TM-G707E_review_PW_2010.pdf

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1、Getting the best value from the second-hand market! A fter a dual-band handheld transceiver, of which Ive covered a few types in past columns, about the most-often purchased transceiver for Amateur use is that of a 144/430MHz (2m/70cm) frequency modulated (f.m.) mobile rig, for use on simplex and re

2、peaters, either from your car or from home. As promised in the last column, this time Ill be looking at a couple of these which could well be of interest, and which have been proven second-hand bargains in the recent past. Ive deliberately chosen two sets with fairly similar features each has 144 an

3、d 430MHz coverage with one band at a time operation, i.e. without dual receivers which keeps costs down. Each offers a high power of 50W on 2m and 35W on 70cm, and each has an easily detachable front panel, just like many car radios. So you can feel reasonably safe in keeping the set in view under t

4、he dashboard of your car while youre away, while you have the transceivers front panel safely tucked into your jacket pocket. Ive used both of these sets in the past as well as fully testing a sample of each on my laboratory radio test equipment. In fact the TM-G707E transceiver, which was subsequen

5、tly given to me as a birthday gift many years ago, I personally used for a number of years in my own car. Whatever mobile radio you buy second-hand, it may sound obvious but ensure that you get the direct current (d.c.) power lead, microphone, and mobile mounting bracket hardware too. Sometimes, the

6、 seller will leave the power lead in the vehicle rather than try to strip it out. In this case you could use a choc block connector with your own lead but this doesnt help when youre trying to take the radio in and out of your car for safe keeping if it doesnt have a detachable head. The most common

7、 fault, if you could call it that, is a scratched display on radios with a detachable front panel. This is usually because the user has repeatedly removed it and simply slipped it in their pocket or bag along with keys and the like. A small cloth storage bag is a most useful accessory here! If yours

8、 does have a scratched plastic display then a proprietary scratch remover paste along with a bit of elbow grease can often restore it to virtually new condition. I suggest that you haggle for a few pounds off the asking price to cover the cost of buying this, unless of course the asking price alread

9、y reflects the damaged condition of the radio. Anyway, now for some information on the radios Ive chosen this month! The Kenwood TM-G707E The Kenwood TM-G707E covers 144-146 and 430- 440MHz with a transmit power output of 50W maximum on 2m and 35W maximum on 70cm, with switchable low power levels of

10、 10W and 5W on either band. Extended receive range is available, see below for a modification. The main body measures just 140mm x 40mm x 189mm. The size is kept down by the use of a controlled fan on the rear panel together with an internal airflow-ducted heatsink. For frequency control, a click-st

11、ep rotary knob on the front, steps you through the channels, and pressing the knob face inwards momentarily changes the variable frequency oscillator (v.f.o.) to 1MHz steps so you can get from one part of the band to another more quickly. Further buttons above the tuning knob change between v.f.o. a

12、nd memory operation, and selection of a quick access Call channel for each band. There are also 180 memory channels, a Priority channel, and 12 extra channels to store lower and upper limits for six programmable v.f.o. scan ranges. Each of the normal memories can be user-programmed with an alphanume

13、ric channel name of up to seven characters in place of the frequency, so that you can see what youve stored in each channel. Theres a variety of scan modes, such as memory scan, priority scan, selected limit v.f.o. scan, 1MHz range scan, etc. Indeed, theres enough to satisfy virtually all listening

14、needs! The set has full continuous tone codes squelch system (CTCSS) encode and decode facilities, a 1750Hz tone-burst is also built in. A CTCSS scan can also be enabled, to display which, if any, CTCSS tone is being used on the channel youre tuned to. The radio also has the facility for 1200 or 960

15、0baud Buying Second-hand Feature Practical Wireless, July 2010 30 This month Chris Lorek G4HCL takes a look at a pair of high power dual-band 2m/70cm mobile transceivers Editorial announcement: Both Chris and the Editorial team are delighted by your feedback on the equipment featured. We would also

16、encourage readers to contact us to request that particular rigs and accessories to be featured. Indeed, this series will rely on your requests and comments, along with Chris G4HCLs extensive experience to be the success we intend it to be. So, lets be hearing from you readers! packet operation on ei

