ELECRAFT K3 Specifications download pdf (Page 3)

From April 2008 QST © ARRL

Receiver Receiver Dynamic Testing

Second-order intercept: Not speciﬁed. Preamp off/on: +79/+79 dBm.

S-meter sensitivity: S9, 50 µV (adjustable). S9 signal at 14.2 MHz: preamp off,

50 µV; preamp on, 14 µV.

Audio output power: 2.5 W into 4 Ω at 2.8 W at 10% THD into 4 Ω.

10% THD.

IF/audio response: Not speciﬁed. Range at –6 dB points, (bandwidth):

CW (400 Hz): 455-840 Hz (385 Hz),

‡

Equivalent Rectangular BW: 364 Hz;

USB: 306-2827 Hz (2521 Hz);

LSB: 373-2898 Hz (2592 Hz);

AM: 202-2802 Hz (2600 Hz).

Spurious and image rejection: 70 dB. First IF rejection, 14 MHz, 98 dB;

50 MHz, 96 dB; image rejection,

14 MHz, 109 dB; 50 MHz, 71 dB.

Transmitter Transmitter Dynamic Testing

Power output: 1.8-14 MHz, 10 W; HF: CW, SSB, typically 12 W high,

18-54 MHz, 10 W (CW, FM), 8 W (SSB); <1 W low; 50 MHz: CW, SSB, typically

AM not speciﬁed. 8 W high, <1 W low.

Spurious and harmonic suppression: HF, 50 dB; VHF, 61 dB.

HF, 50 dB; VHF, 60 dB. Meets FCC requirements.

Third-order intermodulation distortion (IMD) 3rd/5th/7th/9th order (worst case band):

products: Not speciﬁed. (at 8 W) HF, –27/–40/–47/–53 dB PEP;

VHF, –28/–43/–47/–50 dB PEP.

CW keyer speed range: Not speciﬁed. 8 to 65 WPM.

CW keying characteristics: Not speciﬁed. See Figures 1 and 2.

Transmit-receive turnaround time (PTT release S9 signal, 22 ms (SYNC DATA mode).

to 50% audio output): Not speciﬁed. Unit is suitable for use on AMTOR.

Composite transmitted noise: Not speciﬁed. See Figure 3.

Size (height, width, depth): 4.0 × 10.7 × 11.8 inches; weight, 6 pounds (8.5 pounds for the

100 W version, all options installed, not including power supply or external accessories).

Price: K3/10 kit version, $1399.95 ($1599.95 assembled); KFL3A-6K 8-pole, 6 kHz rooﬁng

ﬁlter, $120; KFL3A-400 8-pole, 400 Hz kHz rooﬁng ﬁlter, $120.

*Reduced sensitivity around the 8.215 MHz IF. The optional KBPF3 bandpass ﬁlter is required

for full general coverage receive.

**FM and AM require optional IF ﬁlters.

†

The optional KFL3A-400 8-pole, 400 Hz rooﬁng ﬁlter was used for optimum performance.

The noise ﬁgure is approximately 1 dB less than the 500 Hz ﬁlter.

‡

Varies with pitch control setting.

250 Hz. The 6 kHz filter is required for AM

transmission. A wider 8 pole FM-bandwidth

filter was not yet available at press time.

Other 5 pole roofing filters are available for

500 Hz and 200 Hz.

There are five filter slots available on

the main RF board and another five can be

used on the forthcoming KRX3 subreceiver.

Once again, you don’t need a narrow roofing

filter to operate at narrow bandwidths (say

500 Hz) in CW or data modes — bandwidth

filtering is provided by the DSP. But install-

ing one will improve dynamic range at very

close signal spacings. Unless you plan to

use the radio in demanding environments

with lots of strong signals on adjacent fre-

quencies, you may not need anything more

than the stock 2.7 kHz unit. I’ve ordered the

6 kHz and FM bandwidth filters to be able

to operate AM and FM, but am not adding

any more for now.

The ARRL Lab added an 8 pole 400-Hz

roofing filter for testing. As shown in Table 1,

the results are impressive. Overall receiver

performance is right up there with the best

radios the Lab has ever measured, and this

is the first receiver we’ve tested with better

than 100 dB IMD dynamic range at the

closer signal spacings.

Bandwidth and Shift Filtering

DSP bandwidth and shift filtering are

coordinated automatically with whatever

suite of roofing filters is installed. There are

four kinds of filtering: bandwidth and shift

for CW and phone, dual passband for CW,

and dual-tone for RTTY.

The K3 DSP bandwidth filter can be ad-

justed as narrow as 50 Hz and it still sounds

fine without ringing — a remarkable accom-

plishment. A special dual passband filter

designed for CW combines a steep-skirted

narrow filter focused on the signal of interest

with a broad-skirted variable wide filter that

allows the operator to hear adjacent activity

as well at a lower volume.

Figure 2 — Worst-case spectral display

of the Elecraft K3/10 transmitter during

keying sideband testing. Equivalent

keying speed is 60 WPM using external

keying. Spectrum analyzer resolution

bandwidth is 10 Hz, and the sweep time

is 30 seconds. The transmitter was being

operated at 10 W PEP output at 14.2 MHz.

00.010.020.030.040.050.060.070.08

QS0804-PR01

1401514017 1401914021 140231402

-100

-80

-60

-40

-20

QS0804-PR02

-180

-160

-140

-120

-100

-80

-60

-40

-20

QS0804-PR03

Figure 1 — CW keying waveform for

the Elecraft K3/10 showing the ﬁrst two

dits in full-break-in (QSK) mode using

external keying. Equivalent keying speed

is 60 WPM. The upper trace is the actual

key closure; the lower trace is the RF

envelope. (Note that the ﬁrst key closure

starts at the left edge of the ﬁgure.)

Horizontal divisions are 10 ms. The

transceiver was being operated at 10 W

output on 14.2 MHz.

Figure 3 — Worst-case spectral display of

the Elecraft K3 transmitter output during

composite-noise testing. Power output

is 10 W at 14.2 MHz. The carrier, off the

left edge of the plot, is not shown. This

plot shows composite transmitted noise

100 Hz to 1 MHz from the carrier.

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ELECRAFT K3 Specifications Page 3

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