I'm not implying that that your radio is defective and that Icom America is responsible for any out of warranty repairs. Your Icom was manufactured with the highest standards and designed to give you many years of service




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In the mid 80's, Icom introduced the IC-745 transceiver and R71A short-wave receiver. A few years later the IC-751 (HF), along with the IC-271 (VHF) and the IC-471 and IC-1271 (UHF) transceivers were also available. All six models were frequency synthesized and microprocessor controlled using the same replaceable plug in memory module.

It didn't take long for someone to discover that a defective or dead lithium battery on the memory board caused the radio to become inoperative. The Icom module stores the radios 32 memories along with important data that's used by the microprocessor's operating system. When the backup battery fails, the memories and data is lost and the radio no longer functions!

I'm not implying that that your radio is defective and that Icom America is responsible for any out of warranty repairs. Your Icom was manufactured with the highest standards and designed to give you many years of service.

Icom selected the RAM based system to support multiple versions for shipment to other countries. In the mid 80's, small inexpensive RAM memory chips were available and before shpping the radio, Icom used computer controlled programming fixtures to load the memory module with the appropriate version. Back then 32K EPROM's carried a high price tag and low power, battery backed, 32K Random Access Memories were not available.

The lithium battery had a projected life expectancy of 10 years and some batteries, at room temperature, can last longer than 15 years. Unfortunately, Hams don't always operate their equipment at room temperature. Depending on the environment, mobile or portable operation for example, the battery life can be reduced.

The Willco ICM-1024B "NO FAIL" memory is a replacement memory module that contains a Read Only Memory (ROM) that permanently stores the radio's important data and a battery backed Random Access Memory (RAM) that stores the radio's 32 (or 1024) memories.

The Willco ICM-1024B was originally designed for the R71A receiver and a modification that connects the ribbon cable to IC pins on the radio's Matrix Board is optional. The modification satisfies the memory requirements for short-wave listeners by increasing the radio's memory capacity to 1024. We also provide a log sheet and Utility World's "Hot 250 H.F. frequencies are pre loaded in RAM.

For Ham radio applications you probably don't need 1024 memories and for you, the modifications aren't necessary. You can remove the ribbon cable from the ICM-1024 and simply unplug the Icom memory module from your IC-745, IC-751/A, IC-271A/H or IC-471A/H. Install our board and your radio will operate normally.

When the "mods" are performed on an R71A or IC-751/A, 32 banks of memories can be accessed directly from the front panel without adding push buttons or switches (the IC-745, IC-271A/H or IC-471A/H will require external switches). The heart of the ICM1024 is a custom integrated circuit that handles memory data and bank switching.

Even with Icom's IC-EX310 speech option installed, the SPEECH button on your R71A or IC-751/A can be used to change banks. Simply rotate the MEMORY-CH knob and select a memory. Then press the SPEECH button and the bank, that corresponds to a memory number, will be selected. It's like having 32 radios in one! Each time you press the SPEECH button on the IC-751/A you step to the next bank. The FUNC button reverses the step direction and the XIT/RIT RESET button jumps you back to bank 1.

The IC-745, 751/A and the R71A was not designed to handle 1024 memories. Therefore, by storing a frequency that corresponds to a bank in channel 32, for example, you can determine which bank is being selected. 22 MHz in memory 32 can indicate that bank 22 is selected. 11 MHz in memory 32 indicates bank 11 is selected.

Icom used the RAM based design so that they can easily modify the radio's frequency limits for operation in other countries. We took advantage of that and extended the H.F. frequency limits from 10 kHz to 31 MHz and VHF limits for the IC271A from 139 MHz to 152 MHz. If your a "Lowfer", using an Icom R71A receiver, for example, you can copy NSS on 21.3 kHz (the USN Training Center in Annapolis Maryland).

By simply adding a jumper, the ICM-1024 can be installed in an R71/R71A, IC745, IC-751/A or the IC-271A and
IC-471.


You can contact us via E-mail at:
willcoele@ameritech.net,

call or write us at: P.O. Box 788, New Lenox IL. 60451
Home Office Tel: 815-463-9365


Audio Upgrade

Kiwa offers an audio upgrade kit to improve the audio quality of the R71 receiver. This receiver has an audio quality that some have described as "whooly" or "muddy" which makes listening difficult for extended periods of time.

