AMATEUR RADIO
By GARRY CHATT, VK2YBX
Yaesu's new FRG 8800
•
shortwave receiver
Just when you thought that you owned the ultimate
receiver, a new all singing, all dancing model
arrives on the market. You ask yourself just how
good is the receiver in my shack? That's what I did
when the latest receiver from Yaesu, the FRG-8800,
arrived for evaluation.
The Yaesu Musen company of
Japan has, for years, produced
receivers for both shortwave
listeners and amateurs alike.
Among its offerings over the last 5
years have been the FRG-7 (or
"Frog-7" as it was commonly
known at the time), the FRG-7000
which like the FRG-7 used the
Wadley Loop principle, the
FRG-7700 (a PLL synthesised
receiver), and now the FRG-8800
which is an even more advanced
"semi-professional" receiver.
Considering the expense of such
receivers, I thought it would •be a
worthwhile exercise to do a direct
hands-on comparison between the
FRG-8800 and its predecessor, the
FRG-7700.
Computer control
Perhaps the most advertised
feature of the FRG-8800 receiver is
its ability to interface to a computer
via an RS232 connection. This
feature allows computer control of
the frequency and mode of reception, and the selective scanning
of any frequencies within the
coverage of the receiver (150kHz to
29.999kHz).
In addition, there is a facility to
enable the "S" meter and squelch
status to be recordes by the computer, thus virtually turning the
unit into a programmable multimode HF scanner, complete with
expanded memories (using the computer RAM or floppy disc).
For example, as many shortwave
broadcasters use several bands
simultaneously for optimum coverage, a program can be written to
turn the receiver on at predetermined intervals and test each frequency for signal strength, then
select and change the receiving frequency, depending upon propagation conditions, for optimum reception. All this information can be
stored in computer memory, providing a log of conditions, frequencies, dates, times and station
callsigns.
Of course, considerable effort
must be expended to minimise the
effects of computer generated noise
on the receiver itself, but the
FRG-8800 is certainly capable of all
this, whilst the FGR-7700 is not.
Improvements
The Yaesu FRT-7700 antenna tuner is a worthwhile optional extra with the
FRG-8800. Other optional extras include internal and external VHF converters,
a lowpass filter and an active antenna.
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SILICON CHIP
Apart from the CAT (computer
aided transceiver) features, it is
pleasing to see that Yaesu has improved some of the shortcomings of
the FRG-7700. These improvements
include wiring the headphone
socket so that either mono or stereo
units can be used, an enhanced
LCD display, a multi-mode squelch
which really works and is not
limited to FM reception only, a
"Woodpecker" noise blanker,
memory scanning, and a direct frequency entry keyboard.
The direct entry keyboard allows
The FRG-8800 can be linked to a computer, thus turning it into what is virtually a programmable multimode HF
scanner. The keyboard allows direct entry of the desired frequency.
the user to rapidly change from one
frequency to another without
endless rotation of the main tuning
dial, which was an annoying
necessity with the FRG-7700. One
simply enters the desired frequency
in either megahertz or kilohertz
directly on the keyboard. Tuning is
made easy by the provision of
"fast" and "slow" modes, which
result in tuning rates of either
125kHz or 6.25kHz per complete
turn of the tuning knob.
Another improvement in the
FRG-8800 is the ability to connect a
VHF converter (the FRV-8800) internally. This greatly simplifies
antenna connection if using a
dedicated VHF antenna and an
antenna tuner with the receiver.
This applies particularly if it is the
genuine Yaesu (FRT-7700), as the
wiring when using an external VHF
converter (the only type available
for the FRG-7700) can become quite
a mess!
In terms of RF performance, the
specifications are little changed.
Perusing the specifications for
both receivers, it can be seen that
the sensitivity and selectivity
figures are identical, as are power
consumption, size, weight, modes of
reception and frequency range.
About the only improved specification with any relevance to the actual reception of signals is the
receiver stability which is considerably improved at less than
300Hz quoted drift during the first
30 minutes of operation from cold
start. Even this parameter is not of
extreme importance to shortwave
reception.
On-air tests
On air testing revealed that there
were some small differences in the
performance of the two receivers
when connected to a "long wire"
antenna. Perhaps the most noticeable, in the presence of a weak
signal, was the slight interference
internally generated by the processor in the FRG-8800. This does
slightly reduce its ability to recover
intelligent speech.
The FRG-7700 does not suffer the
same problem. However, this inter-
r-
nally generated noise probably
would not cause any significant difference when the receiver is connected to a suitable coaxially fed
dipole or Yagi antenna.
Eventually the considerations
can be simplified to a tradeoff between additional purchase price
and enhanced operator features.
The FRG-8800 offers all the
features that the amateur could
want at an affordable price.
However, if " no frills" shortwave
listening is the ultimate goal it could
be that your existing receiver fills
the bill.
The FRG-8800 is available from
Dick Smith Electronics stores
around Australia for $1295. The
FRV-8800 VHF converter is
available for $169. Both units come
with a two year warranty.
~
◄ -- l -~
►1
\
"Length"
In sulator
Insulator
COAX Cabl e
Dipole Antenna
A simple resonant
dipole antenna will
provide fair to good
performance over a
specific frequency
hand. The dipole
should be cut to
resonate at the
centre of the band
according to the
formula: length
(metres) =
142.5/frequency
(MHz).
JA N UARY 1990
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