By W0QL - Mark Edwards
Updated December, 2010
ICOM's new whiz-bang HF/6m transceiver has just come out and it's probably going to make waves. Here's one ham's opinion of what ICOM did right and what could have been done better.
I hate reviews that praise new radios as being the best thing since sliced bread. So if this review sounds like that I guess I'm saying that it really is a revolutionary radio. It's been a long time since I've been this excited about a new radio. It has tons of fantastic features but those are not why I bought the radio, nor will I waste your time reviewing those. You can read the sales brochure. What makes this radio worth buying could be said this way, "It's the DSP, stupid." Ever since I bought my first add-on DSP unit years ago I instantly realized that DSP would be great except for one thing. How can you clean up a signal after it's already been passed through the whole radio? What we really need is DSP that can act at the RF frequencies or at the least, the IF frequencies. Obviously I wasn't the only ham to say this because many radios have come out since with "IF DSP". Some of them make me laugh when they define the IF frequency in the audio band. Come on now.
When I first saw the ad for the IC-756PRO one phrase caught my attention, "Newly designed, 32 bit floating point DSP - AGC loop operation." Really? This could be very important. Let's step back a moment to traditional radios that have crystal filters. Those radios are so great because the undesired signal is filtered out before it can pump up the AGC. The problem with DSP so far is that they all work after the AGC loop. Strong signals still cut back the gain of the radio even if the DSP has filtered the strong signal out of the output. The IC-756PRO promises to keep that from happening, just like crystal filters. My question is, "Does the PRO do what the ads say?" You've probably already guessed that the answer is going to be yes so let me skip forward to explain how I measured it.
I found two PSK31 signals that were side by side. I chose PSK because they are steady signals as opposed to SSB or CW and that makes them easy to measure. One of the signals was 20db over 9 and the other was much weaker. If there is one thing my good friend Bill Rinker has taught me that is you've got to make S meter comparisons in the region below S9. So I added attenuation until the strong signal was S9. Next I centered a filter on the strong signal. The big question is whether the S meter would drop or continue to report the level of the stronger signal. Hallelujah! It dropped to S2. This means the strong signal was filtered before the AGC. I've been waiting years. I can center a filter on a CW signal, for example, jammed right up against a much stronger signal and pull the weak one out. Just like good crystal filters. But the narrowest crystal filters I have are 250Hz. There can be a ton of strong CW signals in a 250Hz passband during a good contest. With the PRO I can set a filter as narrow as 50Hz. Try that with any other radio. It's pretty nice turning a knob watching the passband narrow knowing it's happening in the IF, not just in the audio. I can even use the PBT feature to narrow down to 25Hz! This is better than sliced bread.
Okay, Okay, calm down. Does this radio have any other redeeming features to justify the $3000 price tag? Well, I like the color LCD display with a built-in two color spectrum analyzer - one color for instantaneous signals and another to freeze them in a "history" display. Oh, and it has a built-in RTTY decoder so you can print RTTY right on the display. How's that for whiz-bang? Also a memory keyer for both CW and voice. And where are all those confusing DSP knobs and buttons that I see on other radios? In a rebellion against complexity, they're not there. There isn't even one knob or button that says DSP. That's because the DSP function is transparent to the operator. I like pressing a button labelled "NB" a lot better than trying to figure out how to set up a DSP unit so that it will reduce line noise. Same with "NR". Noise reduction is a breeze to operate, not a challenge.
But does it work? Does it make a difference that I can notice with my ear, not just on a test bench? Unequivocally it does. I have a Yaesu FT-1000 sitting beside the PRO with an A/B switch on the antenna. I can pull out CW signals and SSB signals on the PRO that I can only faintly hear on the FT-1000. They are clobbered by line noise on the 1000 and my add-on DSP doesn't help. With the PRO I can copy signals that I cannot copy on the FT-1000. And that's the whole name of the game. It does make a difference that I can hear with my ears. I can't wait for the QST reviews. I am dying to see if the numbers from the lab confirm this impression.
