IC-706MKII

Likes:

• Compact and provides full 100W on HF and 6m with 20W on 2m.
• Remote face option, great for mobile use..
• Well engineered and robust, mine has spend lots of time in a car, on a yacht and in a backpack and always worked when needed.

Dislikes:

• High current draw (1.5A+) even when just in RX mode. This makes it unsuitable for backpack work.
• I have had problems with spurious emissions, especially on 6m. This is on SSB as well as CW ! but was probably caused by the point below.
• Rig very sensitive to magnetic fields !, this can cause all kinds of strange behavior.
• Power spike when starting to TX causing problems with some (mostly solid state) amplifiers. Even with the output turned down to 5w the radio will still produce a spike close to 100w when first keyed, on CW or SSB !
• I have had problems with intermod on 2m when running this radio connected to a big antenna, I suppose that can be expected from a small radio like this with such a wide bandwidth.
• The wide front-end of the receiver does not make it an ideal radio for serious DX-peditions or contesting.

IC-756

Comparing the IC-756 with other popular radios, ARRL results.

Likes:

• Display !, I find it sharper (higher resolution?) and more focused than the PRO/PROII even if it is not in color.
• VERY easy to operate, you do not need the manual all the time if you want to use some of the special features.
• RX, better than IC-756PRO/PROII !. Both selectivity and sensitivity. I had both mine tested in the lab, on 50.110MHz both could detect a signal at 0.036 micro volt, the lowest the instruments could go !, AMAZING !
• Robust construction and cool running even under high duty cycle conditions.
• DSP that works well, the fact that you can change the level from the front panel and not in an obscure menu helps !
• Great layout of front panel with all the most needed controls available without searching through menus !
• Dual watch, I know it is not the same as dual RX like in the FT-1000MP but it works well for what it is intended and along with the scope it is magic! If you see a signal on the scope you can go and listen to it while you are busy in a pile-up.
• Spectrum scope, the 756 works well and is actually 1.2-2 times faster than the PRO/PROII.
• "Fuzzy logic" tuning rate, easier to use than a fast button or shuttle jog tuning.

For those of you who keep track of the QST test reports, you might have noticed that this radio holds second place of best receiver characteristics ever tested there, right behind the IC-775. The IC-756 is actually better than the IC-781, a superb radio in its own right, which it replaced.

Icom won’t tell you, but the latter models of the 756 (PRO and PROII) are basically cost-reduced versions of the original 756. The latter was too expensive to produce. Accordingly, the PRO and PROII have considerably less-good receiver characteristics, just compare the QST reports!, what they do have is more bells and whistles, and color ....

I have to admit that I have now fallen so badly in love with the spectrum scope that I feel lost without it, I do not believe I will ever be happy again with a radio without this feature and I am even prepared to scarify some other features for this one. Combined with dual watch it is the ideal way of finding the right spot during a split pile-up or a calling frequency during a contest. My Kenwood and Yaesu rigs have been gathering dust since the 756's moved into the shack! Take note Kenwood and Yaesu! 

Dislikes:

• Low spectrum scope sensitivity (easy modification, if you have good eyesight and a steady hand, available, contact me if you would like to know more).
• Small flimsy knobs for microphone gain etc. (same on all models of 756 and 746).
• Would have liked more slots for filters but I find a 9Mhz CW filter (250 or 500Hz) and a 455KHz SSB filter (1.8KHz) allows you to work both modes with one radio.
• Lack of internal voice recorder.

IC-756PRO

Likes:

• Colorful Display.
• Robust construction and cool running even under high duty cycle conditions.
• Dual watch, I know it is not the same as dual RX like in the FT-1000MP but it works well for what it is intended and along with the scope it is magic !, if you see a signal on the scope you can go and listen to it while you are busy in a pile-up.
• Great layout of front panel.
• Software, DSP filters.
• Voice recorder, really helps saving your voice during a SSB contest!

Dislikes:

• Noisy and insensitive RX (see below).
• Low spectrum scope sensitivity (maybe this could be modified like the 756, I have not tried...)
• Small flimsy knobs for microphone gain etc. (General Icom problem)
• Slow (compared to original 756) update of spectrum scope.
• Resolution of display seems to be lower the original model.

