IC-7200_review_RC_2009.pdf

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1、NEW KID ON THE BLOCK. The IC- 7200 is the latest radio from Icom. First seen in the UK at the recent RSGB HF Convention, it is billed as an entry- class transceiver but it is certainly not short on essential features. As a midi- sized radio with rugged looks and rugged construction, it is equally su

2、ited to outdoor use and travel as well as normal operation from home. Although not waterproof, it has a measure of protection against the weather using techniques that Icom has developed for their range of marine radios. BASIC FUNCTIONS. The IC- 7200 is a 12V operated radio measuring 241 x 281 x 84m

3、m ( W x D x H) and weighs about 5. 5kg. The receiver tunes continuously from 30kHz to 60MHz. The transmitter is enabled only within the amateur allocations appropriate to each country area, with 100W maximum output power on all bands. 5MHz transmit frequencies are not enabled as received out of the

4、box in the UK but Icom agents can enable these channels on request. SSB, CW, AM and RTTY modes are provided but FM is not. A scroll button selects modes and a long press gives alternative ( opposite sideband) modes on SSB, CW and RTTY. Modes can be inhibited for simplified operation if desired. RTTY

5、 uses a digital FSK transmit interface to an external terminal unit. For AFSK audio tones, a data mode on SSB may be enabled via the set- up menu, rather less convenient if you need to switch frequently between voice and data modes. More on data modes further in this review. The front panel contains

6、 three dual concentric rotary controls and a chunky tuning knob. Most of the functions of the radio are accessed by pushbuttons, which in most cases are multifunction and are dependent on whether a short or long press is given. Microphone and headphone jacks are mounted on the front with a CW key ja

7、ck on the rear and unusually a front panel- mounted speaker is fitted. At 40mm diameter, this is very small but gives surprisingly good results with good bass and quite high volume levels although there are some rattles. From the audio point of view, the front panel is really the best place to mount

8、 the speaker but panel area for the operating controls is at a premium and they usually take priority. A long push on many of the pushbutton selected features accesses a set- up level or a sub- selection function. In addition, a further 52 items are customisable via the set mode scrolling menus. Som

9、e 11 of the more commonly accessed items are grouped into the quick set- mode needing a single key access and the remainder into the standard set- mode needing double key access. The last accessed set- mode item is returned first on reselection so, for example, switching data mode on and off if you

10、use voice and data modes frequently is not so tedious as might first be thought. Overall, access to the functions is well thought out given the constraints on front panel area and the necessary number of controls. The display uses an amber backlit LCD panel with excellent brightness and visibility a

11、nd a wide viewing angle. It is a monochrome display showing frequency and all the usual functions with a bar- graph meter and shows everything that is really necessary. Voice readout of frequency, mode and S- meter reading is provided as standard at the touch of a button. The rear panel carries a si

12、mple set of interface connectors. There is a single antenna socket ( two would be more convenient for HF and 6m) and no separate receive antenna socket. A 13- pin accessory socket ( plug supplied) provides general interfacing to linears, automatic ATUs, FSK and AFSK signals for data terminal units a

13、nd has band data available. Two phono sockets provide T/ R control and ALC for general amplifier switching but with 16V maximum open circuit on the T/ R switching line an isolating relay is necessary for many older style valve linears. A separate socket for control of the AH- 4 automatic ATU is prov

14、ided and a CI- V remote interface for PC control via a level converter. One interesting new feature is the provision of a USB port. This can be used to provide full PC control as an alternative to the CI- V interface. Also via the associated built- in codec, the USB port transfers receive and transm

15、it audio to and from the PC without the need for a sound card. This can simplify operation on data modes, and with appropriate software in the PC can be used for transmitting contest voice message stores and recording virtually an unlimited amount of receiver audio. The radio is provided with an HM-

16、 36 hand microphone and an instruction manual that runs to 100 pages and is thorough and well written. It includes a set of circuit diagrams and remote control commands. RADIO DESIGN AND ARCHITECTURE. The receiver in the IC- 7200 adopts a triple superhet architecture with a first IF of 64. 455MHz, a

17、 second IF of 455kHz and a third IF of 15. 625kHz that directly feeds the DSP for all further signal processing. The first mixer uses a quad arrangement of FETs and 10 diode- switched bandpass filters cover the tuning range of the receiver. A 15kHz wide roofing filter is fitted at the first IF , a 6