17、ther band. Removing a small cover at the bottom left of the sets front body reveals a dedicated six-way mini- DIN connector for a packet TNC. The supplied hand microphone has the usual push-to-talk (p.t.t.) and Up/Down buttons for frequency/channel control, plus four extra buttons labelled Call, VFO

18、, MR and a user- programmable function such as power on/off, squelch defeat, high/low power selection etc. All the four microphone buttons are, in fact, programmable in this way, giving you a remote control to suit your needs. Pressing the PM button on the front panel brings up a sub-display of 1, 2

19、, 3 and 4, and each is appropriately just above the four buttons next to the liquid crystal display (l.c.d.). All you need do is press the appropriate button to change between personalities. This can be useful when youre switching between, say, shack and mobile use of the rig. Theres also a selectab

20、le Advanced Intercept Point (AIP), which switches out the front-end pre-amplifier to improve the strong-signal handling of the set, albeit with a slight loss in sensitivity. A transmit time-out-timer is fitted, which limits the transmission time to 10, 5, or 3 minutes. This cant be disabled and pers

21、onally speaking, I found it a bit of a pain to use but others may disagree! On The Air Within the 77-page user manual is a one-page, seven step, Your First QSO guide, which helps to get you on the air quickly. Besides normal operation the transceiver also has an Easy Operation mode, where the first

22、three buttons on the front panel just select between three pre- programmed memory channels, with the fourth button selecting the transmit power level. Operating the set this way was just like using a car radio. After Id tuned into a frequency, a press of one of the channel buttons for more than a se

23、cond automatically stored that into memory, recall being a quick press of the same button. The detachable front panel contains all the user controls and an optional remote kit is available so that you can mount the control/display unit wherever you wish, the main body unit fitting elsewhere. When I

24、tested the set over a prolonged period, I found the receiver to be exceptionally sensitive on 144MHz, easily capable of receiving distant repeaters. The high transmit power level allowing me to reciprocate in getting back to the distant repeaters to join in. Incidentally, I often suffer from strong-

25、signal breakthrough when I use a dual-band rig from home with it connected to my rooftop antenna system, primarily with hand-helds but it also occurs with the occasional mobile. However, Im pleased to say Ive had no problems at all with the TM-G707E here. Out and about operating mobile, the set perf

26、ormed equally impeccably, with good and loud audio from the sets top-panel mounted peaker. It also has a very easily to read display, which I certainly appreciated. My lab tests confirmed the good on-air performance, and I ended up using a TM-G707E as y personal choice for quite a number of years. E

27、xtended Coverage Ranges Lets now look at extended receive and transmit ranges and here, you may find that your transceivers already had this modification done by a previous owner. But if its restricted to just the Amateur bands on receive and transmit and youd like it extended, or indeed reverse the

28、 modification to get the radio back to original heres how. First, remove the detachable front from the transceiver, and then remove the bottom case lid. Next, position the transceiver in front of you, upside down, with the antenna connecter pointed towards you. In the upper right hand corner, behind

29、 the display adapter, youll see a small set of vertical printed numbers, 0, 1, 2 and 3, next to a group of four small surface-mount zero-ohm resistor links. For extended receive range, use a soldering iron and carefully lift the resistor marked 0. Youll find it easier to heat the solder at one end o

30、f the resistor, then quickly transfer to the other end and use the soldering iron to lift that end. Then transfer back to the other to remove the resistor. After this, youll find the receiver will cover the following bands; Receive band 1; 118-136MHz a.m. Receive band 2; 136-174 MHz f.m. Receive ban

31、d 3; 300-400 MHz f.m. Receive band 4; 400-520 MHz f.m. Receiver band 5; 800-999 MHz f.m. If youd also like extended range on transmit then, while youve the set open, remove resistor 3 in the same way. After this, the transmitter will cover the following bands; Transmit band 2; 136-174 MHz f.m. Trans

32、mit band 4; 400-520 MHz f.m. If you ever want to reverse these modifications, you can just use a short piece to wire soldered across the original resistor positions to restore the original band limits. Transmit Deviation If your set has too much deviation on 144MHz, as they originally came set with

33、5kHz peak deviation for 25kHz channel spacing for both 2m and 70cm operation. Its relatively easy to adjust and you wont need to open the set up to do this. Youll first need to place the radio into Service Adjustment Mode by shorting pins 3 (PKS) and 6 (SQC) on the data connector on the front left s

