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Chapter 1

 

Chapter 1:  Ordering Your K3

 

1.1    Ordering Your New K3

Before ordering your new Elecraft K3, you must decide on the options you need or want initially. Fortunately, you can start with a very basic K3 and easily add options at any time. These include

·            the array of roofing filters for the Main and Sub receivers,

·            whether or not you choose a Sub receiver (KRX3),

·            the power output (KPA3),

·            an automatic antenna tuner (KAT3),

·            digital voice recorder (KDVR3),

·            general coverage receiver filters (KBPF3),

·            transverter, receive antenna interface, and connection to the receiver’s intermediate frequency (IF) (KXV3A[1]),

·            and high-stability temperature compensated crystal oscillator (KTCXO3).

If you're on a tight budget, or not sure what you need, consider buying a radio with fewer options and then adding what you need later. An important exception is if you're going to buy the Sub receiver. It is a very tight fit, and, once it's installed, you must remove it to add even the simplest of options (like roofing filters), then re-install it. So if you're buying a Sub receiver, try to buy everything you want the first time. A good way to go might be to buy the basic radio without the Sub receiver, use it long enough to learn what options you might want to add, and then add those options and the Sub-Receiver. The bottom line – try to make the Sub receiver the last thing you add.

1.1.1    Factory Assembled or Kit?

. . .

1.1.2    K3 Roofing Filters

A question all K3 buyers must answer is "What filters should I purchase with my K3?" A search of the Elecraft email reflector gives many comments and lots of advice for the prospective K3 owner. The filters you choose depend on the kind of operating you are doing and how you would like the K3 to perform. Chapter 5 covers the operation of the K3's roofing filters more fully, but here is a brief explanation to help you with your purchase.

Figure 1‑1 shows a basic diagram for the K3 receiver. RF signals from the antenna pass through one of a set of bandpass filters designed for each of our operating bands. After some amplification they are converted to the first IF (intermediate frequency) where they are filtered by the roofing filter. The next frequency conversion is to the second IF where the received signals are converted to digital form by the analog-to-digital converter and then processed by the digital signal processing to become the audio to which you listen.

 


Figure 11.  Basic receiver block diagram.

 

 

Figure 1‑2 illustrates how the roofing filter works. You must have at least one in your K3, and the basic K3 includes the KFLA3A-2.7K, 5-pole, 2.7 kHz filter. Consider signals falling out of the sky onto the receiver front end. In the K3, signals from your antenna pass through the bandpass filter tuned for the present band and then are converted to the 8.215 MHz first IF. The first IF electronics have been carefully designed to provide a wide dynamic range to be able to cope with both weak and strong signals, but there is a limit to the RF energy succeeding electronic stages can handle. The crystal roofing filter limits the total RF energy sent to the following mixer and digital signal processing stages by blocking signals outside its pass band. Thus, a narrower band of frequencies has to be processed by the electronics in the digital signal processing filter, which finally establishes the listening bandwidth. The beauty of this system is that if you operate in a noisy environment, or one with many signals, such as in a contest, you can protect the electronics from becoming overloaded and thus greatly improve receiver performance.

 

Figure 12.  The K3's roofing and DSP filters.


 

 

1.1.3    Choosing your Filters

. . .

 

Table 11.  CW and DATA roofing filters.

CW Filters

Filter

-6 dB BW

-60 dB BW

Shape

Factor[2]

Model

$

Typical Use

200 Hz,

5-pole

 

 

 

KFLA3A-200[3]

$90

Very narrowband to reduce adjacent channel noise. Useful for CW and for PSK-31.

250 Hz,

8-pole

370 Hz

785 Hz

2.1

KFLA3A-250

$131

Very similar to the 5-pole 200 Hz filter; may be better for FSK data modes in noisy conditions; also useful for CW.

250 Hz,

8-pole

370 Hz

785 Hz

2.1

Inrad #708[4]

$136

"

400 Hz,

8-pole

435 Hz

935 Hz

2.1

KFLA3A-400

$131

General purpose, all around filter for CW and FSK modes.

400 Hz,

8-pole

450 Hz

950 Hz

2.1

Inrad #701

$136

"

500 Hz,

5-pole

 

 

 

KFLA3A-500

$90

"

500 Hz,

8-pole

 

 

 

Inrad #728

$136

"

1 kHz,

8-pole

1.063 kHz

1.650 kHz

1.6

KFLA3A-1.0K

$131

Useful CW filter for uncrowded band conditions.

