IC-R75-RFP
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This is an IC-R75 mounted
in a standard rack panel (3U
 size = 5 1/4" high).

Basically, I just added some
of the
"Type-6" and "RFP"
Preconditioner/Preselector
circuitry to the unused
portion of the panel.

Shown below is the
prototype label printed on
paper. Top photos are the
final label.

The R75 is an excellent
receiver, especially in terms
of noise floor (MDS),
dynamic range (head room),
selectivity and sensitivity.

By adding the low noise
preamp, a true RF Gain
control and a very high-Q
preselector filter, the receiver
really comes into the  
commercial grade category.

The high-Q preselector is
very sharp and in initial tests
gives a 10 KHz bandwidth of
between 18 and 48 dB --
depending on the frequency.
This one is designed to
function from about 30 KHz
to 15 MHz. This filtering
scheme nulls all out-of-band
signals, including noise,
thereby giving the effect of
gain by better matching the
line to the radio and an
improved S/N ratio by
eliminating noise outside of
the tuned band.

For informational purposes,
I have included the graphics
layout, below.
Counter
This graphic was layed out in Pagemaker, an Adobe s/w program.
Closeup of the
temporary
label, with the
receiver in
various modes.
Below are some
shots of the back
side.
It's really not as
messy as it looks,
and I have since
dressed many of
the wires and
added a brass
shield over the
preamp.
Details of the inductor cluster which ranges
from 100 mH down to 1 uH.
Values in uH: 1, 3, 6, 10, 30, 100, 300.
Values in mH: 1, 3, 10, 30, 100
Above: The toroid transformer not
only offers maximum energy transfer
(match) from a mismatched antenna,
but also provides a DC path to
ground for static buildup on the line.
This core is type-43, to cover the LF
and VLF bands (5 turns secondary).
If you don't need (want) the LED
indicators, the wiring and switches
will be simpler -- red and black is the
12V wiring.
If your browser re-scales these images, you may copy
(right click, then <copy>) and paste into your own
viewer where they can be blown up.
... the ol' R75 really comes alive.
Development Process