Antenna to Detector/AGC
Detector/AGC to Audio
Tube (and SS diode) Complement
The SRR-13A uses subminiature tubes
and a few
solid state diodes. The diodes were not part of the original design, but
were included in receivers above SN 1431. A late modification changed the
power supply rectifiers to solid state diodes in all SRR-series receivers.
Input and Output Connections
Each receiver has a antenna and power inputs, a 200 KHz IF output, plus
line and headphone audio outputs, on the rear panel. The SRR-12 and 13/13A
also have a 1600 KHz panadapter output and detector AGC input/output connectors.
All receivers have 2 local headphone jacks on the front panel. The audio
output is relatively anemic -- only 200 millwatts into a 600 ohm line --
but the receiver was designed to be used with military audio distribution
amplifiers. The antenna input can be configured for either low (70 ohm)
or high impedance via movable links. AGC can be similarly configured on
the SRR-12 and 13 for dual-diversity receiving. Separate metering is provided
for RF carrier and audio output levels.
Other neat stuff...
IF selectivity is provided by LC (8 KHz) and mechanical (3.2 KHz) filters.
The SRR-13 has an even narrower 1 KHz filter for CW use. An adjustable
squelch (labelled silencer on the panel) is available on the SRR-12 and
13. The frequency of operation is projected onto a window above the tuning
. Frequency calibration is provided by tuning in the built-in calibrator
or a standards station and then twiddling the projections controls to make
the dial read that frequency (This is the opposite of the R-392, where
the frequency must be set and locked, and then the receiver tuned blind
to find the cal signal). A 0-1000 dual rate logging scale is also provided;
the outer scale has markings every 100 units and revolves slowly, the inner
scale is marked 0-100 in increments of 1 and revolves quickly.
They don't make them like this anymore....
The receivers have modular construction
complete receiver chassis slides out of the cabinet and can be tilted and
locked at different angles for servicing. Each of the major functional
units is a removable module. The subminiature tubes are soldered (with
leads to the pins) rather than plugged into sockets. You can't easily substitute
tubes to troubleshoot this receiver! Complete module replacement and stage
gain charts are used to diagnose possible tube problems.
The mil-spec construction
method is impressive (and heavy!). The manual, which is about 4 inches
thick, is comprehensive. It contains complete theory of operation and circuit
descriptions plus the physical layout (several views) and schematics of
each module as well as the overall receiver. There is even a table which
describes each inductor used in the receiver, its wire size, number of
turns, dc resistance, inductance value and method of winding!