18、kHz wide filter at the second IF and all remaining filtering, demodulation, noise reduction, audio processing, AGC and transmit signal generation is performed by the DSP. The DSP is a 400MHz unit with 24 bit A/ D and D/ A converters. The AGC circuitry employs two loops, one within the DSP following

19、the channel filtering and the other acting on the earlier IFs to prevent overload of the A/ D and DSP circuits. 66 EQUIPMENT REVIEWPETER HART, G3SJX E-MAIL: PETERG3SJX.FREESERVE.CO.UK Icom IC-7200 Peter Hart looks at this new HF there is no multiple band stack register. The radio is fitted with a 45

20、mm diameter tuning drive with a nice feel and flywheel action but only 150 steps per knob revolution. Normal tuning is 10Hz per step but 1Hz per step can be selected for fine tuning. A faster tuning rate programmable in steps between 100Hz and 10kHz can also be selected. Auto speed- up increases the

21、 tuning rate on fast sustained tuning but this can be disabled. The radio can also be tuned from the microphone or the frequency entered directly through the numeric keypad. The normal A/ B twin VFOs are provided with split operation and quicksplit for equalising the VFOs. Monitoring and tuning the

22、transmit frequency during split frequency operation may be done by a push and hold button press ( XFC function) . This is similar to the Yaesu TXW function. RIT is available ( up to 10kHz with a lot of knob winding) but no transmit XIT. There are 199 regular memory channels that store frequency, mod

23、e and IF filter bandwidth setting but no fancy features such as labelling or quick access stacks. Scanning between two programmable frequency limits or across the stored memory channels is also provided. A switchable front- end preamplifier and a switchable attenuator allows the receiver to be optim

24、ised for weak or strong signals and a combined RF gain control and squelch is also provided. The AGC can be switched between fast and slow settings or turned off. A noise blanker is provided for pulse- type noise and is fully adjustable for level and pulse width. Digital noise reduction is also incl

25、uded with adjustable level setting. The same comprehensive set of IF channel filters as fitted in the Icom top- end radios is also included in the IC- 7200 with 41 different passband widths on SSB and CW ( 50- 3600Hz) , 32 passband widths on RTTY ( 50- 2700Hz) and 40 passband widths on AM ( 200Hz- 8

26、kHz) . Three separate bandwidths are immediately available for each mode, selectable by a simple push of a front panel key, from the available menu of bandwidths. In addition, two filter profiles are selectable on CW and SSB modes, a sharp profile with a flat passband and a soft profile with a more

27、rounded passband. Twin passband tuning is also provided, which enables the filter sides to be both independently moved and narrowed. A manual notch filter is provided with three different width settings and an auto- notch on SSB and AM modes. On RTTY mode, a twin peak filter can be enabled with shar

28、p peaks on the 2125/ 2295Hz tones. This is not available for shifts other than 170Hz or on the AFSK data modes on SSB, which uses an audio passband centred on 1500Hz. TRANSMIT FEATURES. The transmitter contains a 100W power amplifier. Power is adjustable down to less than 2W from the quick set menu

29、with different settings possible on HF and 6m. There is no provision for a built- in ATU but a tuner button provides control of Icom external ATUs AT- 180 and AH- 4. The bargraph panel meter can be switched to read RF power output, ALC level or antenna VSWR. Audio modulation input may be selected fr

30、om the microphone socket, the accessory socket or both, or via the USB port. Separate selections for voice operation or data operation may be set via the menu. VOX is provided on SSB and AM voice modes but only if the microphone socket is used for audio input. A speech compressor is also provided on

31、 SSB. There is no adjustment of the transmit audio bandwidth or audio monitor facility. On CW, there is the usual provision for full and semi break- in and a keyer. The keyer is adjustable for weighting and speed over the range from 6 to 60wpm and accommodates different paddle types including the mi

32、crophone up/ down keys. There are no memory stores. MEASUREMENTS. The full set of measurements is given in the table. The sensitivity is excellent across the HF tuning range. Below 1. 6MHz an attenuator is inserted and sensitivity drops sharply below 100kHz. At 136kHz it is about 3V for 10dB S+N: N.

