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There is no apparent change in filtering in AM, AMS, FM, or FMW modes.

USB Mode:

4.50 kHz Loose:

4.50 kHz Sharp:

2.70 kHz Loose:

2.70 kHz Sharp:

1.80 kHz Loose:

1.80 kHz Sharp:

RTTY Mode:

1.00 kHz Loose:

1.00 kHz Sharp:

But what does it sound like? Here are two tests, one with a bandwidth of 1.80 kHz, the other with a 2.70 kHz bandwidth, both in USB mode. Each test starts in with the loose setting, then changes to the sharp setting about half way through. I am sure you can tell when the change takes place.

1.80 kHz USB Mode

2.70 kHz USB Mode

My observations: For the 1.80 kHz test, the audio sounds much worse with the sharp setting. For the 2.70 kHz test, they sound very close to the same, perhaps even slightly better in the sharp setting. But one thing that makes it difficult to tell is that for the 2.70 kHz case, the volume is much louder with the sharp setting. There is no apparent volume change in the 1.80 kHz case.

I do not believe there is "one correct setting" for loose vs sharp. It all depends on what you are trying to listen to, and the conditions. One of the advantages of the 545 over most other radios is the fact that you can change so many settings, and you have a lot of control over filter characteristics. Remember that most non DSP radios give you two or three IF filers to choose from, that's it! Don't be afraid to play around with the settings, and see what works best for you, for certain stations, under certain conditions.