Rick,
The Hi-Cut and Lo-Cut do essentially the same thing as Width and Shift,
but they make voice signals easier to deal with.
If you have played with Width and Shift on the K3 or other transceivers,
you will know that anytime you change the width control, you have to
also change the shift control to maintain intelligibility for the
received voice signal.
The main reason is that you must have some audio content in the 300 to
500 Hz range to have intelligibility in the human speech range. So if
you have your Width set at 2.7kHz and the Shift set at 1500 Hz, you will
be receiving 300 to 3000 Hz. Now move the width to 2.1kHz and the
passband changes to 600 to 2700 Hz, and you have lost much of the low
frequency content of the signal - changing the Shift control to a lower
frequency will recover that 300 to 500 Hz segment of the audio spectrum
that is essential to communications fidelity.
OK, the Hi-Cut and LoCut controls work in a similar manner as the Width
and Shift. HiCut reduces the high frequency content in the received
signal while not changing the low frequency end. That is ideal for
voice communications where the 300 to 500 Hz content must be preserved
for good intelligibility. Try an experiment - set LoCut at 300 Hz and
then tune in an SSB signal. Reduce HiCut until you can no longer
understand the vocal content. If my guess is correct, you will still be
able to understand the voice content when HiCut is at 1500 Hz (that is a
width of 1200 Hz).
Now try the same thing using Width and Shift - it will likely be
cumbersome to adjust both the Shift and Width to accomplish the same
1200 Hz width while keeping the 300 to 500 Hz content active with the
shift control.
So the result is to use Width and Shift for CW where the center
frequency is well defined, but on SSB (or other voice modes) the use of
HiCut and LoCut makes things a lot easier - set LoCut somewhere between
200 and 400 Hz and leave it there - HiCut can be reduced to remove high
audio frequency 'garbage' as desired. If you run into interfering
signals on the low audio frequency range, there is not much you can do
about it without reducing signal intelligibility (time to QSY).
73,
Don W3FPR
On 11/27/2012 5:16 PM, Rick Stealey wrote:
I'm confused as to the function of the receive equalization vs the width vs the
hi
and low cut.
Example - The traditional SSB filter is, say, a 2.7 KHz wide filter with the
bfo carrier 300 hz from one side of the filter passband. This provides audio
response
of 300 hz to (300+ 2700) = 3000 Hz.
So I can set my K3 to 2700 bandwidth and adjust the SHIFT control to give the
same response as above. But in addition I can adjust the 8 band receive EQ to
roll
off or peak this spectrum, right? I assume this filtering is at audio, after
the detector.
Then what are the hi cut and low cut front panel controls for? What do they
control?
Rick K2XT
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