1.0 kHz,

8-pole

1.063 kHz

1.650 kHz

1.6

Inrad #718

$136

 

 

Table 12.  SSB roofing filters.

SSB Filters

Filter

6 dB BW

60 dB BW

Shape

Factor

Model

$

Typical Use

1.5 kHz,

8-pole

 

 

 

Inrad #727

$136

SSB; useful for crowded band conditions to block nearby strong stations, although may be too narrow for rapid and easy tuning.

1.8 kHz,

8-pole

1.913 kHz

2.863 kHz

1.5

KFLA3A-1.8K

$131

SSB; useful for crowded band conditions to block nearby strong stations; should perform nearly as well as the 1.5 kHz filter.

1.8 kHz,

8-pole

1.838 kHz

2.850 kHz

1.6

Inrad #711

$136

"

2.1 kHz,

8-pole

2.175 kHz

3.213 kHz

1.5

KFLA3A-2.1K

$131

Being slightly wider than the 1.8 kHz filter delivers better quality SSB audio.

2.1 kHz,

8-pole

2.175 kHz

3.213 kHz

1.5

Inrad #709

$136

"

2.7 kHz,

5-pole,

 

 

 

KFLA3A-2.7K

 

Standard with the K3.

2.8 kHz,

8-pole

2.888 kHz

4.488 kHz

1.6

KFLA3A-2.8K

$131

You can replace the standard KFLA3A 2.7 kHz, 5-pole filter with this filter when you order your K3 and KRX3 for $121.

2.8 kHz, 8-pole

2.888 kHz

4.488 kHz

1.6

Inrad #716

$136

 

6 kHz,

8-pole

6.125 kHz

9.350 kHz

1.5

KFLA3A-6K

$131

Required for AM/ESSB.

6 kHz, 8-pole

6.250 kHz

9.600 kHz

1.5

Inrad #710

$136

"

13 kHz

 

 

 

KFL3B-FM

$131

Required for FM.

13 kHz, 8-pole

 

 

 

Inrad #725

$136

"

 

 

 

 

KBPF3

$140

General coverage receiver filter for shortwave listening outside the ham bands.

 

 

Exercise

I am a CW operator and only occasionally operate SSB. I enjoy CW contesting and frequently operate in crowded band conditions. What roofing filters should I consider?

· · · 

For occasional SSB operation, the standard 2.7 kHz filter with DSP control would be sufficient. For CW contesting, at least the 400 Hz and possibly the 200 or 250 Hz filter should be added.

 

Exercise

I never operate CW or any of the digital modes but I do enjoy SSB contests. What roofing filters should I consider?

· · · 

The standard 2.7 kHz or 2.8 kHz filter is the place to start, and one of these is required. For contest operations, the 2.1 kHz and/or 1.8 kHz filters should be added.

 

Exercise

I operate SSB on all bands and FM on 10 and 6 meters. What roofing filters should I consider?

· · · 

As a minimum, choose the standard 2.7 kHz or 2.8 kHz filter, and the 13 kHz FM filter.

 

Exercise

I operate a lot of RTTY and other digital modes. What roofing filters should I consider?

· · · 

The normal RTTY frequency shift is 170 Hz,  The 250 Hz filter, which is really more like 330 Hz, is the best choice for RTTY and other digital modes, although some external software for PSK-31 often provides a waterfall display and so the 2.8 kHz or 2.7 kHz filter would be used then.

1.1.4    KAT3 100-W Antenna Tuner

. . .

1.1.5    KPA3 100-W Power Amplifier

. . .

1.1.6    KDRV3 Digital Voice Recorder

. . .

1.1.7    KBPF3 General Coverage Receiver Filter

. . .

1.1.8    KXV3A Receive

. . .

1.1.9    KTCXO3-1 High-Stability Temperature Compensated Crystal Oscillator

. . .

1.1.10 PR6 Six Meter Preamplifier

. . .

1.1.11 P3 Panadapter

. . .

1.1.12 K144XV

. . .

1.2    Key to Symbols and Text Style

. . .

1.3    Glossary and Definitions

. . .

1.4    More Information

. . .