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GENERAL PURPOSE
COMMUNICA TlONS RECEIVER
I
INTRODUCTION
In the design of a high frequency radio receiver,
there are four important qualities for consideration:
1.
Usable sensitivity.
2. Selectivity.
3.
Frequency Stability.
4.
Reliability.
The sensitivity of this receiver is limited only by
the tube noise originating in the first tube and its asso-
ciated circuits. A large ·part· of this noise is due to
"shot" effect and thermal agitation in the first tuned
circuit. A signal, to be readable, must produce a volt:
a&-e on the grid, of the same or
greate~
ordet: of mag'
I1Lt!Jde than this inherent noise voltage. Therefore, an
efficient coupling system between the antenna and the
first R,F tube of the receiver is of great importance.
This has been the subject of considerable develop"
ment, and the system used on this receiver gives opti,
mum coupling with antenna or transmission line im'
pedances of
200
ohms, over the entire frequency
range of the receiver, except on the broadcast band.
On the
broa~ast
band, a low frequency primary is
used, resonating well below the band with a 200 mmf
antenna.
The second quality of a receiver, selectivity, is nec'
essarily a compromise with fidelity of the reproduced
signal. This receiver is designed to have five degrees
of selectivity, three of which include a crystal filter.'
1'0
secure good frequency stability, rugged con'
struction of parts and wiring in the high frequency
heterodyne oscillator circuit has been included in the
design. This, together with voltage stabili2;ation of
the oscillator plate supply, temperature compensation,
and proper oscillator excitation, provides a high de'
gree of stability.
Reliability depends
to
a large extent on the quality
of material and workmanship. Throughout the AR,SS
Receiver the best material obtainable is used for each
particular purpose and all workmanship is of the best.
The following instructions should be studied before
the installation or operation of this equipment is at'
tempted, in order that optimum performance may be
obtained.
11
EQUIPMENT
The equipment furnished consists of the Receiver
Chassis Assembly, including control panel and
tubes and cabinet for complete enclosure for table
mounting.
Additios:al equipment required includes headphones
or loudspeakers, an antenna system, and an AC sourCe
of power, batteries, or Vibrator Power Supply Unit
MI'8319.
III
DESCRIPTION
This receiver covers short wave, standard broad,
cast, and
r;:,w
service; its principal use is for short
wave. communications. It
is
designed to withstand
severe climatic and line voltage variations without ap'
preciable impairment of performance.
Its features include: .
Mechanical Band Spread with Single Control for
ease of tuning a previously logged station.
Automatic Noise Limiter which automatically
limits interference to a percentage of modula'
tion determined by the Noise Limiter Control.
Noise Limiter Control for setting Noise Limiter
to
operate at any desired percent modulation.
Noise Limiter Switch for switching Noise Lim-
iter on or off.
Continuously variable High Prequency Tone
Control.
$
nntenna trimmer for circuit alignment.
Crystal filter for ultra'sharp selectivity when re-
quired.
Tuning meter for indicating relative strength of
incoming signals.
Exceptionally good oscillator stability through
normal variations in line voltage.
Pour'gang Condenser giving high image ratio on
all bands.
Twelve Tuned I,P Circuits giving a very high
degrelllOf selectivity.
Temperature compensated oscillator circuits on
all bands.
Ceramic Insulation throughout on gang conden-
ser, sockets, range switch, and selectivity
switch.
Tuning Lock for service under extreme condi,
tions of vibration.
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