IC-706MKII ... Whats New Over The IC-706:

Product Review Edited and Reviewed by Rick Lindquist, N1RL
Senior Assistant Technical Editor, QST

Since ICOM came out with the IC-706 a couple of years ago, we have been expecting (well, at least half expecting) another manufacturer to attempt to top ICOM's triumph. After all, the IC-706 was the first transceiver (and as of this printing the only) to integrate 160 through 2 meters in a single, very compact package that also includes general coverage receive, a choice of modes, and a detachable front panel that lets you install this radio just about anywhere in one of today's vehicle “cockpits.” Curiously, no one has seemed equal to the task of beating ICOM at its own game. Even so, last spring ICOM felt compelled to trump its own ace with the IC-706MkII. Not only has ICOM managed to make its best little radio even better, it kept the price the same! Let's face it. The IC-706 was a hard act to follow. What could ICOM do to improve what we called “one of the most exciting new products to come along in years”? Well, for starters they must have taken our review of the original IC-706 (see “Product Review,” QST, Mar 1996) to heart. While we heaped a lot of praise on the original '706, we also pointed out a few rough spots (very possibly a consequence of its having been rushed to market). Subsequently— and with little evidence that the competition was breathing down its back—ICOM went back to the drawing board to upgrade the basic '706 to smooth out the bumps without compromising a great (and rugged) basic design. Then they added some newfeatures as icing on the cake. Let's see how it turned out.

What's new? ICOM's reworking has been successful enough to prompt even some diehard '706 owners to trade up to the MkII. None of the changes is terribly obvious. It's pretty easy to confuse the old radio with the new model when they're sitting next to one another. Among other new features, ICOM has given the MkII twice as much output power on 2 meters, an extra filter slot, real BAND buttons (which used to be UP and DOWN buttons), and expanded the role of the RIT knob to also serve as a sub VFO knob. A lot of the changes are hidden within the radio's many menus (no, those didn't go away in the MkII). The MkII has a bigger, better speaker, a thermostatically controlled cooling fan, a new fine-tuning mode (activated by a menu choice labeled 1/4—I had to look this one up), and improved wideband receive performance (no more “yellow wire mod”). As we has pointed out in our review, the original IC-706 suffered from poor sensitivity over much of the 60 to 200 MHz range. Tone squelch is available as a option. Another change that will eliminate hassles for many ops is that power output now can be set independently for HF and for both VHF bands. You can set one power level for HF, another on 6 meters, and yet another on 2 meters! On the original IC-706, HF and 6 meters shared one power level setting and two meters another. A new M-CH knob lets you step through Stepping through the modes on the MkII is just a little bit different. On the original unit, you'd toggle between RTTY and AM if you pressed and held in the mode button while on one or the other mode. Now, you toggle between RTTY and RRTTY (reverse). The AM mode shares a position on the next stop with FM and FMW (wide). The ability to swap or invert the RTTY signal is a real plus for those using the radio in that mode.While most of the changes proved to be improvements, a couple (just a couple) prompted us to ask, “What, that's better?” More on these later. First, some details. Moving around No longer will '706 users have to rely on the TS button and the main tuning knob to move from band to band. As we mentioned, the MkII has real BAND buttons where the UP and DOWN buttons used to be. This is a great change that means much less button pushing and fewer errors (how many times have you IC-706 owners pushed the TS button and started turning the knob only to realize you've got the tuning step indicator in the wrong place?). The TS button lets you select 1 Hz and 10 Hz tuning steps in CW, SSB and RTTY modes. When you're in the 1 Hz tuning step mode, a 1 Hz digit appears on the display. One difference here is that you can only apply the 1 MHz “quick tuning” step in FM, WFM or AM mode on the MkII. Some users of the newer model considered this a disadvantage. The old '706 let you apply the 1-MHz step in any mode. The changes involving the RIT may turn out to be a matter of good news/bad news, depending on your perspective. First, the good news. Now, when you turn the M-CH knob (formerly the RIT knob) after pressing the RIT/SUB button to enable RIT, the frequency change is displayed (briefly) in the menu portion