Suggestion is to improve the Base code so that COM & NAV radio INC/DEC frequency function does not blindly add or subtarct a given amount to the current frequency, but rather advances, or retards the frequency to the next VALID one.
That way, there can never exist (or remain) an invalid Freq,
Currently, if the Khz part of a COM radio is Invalid, the INC/DEC unction does not even work at all, it only works on existing valid KHz values.
The Radio Freq “can” get corrupted, (ie wit faulty state saving & restoring)…
With the above improvement in the INC/DEC that would always automatically get corrected on the next INC/DEC.
Far better for this to be done C0RRECTLY in the ASOBO /WT base code, than by each 3PD trying to do their own versions, with varying success.
Reproduce TESTs
(1) set COM1 standby to an invalid freq (say 128.111)
(2) Then try to INC/DEC it , it wont move
(3) Note Needs to correct for both 25Khz & 8.33Khz spacings
or for Nav
(1) set Nav1 Standby to 111.11
(2) Then try to inc/dec
(3) For Nav radios, it will INC/DEC, but by a FIXED amount, so it always remains an invalid Freq
Currently, you can use the current version of pms50’s GTN750 Menu Pulldown GPS, to set invalid frequencies, but now he is aware that his GPS can enter Invalid Frequencies (The Real GTN750 cannot), the next update to his GTN750 is expected to fix this, so you will not be able use that later version to test & force Invalid Frequencies.