DRAKE SW 1 Bedienerhandbuch PDF herunterladen (Seite 8)

78 October 1997

elsewhere in reality. Connecting a resonant

antenna reduced this effect significantly. Us-

ing an antenna tuner might also help.

We found the

RF GAIN

and

VOLUME

knobs a bit wobbly. Also, the

RF GAIN

con-

trol did not seem to have the expected effect.

It appeared to be more of an attenuator than

an actual RF gain control.

Manufacturer: R. L. Drake Co, 230 In-

dustrial Dr, Franklin, OH 45005; tel 513-

746-4556; fax 513-743-4510. Manufac-

turer’s suggested retail price, $299.

Radio Shack DX-394

This is Tandy’s top-of-the-line general-

coverage receiver, the latest of its type in

Radio Shack’s consumer electronics lineup.

Since it debuted on the market, the DX-394

has gone through two updates, identified by

an A or B suffix after the model number on the

back panel. When we purchased our DX-394,

our local Radio Shack store still had A-suffix

models in stock, and that’s what we tested.

The A-suffix units include decreased gain of

the second mixer, extended AGC release time,

and modified audio compensation for SSB.

The DX-394 touts lots of features, espe-

cially considering its price class: continuous

coverage from 150 kHz to 30 MHz; AM,

SSB, and CW modes; 160 frequency memo-

ries; digital readout; dual clocks; a mike-

level tape-recorder output; search and scan;

and direct frequency entry from its front-

panel keypad.

This is a compact set in a charcoal-gray

plastic cabinet with two fold-down front legs.

It features a large LCD display, five front-

panel controls, plus a bunch of push but-

tons—including a keypad. Like the SW1, this

set is a dual-conversion superhet (the IFs also

are 45 MHz and 455 kHz) with PLL synthe-

sized tuning. You can dim the green-back-

ground display but you won’t want to. The

DX-394 has a built-in power supply, so you

can plug it right into the wall outlet. It also

can run off 13.8 V dc, and it has a little built-

in telescoping whip antenna on top of the

case, making it fairly portable.

Front-panel push buttons let you jump

immediately to any of the international

shortwave broadcasting bands—from 120 to

11 meters (the 11-meter BC band is right

below the 11-meter Citizens Band). The dis-

play clearly shows which BC band you’re

listening to (ie, 41 m, 19 m). There’s a front-

panel mini-jack for headphones.

You can set the tuning step size (100 Hz,

1 kHz, 5 kHz or 10 kHz) using two front-

panel

STEP

keys, and it displays the selec-

tion on the front panel (9-kHz AM channel

spacing used in some parts of the world is

available as a power-up option). Program-

mable timers let you store frequencies and

on/off times. The front panel also includes a

digital replication of an analog S meter. AGC

is not adjustable.

Using the manual tuning knob can be a

little squirrelly, since the actual tuning rate

varies with the speed with which the knob is

spun (something the Owner’s Manual did not

explain). Tune very slowly and carefully, and

it covers approximately 2.5 kHz per rotation

when you’re set to the smallest tuning step

(100 Hz). Spin it very rapidly and you’ll

move up or down 15 or 20 kHz or more in

short order. A continuous-tuning

FINE TUNE

control gives you somewhat greater control,

covering approximately 2 kHz per rotation,

independent of step size.

The rear panel includes connections for a

high- or low-impedance antenna, an exten-

sion speaker, tape out, and external dc power.

It also has a recessed button to perform a hard

microprocessor reset. The set also has a rear-

panel 20-dB

ATT

enuator switch, which we

left on when the set was connected to an ex-

ternal antenna; it engages a passive attenua-

tor. Hooking it up to an external antenna is

neither necessary nor especially desirable,

except that an external antenna might be less

prone to pick up household interference. The

noise blanker was not very effective in reduc-

ing interference from an oil-burner igniter.

