IC-718_review_QST_2000.pdf

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1、 July2000 63 PRODUCT REVIEW Joe Bottiglieri, AA1GW Assistant Technical Editor ICOM IC-718 HF Transceiver Reviewed by Steve Ford, WB8IMY QST Managing Editor Anticipating a larger number of HF opera- tors in the wake of license restructuring, many manufacturers are eager to introduce new lower-priced

2、HF transceivers. ICOMs entry in the race is among the first out of the gate: the IC-718. At approximately 4 9 9 inches, the IC- 718 is a compact desktop rig with a functional “military” appearance. The front panel is domi- nated by a sizeable amber LCD display, large VFO tuning knob and forward-firi

3、ng speaker. Concentric AF and RF/SQL gain pots are po- sitioned immediately below the display along with concentric RIT andIFSHIFT controls. But- tons you are likely to use most oftenMODE, FILTER and TS (tuning step)are prominent and easily accessible above the VFO knob. Most of the remaining button

4、s, including the direct-entry frequency keypad, occupy the right side of the front panel. Although the trend during the past several years has been to use modular microphone jacks and 1/ 8-inch headphone jacks, the IC-718 reverts to the more traditional 8-pin conventional mike connector and 1/4-inch

5、 headphone jack. The rear panel lineup is refreshingly spartan. There is an SO-239 antenna port, a “standard” 6-pin Molex dc power jack, an antenna tuner control jack (for use with ICOMs external autotuners), and a 13-pin accessory jack. Jacks are also provided for computer control (using ICOMs opti

6、onal CT-17 CI-V level converter), external speaker and CW key or paddle. There are separate RCA-type ALC and SENDjacks for controlling linear amplifiers. The IC-718 provides 100 W on SSB, RTTY and CW and 40 W on AM. The RF power output is continuously variable between approximately 5 and 100 W (from

7、 2 to 40 W on AM). TheNo-ManualTest Like any kid with a new toy, I tend to be more than a little impatient. When I pop open the box and catch the first whiffs of that new-radio fragrance, the last thing I want to do is read documentation. I want to use the radio now! In the time-honored tradition of

8、 rede- fining ones own personality defects as an aptitude for creativity, Ive devised the “no-manual” test. Not only is it an expedient way to determine the user friendliness of a radio, the no-manual test satisfies my in- ability to defer gratification. The concept is simple: use the manual to hook

9、 up the various cables, then toss it aside. The idea is to see how long it takes to get the radio on the air using your own intuition. Im an IC-706MKII user, so hooking up the IC-718 was particularly easy. I just unplugged the IC-706MKII cables and swapped them onto the 718. This included the contro

10、l cable for my ICOM AH-4 remote-controlled antenna tuner. I use this device to feed a 90-foot length of wire strung between my tool shed and a tree in my backyard. Pressing the front-panel PWR button, the IC-718 awoke with a metallic ka-thunk. Lets see if the IC-718 is anything like my IC-706 the fr

11、ont panel DN/UP buttons should step me through the band selections. Bingo. I jumped to 10 meters, selected USB, set the RF/SQL control to fully clockwise and turned up the audio. Nothing! The S meter was twitching madly, but the speaker was utterly dead. Was the BottomLine The ICOM IC-718 offers a n

12、ice collec- tion of the more desirable features that are typically absent from transceivers in its price class. control set for maximum squelch? I spun the ring full counterclockwise, which I assumed would be the open-squelch position. Still nothing. Now what? Was it time to admit defeat and read th

13、e manual? After a few more minutes of futile experimentation I decided to resort to the manual. Sure enough, the answer to the mystery appeared on page 15. I discovered that the default configuration of the ring is to function as an RF gain control between the 7 oclock and 12 oclock positions, and a

14、 squelch from the 12 oclock to 5 oclock positions. I followed the instructions in the manual, set the contol to 12 oclock and was rewarded with a flood of audio Subsequent manual reading revealed that you can access the IC-718s menu system and redefine the dual-function ring configu- ration, choosin