34、ide of the radio, Practical Wireless, July 2010 31 There are plenty of radio goodies about and Chris will guide you to the best buys. w o s i a s s a d a c p u m q Buying Second-hand youll find this under the small oval-shaped removable cover. To locate which pin is which, while youre looking at the

35、 connector from the front of the transceiver with the connector on the left hand side, pin 3 is at the 3 oclock position and pin 6 is at the 10 oclock position. If youre unsure of poking wires into the connector, then you could get yourself a PC keyboard extension cable and use this to plug into the

36、 set and link the wires on it, the connector is exactly the same. With the pins linked, simultaneously press the F key and Tone key while you switch the set on. Then select v.f.o. mode and tune to a 144MHz frequency, which you can monitor on another receiver, or even better a radio communications te

37、st set to measure transmit deviation if you have access to one (or use a PC and monitor receiver, read on in this months column). Next press MNU to select the adjustment mode, and use the keys to select DEVI. Press the mic PTT and speak into the mic, and use the rotary encoder knob to adjust the tra

38、nsmit deviation until you get to the right level. Youll see the display will indicate a two-character level as you adjust this. Once youre at the right deviation level, ideally 2.5kHz maximum deviation, press the OK button to save this adjustment level into the sets memory. Then press the MNU button

39、 to return the set into v.f.o. mode. If you need to adjust the 430MHz deviation level, you can simply tune to a 70cm channel to do the same series of operations. The deviation level for v.h.f. and u.h.f. is stored separately inside the transceiver. When youre finished, switch the set off and remove

40、the wire short on the connector. The Icom IC-207 Next, Im turning to the Icom IC-207, a set that provides you a 50W 144MHz rig and a 35W 430MHz rig squeezed into the same box, a band button switching between the two bands. Wide-band coverage is also available (see later for this) the modification fo

41、r this. The sets case measures a very small 140 x40 x185mm, so you should be able to fit it in into the tiniest of available positions in a car. The transceivers front panel offers a number of operating knobs and buttons. A detachable microphone cover reveals a fully-fledged remote control system fo

42、r the set, with each button being backlit for night-time use. The microphone control even provides Up/Down volume and squelch controls, as well as handy facilities such as a reverse-repeater monitor and transmit power selection. There are 150 memory channels plus extra call channels and the like ava

43、ilable for frequency storage and one-touch scanning. A bright yellow back-lit liquid crystal display is used, with the functions for the six push-buttons below the panel also being shown on the display. Along with the detachable front panel, a separation kit is also available, so the transceiver its

44、elf can be mounted remotely with just the small display fitted in a more easily-viewed position on your dashboard. Together with a 1750Hz tone-burst facility from the microphone for repeater access, the IC-207H also has full CTCSS (sub- audible tone) encode and decode built in, and tone scan lets yo

45、u check which, if any, sub-tone is being used on an active channel. For packet radio use, a 6 pin mini-DIN connector is fitted to the rear panel, the transceiver accommodating both 1200 and 9600baud speeds. On The Air When I used the set, I found it was very easy to operate and within a few minutes

46、of switching on I was enjoying a QSO on my local repeater. I found the sets front panel controls were intuitively very simple to use. With the plastic cover in place on the supplied microphone, it offers a smaller number of controls, such as youd typically use for normal operation, like Up/Down freq

47、uency or channel change, VFO/memory switching, band switching, and so on. About the only awkward operation mode I found with the set was that of generating a 1750Hz tone for initial repeater access this needed the microphones plastic cover removed, with a sequential press of two different buttons be

48、neath the cover. I found this rather awkward in practice, although if you know the CTCSS access tone for the area youre using the set in and pre-program it, this isnt too much of a problem. This rig also includes a handy facility, which consists of five scratch pad memories for each band. Here, the

49、set automatically memorises the operating frequency every time the p.t.t. is pressed, storing the last five frequencies (including repeater shifts) on each band into separate memory channels. Recalling these just needs a quick press of the M/Call button, the tuning knob then selecting between them very useful and especially handy when on the move. Operating from home, with the set connected to my rooftop collinear, it showed a good level of performance without a trace of the typical intermodulation problems Ive learned to expect on 144MHz in my r.f. congested location. Icom