I generally agree with Joe's advice, but will differ here. Joe is right
that full bandwidth (with the 2.7 or 2.8 kHz filter) is 2.8 kHz, but
optimum spectrum for speech intelligibility with this bandwidth limit is
400 Hz to 3.2 kHz. This is fundamental stuff -- Bell Labs, probably the
premier engineering institution on the planet back then, figured it out
at least 100 years ago, and lots of research in the years since has
confirmed it.
I own 1.8 kHz roofing filters, but find them too narrow for my
ear-brain. We're all different, so YMMV. I have a 2.1 kHz filter in one
of my K3s, and like it. I rarely set my IF narrower than 2 kHz for SSB.
As Joe has noted, RXEQ can be adjusted to tilt the response a bit. If
like many of us old guys you have much hearing loss, you might want to
boost the top octave band in RXEQ by 3 dB.
There are two other issues at play here. First, the K3 has a pretty good
but pretty small speaker. Second, chief engineer Wayne Burdick has
strong roots in backpacking, so his audio stages tend to be a bit
current starved.
73, Jim K9YC
On 10/18/2017 5:31 PM, Joe Subich, W4TV wrote:
> Is there some adjustment I’m missing?
Try adjusting the center frequency (shift) or decreasing the Low Cut
(FL) and High Cut (FH) by similar amounts. In general, the important
spectrum for speech is 400 - 2200 Hz while simply "dialing down" the
width causes the Low Cut to raise too quickly.
The K3/K3S nominal 2.8 KHz bandwidth is set at 100 - 2900 (FC = 1500).
Simply dialing the width down to 1.8 KHz results in a passband of
600 - 2400 Hz (FC remains 1500 Hz). Adjusting FC down to 1250 or 1300
Hz will greatly improve the "clarity" of SSB.
In addition, the K3 has a flat audio response while most rigs have a
slight raising characteristic (about 3 dB/octave). You can emulate
that response using the RX EQ. Set 0.05 = -16, 0.10= -16, 0.20= -6,
0.40= 0, 0.80= +3, 1.60= +6, 2.40= +8, 3.20= +9 and the audio will
emulate "other rigs". You can also set 3.20 to -6 to minimize high
frequency noise.
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