Around 1978, Sony came on the market with their CRF-320, a very pricey and voluminous
multiband receiver - because of it's high catalogue price of around 4000.- DM /
3800.- SFr. it has not been sold in large quantities, but it was the dream receiver
on many shortwave listeners in those years. It's shortwave performance is still above
averyge from todays point of view. The wadley Loop based receiver featured a high
frequency stability and had no problems with poor contacts on a turret tuner arrangement,
but it would cost You twice as much as Grundig's Satellit 3400,
a set that never has been sold for cheap, either.
The Sony CRF-320 is a huge multiband receiver; with it's front panel protective
cover, it looks like a compact suitcase. The dimensions of the CRF-320 are 45 x 31 x 21 cm
and it's weight 13 kg, whicht means it can becarried around, but You might soon
feel exhausted, the radio has a better place on Your desk in the shack or even in
the living room.
The receiver can be used independant from mains, it can be powered from batteries
and both telescopic antennas are well adapted to the receiver circuitry.
In the left upper corner of the front panel, You find a digital clock / timer,
in older models, it's a mechanical digital clock, in later models an electronic
Below, in the left half of the front panel, You find two circular auxiliary dials
for the VHF FM band and long- and mediumwaves. In these frequency ranges, the
frequency is not displayed electronically in the LED display. Below the FM dial,
there are the switches to activate the AFC and a squelch when in FM mode.
In a vertical row right in the middle of the frontpanel, You find the analog signal strength
meter, which is not calibrated in S units, the AM mode pushbuttons which also
select the narrow and wide AM filters and below the bandswitch pushbuttons for
FM, MW, LW and shortwave.
The complete shortwave range is divided in band segments each 1 MHz wide, there
are two rotary controls to select the 10 MHz and the 1 MHz numerals of the reception
frequency, the kiloHertz digits are tuned with the VFO driven by the large main tuning
knob. The frequency is displayed on the big analog semicircular dial with an accuracy
of 1 kHz and on a red LED frequency display acting as frequency display with a resolution
of 1 kHz. At the right, You find a preselector designated as "antenna tuner" which
has to be peaked for maximum reading on the signal strength meter after every frequency
change, the switch for the noise blanker and the rotary control for the R.F. gain.
Below, You find the jacks for headphones, a cassette or tape recorder and a timer output
to control the cassette tape for automatic recordings, at the right side of the speaker
the rotary controls for bass and treble and volume / A.F. gain. The main switch has
one position to set the radio in STANBY for timed operation.
On the rear face, You find the compartments for batteries and mains cable and
screw connectors for externalFm, mediumwave and shortwave antennas.
The CRF-320 is technically a double conversion receiver based on a Wadley Loop
"drift cancelling" circuitry. Signals every 1 MHz generated in a PLL synthesizer
are mixed with the signal of a linear VFO running from 3.455 - 2.455 MHz to arrive at
the first hich intermediate frequency of 45,145 MHz; as this i.f. is higher then the
upper edge of frequency coverage, mirror signals can be suppressed.
The R.F. signal coming from the antenna is led through a 35 MHz low pass, an electronically
controlled 5 range band pass filter and the preselector to the first mixer.
After this, signal peaks will be clipped by the noise limiter and the signal is fed
to the second mixer to generate the standard 455 kHz second intermediate frequency.
After having passed the electronically switched i.f. filters, the signal is fed
to the diode demodulator for AM or the produc detector for single sideband reception.
The CRF-320A offers true USB and LSB reception, a BFO is added for the reception
of CW / A1 signals.
In practical use, press in the telescopic antenna, it will pop out a little bit
from the cabinet, pull it out for maximum length. Press the buttons for shortwaves (SW) and AM wide,
select the 10 and 1 MHz digits of the desired reception frequency with the rotary
controls in the right upper corner anduse the main tuning knob to tune the kHz digits
for the desired frequency. You might already hear soething from the speaker,
adjust volume for a slight hiss.
The next important step is to tune the preselector to signal peak and maximum
reading of the signal strength meter. This should be done after every frequency
change, it might take a while to tune the receiver new, when You just want to check
a few parallel frequencies.
Remember, this receiver has been designed in the late seventies, in those years,
a full PLL synthesized microprocessor controlled VFO and electronic frequency
memories were features only found on a few semiprofessional and professional grade
communication receivers - and Sony always aimed at the domestic market with their
equipment. So the CRF-320, despite being the flagship of Sony's shortwave receiver
line in those years, came without passband tuning, a notch filter, selectable
AGC speeds and the filter selection is quite poor for it's price range.
The price has been the main problem ot make this radio quite rare in Central
Europe. This "dream receiver" of many did cost twice as much as the Grundig Satellit 3400
(which offered digital frequency display in the FM band, but only single conversion
with many mirrors in the tropical band ranges) and was even more costly then
what JRC offered in the high end NRD shortwave receiver series. - So not too many
CRF-320(A)s might have been sold, the CRF-330K which is virtually tha same receiver
but with an integrated cassette recorder is even more rare.
The CRF-320 is in summary a DXers dream receiver from the early eighties
with a quite conventional technical design but very high design and production
standard (only the gears of the FM and MW subdials are made from plastic and tend
to break over the years), it offers excellent performance on it's internal antennas
and can even be battery powered.
When looking for a high end communications receiver to feed a radioteletype
converter or for decoding faint signals in extraordinary transmission modes,
You might rather look around for a more technically looking set from a manufacturer of
semiprofessional Amateur radio oder commercial receivers.
But in my collection of Sony shortwave receivers, the CRF-320 is a gem and I love
it for everyday use.
© Martin Bösch, 20.7.2003