The IC-R71 is a glorious MW/SW radio receiver produced by Nippon Icom Inc.
(Osaka) for ham and professional fields in the '80 and '90 years. At that
time it was surely the best SW radio outstanding on the market. The fantastic
dynamic (105dB!) and the great technical features have made it famous in radioamateur
world and also for the government and professional services. I was lucky to buy
someone coming from a UK governament stock of goods and sold
out just €200, but today
it still has a price much
higher than I payed, despite the circuitry is 20 years old.
produced in different versions: version “A” was destined to the American market,
“E” reserved for the European market.
After the first power-up I tried to tune it on MW band and I have seen how much
it deaf there, so I went looking for on Google and discovering that the
receiver was designed to avoid the front-end stage saturation by the strong MW
broadcast emitters. If it is not changed, the preamp stage doesn't work on MW
band and an inside "T" resistor-based attenuator mitigates too much the signals
on medium-waves band. I have early modified it following an useful
compendium with a lot of modifications, tips and tricks about the IC-R71 by
Donald E. Noman (link). Here the manual too:
Enabling preamp for MW band
About the MW
sensitivity improvement, you can lift one leg of D23 or
remove entire diode located on RF board (right side of the radio). This
operation allows to take about 1/1.5 dB
How to exclude the
There is a
small attenuator consisting
resistors located on
the RF MW input
chain. This one must be inhibited:
To by-pass that, R13 lifting or removal
and the shorting of R11-R12 series is called for.
step1: raise R13
step2: shorting of R11-R12 series
The MW attenuator by-passing procedure,
allows to gain another 5/6 dB.
In the video below you can feel and see
the differences before and after two modifications: