This radio has been made for Siemens by the Taiwanese Sangean company.
Sangean also sells the radio under its own brand name (the ATS 818CS) but
it doesn't have the factory pre-programmed stations in it. Radio Shack
have also launched a set called the DX-390 which is similar, except that
the cassette recorder mechanism is not included. As a result, a larger
speaker is used.
The Siemens RK-670 is designed as a table-top receiver. You can either
operate the set upright, which makes the buttons for the cassette recorder
easy to operate, or unclasp a stand on the rear of the set. This lets you
tilt the front panel at 45 degrees, making the radio operation much
easier. A total of seven batteries are needed. Three penlights are used to
run the clock and computer section of the radio. An additional four "D"
size cells are needed to power the radio itself. Power consumption at an
average listening volume is 80 mA. Switch on the cassette recorder and the
consumption rises to 150 mA.
If the radio is playing, and recording to the cassette at the same time,
power consumption is in the region of 200 mA. We obtained a battery of
life of just 4 hours with cassette and radio playing simultaneously,
before the four alkaline "D" cells needed replacing. This is a noticeable
increase in distortion, and a letter "E" is displayed. So it makes sound
economic sense to use the 6 V DC mains adapter that is supplied, at least
with the Siemens version of the radio.
Tuning
The radio has a keypad for direct frequency entry. You push a button
marked frequency and tap in the desired channel. The software is
clever..."9890" is recognised as a shortwave channel, where as "98.90" is
regarded as FM. There's a simple button sequence the find the lower end of
each of the shortwave bands.
Manual tuning is achieved in two ways. "UP" and "DOWN" buttons allow you
"jump" to the next channel. On shortwave the steps are 5 kHz apart. On
medium/longwave the steps are 9 kHz apart, but unfortunately the steps do
not correspond with the new longwave plan for Europe. The set jumps to 200
kHz for BBC Radio 4, when in fact the station is on 198 kHz. If you
depress either of the UP-DOWN buttons for more than a few seconds the
radio starts to scan, stopping when it hits a strong signal.
A tuning control on the side of the set can either be set to do exactly
the same as the "UP-DOWN" buttons, or set to a "FINE" position. This
allows tuning in 1 kHz steps on LW, MW, and SW, 50 kHz on FM. The receiver
can receive single-sideband signals thanks to a beat frequency oscillator.
A small rotary knob is used to clarify the signal....not as easy as with
sets that have USB or LSB selection.
The Siemens version of the radio comes with 18 radio stations pre-
programmed at the factory. For the most part these are stations which
have German language programmes, not surprising seeing that the main
market for this set is in the German speaking parts of Europe.
A tuning control on the side of the set can either be set to do exactly
the same as the "UP-DOWN" buttons, or set to a "FINE" position. This
allows tuning in 1 kHz steps on LW, MW, and SW, 50 kHz on FM. The receiver
can receive single-sideband signals thanks to a beat frequency oscillator.
A small rotary knob is used to clarify the signal....not as easy as with
sets that have USB or LSB selection.
The Siemens version of the radio comes with 18 radio stations pre-
programmed at the factory. For the most part these are stations which
have German language programmes, not surprising seeing that the main
market for this set is in the German speaking parts of Europe.
Performance
The RK-670 is sensitive enough on all the bands, although in low signal
strength areas, a piece of long wire clipped to the antenna may be needed
for the reception of signals higher than 15 MHz. The receiver offers two
bandwidth filters (6/2.8 kHz @ -6 dB) for AM/SSB reception. The shape
factor of the filters is fair. Image rejection on medium wave was found to
be mediocre, and on shortwave it is also only fair. The RF gain control
didn't seem to have much effect on reducing spurious signals, except to
demand that you turn up the volume.
The inclusion of the cassette recorder means the speaker in the radio has
been reduced in size. In fact there are two, one 2 cm tweeter and a 7 cm
woofer. In general we found the audio to be somewhat muffled, this being
especially noticeable when headphones are connected. Reception on FM, and
cassette playback, is in stereo using headphones.
Cassette Recorder
The stereo cassette recorder has a tape-type selector switch but no Dolby.
The timer in the radio can be used to switch the recorder on at a pre-
determined time to tape a programme unattended. The set has a built-in
microphone, but you can only use it for logging notes. The background hum
from the drive mechanism rules out any serious recordings.
Conclusions
The Siemens RK-670 retails at around US$300 in Europe. The addition of a
cassette recorder has compromised the sound quality of the radio, but the
price is attractive for those who want an "all-in-one" unit. It is more
than adequate for general programme listening, although the image
rejection may create problems for those interested in digging the weaker
stations out of the noise. We rate it as a good value buy. In the US,
Radio Shack sell the DX-390 for US$240, which is somewhat expensive
bearing in mind the features and performance are almost identical to the
DX-440 which retails at 40 US$ cheaper. The DX-390 has no cassette
recorder. We found the ATS-818 (no cassette recorder) on sale in the UK at
£170.
