set the knob a little off the face of the radio. This is because the tuning knob is also a push-button used to change what decimal (ie. HZ, KHZ, or 100 KHZ) you are tuning. If the knob is flush with the face of the radio, you won't be able to push it down. This is easy to do, since all the knobs are attached using set screws.
Also, when you look at new knobs, measure the maximum D you can use. In this case, the first button I'd hit with a new knob would be the "ATT" button, so I simply measured from the middle of the tuning knob to the edge of the ATT button to get the maximum Radius, and hence the maximum D (remember D=2R) I could consider.
Be sure to check out MFJ Enterprises, as well as Mouser Electronics.
If you enjoyed any of my content, please consider supporting it in a variety of ways: