[ICOM] IC-R71 questions...

[Lars E. Pettersson]

Hi!

Some R71 questions. I tried the R71 mailinglist on yahoogroups but got
no replies, so I will make a try here also.

Just received my R71 and have done some googeling about filters.
Especially for an AM filter in the second IF, as I want to have the
selectivity as early as possible in the IF-chain.

There seem to be a mod using the FL-33 filter. But looking at the
IF-frequencies used in the R71 I wounder how it can be compatible with
the R71. According to the specifications the second IF is 9.0115 MHz,
but the center frequency of the FL-33 is 9.0100 MHz, i.e. 1.5 kHz lower.
Do one have to change something else to use this filter? Or do one have
to side tune 1.5 kHz? Or have I missed something in how the R71 AM mode
works?

Any comments?

Continuing testing my new R71E I have noted that the pitch
differs between USB and LSB, USB is much more high pitched, and contain
a bit more white noise/hiss than LSB. This regardless of bandwidth (wide
or normal) I have checked all frequencies (with an HP5328A) and they are
spot on (giving some 10-15 Hz in some cases.)

This receiver have the original filters, no FL44A, or any other options
installed, so a pure basic IC-R71 receiver.

Any ideas on what may cause this?

I have also noted some extra white noise/hiss quite audible even with
the volume fully CCW (both internal or external load speaker.) If I turn
RF gain fully CCW, and the volume fully CW this noise gets a bit higher
(I can also hear one extra noise, coming from the display board.) So at
least some of the noise seem to come from the stages before the AF power
amplifier. There seem to be a bit more noise using AM, than the other
modes. What is this white noise/hiss coming from? Any ideas? There is a
note about electrolytics on the Icom America web page, but they also
mention change of color of the electrolytics, turning brown, from the
original blue. Mine are all clear blue. I have an ESR meter so I intend
to check the capacitors to see if they are bad or not, but I think that
this extra hiss, not the one coming from the display board, emanates
from some other source than bad electrolytics, or may even be due to how
the AF circuit is built. I have seen the Kiwa modification, perhaps that
will cure my problems.

Anyone have any thoughts of this?

I have had two IC-R71 before this one, and can not seem to recall that
those had these problems.

73 de Lars, sm6rpz
-- 
Lars E. Pettersson <lars at homer.se>
http://www.sm6rpz.se/