Specifications

From January 2005 QST © ARRL
Table 1
Elecraft KAT100 Automatic Antenna Tuner
Manufacturer’s Specifications Measured in ARRL Lab
See below.
Not tested.
SWR range matched: Up to 10:1 typ (varies with band,
smaller range on lowest bands).
Tuning time: 1-5 seconds typical for initial tune-up,
<
1
/2 second to recall stored settings.
SWR display: 1.0:1 to 9.9:1 (on K2 LCD); 1:1 to 5:1 on
10 front panel LEDs.
Current drain: 200-300 mA typical, 700 mA max.
Enclosure size: 1.3
× 7.8 × 8.3 inches (HWD).
Weight: 3 pounds (approx).
SWR Load ( Ω ) Band: 160 80 40 20 10
Input SWR No match No match 1.8:1 1.6:1 1:1
16:1 3.125 SWR BW % Note 1 Note 1 Note 1 Note 1 6
Power Loss % Note 2 Note 2 Note 2 40 <10
Input SWR 3.0:1 1:1 1:1 1.4:1 1:1
8:1 6.25 SWR BW % Note 1 20 15 Note 3 11
Power Loss % Note 2 <10 20 35 12
Input SWR 1:1 1:1 1:1 1.1:1 1.1:1
4:1 12.5 SWR BW % >20
3
31 25 28 28
Power Loss % <10 <10 10 20 15
Input SWR 1:1 1:1 1:1 1:1 1:1
2:1 25 SWR BW % >33
4
63 60 70 79
Power Loss % <10 <10 <10 12 <10
Input SWR 1:1 1:1 1:1 1:1 1:1
1:1 50 SWR BW % >100 >100 >100 >100 >100
Power Loss % <10 10 <10 <10 14
Input SWR 1.2:1 1.2:1 1.1:1 1:1 1:1
2:1 100 SWR BW % 100 94 47 27 16
Power Loss % <10 <10 10 <10 24
Input SWR 1:1 1:1 1:1 1:1 1:1
4:1 200 SWR BW % 28 29 28 26 16
Power Loss % <10 <10 <10 <10 22
Input SWR 1:1 1:1 1:1 1:1 1:1
8:1 400 SWR BW % 17 17 11 16 8
Power Loss % 19 18 16 <10 25
Input SWR 1:1 1.1:1 1:1 1:1 1:1
16:1 800 SWR BW % 11 11 11 9 6
Power Loss % 13 20 20 25 30
Notes
1
The span of frequencies between which the SWR is 1.5:1 or less could not be determined
because the minimum SWR was not better than 1.5:1 in this band.
2
A reasonable match must first be obtained in order to measure loss.
3
1.5:1 SWR BW could not be measured in this case due to difference in SWR measured by
external means and SWR as reported by the K2.
4
SWR was below 1.5:1 at the lower frequency limit, so the exact 1.5:1 SWR bandwidth could
not be measured.
end of every Morse element. A growing
consensus seems to be that a key-up wave
shape that more closely matches the
slightly rounded key-down characteristic
is more desirable.
This modification requires main
controller firmware revision 2.04H or
later and I/O controller firmware version
1.09 or later. You can check the firmware
version of your K2 by holding any front-
panel button while turning on the radio.
The display will show the firmware
revisions.
The keying bandwidth mod involves
cutting a trace on the control board,
replacing one diode with a resistor and
replacing a resistor and a capacitor. It also
involves adding a monolithic ceramic
capacitor and an electrolytic capacitor on
the bottom of the control board. One
diode on the bottom of the RF board must
be replaced by a PIN diode.
As expected, the instructions clearly
explain the steps involved, and a pair of
illustrations help you find the appropriate
locations for the control board changes.
The whole process took me about a half
hour. I brought my K2 into the ARRL Lab
and asked Michael Tracy, KC1SX, to
measure the new keying waveform. Figure
5 shows the results, which matched the
sample shown in the modification
Instructions.
KDSP2 Audio DSP Filter
This kit includes one small bare circuit
board to be “stuffed” and another small
circuit board that is already built, including
the DSP processor. The first board will
plug into the right side of the K2 control
board. If you already have the KAF2 audio
filter installed, the KDSP2 module will
replace it. If your radio does not have the
audio filter, you will have to make a couple
of small modifications to the K2 control
board to accept the KDSP2 board.
Building the DSP board was pretty
easy. There were no toroids to wind or
trimmers to tweak. In fact, the most
difficult part of the assembly was bending
the leads on the monolithic ceramic
capacitors to make them fit close to the
circuit board.
Before putting the top cover back on the
K2, the instructions called for me to turn
on the K2. All of the proper display items
came up as I went through the rest of the
initial checkout procedures.
Operating the KDSP2
The KDSP2 provides four audio filters
each for SSB and RTTY. In effect it
provides eight filters for CW because each
of the four filters have both a “normal” and
a “soft” filter setting. The soft selection
provides slightly less skirt selectivity than
the normal filter, but has a bit better
ultimate rejection outside the passband.
The soft filters may also have slightly less
ringing at the narrowest bandwidths.
The default filter settings seem to
provide a good set of choices for each
mode.
These filters are selected by pressing
the
AFIL button on the K2. If you have your
K2 crystal filters set to a center frequency
other than 600 Hz, you will have to adjust
the CW filter center frequencies. If you
would
prefer a different set of bandwidths
you can change those as well. Likewise, if
Figure 5—This is the modified CW keying
waveform for the K2/100, showing the
first two dits in full-break-in (QSK) mode.
Equivalent keying speed is 60 WPM. The
upper trace is the actual key closure; the
lower trace is the RF envelope. Horizontal
divisions are 10 ms. The transceiver
was being operated at 100 W output
on 14.2 MHz.