I would guess if you called the CG you would find out that they don't feel it is their responsibility to make sure your radio works. Otherwise all they would do is radio checks all day long, especially in busy areas. If they answered every radio check that asked for position to check how well equipment worked, that would also be a very easy way for drug smugglers, etc. to keep track of the CG vessels. The reality is also that hand-held marine band radios are notoriously ineffective for range.