There are plenty of radio goodies about and Chris will guide you to the best buys.
T
he summer Amateur Radio rally and boot sale
season has been in ‘full steam’ and I hope
that, if you’ve been able to visit one, you’ve
managed to pick up a bargain or two. Maybe helped by
recent Buying Secondhand articles in this series.
This time, as promised, I’ll be detailing a couple
of ‘get you going’ high frequency (h.f.) transceivers,
ideally suited for a first ‘all round’ rig and at a price
which hopefully won’t break the bank. The Icom IC-706
and Alinco DX-70 transceivers both offer the ability
of fixed, mobile, and portable operation, and have
broadly similar capabilities.
The first models of each were launched back in
1995, and over the years each transceiver model has
had three different variants, generally an increase in
power at v.h.f., etc. (Please see the description later on
the individual transceivers for more details).
What’s The Cost?
I know one of the first questions readers will ask will
be, “What will one cost me?” This is of course often
hard to say, as in the past when a second-hand ‘buy’
is prominently featured in a magazine such as PW,
this increases the desirability of the rig. However, it
can also often ‘wake up’ people who already have one
that’s lying dormant and unused under the shack desk
or in the house loft and prompt them into selling it!
So, the resultant price – at least for a short while
after such a feature – can either go up or down from
what it was before! But as a guide I believe you
should be able to pick
up first, i.e. early, model
variants of the DX-70 for
under £200 and a first
model variant of the
IC-706 for under £250.
Later models, with more
features and of course
being newer and thus
less-used, will of course
usually attract higher
prices.
I’ve been fortunate
in using various models
of both the DX-70 and
the IC-706 myself in the
past, each of them at
home and out and about
in my car. This as well
as being able to fully
and stringently test them at the time for technical
performance in my measurement lab. So, I’ve no
hesitation in recommending either to readers as a
second-hand radio, providing of course you follow my
advice regarding each one!
I know the DX-70 has been, and probably still is,
a ‘favourite’ of the PW Editor Rob Mannion G3XFD.
I must admit to having a personal preference for the
IC-706GMkII (albeit available at a higher price), but that
again is personal preference and each radio would be
ideal as starter or all-rounder transceiver.
Having said that, the DX-70 has stood the test of
time and after 15 years from its launch, the latest
model in the DX-70 series, unlike other radios that
have faded in the past, is still here on the market and
selling well!
Now for couple of points to watch out for when
you’re buying second-hand. The first is the inclusion,
or not, of CTCSS (sub-tone) in the IC-706, or whether
you need to add an optional module for this. It will be
important if you’re interested in 50, 144 and 430MHz
repeater operation rather than single sideband (s.s.b./
c.w. (Morse).
Secondly, you should check whether either rig
has extended 7MHz (40m) band transceive coverage.
Additionally, you need to check for
5MHz band
c
over
age transmit if you’re licensed for this or hope
to be in the future. If not then don’t worry too much,
because for each transceiver model featured I’ve given
details on how to add this to a second-hand radio.
The Alinco DX-70
The first DX-70, Fig. 1, first
appeared in early 1995,
and offers h.f. and 50MHz
transceiver coverage on
amplitude modulation
(a.m.), c.w., narrow band
frequency modulation
(n.b.f.m.) and s.s.b. The rig
has 100W output on h.f.
(switchable to 10W for low
lower operation) plus 10W
on 50MHz, switchable
to 1W low power. A little
later came the DX-70T,
which was virtually the
same as the DX-70 but
with narrow filters fitted
as standard.
Fig. 1: The original Alinco DX-70 with its matching antenna ‘tuning’ unit.
Buying Second-hand
Feature
Practical Wireless, November 2010
42
Chris Lorek G4HCL takes a look at several h.f. transceivers which you can hopefully
pick up at a bargain price.
Finally, in 1999 the
DX-70TH, Fig. 2, was
launched, and this model
is in fact still available and
on current sale – it’s similar
to the DX-70T but the ‘H’
signifies it has a higher
power of 100W on 6m. The
operation and appearance of
each is identical apart from
the model number on the
front and rear panels.
Each model has a transmit
frequency range within the
normal Amateur bands, and
a receive coverage of 150kHz
– 30MHz and 50 – 54MHz. A
built-in continuous tone coded
squelch system (CTCSS)
tone encoder is included –
invaluable for 28 and 50MHz
n.b.f.m. (usually referred to as
f.m.) repeater use.
Narrow (1kHz) and wide
(2.4kHz) intermediate
frequency (i.f.) filters are
available for c.w./s.s.b. and
‘narrow a.m.’ receive. These
being switchable from the front panel, together with a
further wider filter for normal a.m. and f.m. use. A 500Hz
filter is automatically switched in when c.w. mode is
selec
ted.
An IF s
hift control helps in fighting adjacent frequency
interference on a crowded band, and switchable 10dB and
20dB receive attenuators help guard against overload, a
10dB preamplifier also being fitted. This is for use when
needed on a ‘quiet’ band or for example whilst mobile
with a small antenna. Two antenna sockets are fitted to
the rear panel, one for h.f. and the other for 50MHz. The
set’s dimensions are 178 W x 58 H x 228mm D.
The front panel can be detached and an optional
cable used to link this to the main transceiver ‘body’,
which you can then mount elsewhere, maybe next to
the feed-point of your mobile h.f. antenna. However, the
microphone and speaker connections stay at the main
transceiver end, so although you’ll need extension leads
here, but you can detach the front panel without any
further connections and take it with you when you leave
the car.
For on-air use, there’s an internal speech processor
and for c.w. operators,
full and semi-break in. When I
u
sed th
e set on-air I found the smooth VFO knob control
easy to use although I quickly learned how to use the set
by touch alone for mobile use. I also quickly learned that
I – invariably – had to use the Dial Lock button to keep
me on frequency during a contact on the move as I found
that I could easy accidentally knock the
VFO control
kn
ob.
F
or normal mobile use, the set’s 100 memory
channels were useful. These, combined with a single
button-push ‘memory to VFO’ operation enables this to
act as a band switch for Amateur and broadcast bands.
At home I must confess,
I found the set’s receiver
often suf fered on busy
bands if I connected my fullsize dipole on the l.f. bands,
or my tower-mounted
3-element quad-bander
Yagi beam on the higher
bands and pointed at a busy
Europe.
But then, the DX-70TH
is a small set, and the
attenuator function was
useful here. However, in
fairness – many users
of a transceiver such as
this may not be using
‘monster’ antennas, using
more compact types. My
conclusions after I’d used
the rig those years ago were
that Alinco had surprised the
Amateur Radio world with
a radical departure from
their previous v.h.f./u.h.f.
f.m. only offerings. But that
they’d managed to do a very
good job, as I found no real
limitations with the set considering it’s size and features.
Things To Watch For
Now, let’s look at the things to watch for on the DX-70
series of rigs. As well as the usual ‘bewares’ which I gave
details of in the first column in this Buying Second-hand
series, such as buying and ownership warnings, look out
for severe scratching to the case if the previous owner or
owners have repeatedly taken it in and out of a car. If just
the front panel has been removed this won’t usually be
an issue, but here check the connections aren’t corroded
nor the front panel display fascia scratched.
See my recent article on the TM-G707E and IC-207
in the July 2010 issue of PW for information on how
to remove any scratches if your seller hasn’t been too
careful in the past.
Electrical problems with the PIN diodes, which are
used to switch the antenna path between the transmitter
power amplifier and receiver front end circuits, have
to my knowledge been reported causes of failure.
So it would be a good idea to check a second hand
transceiver on-air for r.f. power output (e.g. with an
in-line power meter) and receiver sensitivity – here you
should hear an increase in background noise on the
lower h.f. bands when you connect an antenna.
Extended Transmit Frequency
For the extended 7MHz (40m) band and for the 5MHz
band – if you’d like to use these on transmit, check your
seller has had extended transmit range enabled. But if
not, here’s how to go about it.
Remove the control head, remove the four screws
from the back of this, then remove the rear panel of
the control head – it’s a ‘snap fit’ so you may need to
Practical Wireless, November 2010
43
Fig. 2: The current version of the DX-70, the ‘TH’ version has been improved and
adds more output power of 100W at 50MHz.
Fig. 3: See the text for expanding the transmit receive capabilities of the Alinco
DX-70 series. There is no pad labelled ‘A’ on the left-hand column.
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