IC-756Pro_review_PW_2000.pdf

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1、lig win 111E111n22 14 WIN 0000 - 10.297.80 0 NR The Icom IC-756PR0 HF hand microphone; spare fuses; c.w. keyer plug. Pros: Excellent DSP facilities, selectivity and ease-of-use receiver and transmitter. Greatly improved three colour I.c.d. main display. Excellent real time spectrum scope (Panoramic

2、adapter type facility). Very interesting built-in RTTY decoder and screen display. Cons: Main display could do with slightly increased brightness levels. Viewing angle of small RTTY screen critical for comfort and distance. Some front panel controls slightly fiddly. Fig. 2: Where have they hidden al

3、l the electronics? An inside (top) view of the Icom IC-756PR0 where the advanced use of surface-mount technology gives a false impression of what is actually under the bonnet! Note the very substantial inter- compartment screening which is provided by die-cast aluminium sections. user-friendly DSP t

4、hird i.f., the transceiver comes fitted with a much improved spectrum scope which many will class as a panoramic adapter type display - youll see what I think of this window to the bands later in this review. The layout of the front panel is also well thought out and, even as a left-hander, I found

5、it reasonably easy to use. The only real niggle I have regarding the front panel controls is with the size and positioning of the MIC GAIN, RF POWER, COMP (Compression), KEY SPEED and BK-IN DELAY (c.w. break-in) knobs, which I feel are too small and fiddly. However, the designers obviously consider

6、that these controls are not constantly used - and can be positioned where they are and made smaller. I can understand their reasoning and what theyve done, although I would like to have seem them slightly larger. The main three colour I.c.d. type display on the transceiver is excellent and very info

7、rmative - but doesnt dazzle you with too much comprehensive information. However, although the display is excellent (its the clearest Ive seen recently), I feel that even with the maximum level of brightness selected, theres not a lot of reserve. In other words, I feel that the display could be a li

8、ttle brighter. Although provided I kept the rig out of the direct sunlight (especially when operating portable from my car), it wasnt a major problem. As Ive said, the display is one of the clearest thats come my way recently and once !corn have adjusted the brightness levels, I feel sure it will be

9、 absolutely perfect. Incidentally, Im only mentioning this fact because I really do appreciate the excellence of the IC-756PROs display and that its a major consideration when youre considering a new rig - it only needs a little tweaking from Icom to get it just right. Built-In RTTY Decode As I ment

10、ioned at the start of this review, the IC-756PRO comes complete with a built-in RTTY decoder, capable of resolving Baudot (mark frequency 2125Hz, shift frequency 170Hz, at 45bps). A rather limited facility, the RTTY Gang might consider - but I can tell you that after using the facility, Ive had my a

11、ppetite whetted for RTTY again! I also think that Icom have made a rod for their own back here in that now theyve provided the RTTY facility . just how long can we expect to wait for built-in FAX, Packet and SSTV? All are possible with modern software packages and I really dont think it will be long

12、 before updates are available to enable fortunate 756PRO owners to equip their transceivers. I was delighted (and not a little surprised) to see just how much Amateur Radio RTTY theres is to be seen on h.f. nowadays. I was fortunate in this respect because several contests seemed to bring up RTTY op

13、erators from all over Europe and, in fact, there seems to be a particular interest in RTTY from the former Soviet Union countries - fortunately, they seem to conduct their QSOs mainly in English. I spent many happy hours working on my main computer with the Apple Macintosh screen to my left and the

14、Icom IC-756PROs screen directly in front of me. I was able to sit and work and look in on many QSOs and pick up some tips where the DX was to be found. It was nice to see just how polite the operating practice is on RTTY, perhaps its time I really got active on the mode myself! The built-in RTTY dec

15、oder and (small - because it is a small viewing area) screen built into the main display is clear and relatively easy to read. In fact, at the normal sort of operating distance away from the front panel - at arms length - the screen was perfectly readable. However, I did get an extra crick in the ne

16、ck - and here lies my only real criticism of the RTTY facility! For prolonged RTTY watching (can you be said to be a viewer I wonder?) I think the transceiver should be mounted (or propped up) at around 30 from the horizontal. (This is in addition to the lift provided by the built-in legs, which are

17、 mounted just behind and underneath the main front panel). I experimented with the rig and found that, at 40, the screen was just about at the correct angle for myself. In saying that though, I must admit that the arthritis in my neck causes extra discomfort. The main display, including frequency di

18、splay, spectrum scope, etc., isnt really dependent on the angle for viewing - but for comfortable observation of the fairly small RTTY print out display - I consider that a careful choice of viewing angle is essential. However, having said that, I found the facility absolutely fascinating and it aga

19、in demonstrates the trend to the everything in one box dream of the manufacturers engineering design team - perhaps? With RTTY threshold selection and the ability to select Reverse mode, the decoder is capable of providing a useful monitoring facility and good quality, error-free reception is possib

