Everything You Ever Wanted To Know About the JRC NRD 545
User setup number 32 is called "Digital IF Filter Attenuation Slope". The default setting,
0 is the "sharp" filter. The alternate setting, 1 is "loose". These settings affect the
rolloff of audio outside the passband, with faster rolloff in the sharp setting of course.
(But Were Afraid To Ask)
There is no apparent change in filtering in AM, AMS, FM, or FMW modes.
4.50 kHz Loose:
4.50 kHz Sharp:
2.70 kHz Loose:
2.70 kHz Sharp:
1.80 kHz Loose:
1.80 kHz Sharp:
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.