IC-R71E

The ICOM IC-R71 (IC-R71A and IC-R71E) represented at the time of its introduction the state-of-art in receivers dedicated to the amateur radio market. It expresses good characteristics and is, from the functional point of view, a complete apparatus. It has a notch filter (ndr: not active in AM / FM) operating in IF with an attenuation that reaches over 60 dB, very effective in the contrast to the interference from continuous or narrow band emissions. Then there is the PBT pass-band-tuning built between the 3rd and 4th frequency conversion stage, allows to reduce the bandwidth continuity up to 500 Hz in the modes CW / RTTY / SSB and 2700 Hz in AM. The action is carried out by moving the cutting frequency of the IF chain on the upper or lower side with respect to the central value. A noise-blanker, also continuously adjustable and with the selection between two intervention times, proves to be flexible in allowing the user to optimize the action according to the types of signals. Other functions: AGC time constant that can be set between slow or fast or even off, continuous gain adjustment in IF, squelch, RF preamplifier, RF attenuator, audio tone control. Tuning via a rotary control, with direct input from the keypad, or by recalling one of the 32 memories. A search can be performed between band limits or within the memories. For frequencies lower than 1.6 MHz, using a switch on the back panel, you can select between two antenna inputs with low and high impedance. The output at the first IF enables use with external spectrum / panadapter analyzer.

The receiver to demodulate the FM requires the installation of the IC-EX257, this is optional but most of the IC-R71E incorporate it. Other units that can be added are the high stability CR-64 oscillator with a frequency of 30.720 MHz, the speech synthesizer IC-EX310, the IC-EX309 interface for computer control, and the infrared remote control model RC-11.

In the apparatus there are two positions for the installation of optional filters, one for the 2nd conversion IF and one for the 3rd IF, this allows to improve the selectivity profile within the operating range of the PBT. Follow the compatible models and their own features.

IC-R71 performance and practical notes :

This ICOM model certainly belongs to the list of top receivers of the period. Globally the achievable performances are of considerable level. This applies to the dynamic-range, considering offset in any case greater than a few KHz, and for the selectivity that already with only the standard filters offers a form factor compatible with demanding DX. The signal functions as notch, PBT, NB, have made appreciate the IC-R71 to a large group of enthusiasts with a longevity of production that has expanded beyond the decade. Among the shortcomings we mention the non-operation of the notch filter in AM, a real shame as its steep attenuation would make it useful in following the broadcasting interfered by other emissions. A note should also be reserved for audio quality, mediocre as in all ICOM devices of this generation.

Among the options worth mentioning the infrared remote control, an not common accessory, which proves in some contexts quite comfortable despite the ergonomics is not optimal. In this regard, we point out to the possible purchasers the absence of the STEP control thus obliging to act directly on the receiver if you want to change the tuning step between 10 Hz / 1 KHz in order to make it easy to move quickly in frequency.

An important problem, with a technical nature, instead involves the memory IC where the firmware is recorded. Being in the original project foreseen a RAM the maintenance of the data is tied to a back-up battery that once discharge makes the receiver unusable. To remedy this, the memory circuit must be replaced with an alternative PCB board developed by the fans themselves, and which is easy to find fortunately.

As with many other HF devices, the sensitivity is automatically reduced for frequencies lower than 1.6 MHz, the front-end low-pass filter dedicated to this band incorporates an attenuator that can not be excluded except by modifying the circuit. This is a design choice that affects the ability to listen in medium and long waves. Just in the long waves the IC-R71E presents however a surprise, with an artifice it is possible to extend the tuning range to below 100 KHz that mark the lower limit of the receiver. In practice it is necessary to "circumvent" a processor firmware routine positioning itself around 100~150 KHz and then quickly and suddenly turn the tuning knob until, due to the latency in the control logic response, it is possible to break the threshold carrying the apparatus, for example, on 60 KHz. At this point the frequency should be immediately recorded in a memory. From now on recalling this location it will be possible to monitor to increase the portion 60~100 KHz.

IC-R71 interventions and modifications

The receiver demonstrates good structural strength, there are relatively few reports about failures or serious problems with the only exception related to the battery life that acts as a back-up for the firmware as already mentioned. The ICR-71 is in any case an apparatus from the complex circuit and some parts of it with time may lose alignment. Following your requests on the merits, we report some interventions that could prove useful.