Sensitivity problem.
The fully digital processing of IF signals has the disadvantage of additional "quantization noise" on weak signals (by physics). Even when 24 bits ADC are used, the steps are spread linearly. I.e. steps are relatively greater on small ADC counts.
If you compare sensitivity against an (analogue) Rig, the Pro2 looses. On 6 m or any of the higher bands. Doesn't matter. There is always a few dB disadvantage for the digital concept!

IC-756PROII

I have only had a quick look at this radio but I am hoping to have one of these in the shack soon to compare it directly with some other rigs. One weekend is not enough to really judge a fine piece of hardware like this but I will hang on to my original IC-756's for a while yet!

Comparing the IC-756PROII with other popular radios, ARRL results.

Likes:

• Colorful Display.
• Robust construction and cool running even under high duty cycle conditions.
• Dual watch, I know it is not the same as dual RX like in the FT-1000MP but it works well for what it is intended and along with the scope it is magic !, if you see a signal on the scope you can go and listen to it while you are busy in a pile-up.
• Great layout of front panel.
• Tunable noise blanker works very well.
• The spectrum display sensitivity is much better than previous models and the switch able attenuator helps on the lower bands to keep the scope from saturating.
• Software, DSP filters, ability to customize filters and define new filters is really magic!
• Voice recorder, really helps saving your voice during a SSB contest!

Dislikes:

• Noisy and insensitive RX, better than the 756PRO but still not as good as the original 756 (see below).
• Small flimsy knobs for microphone gain etc. (General Icom problem)
• Slow (compared to original 756) update of spectrum scope.
• Resolution of display still seems to be lower the original model.
• All the fonts and backgrounds for the screen does not make for a better radio!

Having all those DSP features are nice, unfortunately they are behind fairly broad band 1st and 2nd IF's which allows a strong signal to either pump the gain in the third IF (where both the DSP and AGC lie) or add IMD in the first or second due to in-band overload. This makes it difficult to hear a weak signal if there is a very strong signal 3-4 kHz away from the frequency you are listening to with the new ICOM DSP driven units, this was easier on the quad conversion receiver with 9MHz and 455 kHz IF filters like the original IC-756. It would have been best to put the DSP and AGC in the 1st IF but current (CPU) technology is not quite there yet!

Sensitivity problem.
The fully digital processing of IF signals has the disadvantage of additional "quantization noise" on weak signals (by physics). Even when 24 bits ADC are used, the steps are spread linearly. I.e. steps are relatively greater on small ADC counts.
If you compare sensitivity against an (analogue) Rig, the Pro2 looses. On 6 m or any of the higher bands where sensitivity is important, doesn't matter. There is always a few dB disadvantage for the digital concept ! I know this is a theoretical limit but I am doing some tests and I hope to soon have a "real world" report on how this actually affect us in general operation.

IC-746

Likes:

• Compact and well constructed with a nice solid feel.
• 100W on 2m as well as on HF/6m, a real power house.
• FM narrow band (12.5khz) at the push of a button.
• DSP noise filter that really works and seems to be very fast compared to some other radios.
• APF that works well, most of the time you don't need extra filters on CW if you use the APF filter on 320, 180 or 80Hz.
• "Fuzzy logic" tuning rate, easier to use than a fast button or shuttle jog tuning.

Dislikes:

• Power spike when starting to TX causing problems with some amplifiers, my current unit does not exhibit this problem but a previous one did.
• Even when using (IF) DSP TPBF the AGC gets "pumped" by nearby strong signals unlike the DSP in the TS-870S.
• The front-end is not nearly as solid as the 756 but then I suppose you get what you pay for.....
• Really needs additional filters for contest work, I have now installed a 250Hz filter in a 9MHz slot and it really helps! Making this a good radio for mini DX-peditions.

IC-471H

Likes:

• Full size well build base station style all mode rig.

Dislikes:

• Battery backed system software can be lost killing rig when battery dies. This can easily be prevented with a bit of care.

IC-707

Likes:

• Compact and low cost.
• Easy to use for non technical person.

Dislikes:

• Low cost shows, a real plastic "cheapy"!

IC-551

Likes:

• Compact for its age.

Dislikes:

• Bad RX (wide/noisy/deaf).
• Construction not great ! I have had to repair more than one with bad solder joints.