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IC-781 review by Bill Clarke WA4BLC | Radioaficion Ham Radio

IC-781 review by Bill Clarke WA4BLC


The ICOM IC-781

Quintessential DX Rig

The ICOM 781 is ICOM's latest and most complex HF transceiver. It is fully solid state and CPU-based. The mere term "transceiver" doesn't do it justice. The IC-781 incorporates features that used to require a desktop full of extra equipment.

The IC-781 combines a CRT display of functions, frequencies, memories, and spectrum scope with a top-notch transceiver, automatic antenna tuner, and AC power supply, into the most complete one-piece HF ham station available today.

The IC-781 rs Operating Manual

The first mark of the IC-781's high class is its operating manual. It is absolutely thorough—it has nearly 100 pages of instructions, photos, diagrams, and charts. The manual comes in a zippered, heavy-duty plastic bag, the kind meant for re-uset along with the radio's inspection certificate and warranty cards.

After unpacking the radio and placing it on my operating desk, I studied it for a few minutes. I counted 112 separate controls on the front panel, and decided that it would be greatly advisable to read the instruction manual before plugging it in.

Overview of Features

The built-in spectrum scope displays the relative signal strength of radio transmissions up and down the band from your frequency. The band width is selectable between 50,100, and 200 kHz. It is not a true scope, but a well-engineered computer facsimile.

The Terminal Monitor allows you to use the CRT for digital display of RTTY, packet, etc,t and the built-in Automatic Antenna Tuner is for hands-off adjustment of antenna matching (limited to 16.7-150Q. or at less than 3:1SWR). The Direct Digital Synthesizer provides extremely fast " lock-up" times for transmit/receive switching.

Dual Watch lets you monitor two separate frequencies simultaneously, while Fine Scanning tunes slowly through a received signal without stopping. This feature is particularly valuable for CW and SSB. Twin Passband Tuning controls tandemly, or separately, the tuning of the 455 kHz and 9 MHz IFs.

The AGC is fully adjustable. During CW operation, the Audio Peak Filter attenuates unwanted audio components between 500 and 1000 Hz.

Other features are: full break-in keying, 150 Watt output, noise blanker, 105 dB dynamic range, and a multi-function keyboard for digital (fingertip) entry of frequencies. The memory channel holds 99 memories, including two-

band scan entries. You can display these memories, together with a label, on the CRT. Examples of labels are net names or operator notes. The IC-781 has two clocks for local and UTC time settings, and timers for turning the transceiver on and off as predetermined.

This review is made from an operator's point of view; it is not the result of strenuous laboratory testing.

Operator Viewpoint

The IC-781 is quality all the way. The controls feel solid, everything works as expected, and the manual explains all you need to know, in both words and diagrams.

The tuning knob is large and has a fairly smooth action. It tunes at the rate of 5 kHz or 2 5 kHz per revolution, as selected by an internal switch. The knob is not as large or as smooth in operation as the IC-761 's. The main tuning knob has a tension adjustment under the front of the radio.

The frequency read-out has the 10 Hz digit. I find this feature nice, although some operators feel that it makes tuning too critical. This is a matter of choice. You can calibrate frequency without entering the case.

Many of the seldom-used controls, such as VOX, lighting, etc., are pull-out types. The clocks and memories have battery backup. Should the batteries fail, the radio will continue to operate, without memories or clocks.

In general, the IC-781 performs as you would expect a top-of-the-line radio to perform. After learning how to use the many controls, I found it was possible to clean up signals unreadable on older types of radios. For example, signals in the QRM on a TR-4 became completely readabfe on the IC-781.

The speech processing gave an extra punch to the signal that reached out well, yet it did not foul up the intelligibility of the transmission. On a scope, the voice patterns filled in well when I used the processor.

The spectral display of the band revealed the location of the loud stations, and also indicated open places in the band. It afforded a quick look at a band for activity.

Being able to scroll the memory list on the CRT and to enter the frequency and mode with a single keystroke are great features of the IC-781, When dealing with 99 memories, I found the label field very important. It allows you to name a memory (i.e., MIDCARS, VA FON E NET, GULF COAST, etc.) and easily access it.

The IC-781 Receiver

The receiver is very quiet, with little background white noise. With fully variable parameters, it can reduce or eliminate most QRM/N. The twin passband tuning is especially effective in cutting out QRM from adjacent signals. Forty meter evening operation is relatively easy with the twin passband tuning, notch, and attenuators. The notch filter is easily tuned and effectively deep. However, considering the price of this rig, why isn't it automatic?

For more variables, you can use the receive preamp or the attenuators. You can choose 10 and 20 dB for the latter, or switch both on for 30 dB of attenuation

The quality of the receive audio from the built-in speaker is excellent, coming in a close second to my main station speaker. The bass/treble controls improve the built-in speaker's sound quality.

The IC-781 has several methods of scanning. It does memory scan, programmed scan, and mode scan. To use mode scan, you must first go into memory mode. There, mode scan will find channels of only a given mode, e.g. LSB or FM.

Dual watch is nice when you're monitoring a specific frequency for activity, it does, however, have the drawback of being limited to the same band as other operations. There is no crossband dual watch.

The passband tuning arrangement looks like it would be great on RTTY and packet, although I didn't test this possibility.

The Transmitter

The two VFOs make split operation available at the push of a button. The IC-781 can also be easily modified for CAP and MARS frequencies.

The keyer behaved wonderfully, offering full break-in and semi-break-in operations. There is, unfortunately, only an internal adjustment for dit-dah ratios.

The monitor feature allows you to hear your SSB audio component, making it easy to adjust the speech processor, and the microphone's tone and drive, as well as letting you hear other imperfections on your signal. The audio and CW signal reports I received were all good.

The built-in antenna tuner is fast, and it will handle most cleanup jobs caused by excursions within a band. It will not tune "Grandma's bedsprings." It can handle SWR mismatches only to 3:1.

The circuit used to key linear amplifiers is stout enough only for modern 12 volt circuits. To use it on anything else could cause damage. I recommend using an external relay. The IC-781 is not alone in this deficiency; most other makes and models suffer from a similar shortcoming.

Bench Testing

Bench testing is the only true method of measuring the performance of a transceiver. Personally, I feel that all of the currently available CPU-based HF transceivers are capable of performing above and beyond the capabilities of the human ear, and certainly over the poor band conditions that we all too often experience. The IC-781 is no exception to the rule.

I used the following lab equipment to check the performance of the IC-781:

•Leader LDC 8243 Frequency Counter •Marconi Instruments 2022 Signal Generator •Hewlett Packard 606 HF Signal Generator •Hewlett Packard 651A Audio Generator •Bird 43 Wattmeter

•Hewlett Packard 8551B/851B Spectrum Analyzer

•Cushman CE-5 Monitor •Tectronics 475 Oscilloscope

Any Complaints?

There is little fault to find with the IC-781. It is a well-designed unit, built with the operator in mind, There were a few things, however, I didn't care for.

The digital key pad is important for operating dexterity, and allows you to enter a frequency without turning the main tuning knob. I was, however, surprised to discover that when I entered a frequency directly, the digital key pad mode did not automatically change. For example, 7.255 MHz is on LSB, but when you've made that selection from a previous setting of 14.313 MHz (USB), the USB mode will follow. In other words, there is no bandplan programmed into the unit.

Second, I don't care for the dot-type presentation of the surrounding spectrum on the display. A real scope trace is easier to read.

Third, even though the IC-781 's overall appearance is truly a "ten,'1 after setting it up, I noticed that I had a problem reading the control labels, which are medium gray on a nearly black background, A few are red, but

none are easily seen in typical lighting. The white lettering on my 735, 751 A, and 140, is easily readable.

Not all operators will use every feature of the IC-781, and to some the unit would be unacceptable due to its complexity. To others the price might be extravagant. However, feature for feature, the IC-781 is the most capable piece of HF equipment currently available. I feel comfortable recommending the IC-781 as a true state-of-the-art, unique piece of equipment,

Where Do the Dollars Go?

I've heard some interesting comments about the IC-781. Among them are: It costs more than my first house. My pickup truck cost less than the IC-781. Who is going to fix it when it breaks? If I take that home, I'll be getting a divorce. It doesn't do that much more

than a $2,000 radio. It's so heavy, it would crush my desk.

Most of the comments are about the IC-781 "s cool list price of $5,995. That ain't hay, my friend. However, let's put these numbers into perspective. In 1958, you could buy a Collins 32S1, 75S1, and the goodies to go with it, for about $1,590. That was in the day of the $15,000 house and $2,500 automobile. Today the home will cost nearly $100,000 (depending upon geographical location) and the family chariot about $15,000. Perhaps these numbers pface the high price of the IC-781 more in line with today's economy.

I have included a chart of the manufacturer's specifications to show how the various top dollar rigs compare. The IC-735 is included on the chart just to put some depth into the study of cost vs, what you get.

"Thank you" to the folks at the Electronic Equipment Bank of Vienna, Virginia, for the loan of an IC-781, and the use of their very complete test bench -

73 Bill Clarke WA4BLC - 1989

The ICOM IC-781  Quintessential DX Rig

Comparative specifications chart for HF transceivers. This chart was complied by the author

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