The DX-394 is ultra-simple to use. Just

plug it in, extend the little antenna on top, turn

it on, set the

MODE

switch,

VOLUME

and

GAIN

controls and tune away. The DX-394

gives you several ways to tune in stations. You

can manually tune them in using the main

tuning knob, reading the frequency right off

the display. Manual tuning was accompanied

by synthesizer “chuffing” typical of inexpen-

sive sets like this. You also can directly enter

a frequency via the keypad on the front panel.

Or you can use the unlabeled arrow keys. In

addition, the radio’s search mode will auto-

matically look for the next strong signal, al-

though you probably will want to first turn

down the

RF GAIN

control, as the Owner’s

Manual suggests. Otherwise, the radio might

mistake whatever noise it’s hearing for a sig-

nal and not start searching.

Among the best features of the DX-394 is

its memory system. It’s very easy to store a

frequency (and only a frequency) in one of the

memories. The DX-394 sets aside 10 memo-

ries for each of the bands (LW, MW and SW),

plus 10 apiece in each of the “meter” bands,

Table 2

Drake SW1, serial number 6H12910064

Manufacturer’s Specifications Measured in ARRL Lab

Frequency coverage: 100 kHz-30 MHz. As specified

Modes of operation: AM. As specified.

Power requirements: 120 V ac; 12 V dc at 400 mA. As specified.

Size (HWD): 4.4×10.9×7.6 in; weight, 4.7 lb.

Sensitivity (bandwidth not specified): AM, test signal modulated 30% with

2.0 µV or less (typical). a 1-kHz tone. 10 dB (S+N)/N:

100 kHz, 10.5 µV; otherwise,

as specified.

Blocking dynamic range: Not specified. 14 MHz, 87 dB (noise-limited) at

100-kHz spacing.

Two-tone, third-order IMD dynamic range: 14 MHz, 72 dB (noise-limited) at

Not specified. 100-kHz spacing.

First IF rejection: Not specified. 58 dB.

First IF image rejection: Not specified. 67 dB.

IF/audio response: Not specified. Bandwidth at −6 dB points: 4500 Hz.

Audio power output: Not specified. 245 mW @ 10% THD into 8 Ω.

NOTE: All dynamic range measurements were taken at 100 kHz, instead of at the ARRL

Lab standard of 20 kHz.

sized SW1 does exhibit some “synthesizer

chuffing” when tuning manually, but getting

where you want to go is extremely simple via

the

TUNING

knob, up/down buttons or direct

entry. A nice feature was the automatic fre-

quency entry. Punch in a frequency and the

SW1 will automatically enter the frequency

(after a slight pause if the frequency has fewer

than five digits)—or you can just press the

ENTER

key if you’re in a hurry.

It’s also very easy to save stations to

memories—too easy, in fact, because the

SW1 does not warn you that you’re overwrit-

ing a given memory channel—but we some-

times found ourselves wishing for a few more

memories. You could quickly fill up all 32 in

a single sitting on the broadcast or shortwave

bands. An 11-page Owner’s Manual comes

with the SW1, but the radio is quite intuitive.

We had the whole thing figured out even

before we looked at the book—including how

to program the memories.

The sound from the SW1 was pretty as-

tounding for such a little set, although it de-

livers less than 1 W to the speaker. The audio

had a nice rich balance especially suited for

AM broadcasts, but AM operators on the ham

bands sounded terrific on the SW1, too. On

the AM broadcast band, the 5-kHz steps on

the SW1’s up/down keys made tuning across

the standard 10-kHz channels very conve-

nient, yet you still could listen for those sta-

tions in other countries that are sandwiched in

between our 10-kHz channels. With a fairly

large antenna attached, the receiver did a cred-

itable job of separating the AM channels and

keeping splatter or adjacent-channel spillover

to a minimum, even in the neighborhood of

strong local stations. On shortwave, there was

an undercurrent of noise that likely was the

result of various mixing products developed

in the receiver and just plain poor dynamic

range (see Table 2). For example, even in the

vicinity of 29 MHz—relatively quiet at this

point in the solar cycle—we could detect vari-

ous shortwave broadcasting signals that were

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