[Elecraft] KX3 Transmit EQ Settings

[Jim Brown]

On Wed,11/9/2016 9:21 PM, Walter Underwood wrote:
> That “ideal curve” assumes an LC receive filter with a roll off on the high (and low) frequencies. That peak is a pre-emphasis on the high end to correct for the receive filters. Modern crystal filters and FIR filters don’t have that roll off, so it is not needed.

That's not true. There's nothing magic about "modern" filters -- filters 
implemented in DSP emulate filters made with physical components. ANY 
filter has skirts that we think of as only amplitude, but they also have 
phase response. Can't have one without the other. It's just that DSP 
filters can be made far more complex, so they can emulate physical 
filters that would be FAR too complex to actually build, so amplitude 
and phase response can be improved.

For ALL communications circuits where speech intelligibility is the 
primary goal, octave-band TXEQ should have the 60, 120, 240 Hz bands set 
for maximum cut, the 500 Hz band set by ear for something like 6-12 dB 
cut, the bands around 2.5-3.5 kHz should be set for 3-6 dB of peaking, 
and all other bands should be set "flat" -- that is, to 0 dB. In 
general, using "boost" EQ more than about 6 dB is a bad idea, because it 
tends to use up headroom and make it more likely that the signal path 
will clip on peaks.

In Elecraft rigs, the IF filters are in DSP. The only crystal filters 
are roofing filters, and they have that name because they protect the 
DSP filters from overload by strong signals near, but outside, the DSP 
filter's passband.
> Maybe it works for your own voice and that’s great. But it is a choice, not a standard setting.

Yes. The settings I've listed are for a generic "flat" microphone, 
without a "tailored" response. Some ham mics, including some Heil and 
Shure models, have a peak around 3 kHz, and these mics should NOT be 
used with an additional 3 kHz peak in TXEQ.

BTW -- Bob Heil did NOT invent that concept. Shure was doing it in the 
earliest days of SSB (the '50s), and the D104 is a pretty old mic too. 
And the other great US mic company in those days was Electro-Voice, 
which was led by Al Kahn, K4FW, who later started Ten Tec when his 
partner, Lou Burroughs, wanted to sell the company and retire. Al was a 
CW man -- I don't know if they ever did any ham mics. :)  But they OWNED 
the market for broadcast mics, and to some extent still do -- their RE20 
is THE prestigious talk show and DJ mic, and their 635 and DO54 were 
wildly popular for reporters in the field.

73, Jim K9YC