of the window. This is a quantum leap from the original RIT implementation, where you never knew how much RIT you were cranking in until you pressed and held the RIT button to add the RIT tothe main frequency readout. The potentially bad news is that ICOM upped the maximum amount of RIT in the MkII from ±1 kHz to ±9.99 kHz. This sounds like an improvement, but you're likely to find yourself turning and turning the little knob to effect just a minor frequency adjustment, and it cannot be changed to a coarser step. ICOM suggests using the split function if you need more than a little RIT. The MkII's M-CH knob is detented too. The RIT no longer works in FM or AM as it did on the original '706. Menu mods Like the original '706, the MkII has several menu sets you access by pushing or pushing and holding the DISPLAY button on the front panel, then using the MENU button to step through the choices. All the buttons and menu sets can take a little getting used to, but they offer a degree of flexibility once found only in much more expensive transceivers. The menus on the IC-706 offer choices accessible via the four “F” keys below the big backlighted display window. In a side-by-side comparison of old and new, we discovered several changes. For example, in the most-used menu, the M set (M1 through M4), on the MkII a M->V button replaces the former MCL (memory clear) choice on the M2 menu. Other changes are more cosmetic—FIL instead of NAR to pick the optional narrow filter. One menu change eliminates a source of annoyance that most owners of the original IC-706 have run into at one time or another —and it's something we didn't talk about in our earlier review: the IC-706MkII doesn't let you turn on the speech processor (compressor) in the FM mode. This means you can switch from SSB on HF to 2-meter FM and not worry that you've left it on. A TSQ (tone squelch) selection replaces the former COM choice in the M4 menu. We mentioned the 1/4 selection. This fills a formerly blank spot on the M4 menu when you're in CW or RTTY mode. While not necessarily intuitive, this cuts the tuning rate of the main dial to one-fourth of its default rate, a great feature that (once again) eliminates the need to press the TS (tuning step) button. It's not available in SSB. The IC-706MkII Instruction Manual could be a bit clearer on what this does—it would be easy to overlook. Other changes lurk in the S1 through S3 menus. The most obvious one is what shows up as B.S.R (for “band stacking registers”) on the display window in the S3 menu. After B.S.R. flashes on the screen, you can select from among three bands that you can set up yourself. This is a nice feature, but it's a bit hard to reach in a hurry. However, the band stacking registers can memorize preamp or attenuator settings, tuner on/off status (the IC-706MkII can control an optional, external automatic antenna tuner), frequency and mode. Another addition is the choice of a PRImary scan channel on the S2 scanning menu. The G1 through G4 menus are essentially the same as those on the original IC-706, except that a .1M (100 kHz) choice has been added to the selections on the BandScope menu, G1. The MkII still has a Quick Set mode to set various operating parameters that you don't adjust too often, such as output power, mike gain, VOX delay or CW breakin delay, CW pitch, CW paddle configuration, RTTY keying, repeater tone and carrier frequency. There are a couple of changes in the Initial Set Mode menu. The MkII menu has 28 items instead of the 24 of the original '706. This makes room on the menu to include an additional optional filter among other things. You now can disable the noise blanker for AM reception, and there's a power-on diagnostic check that you can disable (MkII owners who are familiar with the original unit will spot this right away at power up). The M-CH (memory channel) dial doubles as either an RIT (the default) or a SUB tuning knob. The Initial Set Mode menu lets you enable one or the other. You press the RIT/SUB button to activate RIT or SUB, whichever is enabled. I found the SUB function a bit puzzling since the knob appears to become just another tuning knob when you select SUB. The main advantage is that this knob—unlike the main dial—is detented. Each click represents the frequency step size you've chosen. Crossband operation The original IC-706 did not operate in crossband mode; you could not receive on one band and transmit on another. This welcome addition to operating flexibility is available on the MkII, however—great for those who want to venture into Modes A, K, or KT on the satellites (Mode A is 2 meters up, 10 meters down; Mode K is 15 meters up, 10 meters down; Mode KT is 15 meters up and 10 and 2 meters down). The MkII