33、 The S- meter bars dwell for about 8dB at S9 and above and about 2dB below S9 and are similar on all modes. The quoted S- meter calibration figures are the median values at each level. IF rejection was greater than 100dB but first IF image rejection was 67 EQUIPMENT REVIEWRADCOM JANUARY 2009 0 -10 -

34、20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -30 -25 -20 -15 -10 -50 5 10 15 20 25 30 Frequency Offset (kHz) Response (dB) Single Tone Dynamic Range Receiver Bandwith 2400Hz DSP Channel Filter Response Reciprocal Mixing Oscillator Sideband Noise FIGURE 1: Composite selectivity curve on USB. rather

35、poor at little over 60dB. Rejection of the second IF image at 910kHz above the on- tune frequency was around 90dB. Other spurious responses, which can be a problem with DDS synthesisers, were generally at a low level of around - 90dB or better, which is quite a good result. The AGC performance was g

36、enerally clean and with no attack hole as seen on some DSP based radios. Third order intercept and dynamic range figures were very good for a radio in this price bracket, holding quite well close- in. Reciprocal mixing results are not as good as I was expecting from a straight DDS synthesiser, avera

37、ge to poor close- in and further out it plateaus at quite a high level. Reciprocal mixing noise is even seen on adjacent bands at this plateau level where the bands share a common input filter. The phase noise benefits of a DDS synthesiser are not really being achieved with this radio. Second order

38、intermodulation with signals on other bands was fairly poor; I suspect the front- end bandpass filters are not particularly sharp. The IF filter measurements show a superb performance with possibly the narrowest skirts I have measured on any radio. These figures are even better than the IC- 7700, su

39、ggesting Icom have been optimising their filtering software. Figure 1 shows the composite selectivity curve. As with most Icom radios, the inband intermodulation performance was exceptionally good. On transmit, distortion products on SSB were fairly good for a 12V operated power amplifier, except on

40、 24MHz. A VOGAD circuit is incorporated into the transmit audio. This is a long time constant AGC, making level setting less critical and preventing gross distortion from overdrive. The processor added minimal extra distortion. AM transmit was clean with low distortion. CW rise and fall times were 2

41、 to 4ms with negligible delay or character shortening under semi break- in keying. With full break- in at 40wpm the characters were slightly shortened. ON THE AIR PERFORMANCE. I took the opportunity to check out the radio during the recent CQWW SSB and CW contests. The receiver coped very well with

42、crowded conditions and no real strong signal problems were encountered. The receiver was clean with a quiet background and very sensitive on the higher bands. On AM broadcast the quality was excellent and although the sensitivity dropped at LF the receiver was again very clean. The audio quality fro

43、m the front panel speaker was good on speech but there were resonances and rattles on tones and on CW. As always, headphone quality is so much better. The filters generally functioned well but narrow CW bandwidths in sharp mode tended to ring or blur the sound more than expected and the soft mode se

44、emed better. The manual IF notch was very effective. Icom claim 70dB depth and, being before the AGC detection point, full sensitivity is retained with strong carriers. The auto- notch also functioned well and was very fast to operate although strong carriers capture the AGC. The noise reduction sys

45、tem also seemed fairly effective. On transmit, I had good audio quality reports on SSB and the CW break- in characteristic was clean and trouble free although the changeover relays were a little noisy on full break- in. I had some problems with RF breakthrough into the headphone leads on 20m when be

46、aming at the house. This could be cured by wrapping the headphone leads through a ferrite ring but could be a potential problem area. Once I had overcome my initial dislike of the two- button band change, I found the overall ergonomics really quite good. It is an easy radio to use but I found the bu

47、ttons needed a good push and must be pressed square- on as many sit in a slight recess in the front panel. The tuning drive is good but I generally prefer more steps per revolution. However, the change tuning speed button is easily accessed from the tuning hand and with 100Hz set for the higher tuni

48、ng rate a good compromise on tuning the bands is achieved. The display is bright, unambiguous and easy to read. To connect the radio to a computer via a USB cable, you first need to install a driver on the PC. Suitable drivers for Windows XP, 2000 and Vista can be downloaded from the Icom Japan supp

49、ort website and full instructions are given in the manual and on the website. I installed drivers on two PCs and had RTTY running using MMTTY in LSB data mode with no problem. Its a pity that VOX doesnt function on data modes: I had to route the PTT line via a serial port. Suitable software could enable this via the USB port. CONCLUSIONS. The IC- 7200 is far more than just an entry- level radio. It is a good performer and has all the features and functions necessary for effective use on all HF modes at home or out in the field. Possible RF breakthrough might be a problem in high RF enviro