Software Defined Radio
- a look at the Flex-3000.
Brian Morgan VK7RR
Do you remember your rst foray into radio? I
certainly remember mine. My boyhood was spent
building crystal sets, then graduating to a one valve
regenerative receiver, then two valves and then,
one day, a two transistor radio built on a masonite
board. I thought all my Christmases had come at
once with its performance so much better than the
valve radios.
The next fty plus years have kept me interested in the
ever changing challenges of amateur radio. Yes, I have
progressed through surplus military receivers, 10 valve
home built receivers with the then innovative product
detectors which made copying SSB so much easier, to
Photo 1: Brian VK7RR at his portable operating desk, the
laptop in the foreground and the SDR Flex-3000 on the right.
Yaesu, Icom and Kenwood transceivers, all the while
Photo 3: A photo of the complete station, with the 10 + 10 watt external audio amplier (referred to in the text) sitting
16 AMATEUR RADIO APRIL 2010
on top of the Flex-3000.
being distracted by building or repairing repeaters or
some home brew project or another.
Three years ago I was exposed to the new concept of a
software dened radio, one which deed almost all of
the then accepted conventions and did not even have
a tuning knob. I was intrigued and could not wait to
purchase the Flex-5000 radio and then, early in 2009, the
Flex-3000.
This is not intended to be a technical article but a
practical description of a new concept in transceivers.
My shack still has a Yaesu FT-1000MP Mark 5 sitting on
the bench but it no longer even has an antenna attached
to it, so taken have I been with the Flex radio.
The 5000 has become my home station and the 3000 is
compact enough to be taken portable as you can see.
And yes, that is snow outside the window.
The Flex-3000 and my laptop both sit inside a traditional
laptop bag. It is slightly bigger and a little heavier than
the laptop, weighing in at four kgs.
The radio puts out 100 watts on all HF bands and six
metres. The power can be varied manually for each
band, by a very accurate drive control but can also be
adjusted by software, so as to drive linear ampliers
and so on, at different drive levels. It does not have
Photo 4: A discrete photograph of the radio on a reective
surface.
Photo 5: A view of one of the hardships the author has to
endure when playing amateur radio in the highlands of
Tasmania.
AMATEUR RADIO APRIL 2010 17
conventional ALC, but then again,
if you set it up correctly, it does not
need it.
The software dened radio, as its
name implies, is as much to do with
computer operating as it is to do with
sitting by a ham rig. It does not require
any more knowledge of computers
than operating Windows XP.
The basic radio comes with Power
SDR, the software which gives you a
transceiver like appearance on your
computer screen and which provides
for all the functions we would expect
in a conventional transceiver.
With additional software, some of
which is obtainable free of cost and
some of which requires a nominal
payment, it is a simple matter to set
up operating on all digital modes,
including, RTTY, Packet, PSK31, SSTV
and so on. No external devices, such
as a modem, are necessary as all
connections are done electronically
through the use of this software.
Let me explain what I mean. In a
conventional radio, if we want to
run in digital mode, we have to run
cables from our radio to a decoder/
encoder or, these days, to the
soundcard of our computer. In the
case of my Yaesu, this required about
a dozen different cables, some to take
audio to and from the radio, one to
enable the radio to be tuned via the
computer (CAT), one to key the radio
for RTTY, another to key it for CW and
I have probably forgotten several.
With the Flex, there is one cable,
that being a common old garden
variety rewire cable. Whilst not as
well known as a USB cable, most
modern computers have a rewire
connection. This permits higher
speed data exchange between the
computer and the radio than one
can achieve with USB2. No other
cables are needed. We do not use the
sound card in the computer because
all processing is done digitally thus
limiting the risk of introducing
unnecessary distortion. By
comparison, most of the processing
in my Yaesu station was done in
analogue.
The difference is immediately
noticeable in weak signal conditions,
where you are competing with the
noise, so that a Software Dened
Radio will decode PSK signals which
are below the audible level.
If you have ever used a computer
for station operation you will have
encountered the problem of trying
to have several programs interact
from one serial port of the computer.
These days we are lucky if our
computer has even one serial port,
much less more than one and I have
had a great deal of trouble using USB
to serial adapters.
A comport (which is the connection
to the computer via the serial or USB
port) can only talk to one device at a
time, so that if you want the computer
to control your radio, antenna and
perhaps rotator all at once, some
other process needs to be used, to
avoid a comport conict where the
rst program to be engaged hogs the
comport and prevents its use for any
other process. In the bad old days I
would nd myself forgetting that I
had a program open, then open, say,
a logging program and then have the
computer disable that program’s CAT
feature because it was already in use.
Because we are talking about a
software dened radio, we can use
software to achieve this. First, there
is a free program (DDUtil), written
by Steve Nance K5FR which works
hand in hand with another program
Com0Com which simulates pairing
of comports from real ones to virtual
comports.
Photo 2: A screen shot of the Flex-3000 at work, in SSB mode, on 40 metres. The
strong signal in the centre was the station to which I was tuned at that time.
With these two programs you can
load and run a logging program, a
digital decoding program and a rig
controller all at the same time, and
again, without needing any leads. It is
all done in software.
Connecting audio between the radio
and the digital programs is also done
in software using a paid program
(NTONYX) which provides a virtual
audio connection between them.