Time now for the nit-picking. Yes, I had to struggle to find it but I did find something I don't like. Actually it's something that I think is wrong with a lot of ICOM radios. Specifically, they don't have a SHIFT knob. How can I get out of first gear without a shift knob? I think the ability to move around these wonderful new DSP filters is essential. Once I see a signal on the spectrum analyzer I want to push the filter button and rotate the shift knob to move the filter over to that signal. Yet the PRO does not have that ability, nor does the predecessor IC-756, nor the 775, nor the 746. Strangely ICOM found a way to put shift on the 706, so why not the PRO?. I know, I know; I can turn the frequency knob or the RIT--but I don't like that.
Another nit-picky thing? I don't like the scale on the spectrum display. It seems confusing to me to have to figure out what each division is. Why not just label them? There's room to do it. Instead ICOM just says each division is so much and lets you figure out how many divisions away from center you are, then mulltiply. Whew! But in defense of the radio let me emphasize that there are many, many, many things I love that ICOM has done right or better than anything else I've seen. It outperforms my FT-1000 and that says a lot because I've thought the 1000 was the best radio ever until now.
Final answer: This radio has something even better than anything I've mentioned. It's one of those things that you know when you experience it. It just has a feel. I bought this radio for its AGC-Loop DSP but I love it for its feel. Impossible to relate but easy to notice in person. It's the particular features ICOM chose and the intuitiveness they've designed into it. Something about it just says, "Come here. Sit down and operate me and have fun with what I can do for you on ham radio." I worked XZ0A, Myanmar on CW barefoot today using just the built-in memory keyer. I pressed the send button with my call programmed on it. When XZ0A acknowledged me I pressed the key that I had programmed a repsonse on. Not very personal but it was a fun way for me to work a Dxpedition. As long as hams can work DX easier on a PRO than on a FT-1000, then this radio is going to make waves. And that's my final answer.
2011 Update: A lot of time has passed to say the least since I wrote this review. I still like the radio enough to have the same IC-756Pro sitting on my ham desk but it is in second place now next to my Elecraft K3. The Pro did prove to be more than popular in sales, but technical reports were not great. The one that cut the deepest was Dr. Rob Sherwood's published results for dynamic range on www.sherweng.com. Rob's measurements placed the Pro below even the IC-701 I had in 1979, the Kenwood 930, 820, and showed the Pro to be just plain crappy. Other reviewers disliked the shape of the CW filter.
Now for some thoughts looking forward: The Yeasu FT5000 has just come out and Rob's measurements show it beats even the K3 and the Flex 5000, the top receivers of recent years. Updated models of the 756 Pro have come and become obsolete already. Kenwood and Yeasu have produce models with DSP in the I.F. over the years. All fell short in Rob's testing. Speaking of falling, I fell for the Yeasu FT2000 when it came out and fell out after two years of fighting it's convuluted human interface. That's even after owning an FT1000 for 10 years and being quite familiar with the Yeasu operation. The K3 roofing filters hooked me and I love the radio for CW operation. I've had the K3 long enough to learn it's operation and it's pretty comfortable it's still not the PRO. After all these years I still miss the feel of the PRO. Yeasu has made a big leap with low band first I.F., meaning narrow roofing filters, in the FT5000. I'm not ready to jump for it due to my past experience with Yeasu's clunky human interfaces. What I'm really waiting for, aside from winning the lottery, is for ICOM to come out with a 7600-like radio with a low band I.F. and narrow roofing filters. Stay tuned. Of course, if I do win the lottery, I'll be waiting for a 7800-like radio with the same.
2015 Update: My 756Pro passed away in the summer of 2014 and I decided to let it stay dead. An Icom repair person said the front panel was probably defective and parts are very hard to find. I donated the radio to the Denver Radio Club and they chose to sell it at a hamfest rather than fix it. After looking at the currently available transceivers I bought another ICOM. This time the IC-7600 mentioned above. Despite Rob Sherwood's measurements there is another lab owned by Adam Farson, VA7OJ/AB4OJ. Adam performs noise power ratio testing of HF receivers and gets good results for the ICOM's. See the March/April 2015 issue of QEX Magazine, p 20. My decision was based on my familiarity and like for the ICOM human interface. Upon reading Adam's test results I am further pleased with the transceiver's performance.