24 October 2005 RadCom www.rsgb.org
REVIEW
24
AOR ARD9000 digital
W
e’re increasingly living in a
digital world, and this isn’t
just limited to commercial
radio applications such as cell-
phones, digital TV and radio broad-
casting. Amateur radio has been
using digital communications from
the very earliest days, when CW
could be arguably termed as the first
ever ‘digital’ mode. Eventually RTTY
came along, then packet radio, fol-
lowed by a plethora of advanced data
modes for keyboard-based communi-
cation. Some of these do such a good
job in weak signal and interference
rejection that you’ll achieve 100%
copy when modes such as manual
CW or analogue SSB wouldn’t stand
a chance of getting through. Some
experimental modes, such as nar-
rowband spread spectrum, are also
suitable for digitising signals includ-
ing speech for weak-signal and inter-
ference-laden work. Indeed any digi-
tal mode capable of data transfer at
a reasonable bit-rate speed could be
adapted for digital speech over an
SSB bandwidth.
In 1999, Andy, G4JNT, and
Charles, G4GUO, published their
results with digital speech over HF in
RadCom [1], followed by papers later
in other publications [2, 3]. There’s
also an excellent description on
G4GUO’s website [4]. Last year, AOR
took a brave marketing decision and
launched a ready-made set-top ver-
sion of a digital modem, the
ARD9800, which was reviewed in the
July 2004 issue of RadCom [5]. This
offered not only digital speech over
an SSB bandwidth, but also file
transmission and optional TV-resolu-
tion picture transmission by adding
a plug-in module. It’s fair to say that
many amateurs, me included, were
greatly excited about this, although I
am sure the price tag of just under
£500 dissuaded a number of ama-
teurs. However, AOR has now
launched the ARD9000 at a typical
retail price of around £169.
FEATURES
The ARD9000 is a voice-only modem,
although it’s fully backward compati-
ble with digital speech with the
ARD9800. Like its multimode prede-
cessor, it acts just like a set-top box
with no transceiver modifications
needed. You just plug it in, possibly
adjust a few audio levels using the
controls on the unit, and off you go.
For the technically minded, a
description of the data mode used is
given in the references and the
RadCom review detailed earlier. It
uses OFDM with a digital vocoder
and DQPSK modulation, employing
36 tone carriers spaced at 62.5Hz,
giving an overall transmitted audio
bandwidth of 312.5Hz to 2,500Hz.
The ARD9000 is quite compact,
measuring just 70 x 33 x 98mm
making it even smaller than most
SWR meters. It operates from an
external DC voltage of between 10-
16V and draws a current of approxi-
mately 100mA at 12V, a plug-in DC
cable being provided. AOR recom-
mends this supply be separate from
the DC feed to your transceiver, no
doubt to prevent earth loops – a
small AC wall adapter would be a
typical choice here. 3.5mm jack
sockets are fitted on the rear panel
for receive audio in and out, togeth-
er with an eight-pin microphone-
style socket for connection to your
transmitter. This is wired to be com-
patible with Adonis microphone
wiring, and a range of optional
ready-made leads are available to
suit a variety of transceivers. A
ready-made receive audio lead is
provided with the unit, together with
a matching 8-pin plug which you
can wire up to suit your transceiver.
But to get you started quickly, a
handy speaker-mic, which plugs
into the 2.5mm and 3.5mm jack
sockets on the front panel, comes
with the unit. Four rubber feet are
fitted to the bottom panel, and a
screw-on circular magnet is also
supplied that can also be attached
to the bottom panel, to keep the unit
in place when it’s positioned on top
of your transceiver’s metal case.
This cleverly prevents the modem
sliding around, especially if you’re
using the speaker microphone.
INSTALLATION
Connecting up was very simple, and
as I already had an Adonis desk mic I
didn’t need to make up or obtain a
suitable lead from the ARD9000 to
my transmitter, although this would
have been a simple job taking just a
few minutes, providing of course I
had a suitable multi-way lead and
transceiver mic plug handy. The first
thing to do was to set up the receive
audio level into the unit for digital
reception, which I did by simply
AOR’s ARD9000 digital voice modem offers
“astounding” sound quality at a modest
price, writes Chris Lorek
(2 pagine)
(28 pagine)
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