ELECRAFT KPA3 Dokumentacja Pobierz pdf (Strona 7)

From January 2009 QST © ARRL

directly into rear connectors without the

need of a special cable adapter. The K3 also

includes a true RF compressor with a front

panel control that works quite smoothly.

Digital Features

The K3 is very much a digital friendly trans-

ceiver. We mentioned the LINE IN connector

earlier, and there is also a LINE OUT connector.

Both directions provide transformer isolated

connectivity and have levels adjustable inde-

pendently of those set for voice modes. The

RS-232 computer serial connection can be set

up to accept PTT (or CW keying) directly from

the RTS or DTR control lines without need for

an interface adapter. With these connections,

sound card modes require only a pair of

⁄8 inch

phone cables and a serial connection. A USB

adapter is available from Elecraft if your PC

doesn’t have a serial port.

Special DSP filter settings enhance RTTY

or other frequency shift keying mode (FSK)

operation. Narrow filter bandwidths can be

established separately for the mark and space

frequencies, eliminating potential interfer-

ence from signals in between the two. This

also improves reception signal-to-noise ratio

by reducing the noise bandwidth, compared

to the usual filter that passes both tones and

all that is between them.

AM and FM Features

The K3 provides for these modes as well.

AM reception is reasonable using the basic

How does the Elecraft K3 perform as a contest radio?

To find out, I used a K3 in two major contests in 2008: CQ

Worldwide WPX CW at the end of May and the IARU HF

World Championships in July. In WPX, I used the K3 as the

primary run radio in my SO2R (single operator, two radio)

contest station. In IARU, I used the K3 mostly for searching

and pouncing (S&P) for contacts on other bands while CQ-

ing with another radio on the main band. I also tested the

K3’s diversity reception capability in IARU, using the newly-

released KRX3 subreceiver module.

Results in both contests were outstanding. As a run radio,

the K3’s receiver is the best I’ve used to date. The adjust-

able AGC action was smooth and allowed me to distinguish

between signals of different strengths in pileups. Thanks to

the K3’s 500 Hz and 200 Hz roofing filters, the AGC wasn’t

overwhelmed by the many strong signals up and down the

band, and there was no hint of IMD. The DSP selectivity was

useful down to 100 Hz without significant ringing. The ability

to store and retrieve passband settings, as well as return to a

baseline “normal” passband setting, was useful after making

changes to avoid temporary interference or to work stations

on the edge of the passband.

The K3’s DUAL PASSBAND feature establishes a narrow

passband inside a wider, attenuated passband. This lets you

hear stations outside the narrow passband, but without be-

ing distracted by strong adjacent stations. In practice, I found

the outer passband to be too wide for practical use on very

crowded bands — adjacent stations were just too loud. How-

ever, the DUAL PASSBAND feature has recently been enhanced

by Elecraft. Among other improvements, the outer bandwidth

can be adjusted. This is one of the best reasons to own a K3

— firmware updates over the Internet can address problems

and implement new features requested by customers.

Other rigs I’ve tried suffer from various shortcomings,

including signals slipping under the filter skirts, filter ringing,

AGC pumping, and inability to sort out calls in a pileup be-

cause of poor AGC action, IMD and too much circuit noise.

The K3 doesn’t suffer from these problems.

Diversity Reception

In IARU, I was able to evaluate the K3’s unique diversity

reception capabilities. Diversity reception allows you to listen

to two different antennas at the same time, one on the main

receiver and the other on the subreceiver. By using antennas

with different properties, such as horizontal or vertical polar-

ization or different peak arrival angles, the combined effect

can overcome selective fading and other propagation varia-

tions more effectively than a single antenna or even a stack

of antennas at different heights. In addition, you can use

diversity reception to listen to multiple directions at the same

time without splitting transmit power.

The key to diversity reception is to use two identical re-

ceivers with their VFOs locked together. Many transceivers

offer a full-featured main receiver and a subreceiver with

reduced performance and capabilities, and most lack the

ability to lock the VFOs. The K3 is the only transceiver on the

market that offers two identical high-performance receivers

with VFOs that can be locked. In addition, each receiver can

accommodate up to five crystal roofing filters. Although some

interesting effects can be created by using different filters for

The Elecraft K3 as a Contest Radio

2.7 kHz roofing filter and tuning on one side

or the other as if it were SSB. If you are

serious about AM, though, you’ll want the

optional 6 kHz filter. It’s also required in order

to transmit AM. If you also have the 13 kHz

wide FM filter, it can also be used for higher

fidelity AM reception, but transmit is limited

to using the 6 kHz filter. For shortwave lis-

tening, you’ll also want the KBPF3 general

coverage receive band-pass filter module.

FM operation requires the optional FM

bandwidth roofing filter. If FM is enabled, the

K3 can be set for default repeater split options

on a band by band basis. Channels can be set

into memory, including CTCSS access tones.

I didn’t have an opportunity to try FM in my

K3, but it might be of interest to those with

local 6 or 10 meter repeaters.

Transverter Features

The K3 works best as a transverter

driver if the accessory KXV3 connection

panel is added. This unit not only provides

dedicated input and output connections for

a transverter, but also a port for a separate

receive-only antenna and a buffered IF output

for panadapter or other use.

We ran into an issue with our early pro-

duction KXV3 when a reviewer attempted

to use the radio with a separate receive an-

tenna located close to the transmit antenna.

Isolation in the KXV3 was insufficient to

prevent transmit RF from entering the K3

through the receive antenna port. Other users

reported this on the Elecraft e-mail list, and

it was promptly fixed in production in late

February 2008. There’s a modification kit

for those who have earlier units — see the

Elecraft Web site.

Not surprisingly, since Elecraft offers a

line of transverters, they have included all

the features needed for seamless transverter

operation. All you need to do is tell the con-

figuration menu that you have a transverter,

what frequency (band bottom) it’s for, what

IF frequency you want (10 and 6 meters are

the most common, but you can select another

band if you need to), the maximum power

level you want to send to it, any frequency

calibration error in the transceiver and then

the correct transverter frequency shows up

as you advance the BAND button, just as

if it were built in! The K3 supports up to

nine transverters, each with potentially a

separate IF range and power level. If you

use Elecraft transverters, a special interface

connector makes sure the correct transverter

is engaged.

One Hardware Failure

The K3 has worked as advertised, or very

closely, but we did have a failure during test-

ing. Following extensive audio output testing,

the speaker output completely disappeared.

Fortunately, the front and rear headphone

outputs continued to operate so the dynamic

testing could continue. The speaker output

amplifier ICs are on a DSP sub-board that was

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