15、g to have the ring act strictly as an RF gain or squelch control. I used a set-mode menu to set the ring to function solely as an RF gain adjustment and lived happily ever after. The IC-718 makes use of two menusa “quick set” and an “initial set” menu. There are 13 quick set menu selections that inc

16、lude the RF power output level, a three-step display dimmer (high, low or off), mike gain and VOX settings, and a handful of choices related to CW and RTTY operation. 64 July2000 Table1 ICOMIC-718,serialnumber001069 Manufacturers Claimed Specifications Measured in the ARRL Lab Frequency coverage: Re

17、ceive, 0.03-30 MHz; Receive, as specified1; transmit, 1.8-2, 3.4-4, transmit, 1.8-2, 3.5-4, 7-7.3, 10.1-10.15, 7.0-7.5, 9.9-10.5, 13.9-14.5. 17.9-18.5, 14-14.35,18.068-18.168, 21-21.45, 20.9-21.5, 24.4-25.1, 28-30 MHz. 24.89-24.99, 28-29.7 MHz. Power requirement: Receive, 2.0 A; transmit, 20 A (maxi

18、mum). Receive, 1.7 A; transmit, 18 A. Tested at 13.8 V. Modes of operation: SSB, CW, AM, AFSK, FSK. As specified. ReceiverReceiverDynamicTesting SSB/CW sensitivity, bandwidth not specified, Noise Floor (mds), 500 Hz filter: 10 dB S/N: 1.8-30 MHz, 0.16 V. PreampoffPreampon 1.0 MHz 120 dBm 129 dBm 3.5

19、 MHz 129 dBm 137 dBm 14 MHz 130 dBm 139 dBm AM sensitivity, 10 dB S/N: 0.5-1.8 MHz, 10 dB (S+N)/N, 1-kHz tone, 30% modulation: 13 V; 1.8-30 MHz, 2 V. PreampoffPreampon 1.0 MHz 5.4 V 1.8 V 3.8 MHz 1.8 V 0.7 V Blocking dynamic range: Not specified. Blocking dynamic range, 500 Hz filter: PreampoffPream

20、pon 3.5 MHz 123 dB* 121 dB* 14 MHz 120 dB* 119 dB* Two-tone, third-order IMD dynamic range: Not specified. Two-tone, third-order IMD dynamic range, 500 Hz filter: PreampoffPreampon 3.5 MHz 88 dB 87 dB 14 MHz 87 dB 85 dB Third-order intercept: Not specified. PreampoffPreampon 3.5 MHz +10.4 dBm 2.3 dB

21、m 14 MHz +6.8 dBm 9.3 dBm Second-order intercept: Not specified. Preamp off, +54 dBm; preamp on, +55 dBm. S-meter sensitivity: Not specified. S9 signal at 14.2 MHz: preamp off, 149 V2; preamp on, 38 V. Squelch sensitivity: SSB, CW, RTTY, 5.6 V. At threshold, preamp on: SSB, 6.4 V. Receiver audio out

22、put: 2 W into 8 at 10% THD. 2.3 W at 10% THD into 8 . IF/audio response: Not specified. Range at 6 dB points, (bandwidth): CW-N (500 Hz filter): 324-849 Hz (525 Hz); CW-W: 182-1980 Hz (1798 Hz); USB-W: 136-2315 Hz (2179 Hz); LSB-W: 178-1988 Hz (1810 Hz); AM: 27-2069 Hz (2042 Hz). Spurious and image

23、rejection: 70 dB. First IF rejection, 14 MHz, 92 dB; image rejection, 14 MHz, 93 dB. TransmitterTransmitterDynamicTesting Power output: SSB, CW, FM, FSK, 5-100 W; AM, 2-40 W. CW, SSB, FM, typically , 1-113 W; AM, typically 1-38 W. Spurious-signal and harmonic suppression: 50 dB. 54 dB. Meets FCC req