Notch calibration

The designers of this receiver have done a great job in creating a IF filter with a deep attenuation point that reduces an interfering signal to 60 dB. A notable function that you can appreciate in SSB and CW listening when there is a more or less continuous tone or even a narrow band transmission, another CW or PSK31 emission to give examples. Inevitably with the years the components that realize the notch modify their own value, a normal aging for the devices, with the result that the filter sees its performance lost. The attenuation depth becomes up to only ~20dB or three points in the S-meter, little compared to the original features. Returning the notch to its maximum performance is not difficult, requiring a very minimal mechanical commitment. The main step is to remove the upper part of the box, so just act on a handful of screws and then pull the frame horizontally. Thus we will see the main printed circuit of the apparatus that we propose in the picture where all the most important elements are highlighted.

IC-R71 board with highlighted where the filter components are located

The notch network uses a quartz whose resonant frequency is controlled by a Varicap diode, for alignment it is necessary to intervene on the inductance L17 and on the compensator C70. Working on these components does not require special care, but be careful to follow the instructions that we will follow. As a further basis for carrying out the intervention, we show the portion of the printed circuit board and the electrical scheme.

PCB area where the notch filter is located

Part of the wiring diagram for the notch filter

With the receiver switched on and placed in LSB or USB search a continuous signal, a stable carrier for example, such that a tone of about 1.4 KHz is heard at the audio output. Do not worry if the frequency will not be exactly this, the important thing is that it is around the center of the bandwidth. Instruments is not necessary being the ear of those who are operating more than enough. Now activate the notch by acting on the dedicated button and turning the knob towards halfway so as to tune the filter. You will be able to ascertain a reduction in the signal. Using a screwdriver, in plastic if possible as are the RF tools, gently rotate the compensator until the maximum attenuation of the audio note is obtained. Having done this move the tuning of the receiver by +/- 1 KHz checking below if the filter continues to drastically reduce the test signal. If this does not happen, intervene, slightly, again on C70 until adequate behavior is achieved within the bandwidth. A couple of operations are enough to achieve a good result, if you want to optimize everything you can naturally repeat the intervention approaching so close to the limit performance of the circuit. The inductance has no role in the calibration described, but if you notice that the frequency range of the notch is not correct, for example because it can not center an audio tone on the lower or upper end of the band, you can move its range of action by rotating, always gently, the ferrite core.

VCO calibration

The IC-R71E adopts four oscillators (VCO) that are connected to the PLL synthesizer that generates the internal signal for the first frequency conversion. Each has a precise range of use with the values shown in the table.

Although it is an extremely rare occurrence one of these oscillators could show an instability in the functioning with the synthesizer which, not finding a secure lock, leads within a portion of frequencies not to correctly tune generating at the same time parasitic signals.

PLL UNIT of the IC-R71 where the components of the VCO are located

The VCO stages can be found on the "PLL Unit" board, as shown in the photo, installed on the side of the receiver. There is a metal screen that then covers this part of the circuit. If you believe that the receiver shows this defect it requires a check on the oscillator related to the frequencies involved, then you can intervene on the small associated variable capacitor. This operation requires an instrumental test to be effective. You must have the availability of a frequency meter and possibly also an oscilloscope, the latter to monitor the presence of spike on the voltage that controls the varicap diodes. If you have minimal technical knowledge in the RF field you will not find any difficulty in completing such a restoration.

IC-R71E price

We have collected for your convenience the ICOM IC-R71E sale price (UK Pounds) and its trend over time. Useful to guarantee a cheaper purchase of this radio and to put it for sale in the second-hand market. Of course offers, accessories, warranty terms and conditions can lead to different figures.

Price	Date	Condition
GBP 210.00 (289USD)	2021-oct	Second Hand Works fine. With three filters installed: FL-44A, FL-30, FL-70
GBP 318.00 (365EUR)	2018-oct	Second Hand Good condition overall
GBP 278.00 (319EUR)	2018-oct	Second Hand Original box
GBP 299.00	2018-oct	Second Hand With manual