20、le for long periods. In fact, most of the errors were obviously being made by the operators, in the same way I have to apologise to readers for my keyboard mistakes on E-mailed letters. The IC-756PROs RTTY facility certainly made me remember the old days when, whilst I was in the Royal Navy, I often

21、 had to work near clattering mechanical teleprinter machines. What a difference between them and the modern equipment - I await the next development with interest and think that FAX and SSTV Practical Wireless, May 2000 Ive had my appetite whetted for RTTY again! oi might be welcome! I was most impr

22、essed when the (much slower and nowhere near as sensitive and useful) earlier versions of the spectrum screen appeared on previous Icom equipment. However, as you would expect . things are getting much better and the spectrum scopes display is now approaching what I would expect from a reasonably pr

23、iced spectrum analyser screen. With the new facility on the 756PRO, the spectrum scopes presentation is constantly on the move (unless you freeze it of course) and is obviously breathing. (By breathing I mean that you can see the display constantly responding to the slightest variation on the amplit

24、ude of the signals its receiving). Gone are the obvious digital steps of previous displays - this one really does seem alive. In other words, the spectrum display on the screen really does seem as responsive to rapid variations in signal levels, etc., in the same way you would expect a spectrum Gene

25、ral Frequency coverage: Receive: Transmit: Mode: No. of memory channels: Antenna connector: Temp. range: Freq. stability: Freq. resolution: Power supply: Power consumption: Transmit: Receive: Dimensions: Weight: ACC 1 connector: ACC 2 connector: CI-V connector: Display: Transmitter Output power: con

26、tinuously Modulation system: s.s.b. a.m. f.m. Spurious emission: Carrier suppression: Unwanted sideband suppression: D( variable range: Microphone connector: analyser or panoramic adapter display to be. In use, the display is so quick that you can now very easily see the wide band interference from

27、thermostats, etc., as their high amplitude signals appear across the screen. You can also see the various ionosonde sweep transmissions as they travel quickly across the screen. Youll also be able to see the spectral display of the many other transmissions in the bands we use and share. Perhaps like

28、 me you may also wonder just what we share our bands with! From observing the regimented internationally agreed frequency channels of the short wave broadcasters, to seeing those annoying carrier swishers in operation on 7MHz (where most of them seem to operate), youll see much to help you. On one 1

29、4MHz s.s.b. QSO I was getting splatter from an extremely strong southern European station. One glance at the spectrum scope told me where he was relative to my indicated centre frequency on the same display - and it was a moments work to adjust the DSP to eliminate the problem. Very satisfying indee

30、d! On The Air The transceiver soon proved itself On The Air and I was able to get it set-up and working very quickly indeed. The more complicated the rig nowadays, the more likely youll have to get your nose stuck into the manual (always a good idea anyway) and to this end the 80-page plus manual is

31、 extremely easy-to-use and very well prepared. However, the 756PRO is user friendly in that respect and after initial switch on I only had to wait for the DSP to calibrate itself, a process which only takes ten seconds. Operating on 7MHz under very crowded conditions and with a high level of static

32、I found the transceiver 3-conductor 6.35(d)mm 3-conductor 6.35(d)mm Phono (RCA) Phono (RCA) Fig. 3: Close-up view of the power amplifier (p.a.) stage board. Note again the substantial die-cast alloy chassis. proved itself very worthy. The whistlers and carrier swishers that seem to live on this band

33、 - usually only bothering s.s.b. QSOs - arent a problem with the DSP facilities. One QSO I listened to on 7MHz (a Special Event station was involved) was plagued with one character who was on frequency most of the time. However, I think the Special Event station was equipped with a DSP fitted rig so

34、, like me, they werent bothered by the nuisance! Because the IC-756PRO is fitted with many ceramic band- pass filters (there are no traditional quartz crystal filters fitted) and the transceiver relies on the very high frequency first i.f., the (as already mentioned) many band-pass filters and the f

35、inal digital (DSP) i.f. - the results are, in my opinion, astounding. For some years now Ive thought that the DSP-equipped Kenwood TS- 870 was unbeatable - but now I think the performance has at last been overtaken. The Kenwood TS-870, in my opinion, was the first Amateur Radio DSP-equipped transcei

36、ver to treat the digital processing as one of the intermediate frequencies (rather than just an add-on unit on the same chassis). However, I now regard the IC-756PRO to be its worthy challenger in this respect. Operating on 3.5MHz on c.w. and s.s.b. under very noisy conditions, I found it possible t

37、o complete QSOs whereas Id have no chance with my Alinco DX- 70TH, unless I was using an add- on DSP unit. The 756PROs Twin Passband Tuning (complimented by a helpful mimic diagram on Electronic key connector: Key connector: Send connector: ALC connector: Receiver 0.030-60.000MHz 1.800-1.999MHz 3.50