24、uirements for spectral purity. SSB carrier suppression: 40 dB. As specified. 60 dB. Undesired sideband suppression: 50 dB. As specified. 64 dB. Third-order intermodulation distortion (IMD) See Figure 1. products: Not specified. CW keyer speed range: Not specified. 6 to 48 WPM. CW keying characterist

25、ics: Not specified. See Figure 3. Transmit-receive turn-around time (PTT release to S9 signal, 290 ms. 50% audio output): Not specified. Receive-transmit turn-around time (tx delay): Not specified. SSB, 12 ms. Unit is not suitable for use on AMTOR. Composite transmitted noise: Not specified. See Fig

26、ure 2. Size (hwd): 3.89.49.3 inches; weight, 8.4 pounds. Note: Unless otherwise noted, all dynamic range measurements are taken at the ARRL Lab standard spacing of 20 kHz. *Measurement was noise-limited at the value shown. Third-order intercept points were determined using S5 reference. 1Sensitivity

27、 degrades below 100 kHz. Noise floor at 30 kHz is 53 dBm. 2S-meter has a rather narrow range between S1 (7.8 V) and S7 (17 V) with a much larger change from S7 to S9 (preamp off figures given). An expanded test result report for this transceiver is available on the ARRL Members Only Web site. Printe

28、d copies are also available for those without Web access. The initial set menu includes selections for controlling a peak-hold function for the meter, a mode lockout feature, key beep, CW sidetone level, scan speed and resume condi- tion, RF/SQL control behavior, key type and paddle sense, and some

29、additional settings associated with the optional accessories. The various menu selections are identi- fied with alphanumeric character strings up to 8 characters long, so its easy to find the specific setting youre looking to change. Once the mystery of the ring was solved, the rest was easy. I punc

30、hed the TUNER button and my AH-4 dutifully responded, tuning my end-fed wire for a 1.3:1 match on 10 meters. I answered a CQ and received a fine signal report from a station in Spain. On- the-air reports indicated that the supplied hand mike produced clear transmit audio, even when I activated the 7

31、18s fixed-level speech compressor. July2000 65 I found that the IC-718 was very easy to operate with a minimum of “manual” intervention. Those of you who actually do spend time reading manuals will be very pleased with the provided documentation. It is complete, well organized and easy to follow. Se

32、parate foldout sheets with detailed schematic and block diagrams are included. FamiliarFeaturesandCharacteristics As an IC-706 user, I found much that was familiar in the IC-718. Other than the fact that the 718 lacks FM capability, or 6 and 2 meters, it performed much like my 706and shared many of

33、the same features. I found myself wondering if the IC-718 was a direct design descendant of the 706. Receive performance was very similar, right down to a similar tendency to become overwhelmed when too many signals popu- late the band. Before you interpret this as a criticism of the 718, bear in mi

34、nd that this radio, like the IC-706, was never intended to have high-end “competitive” receive charac- teristics. The selectivity and dynamic range are more than adequate thoughjust what you would reasonably expect from a radio selling at well under $1000. The ARRL Lab measurement data pre- sented i

35、n Table 1 confirms that the IC-718s receiver performance numbers are very close to those that we reported for the IC-706MKIIG that we reviewed in the July 1999 Product Review column. These num- bers compare favorably withand in some cases slightly surpassthose of the other currently available transc

36、eivers in the 718s price class. Anotherless desirable706-like behavior that is evident in the IC-718 is the 1086420246810 80 70 60 50 40 30 20 10 0 Frequency Offset (kHz) Reference Level: 0 dB PEP 246810121416182022 140 130 120 110 100 90 80 70 60 Frequency Sweep: 2 to 22 kHz from Carrier Reference