lets you do all of these, and, on 2 meters, you have the added advantage of twice the transmitting power of the original '706. Using a MkII to work satellites isn't quite like having a full-duplex setup, though. The MkII still operates in simplex mode, even while it can transmit on one band and receive on another. The disadvantage here is that you will have to calculate (or guess) where your uplink signal will be coming down in the downlink bandpass. This makes operating a wee bit more difficult, but we were still able to make good contacts via RS- 12. KB1HY says he simply called CQ on 2 meters, then looked for a station calling him on 10 meters. “The radio worked very well for this type of operating,” he said. Other changes The new, larger speaker of the IC- 706MkII is something you'll notice right away if you've been used to listening to the tinny, tiny (somewhat under 2 inches in diameter) speaker of the original '706. The speaker in the MkII is about one-third larger and provides a noticeable difference in audio quality and clarity. Even at full volume, there is very little distortion. The new MkII has just a bit less heat sink material on the back than the original IC-706. The heat sink fins that were on the right, rear apron of the original '706 are absent on the MkII. This makes the jacks on that side (and especially the modular mike jack) a bit more accessible. The fan operated constantly on the original unit, alternating between a normal speed and a high speed as required. In the MkII, the fan is controlled by a temperature sensor on the heat sink. The fan now shuttles among off, low, and high. When it comes on is determined by the heat sink temperature (which, of course, can be affected by the outside temperature). In a side-by-side comparison, we found the MkII seemed to get warmer than the original IC-706. This is likely not a result of the missing cooling fins but fan operation. On balance, some operators find cooling fan noise annoying, and since the fan does not run all the time, there's less noise in the MkII. While running, the respective fans generated about the same amount of noise. An additional second optional filter slot is a big improvement to the IC-706 and one that all users appreciated. This lets you have a CW filter and an SSB filter or two CW filters (500 Hz and 250 Hz, for example). In addition, ICOM says it has refined the stock SSB filter. A Measure of Improvement In the ARRL Lab, we measured some important performance improvements in the MkII (see Table 1). Much improved transmit IMD is a prime example. We came down pretty hard on the transmit IMD of the original IC-706 primarily because of the prominence of higher-order products on VHF. We were pleased to discover that ICOM has remedied this problem in the MkII (see Figures 1 and 2). We should point out, however, that on 10 meters, the thirdorder, two-tone transmit IMD of our MkII was somewhat worse than the original IC-706, but fifth-order two-tone transmit IMD was better, with higher-order products at respectably low levels. With the preamp turned off, the receiver in the IC-706MkII is much more sensitive on some bands than the original IC-706 was with its preamp off. On 20 meters, we measured 12 dB more sensitivity on SSB/CW, and another 10 dB on 6 meters. Sensitivity also was up on narrowband FM on 10, 6 and 2 meters with the preamp off. With the preamp on, the sensitivity was approximately the same in both '706 versions. The sensitivity of the original '706— especially above 2 meters—was such that in some places, the signal had to be of rockcrushing amplitude to be heard (in FM mode 76 January 1998 at 200 MHz, we had measured “a dismal –28 dBm” on the original unit). We found that sensitivity, while still not terrific in the upper reaches of the receiver's range, was much improved over the original IC-706. CW sensitivity dropped off gradually above 160 MHz, then more precipitously once you reached 190 MHz, but it was still much better than the original IC-706. At 200 MHz, it was in the vicinity of –80 dBm on FM. In the 160 MHz region—where you might want to check on the National Weather Service broadcasts—we measured FM sensitivity at –118 dBm (0.28 mV) for 12 dB SINAD. Blocking dynamic range numbers also were improved on our MkII—up by as much as another 12 dB on 20 meters. Twotone, third-order IMD dynamic range was approximately the same to just slightly worse—typically in the mid to upper 80s. Almost all dynamic range numbers were noise-limited in the MkII. This was pretty much the case with the original '706, too. The combination of increased sensitivity and the nearly identical two-tone, third-order IMD numbers meant that third-order input intercept numbers we measured with the preamp