The audio upgrade is a kit to replace the capacitors in the audio path with capacitor types that have improved sonic characteristics. The capacitors in both AM and SSB/CW signal paths are replaced. The end result is that consonants like k's or c's and q's will sound sharper with improved detail. This improves the overall intelligibility. The audio upgrade does not eliminate all the distortion because a portion of the audible distortion is created in the mixer stages preceeding the detectors. (Kiwa does not offer a solution for this problem)

The kit comes with complete instructions. Soldering and desoldering experience is required. Approximately 20 capacitors are replaced. No alignment is required after completion. Kiwa also offers an audio upgrade installation if you do not feel comfortable installing the required components.

For more information regarding Kiwa Audio Upgrades - please see Kiwa Audio Upgrades - A Brief History

R71 Audio Upgrade Kit $22.00
Shipping and Handling in North America $2.00
Shipping and Handling outside North America $4.00

Installation by Kiwa Electronics (includes components) $70.00
Price does not include return shipping of the receiver.


Filter Options

The stock wide filter (F15) is a Murata CFW455IT. This has a nominal bandwidth of 6 kHz but depending on the production run and tolerance, the true -6 dB bandwidth may vary from 5 to 7 kHz. Kiwa offers several filter options that are a direct replacement to the original filter. These are all a pin per pin replacement. Installation instructions are included.

LFH2SK (-6 dB BW 3.7 kHz) $25.00
LFH4S (-6 dB BW 6.0 kHz) $20.00
LFH6S (-6 dB BW 8.2 kHz) $25.00


Shipping and Handling within North America $2.00
Shipping and Handling outside North America $4.00
Note: only one S&H charge is required when ordering both the audio and filter upgrade.


Mini Filter Switch Board

A Mini Filter Switch Board can be assigned to the wide filter (F15). The filter board provides two bandwidths: 6 kHz and 3.8 kHz. A toggle switch is mounted on the rear AUX plate (small removable plate). The toggle switch will select either the 6 kHz filter or the 3.8 kHz filter while the receiver remains in the Wide Filter position. Installation instructions are included. The photo below shows the Mini Filter Switch Board mounted to the bottom chassis plate (bottom cover removed).


Mini Filter Switch Board $68.00
Shipping Handling within North America $5.00
Shipping and Handling outside North America $7.00




Kiwa Electronics

503 7th. Ave. N.E.
Kasson, MN 55944 USA
507.634.6134 phone/fax
kiwa@wolfenet.com


Improve the S-meter sensitivity after warm up


Model: IC-R71


Division: Amateur


Note: This service bulletin is meant for technical per-

sonnel with experience working on solid state com-

munications equipment. Damage caused by im-

properly installing this modification may cause

ICOM to charge for subsequent repairs to the

product. ICOM does not warrant this modification.


Bulletin #: R71110884-130


Date: November 9, 1984


Subject: Improve the S-meter sensitivity after warm up


Procedure


1. Replace R114 (470 ohm) with a 680 ohm resistor.


2. Add R207 3.3K resistor from the anode of D70 to the emitter

of Q23.


3. Add R208 a 33D28 thermister (ICOM P/N 915-04228) in parallel

with R114.


This article is printed with permission from mods.dk the 18-09-2006. This printed

article must only be used for non-commercial purposes; this is only for private

use.

© Copyright mods.dk 1996 - 2006


Modifications to the Icom R71A IF filter selection circuit


*Author:* Greg Doerschler

------------------------------------------------------------------------


This article may be distributed or reposted freely provided that it

remains completely intact.


_INTRODUCTION:_


Simple modification to the IF filter selection circuit of the ICOM R71A

general coverage receiver can provide additional bandwidth selection

options in receivers which have been equipped with the optional FL-44A

high grade 2.4 KHz crystal filter (or equivalent). In the AM mode, the

modification enables a 2.8 KHz bandwidth to be selected in addition to

the 6 KHz and 2.4 KHz bandwidth settings which the "FL-44A"-equipped

R71A already offers. In the SSB, CW and RTTY modes, the modification can

be used to enable the PBT knob to function as either a passband tuning

control or an IF-shift control.


The potential benefit of this modification depends to a large extent on

how the receiver is used. R71A owners considering the modification

should take some time to decide whether it is worth the effort before

proceeding. Much of this article discusses the rationale behind the

modification and explains its actual effect. The procedure itself -

described at the end of the article - is not very complex, but it does

involve some delicate soldering and the ability to read schematic

diagrams and identify components on the PC boards.


