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Icom, Osaka

IC - R71

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überarbeitet am 19.10.2010

The Icom R-71 did replace their R-70 in 1986, it came with a direct frequency entry keypad and 32 memories, but sufferes from losing not only memory content but also informations necessary to operate the internal microprocessor, so radio might seem dead after the RAM backup battery failing.

Variants:
Icom IC-R71 A: for Amateur Radio use
Icom IC-R71 E: for the international market
Icom IC-R71 D: German version: coverage 0,15 - 26,1 MHz
Icom IC-R71 A/E without PBT / Passbandtuning: units produced after March 1989

Triple / Quadruple conversion superhet, I.F. 70,4515 MHz, 9,0115 MHz, 455 kHz

Digital display accuracy 100 Hz, 10 Hz markings on the tuning knob, coverage 200 kHz - 30 MHz

AM, CW, USB/LSB, FM (optional)

Sensitivity AM <0,5 uV, CW/SSB <0,15 uV, FM < 0,3 uV

Selektivity(-6/-60 dB) AM 6/18 kHz, SSB 2,3/4,2 kHz, CW 0,5/1,5 kHz (0,25 opt.), FM 15/25 kHz

S Meter, RF Gain, two speed AGC, PBT / IF shift, HF Notch, 32 memories

Icom's IC-R71 the successor of the IC-R70 communications receiver, it is technically very similar, but a microprocessor control and 32 memories as well as a direct frequency entry keypad have been added. It's dimensions are 28,6 x 11,1 x 27,6 cm and it's weight 7,5 kg. There is an optional external speaker in similar sign and grey - blue - black colour, the sound quality is much better then the one with the internal auxiliary speaker.
The set can be powered from different mains voltages, You have to make sure that the corresponding wire bridges are soldered in, a special 12 V DC kit allows You to run the receiver from a car battery.

Many of the IC-R71's controls are quite small and difficult to operate with hefty fingers.
The mains switch is found at the left of the front panel, the controls just above it are used to control the volume when monitoring Your signal if the set is used connected to a transmitter, to select the AGC speed and to switch the noise blanker. The noise blanker technology developed from Icom was one of the best remedies against "Woody Woodpecker", the noise of the pulsed Russian over the horinzon - rader.
The signal strength meter has a pleasant yellow illumination and gives You S readings and dB over S9 as usually found in amateur radio equipment. The fluorescent display has been improved, small indicators signal the selected reception mode and used memory channel. The frequency ist displayed in 100 Hz steps, lines on the main tuning knob of the R-71 indicate 10 Hz gradation as the R-70 tunes in 10 Hz steps.
Below the S meter and to the right of the power switch, You find more controls: In the top rows the pushbuttons to select the reception modes, a FUNCtion key, a sliding switch for the preamp / attenuator and two keys to select a wider oder narrower I.F. filter, there is a bit of strange behaviour in the set as partly, an additional filter with frequency shift is brought into the signal path, when the narrow (SSB) filter is selected, so You have to retune the receiver, at least You can directly access USB and LSB mode with one pushbutton for each sideband.
Two concentric controls act as volume / AF gain and RF gain controls and as TONE ans Squelch control.

The big main tuning knob is spinning easily, use a small screw to adjust it's resistance. The upmost of the four pushbuttons at the left of the main tuning knobs dims the S meter illumination. The other pushbuttons are used for VFO access, scanning and memory modes.

At the right, at the place of the monitor speaker of the predecessor, You find the numbered keys for direct keypad frequency entry, just type in the correct frequency followed by ENT to access the desired frequency. Just below, there are another two rotary controls. The left one is used to select the memory channel to recall a frequency. The concentric knobs of the other control operate the excellent notch filter (active on the R.F. level) and the PBT. In contrast to the passband tuning as found in classic Drake receivers, the IF filter passband can be narrowed up to 500 Hz from either edge of the passband, this will give You the capability to select the less disturbed sideband of a signal in case of interference from a carrier on an adjacent frequency. The passband tuning on the original IC-R71 has been improved over the older set's one with a better quality filter and is active on all reception modes. In sets produced after March 1989, the PBT feature had to be omitted due to a patent / copyright dispute, it has been replaced by a so called IF shift function.
At the rear face of the receiver, You find all sorts of sockets like in a semiprofessional receiver: So239 antenna connector, HF converter (for a 2m or 6m amateur band converter), a panoramic display adaptor, external speaker, muting and a multiconnector socket for different signals and control voltages.

The IC-R71 is a very attractive receiver, but it suffers from the RAM failure problem: when the internal RAM backup battery fails, not only all memories are erased, but the content with informations to control the radios internal microprocessor is lost also, so the R-71 can become completely inoperative and has to be sent in to Icom or has to be equipped with a modified EPROM replacement board to "resusscitate" the radio again. Because of this precedure is time consuming, quite a few sets are sold as "not in operational" state on internet online auctions - beware, You cannot mend this fault just with a bit of contact cleaner somewhere inside the cabinet. There are possibilities, to replace the receivers RAM by a modification using a larger memory EPROM, which was available years after the receiver has been designed, try Willco Electronics for details.
This is no problem with the earlier R-70 which came without such a microprocessor, so no memories, but no trouble with RAM backup failure.

further literature:
e: the Icom R - 71A, a 1991 appraisal, Clark David, fine tuning proceedings
d: Testbericht Icom R - 71, Rainer Lichte, Radiowelt 1984
d/e: model page at www.radiomuseum.org

© Martin Bösch 4.7.2010