off all were lower than on the original IC-706. They were barely in the positive numbers on 80 and 20 meters, but dipped into the negatives on 6 and 2. (The preamp-on numbers, as expected, were comparable to those we measured on the original IC-706.) As we said about the original IC-706, the MkII did not choke badly under strong-signal conditions as some radios in this price class are known to do. It is more than adequate as a mobile or “second” transceiver. On FM, adjacent channel rejection and two-tone, third-order IMD dynamic range was essentially unchanged from the original IC-706 to the MkII, with all numbers (preamp on) hovering in the 60s. We had not measured the two-tone, third-order IMD dynamic range at 10 MHz spacing on the original IC-706. On the MkII, this was a respectable 77 dB on 2 meters. Image rejection was improved on 20 and 6 meters, but off on 2 meters by 31 dB (preamp off). Just the Same We found that other stations could not detect the difference on the air between the transmit of the old IC-706 and the new MkII, although ICOM claims the MkII has “improved transmit audio.” We got the identical “excellent audio” reports on both radios. We also found the noise blanker worked about the same in the MkII. It's OK for moderate ignition noise and probably what you'd expect in any other radio in this price class. Users still are limited to two AGC selections, fast and not fast (actually, the display only indicates when the AGC action is set for fast; it displays nothing at the slower setting). CW keying in the full-break-in (QSK) mode on the original IC-706 was clipped significantly at higher speeds. Semi-breakin mode looked much better, with only clipping of the initial dit in a series. Anyone who has heard one of these radios on the air when the operator has it in QSK (and especially while using the internal keyer) at more than 30 WPM knows exactly what we're talking about here. This has not changed in the IC-706MkII, and maybe the best philosophy to adopt in this instance is: “You can't have everything” (especially in a radio priced at just under $1600 that already includes more features than most ops had heard of 10 years ago). The MkII has 102 memory channels and you can apply alphanumeric names of up to nine characters apiece to help you keep track of them. There are 99 split memories that can memorize both transmit and receive frequencies (for repeater channels or crossband work, for example). The original '706 was unable to key an external amplifier relay directly. The MkII cannot either. It will switch 20 mA. You'll still need an external relay or switching circuit like the one in “Cure for the 'Missing First Dot' Problem . . .” (QST, Nov 1995, p 84). There's another amplifier-related issue that we overlooked when we reviewed the original IC-706. When first keyed (ie, in CW or in a continuous-carrier mode), the radio generates an leading-edge high-power “spike” of very short duration—maybe a few milliseconds before the ALC takes hold and reins in the output to conform to the power setting (this is visible on Figure 3). This means that even if you've set the power output at, say, 10 W, the radio can generate a brief burst of power—more than 100 W— that could damage some amplifiers or trip protective mechanisms in others. A Raised eyebrow We did not encounter any serious problems with the IC-706MkII. However, we did discover that the spectral purity measurements we got in the ARRL Lab did not quite come up to ICOM's better than –50 dB specification for HF (ICOM specs –60 dB for 50 and 144 MHz). On 20 and 17 meters, we measured approximately –42 dB, which still meets FCC requirements. In truth, ICOM was more concerned about this discrepancy than we were. They asserted our radio was defective and asked us to return it for a look. In the meantime, we checked two other IC-706MkIIs (one a loaner from ICOM and another from a retailer's shelf) and both met the –50 dB specification.

An in conclusion . . . The new ICOM IC-706MkII certainly offers a substantial level of improvement in a product that already had a great deal to offer. Even with the shortcomings of the original '706, it was hard to imagine that ICOM could top its original coup. That ICOM did so without raising the price is doubly praiseworthy. Many thanks to Peter Budnik, KB1HY, Steve Ford, WB8IMY, and Mike Tracy, KC1SX and Ed Hare, W1RFI, of the ARRL Lab, for their assistance in preparing this review. Manufacturer: ICOM America, 2380 116th Ave NE, Bellevue, WA 98004; tel 800-858-6252. Manufacturer's suggested retail price, $1599; FL-100 500-Hz or FL- 101 250-Hz CW filter, $133; FL-223 1.9 kHz SSB filter, $105; OPC-581 12 ft. separation cable, $61.

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