38、0-3.999MHz 7.000-7.300MHz 10.100-10.150MHz 14.000-14.350MHz 18.068-18.168MHz 21.000-21.450MHz 24.890-24.990MHz 28.000-29.700MHz 50.000-54.000MHz u.s.b./1.s.b./c.w./RTTY/a.m./f.m. 101 (99 regular, 2 scan edges) SO-239 x 2 and phono (RCA; 50(1) -10C to +50C less than t0.5ppm 1 min. after power on (-10

39、 - 50C) 1Hz 13.8V d.c. t15% Max. power = 23A Standby = 3.0A (typical.) Max. audio = 3.5A (typical.) 340(w) x 111(h) x 285(d)mm (projections not included) 9.6kg (approx.) 8-pin DIN connector 7-pin connector 2-conductor 3.5(d)mm 5inch (diagonal) TFT colour I.c.d. - 50-100W (s.s.b./c.w./RTTY/f.m., adju

40、stable) - 5-40W (a.m., continuously adjustable) PSN modulation low power modulation phase modulation 50dB (h.f. bands) 60dB (50MHz band) 40dB 55dB 9.999kHz 8-pin connector (6000) Manufacturers Secifications Receive system: Triple conversion Intermediate frequencies: 1st:64.455MHz 2nd: 455kHz 3rd: 36

41、kHz Sensitivity (typical): s.s.b./c.w./RTTY (10dB S/N) = 0.16pV (1.80- 29.99MHz)*1 and 13pV (50.0-54.0MHz)*2 a.m. (10dB S/N) = 13pV (0.5-1.799MHz), 2pV(1.80-29.99MHz) and 1 pV (50.0- 54.0MHz) f.m. (12dB SINAD) = 0.5pV (28.0-29.99MHz) and 0.32pV (50.0-54.0MHz) *1 Pie-amplifier 1 is ON. *2 Preamplifie

42、r 2 is ON. Squelch sensitivity: s.s.b3c.w./R11Y - less than 5.6pV (Pre-amp OFF) f.m. - Less than I NV Selectivity: s.s.b./R11Y (BW: 2.4kHz): more than 2.4kHz/-6dB less than 2.8kHz/-60dB c.w. (BW: 500Hz): more than 500Hz/-6dB less than 700Hz/-60dB a.m. (BW 6kHz): more than 6.0Hz/-6dB less than 15.0Hz

43、/-60dB f.m. (BW: 15kHz): more than 12.0Hz/-6dB less than 20.0Hz/-60dB Spurious & image rejection ratio: more than 70dB (except i.f. through on 50MHz band) AF output power (at 13.8V d.c.) more than 2.0W at 10% distor tion with an so load RIT variable range: t9.999kHz PHONES connector: 2-conductor 6.3

44、5(d)mm External SP connector: 2-conductor 3.5(d)mm/80 Antenna Tuner Matching impedance range: h.f. bands: 16.7-15052 unbalanced (less than v.s.w.r. 3:1) 50MHz band: 20-125fI unbalanced (less than v.s.w.r. 2.5:1) Minimum operating input power: 8W Tuning accuracy: v.s.w.r. 1.5:1 or less Insertion loss

45、 (after tuning): less than 1.0dB Practical Wireless, May 2000 25 The Icom IC-756PR0 HF & 50MHz Transceiver Review Listening And Looking In On The Bands 41111111. I feel sure the IC- 756PR0 is a model well be seeing many facility updates provided for in the future. In fact, like the Kenwood TS-870 be

46、came a few years ago - I feel that the 756PRO will become another classic and I look forward to having one in my shack to update! Try as I might, even if I had ten pages in PVV, I still couldnt do full justice to the achievements of the Icom designers so far. So, all I can do is to sug- gest that yo

47、u try the hands on approach by visiting an Icom dealer. I can only give you a short taster of the technology invested in this transceiver - to appreciate it yourself youll have to see it in action! t, My thanks go to: Martin Lynch & Sons Ltd. 140-142 Northfield Ave Ealing London W13 95B Tel: 0208-56

48、6 1120 FAX: 0208-566 1207 E-mail: salesMLandS.co.uk For the loan of the IC-756PRO. the main I.c.d. screen which indicated how the filter was configured, also proved very helpful. Up on 14MHz I experienced the usual problems of QRM on the International Beacon Projects frequency. Here, the various bea

49、cons around the world are subject to frequent inteference from adjacent channel h.f. Packet stations. In fact, the Packet transmissions sometimes drift right down onto the Internationally agreed beacon frequencies themselves. When this happens theres not much you can do, but provided the Packet transmissions arent right on top of the relatively low powered beacon frequency (where, of course, the various beacons step down to milliwatt power levels f