Brian Hummerstone, G3HBR
Issue 66, August 2000
The
IC756PRO set up in Brian’s shack. The ‘grass’ on the spectrum display is
someone a couple of gardens away using a clapped out old grass strimmer!I was very pleased to be given the opportunity to review the 756 PRO from the viewpoint of a six-metre user. Unfortunately, the rig turned up just too late for the results to be published in our last issue but that meant that I had more time to give it a thorough airing.
I do not have access to professional measuring equipment, so readers who like a detailed technical review should read the excellent feature by Peter Hart in RadCom for March 2000. However I do have the earlier model IC 756, a Kenwood 680s and an Alinco DX70TH in the shack for comparisons.
General
The PRO is 12V-operated and requires a separate power supply which can provide at least 23 amps. In appearance it is very like the previous model 756 and most of the front panel controls are the same. Many of the features are the same or are similar to those reported by Frank (then PA3BFM) in his review in ‘Six News’ for August 1997. The large display is in colour and is easier to read than the blue/mauve one of its predecessor.
The 756 PRO comes with a full inventory of features and everyone will find something of interest and use to them. Internally the major advance is in the extensive use of digital signal processing; its application, particularly to IF filtering, is impressive. As with most other modern sets the received audio is much improved by use of good quality headphones or an external forward facing loudspeaker.
Although there are very many options and an 80-page manual to go with them, the default values already set up mean that the transceiver can be used with confidence soon after the antenna, power supply and mike/key are plugged in. Within a short time of first switching on the set, I had worked G0JHC on Six and VK6WD and VP8DBL (Chris, G3WOS in disguise) on 28885.
The transmitter
It is unusual these days to come across a commercial rig which does not put out a good signal when correctly operated, and the Pro is no exception. It easily achieves the full rated output of 100 watts, just a little over in fact. The auto tuner works well. All the keying features you would expect are present and the rig retains the memory keyer features which I like so much in the original 756; these are most useful for contests and MS work. In addition it has voice memories for use on SSB which will certainly offer great relief to the vocal chords in contests. There are four memories for CW which will each store up to 54 characters and four for speech each of which will hold a 15 second message (I was surprised how much I could say in 15 seconds!)
The bass/treble adjustment and speech processing are a noticeable improvement on the older brother and very crisp, readable speech results from careful use of the available adjustments and options - which include filter bandwidth when compression is used. A meter indication is provided to help set up the processing level.
The receiver
Because of poor conditions and lack of activity on six, I found it necessary to use 40m, 20m and 10m to check out some of the features. My favourite mode of operating is CW and I really enjoy trying to winkle out weak signals in big QRM. The Pro is a pleasure to use for this sort of work. The ability to tailor the IF bandwidth to your liking is a delight, it is useful and informative to be able to display the bandwidths on the screen and watch your adjustments take effect. There is no noticeable ringing at even the narrowest useable bandwidths. The notch filter works very well.
On six metres, I don’t think you will be able to detect any signals that you can’t on any other halfway decent set, however you may be able to do a little more to improve the readability of them. In common with most other HF/50 transceivers the PRO is a little short of front-end gain on our favourite band. This shows up on the S-meter, where an audible S9 signal registers S6, and on that most useful feature, the spectrum scope, where signals below S5 virtually do not register at all.
This latter feature is worth dwelling on. Since having a 756 I have become hooked on the scope, particularly for its usefulness in showing activity away from the frequency currently in use. However I want to see that activity before an S9 local comes up calling there!
Because of the gain shortfall on most sets, I have for many years used an outboard low noise pre-amplifier from RN Electronics and with this in use on the Pro the weak signals do show up on the scope. On the older 756 with the LNA in line, one or two very big signals sometimes cause the screen to look very strange. This occurs because there is a limit to the dynamic range of signals that can sensibly be shown on the screen. The new Pro incorporates a switchable attenuator in the scope system, which so far as I can tell solves the problem.
The scope is also useful for monitoring the quality of incoming signals! Using the scope on one of its narrower bandwidth settings (100kHz, 50kHz, 25kHz and 12.5kHz are available) it is interesting to see how close to a big signal you can tune before hearing anything of it at all. This readily demonstrates the superb filtering in the Pro and I was able to give it a good checkout in a recent contest on Six.
The noise blanker shows no improvement over the one in the 756, which is a disappointment but the noise reduction feature, which is of marginal benefit in the earlier set, is more effective in the Pro.
The set retains the dualwatch facility but this is something I do not use often because I always have another rig running on 28885, and in the summer often one also on 70200. I have occasionally used it to monitor the beacon frequency of an expedition but so far without result. Using it does worsen the noise performance and can lead to severe mental confusion for an old G3 when two loud signals come up at once. Nevertheless I can see its potential value.
There are enough memory channels (101 to store lots of beacon frequencies, for those who wish to do so. I just use a few, in particular one for the 49.750MHz TV frequency and one for 48.250. It is very useful to switch to one of these two and look for the offsets on the scope. There are adequate scanning facilities and I like the triple band stacking registers for each band.
Voice recording facilities are provided on receive, however these only give four 15 second memories and it is necessary to do a bit of finger work to implement them so they are not especially useful. What would be nice would be continuous recording of the last minute on a rolling basis with a stop button. This would be sufficient to confirm QSOs under difficult conditions and perhaps prevent ‘insurance’ repeats. Although I could not find a reference to it, it is possible to record in CW mode by setting up as per manual in SSB or FM mode and then changing mode to CW after the recorder screen appears.
An RTTY decoder is incorporated which displays the received text on the screen. Although this is not really my scene, I happened across an RTTY contest and I found it quite enjoyable to do a little short-wave reading for a change. I was most impressed with how well weak signals could be copied. Not likely to be of much interest to a serious six metre op’ but it does provide something else to do when the band is dead.
Normal CW operation is in LSB, as it is with all the other ICOM sets I have tried, and although CW Reverse is available which enables USB to be read there is still an 800Hz offset. This can be overcome by setting the IRT appropriately, if you can remember which way to go. It is not a problem on other bands where cross-mode operation and rapid switching between modes are rare, but it is an irritant for the six-metre user. This is not just a personal niggle, as every other six metre DX operator I know who uses ICOM equipment makes the same complaint. I guess ICOM do not have a dedicated six-metre operator as a member of their design team.
Conclusions
The IC756 PRO is an excellent HF band transceiver. It is very comfortable to use. If you like the display on the 746/756 you’ll love the one on the Pro. If the CW/SSB offset could be corrected, an additional switchable 10dB of front-end gain provided for 50MHz, and receive recording implemented as a continuous riro system, it would be an ideal six-metre rig.
As it stands it is very good. At the current RRP it is quite expensive even though there are no additional filters to buy, but so was the earlier 756 when first introduced. Once all the folk who buy the latest new box as soon as it appears have obtained theirs I’m sure the price will start to come down, perhaps even by the time this review appears.
Acknowledgement
Our thanks are due to Martin Lynch and Sons for providing the set for review.
