This is sort of related to the OP's question.
I recently flew to Montgomery Field (KMYF) in southern California. After clearing the runway, tower told me to contact ground on 118.22.
I was in a Cessna 172 that has a 25 kHz version of the Bendix KX 155A Nav/Com, like this:
This is a “25 kHz” radio that moves in 25 kHz increments, aka .025 MHz increments.
Dialing in ground on "118.22" should have been easy because the radio should move through this sequence of frequencies (in MHz):
However, no matter what I did, I couldn’t get the radio to display 118.22. I was stumped and getting a little frustrated.
I finally figured it out after a minute or so and never looked into more closely until I saw this thread.
As it turns out, my problem related to the “
PULL 25K” legend right below the big and little frequency knobs. Somehow I or the previous pilot had pushed it in. According to the manual, “it will change in increments of 50 kHz when the knob is pushed in and 25 kHz when the knob is pulled out.”
If the radio is limited to increments of 50 kHz (aka .050 Mhz), there’s no way to dial in 118.22, because it skips over the .025 and .075 frequencies. Apparently, the goal is to let you move more quickly through whole and half frequencies:
Oops.