I can attest that my modified R71A performs as indicated, but I assume

no responsibility for the outcome of anyone's modification efforts. Make

sure you understand and are comfortable with what you are doing, and

proceed at your own risk. While not absolutely critical in this case, it

is generally smart to have a service manual handy when modifying equipment.


_BACKGROUND:_


Intermediate Frequency (IF) bandwidth filtering in the R71A is

accomplished by filters in the 9 MHz 2nd IF stage and in the 455 KHz 3rd

IF stage. The stock R71A comes with the following standard filters:


2nd IF: FL-70 (2.8 KHz) 3rd IF: CFW455IT (6 KHz)

FL-30 (2.3 KHz) CFJ455K5 (2.8 KHz)


While the 2nd IF filters are of reasonable quality, the 3rd IF filters

are inexpensive ceramic filters. ICOM offers the FL-44A 2.4 KHz high

grade crystal filter as an optional replacement for the 2.8 KHz

CFJ455K5. Other filter manufacturers have comparable replacements

available too. One of two optional (additional) CW filters may also be

installed in the 2nd IF; the FL-32 (500 Hz) or the FL-63 (250 Hz).


With only its stock filters, the R71A utilizes the following filter

combination in its various modes:


2nd IF 3rd IF

AM wide...............(none)................ 6 KHz (CFW455IT)

AM normal............ 2.8 KHz (FL-70)....... 2.8 KHz (CFJ455K5)

SSB/CW/RTTY wide..... 2.8 KHz (FL-70)....... 6 KHz (CFW455IT)

SSB/CW/RTTY normal... 2.3 KHz (FL-30)....... 2.8 KHz (CFJ455K5)


At first glance, one might think that it would have been more logical to

use both 2.8 KHz filters in the SSB "wide" position (similar to the AM

"normal" position), rather than a 2.8 KHz filter followed by a 6 KHz

filter. (Since the narrower of the filters in the IF chain really

determines the overall bandwidth, the 6 KHz filter is actually doing

nothing.) However, if things had been set up this way, replacement of

the 2.8 KHz 3rd IF filter with the optional FL-44A 2.4 KHz high grade

crystal filter would have restricted the SSB "wide" bandwidth to 2.4

KHz. The SSB "wide" and "normal" bandwidths would then have been

virtually identical.


Observe that the installation of the FL-44A does in fact reduce the AM

"normal" bandwidth from 2.8 KHz to 2.4 KHz. Here's how the filter chart

would look for an R71A with both the optional FL-44A and the optional

FL-32 CW narrow filter installed:


2nd IF 3rd IF

AM wide.................. (none)................ 6 KHz (CFW455IT)

AM normal................ 2.8 KHz (FL-70)....... 2.4 KHz (FL-44A)

SSB/CW/RTTY wide......... 2.8 KHz (FL-70)....... 6 KHz (CFW455IT)

SSB/CW/RTTY normal....... 2.3 KHz (FL-30)....... 2.4 KHz (FL-44A)

Narrow-all modes......... 500 Hz (FL-32)....... 2.4 KHz (FL-44A)


Having the razor sharp 2.4 KHz bandwidth of the FL-44A accessible in the

AM mode can sometimes be great for critical DXing, but AM audio at that

bandwidth does lack sufficient fidelity for comfortable listening.


With some minor rewiring of the filter selection hardware, the 2.8 KHz

AM bandwidth can be restored in "FL-44A"-equipped R71A receivers. This

is done by making the AM "normal" setting select the same 2.8 KHz

(FL-70) / 6 KHz (CFW455IT) filter pair which is used in the SSB "wide"

setting. For experimental purposes, I had temporarily configured my R71

to select this filter pair in the AM "wide" setting in order to make

direct receive fidelity and skirt selectivity comparisons against the

2.4 KHz AM "normal" setting.


My findings revealed that with the receiver tuned directly to a

broadcast station, both bandwidths produced very similar sounding audio

without much fidelity. But by tuning the R71A's main tuning dial 1.5 KHz

away from the AM carrier frequency, the 2.8 KHz filter passed the

carrier and enough of one of its sidebands to provide halfway decent
  1   2   3

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