Repeater: TX offset instead of TX frequency

[gullradriel]

Actual Repeater is using frequency_b as a defined frequency and not as an offset of frequency_a.

This is due to various places in freqman files expecting a frequency to be positive.

We would like to implement support for the negative values in freqman entry for Repeater type, allowing us to set an offset instead of a direct frequency.

[NotherNgineer]

I think the rest of the firmware could use the frequency_a and frequency_b as is, and only the parsing (and writing) of the freqman file would need to change to recognize the "o=+600kHz" and add or subtract that value from frequency_a.

Notably, in amateur radio terminology the "listen" frequency is the frequency that the repeater transmits on (and the users listen to), not the input (receive) frequency to the repeater, so probably "L=" is not the best choice to indicate the input frequency. If "o=" is too much trouble to support, consider changing the "L=" to perhaps "i=" to indicate the input frequency.

Here's more information on repeater offsets on this web page: https://www.hamradioschool.com/post/repeater-offsets-in-2-meter-band-t2a01