Here's a couple of shots of the finalized layout before the front (nomenclature) decal gets stuck on. All controls
and indicators are layed out on a 1/4" grid to make use of the graphics program more precisely.
and indicators are layed out on a 1/4" grid to make use of the graphics program more precisely.
Before generating the plastic decal, I wanted to finalize any last-minut changes. The first 4 switches are: power,
antenna/shunt, system operate/standby, and system bypass, respectively. The first 3 knobs are for a Pi
network tuner (to establish a good impedance match for the preselector, the next 2 knobs are the bandpass
filter with "L" and "C" controls (the switch between the knobs selects L, C, or L+C as indicated by the green
indicators), likewise the next 2 knobs are the band-stop filters. Third from the right is the overall system
attenuator, followed by the RF Preamp with an input sensitivity control and an output gain pot. Note that all
functions may be switched out of the circuit with the switches above the knobs and LEDs which indicate their
mode. The reason for this added complexity is to allow a "set-and-forget" convenience of the controls - when
not needed, or wanted, the control can be switched out of the circuit without changing its setting.
antenna/shunt, system operate/standby, and system bypass, respectively. The first 3 knobs are for a Pi
network tuner (to establish a good impedance match for the preselector, the next 2 knobs are the bandpass
filter with "L" and "C" controls (the switch between the knobs selects L, C, or L+C as indicated by the green
indicators), likewise the next 2 knobs are the band-stop filters. Third from the right is the overall system
attenuator, followed by the RF Preamp with an input sensitivity control and an output gain pot. Note that all
functions may be switched out of the circuit with the switches above the knobs and LEDs which indicate their
mode. The reason for this added complexity is to allow a "set-and-forget" convenience of the controls - when
not needed, or wanted, the control can be switched out of the circuit without changing its setting.
The wiring completed. Note that only the (high gain) outputs are wired with shielded cable (RG-174 coax).
Eventually a sheet metal enclosure will be fabricated to shield the entire assembly.
Wiring code: Red wire = power, yellow = signal returns, green = signal path, black = grounds.
Eventually a sheet metal enclosure will be fabricated to shield the entire assembly.
Wiring code: Red wire = power, yellow = signal returns, green = signal path, black = grounds.
Closeup details. The assembly of the
inductors to the 12-position switches
were wired as three seperate modules.
The power, signal, and ground wires
are harnesses and routed away from
one another, since there is 18-20 dB
of RF gain available and oscillation is
easy to come by.
Note the redundant ground bus
running along the top of the panel
above the LEDs, to avoid ground loops.
I spent several hours testing this thing
last night - it's amazing what
capabilities a receiver has when fed a
healthy diet!
Chances are, you never really heard
your radio, at its best!
inductors to the 12-position switches
were wired as three seperate modules.
The power, signal, and ground wires
are harnesses and routed away from
one another, since there is 18-20 dB
of RF gain available and oscillation is
easy to come by.
Note the redundant ground bus
running along the top of the panel
above the LEDs, to avoid ground loops.
I spent several hours testing this thing
last night - it's amazing what
capabilities a receiver has when fed a
healthy diet!
Chances are, you never really heard
your radio, at its best!
This is typical of the control wiring.
Since they never seem to fail, the
LEDs are cemented into the front
panel. They now run at between 6 and
12 mA, depending on the color and the
brightness needed.
The wires with service loops are there
to allow removal of the sub-chassis for
mods, servicing, etc.
Click above to go to the next page and
see the front panel labeling.
Since they never seem to fail, the
LEDs are cemented into the front
panel. They now run at between 6 and
12 mA, depending on the color and the
brightness needed.
The wires with service loops are there
to allow removal of the sub-chassis for
mods, servicing, etc.
Click above to go to the next page and
see the front panel labeling.
Preselector The Testing Phase