37、Level: - 60 dBc/Hz Vertical Scale: dBc/Hz existence of a leading-edge high-power “spike” in CW or continuous carrier modes (see Figure 3). A brief power surge might trip protective circuitry or possibly cause damage to some amplifiers. Even with the transceivers RF power output level throttled back

38、to 25 W, a spike on the order of 50 W was observed. Our IC-718 had the UT-106 DSP option installedthis is the same accessory unit thats applicable to a number of different ICOM transceiver and receiver models. The DSP board adds an automatic notch filter and a noise reduction feature. The adjustable

39、 noise reduction worked extremely well, doing an outstanding job of cleaning up noise. The automatic notch filter was a pleasure. When youre operating SSB and the inevitable “tune-up” interference appears, you jab the front-panel ANF button once andpoofits gone. It may have been my imagination, but

40、the IC-718s IF shift seemed to be particularly sharp. With both CW and SSB signals, I was able to manipulate the IF shift to eliminate or reduce interference successfully in many instances. GettingAroundtheBands As Ive already mentioned, selecting a band is as easy as punching the front panel UP or

41、DN buttons. You can use this method to hop from 160 through 10 meters in no time. If spinning the VFO is more to your liking, the IC-718 makes it easy with the TS function, which allows you to vary the tuning incre- ments to cover a lot of spectrum very quickly. In addition, as you spin the VFO knob

42、 faster, the tuning speed increases automatically. If you know exactly at which frequency you wish to operate, just press the F-INP/ ENT button on the IC-718 keypad, punch in the frequency digits, then press the button again. Thats all there is to it. Of course, the IC-718 has frequency/ mode memori

43、es101 of them, in fact. You can store all of your favorite frequencies into memory, then use the CH button in combina- tion with the UP/DN buttons to step through the channels. Alternatively, you can simply enter a desired memory channel number into the keypad. Spinning the VFO knob al- lows you to

44、tune above or below the selected memory channel frequency. Figure1Worst-casespectraldisplayoftheIC-718transmitter duringtwo-toneintermodulationdistortion(IMD)testing.The worst-casethird-orderproductisapproximately25dBbelow PEPoutput,andtheworst-casefifth-orderisapproximately39 dBdown.Thetransmitterw

45、asbeingoperatedat100Woutputat 7.200MHz(seetext). Figure2Worst-casespectraldisplayoftheIC-718transmitter outputduringcomposite-noisetestingat 14MHz.Poweroutputis100W.Thecarrier,offtheleftedgeof theplot,isnotshown.Thisplotshowscompositetransmitted noise2to22kHzfromthecarrier. Figure3CWkeyingwaveformfo

46、rtheIC- 718showingthefirsttwoditsinfull-break- in(QSK)mode.Theequivalentkeying speedis60WPM.Theuppertraceisthe actualkeyclosure;thelowertraceisthe RFenvelope.Horizontaldivisionsare10 ms.Thetransceiverwasbeingoperated at100Woutputat14.2MHz.Notethat bothditsaresomewhatshortened.Only thefirstditisshort

47、enedinsemi-break-in mode.Alsonotethehigher-power“spike” ontheleadingedgeoftheCWwaveform (seetext). 66 July2000 The IC-718 supports two VFOs for split- frequency operation and the splits can be stored in memory as well. Two scanning modes are offered in the IC-718. The memory scan steps through the d

48、esignated memory channels. There are no provisions however, for locking specific memory channels out of a memory scan operation. The programmed scan seeks signals between two specific frequencies. With the wide variation between signal strengths and the random noises encountered on the HF bands, pro

49、grammed scanning can be problematic and, frankly, doesnt work all that well in most HF transceivers. DigitalOperation Operating RTTY or PSK31 with the IC-718 was a breeze. The audio inputs and outputs, along with the transmit keying lines, are available at the 13-pin acces- sory jack. The pin designations matched my IC-706 closely enough that I was able to merely plug in my existing cable and go. Although wiring up a 13-pin connector can be a considerable test of your soldering skills, at least youll find clear descriptions of the connecto