Icom R71a receiver comparisons

An Icom R71a general coverage receiver I recently purchased seemed extra sensitive to me. Here I compare it to another one that I have had for a while and THOUGHT that IT was sensitive. I didn't know what I was missing!

Category:

Howto & Style

Tags:

• Icom
• R71a
• general
• coverage
• receiver
• ham
• radio
• swl
• shortwave
• dx

[ciucciofrullo]

K9rzz, perform the change of the three shorted capacitors and the two IC-R71 will be equal in sensitivity. I personally performed this repair on at least 30 units passed in my lab :)

Cheers

[ciucciofrullo]

Knowledge Base Article 5BMC5154A1

R71 has marginal sensitivity, or sensitivity is reduced when coax shield is connected to the antenna jack. Inspection reveals 6 (or 9) volts DC at center if the antenna jack.

Resolution: RF overload through the antenna jack has shorted capacitors on RF unit. Cure: Replace shorted C1 capacitor (0.047 uF, 16v) on RF unit. Also check C7 and C11 capacitors for shorts.

For future reliability, you may wish to replace a leaky C1 capacitor with a 50-volt version.

[usmelly]

Its a good video, and a good theory, but not that scientific. Too many variables (sw meter isn't calibrated, gain setting may vary between one and the other, ect...) The solution is to make the test binary. That is, yes or no, more sensitive or not. This is done only in one way - dx a signal on the bottom radio which you can't on the top. Good video otherwise, very interesting and thanks for posting.

[mkrubsack]

Elecraft makes a kit, the XG2 Three Band Receiver Test Oscillator / S-Meter Calibrator, for $80 which can be used (among other things) to calibrate S-Meters. Outputs a 50 microvolt signal for S-9.

[g7txu]

Nice to have someone who can actually narrate to provide a context.

[k9rzz]

Ahhhh ... good point! I hope that the S meter alignment is included in the service manual procedure, which I have. :^)