Alinco_DX-70_review_2010.pdf

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1、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 youve been able to visit one, youve managed to pick up a bargain or two. Maybe helped by recent Buying Secondhand article

2、s in this series. This time, as promised, Ill 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 wont break the bank. The Icom IC-706 and Alinco DX-70 transceivers both offer the ability of fixed, mobile,

3、 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 transcei

4、vers for more details). Whats 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. Howeve

5、r, it can also often wake up people who already have one thats 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

6、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. Ive been fortunate

7、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, Ive no hesitation in recommending either to re

8、aders 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

9、 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 ma

10、rket and selling well! Now for couple of points to watch out for when youre 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 youre interested in 50, 144 and 430MHz repeater opera

11、tion 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 coverage transmit if youre licensed for this or hope to be in the future. If not then dont worry too m

12、uch, because for each transceiver model featured Ive 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

13、(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 wit

14、h 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 avai

15、lable and on current sale its 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 re

16、ceive 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./

17、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 selected. An IF shift control helps in fighting adjacent frequency interference on a crowded b

18、and, 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 50

19、MHz. The sets 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 sta

20、y at the main transceiver end, so although youll 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, theres an internal speech processor and for c.w. operators, full and semi-break in. When I used

21、the 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 accid

22、entally knock the VFO control knob. For normal mobile use, the sets 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 sets receiver often suffere

23、d on busy bands if I connected my full- size 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 transce

24、iver such as this may not be using monster antennas, using more compact types. My conclusions after Id 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 theyd managed to do a ve

25、ry good job, as I found no real limitations with the set considering its size and features. Things To Watch For Now, lets 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 b

26、uying 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 wont usually be an issue, but here check the connections arent corroded nor the front panel display fas

27、cia 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 hasnt been too careful in the past. Electrical problems with the PIN diodes, which are used to switch the antenna path between the transmitter po

28、wer 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 n

29、oise 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 youd like to use these on transmit, check your seller has had extended transmit range enabled. But if not, heres how to go about it. Remove the control head

30、, remove the four screws from the back of this, then remove the rear panel of the control head its 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 th

31、e text for expanding the transmit receive capabilities of the Alinco DX-70 series. There is no pad labelled A on the left-hand column. Buying Second-hand prise it off. Looking at the printed circuit board, with the display fascia away from you and the tuning knob on the left hand side, youll see on

32、the bottom right hand side of the board two columns of solder pads for surface-mount resistors, five on the left hand row and seven on the right hand row, Fig. 3. Note that not all resistors may be fitted and that theyre not labelled. Above each row is a distinct solder pad. To extend the transmit r

33、ange, refer to Fig. 3 and remove diodes labelled C and E on the diagram (second and fourth down in the left hand column). Following this, reassemble the control head and perform a reset of the transceiver by keeping the F button pressed at the same time as you switch the radio on. Your memory channe

34、ls, etc., will be re-set but the radio will now operate with extended transmit range. The Icom IC-706 . The IC-706: On the main printed circuit board (p.c.b.) by the filter option location, youll see a row of five surface mounted dual diodes, Fig. 6, next to a jumper wire. Using a small (but hot) so

35、ldering iron, lift up the lead(s) on one end of D59 to disconnect it (or if you wish) also then heat up the lead(s) on other side and remove it completely. The IC-706MkII: On the main p.c.b., youll see an oblong metal can, and near to this are a few rows of surface mount diodes. Take a look at the a

36、ccompanying diagram, Fig. 7, and, using a small (but hot) soldering iron, remove D116 and D118 by applying heat to one of the legs and lifting the diode away from the board. The IC-706MkIIG; On the main p.c.b., under the speaker near to the crystal, youll see two rows of solder pads for surface moun

37、t components, Fig. 8. On position 10 along this row from the left youll see a diode, D2030, soldered in. Simply remove this diode using a small (but hot) soldering iron on the leads. After you re-connect your d.c. supply the radio will be automatically reset and the transmit range expanded on h.f. a

38、nd v.h.f. Next Time Thats it for this month and I shall be back soon with a further Buying Second-hand column. If youd like any particular types of radios covered in this series then please do get in touch. Ive already a nice pile of ideas and information in the pipeline but Id welcome being guided

39、further by readers interests. I can be contacted by E-mail to g4hclrsgb.org.uk or by post to PO Box 400, Eastleigh, Hampshire SO53 4ZF, UK. Bye for now, see you next time! ? ? Practical Wireless, November 2010 45 Fig. 6: Expanding the capabilities of the original IC-706 is as suggested in the text. Fig. 7: To expand the capabilities of the MkII version of the IC-706, see text for more detail. Fig. 8: And the IC-706MkIIG has another version of expanding its capabilities. See text for the differences of the various models of the IC-706.