On Tue, 07 Oct 2003 13:08:00 +0200, Stephan Grossklass
wrote:


No, these 80s beasts
don't use 455 kHz as last IF for AM/SSB yet, just as 3rd IF for for FM,
which means good replacement filters virtually have to be crystal ones.
The current IC-R75 uses a 2nd IF of 9.0115 MHz and a 3rd IF of 455 kHz,
and allows using filters on both.

Actually, the architecture of the R75 is derived from the R71A (I have
one of each, and service manuals with schematics for the R71A and for
my IC-751A, whose receiver section is, basically, an R71A).

All have an up-conversion 1st IF, followed by 9MHz 2nd IF and 455kHz
3rd IF. Both my R71A and my 751A have Collins mechanical filters which
I installed in their 455kHz IFs.

The R75 is basically a cost-reduced R71A, with decent audio (relative
to the muddy audio of the R71A) and with dual PBT which is an
improvement on the less flexible PBT on the R71A (and 751A).

All are excellent utility monitoring receivers, with the R75 having
slightly higher sensitivity and a slightly better noise floor. The R75
can also be used as a decent SWL broadcast listening receiver.

None of the three can stand up to an RX340, but then again their
combined cost is less.


Good listening,
Al
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Location: 42N39, 71W09 (Near Boston, MA)
HF Antennas: 65ft TFD, 45ft T2FD, 28ft vertical, 65ft doublet
HF Receivers: Ten-Tec RX340, RX320, Harris R2368, Cubic R3030A
Decoders: Code300-32, Universal M-8000, PK-232MBX/DSP
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