In my home station, I was running
a 4 element SteppIR until high
winds earlier this year re-shaped the
driven element. I am still waiting for
SteppIR to provide the promised
replacements. However, that is
another story.
The SteppIR is designed to
follow band change commands
automatically, and also, within the
band, it will adjust the element
lengths as you tune up and down the
band.
My rotator is an Alphaspid which
is also designed to integrate into
the CAT commands coming from
18 AMATEUR RADIO APRIL 2010
the computer, so that my logging
program will tell it the short or long
path bearing of the station I wish to
work, and without touching a button,
the antenna as if by magic turns in
that direction. All of these functions
occur without any conicts, through
the use of the software outlined
above.
There is of course a cable to the
rotator and the SteppIR controller,
but we can’t have everything!
At my weekender in the central
highlands of Tasmania, I have one
antenna at present, a full wave loop
on 80 metres. The Flex 3000 has a built
in ATU which, so far, I have found will
present me with a satisfactory match
on all HF bands.
I am sitting here
writing this article
on the computer
which is also
driving the radio,
whilst I listen to
a busy Saturday
afternoon of
activity on 40
metres. Boy the
ZL’s are strong
today.
The one feature which most struck
me by the demonstration of the
Flex radio was its narrow band
performance. It is quite amazing to
reduce the receiver pass band on CW
to, say, 100 Hz and be able to read
the other station without any of the
ringing that we have come to expect
with narrow crystal lters. With a Flex
radio, there are also no more lters to
buy; they are all on board, in the form
of software.
The other features, which I have
now come to treat as a must, are
the panadaptor and the waterfall.
These give you a digital picture of
the segment of the band that you are
tuned to. I have found on a number
of occasions that six metre beacons,
which are too weak to read, can be
seen on the waterfall. Indeed, as the
MUF increases, you can sit and watch
as these signals climb above the noise
oor until ultimately the human ear
can start to read them.
you can load and run a logging
program, a digital decoding
program and a rig controller all
at the same time, and again,
without needing any leads. It is
all done in software.
And if you are using digital modes,
with the Flex-5000 or 3000, centre the
cursor over a station showing on the
panadaptor, click on the right mouse
button and then left click and you are
tuned to that station.
I have experimented with MixW
and TRX-Manager, to name the two
that I have most used, as rig control
programs, which also allow me to
keep a digital log. There are a number
of others, including Ham Radio
Deluxe. At the end of the day, I think
it comes down to personal choice.
Each of these programs has certain
features that the others don’t have.
In my case I have cheated a little as
I have added several features which
allow me to do additional functions
in the program of my choice.
Now to the Flex-3000 itself. On the
front it has an illuminated, in blue,
on/off switch, a 5 mm socket for a CW
key, a ubiquitous RJ45 for the mike,
and a 5 mm socket for headphones.
On the back are the antenna input
BNC connector and controls for
external PTT, such as a footswitch,
a logic out for switching a linear,
line level out for audio to external
amplied speakers and the ex wire
cable from the computer. A robust
four pin connection for 13.8 volts at
25 amps completes the layout.
The Flex 3000 does not have multiple
antenna sockets, whereas the Flex
5000 does. I do not see this as a
disadvantage because the radio is
intended to be used as a portable
rig so that external connections are
necessarily kept to a minimum.
speakers in enclosures to powered
computer speakers in plastic
containers.
The excellent received and
transmitted audio from the
Flex radios has frequently been
commented on by people exposed
to them for the rst time. On SSB,
the audio can be shaped by a graphic
equalizer which can adjust transmit
and receive audio to your own
preference.
And as if that is not enough, because
this rig is set up to operate via a
computer, if you are connected to
the Internet at each end, you are able
to operate it remotely. Band change
is by the ick of the mouse, tuning
is by the scroll wheel, audio gain is
again by the ick of the mouse and
transmit and receive audio are, in
my case, carried via Skype. The two
computers are linked by Tight VNC, a
very simple program to set up.
With a Flex radio this process
is just so simple and would be
used between my home and my
weekender, if only we had broadband
there!
In conclusion, my experience with
the big brother, the Flex-5000 left
me wanting its younger sibling and
mine was in the rst batch ordered.
I received it about a month ago and
have been extremely happy with it to
date. I am still in the learning phase,
but set up probably had me on the
air within an hour of unpacking. And
that also required me to make up an
adapter for my headset to t the RJ45.
If you are thinking of changing rigs
then these are excellent value for
money. Indeed, I would have to
say that by comparison with the
Big Three, in my humble opinion,
the receiver on the Flex-5000 is the
best that I have used. It is too early
to make any denitive comments
on the Flex-3000 but it has some
very unusual features, as it started
to snow outside whilst my XYL was
taking the photos for this article.
That is a feature that I have not seen
mentioned in the detailed instruction
manual!
You no longer have to sit tuning up
and down the bottom part of six. All
you need do is cast an occasional
look at the computer screen and this
will tell you what the band is doing.
In the shack, I found it useful to build
a dual channel 10 watt audio amplier
which is in a box painted, as close as
I could nd, to the distinctive blue
of the Flex-3000. I prefer using large
Photos 1, 2, 3 and 5 by Sue Morgan
VK7KSU; Photo 4 by the author.
ar
AMATEUR RADIO APRIL 2010 19
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