When the radio is cold, and you try to use the sideband, it will be off frequency.....you can tune it on frequency but as it warms up then you'll again be off frequency. You'll have to keep adjusting the clarifier. Some do not like that.
Not all sideband radios are like this....some are very stable on SSB regardless of how hot or cold it is. But Galaxy is not one of them.
Where Galaxys shine, is on AM and for those who like looking at a pretty starlight face with a big meter.
Galaxy radios are also known for cold solder joints which can play havoc on the radio depending on how hot or cold it is and how much bouncing around the truck does.
Well there is a reference crystal in the radio, when the temp of this crystal changes so does its output frequency. So when the base frequency that is multiplied by to the operating frequency, so does the operating frequency.
When Galaxay 99's transmit they generate a lot of heat, which warms the crystal which changes the frequency.
Again to repeat my point these radios are made poorly to begin with.
The odd thing is about the frequency tolerance of the crystals in these radios is I've never heard this anywhere but in export radios. I am thinking that they are using very cheap 1000PPM tolerance crystals and not a good design to compensate for the temperature swing.