Hallicrafters Dd1 Communication Receiver Instructions

DD 1 INSTRUCTION BOOKLET 
CONTENTS PAGE  
1 Discussion of Diversity Action 
2 Antenna Recommendations  
3  
4  
5 Operating Suggestions  
6  
7 
8 
9 Rejecter Theory and Operation  
10 
11 
12 Four Curves on Rejecter Operation  
13 I.F. Selectivity Curve, Sensitivity Curve, S units, M/V input curve. 
14 Image ratios curve  
15 A.V.C. characteristics curve, Audio Fidelity Curve, Overall Fidelity Curve 
16 Functional Schematic of Receive 
  
DISCUSSION OF DIVERSITY ACTION 
The advantages to be gained from...

over paths differing in direction and length. Additionally, these waves upon reaching the 
receiver are of varying amplitude and phase.  
Fortunately for our solution to the problem of fading, a signal does not fade identically in two 
antenna locations at the same instant - even when the two antennas are spaced a relatively 
small distance apart, or when they are near to each other and in different planes of 
polarization. What is happening is that the phase angle between waves arriving over varying...

greatly minimized. The reason for this is clear when we understand that the receiver in control 
at any instant is the one which is delivering the greatest signal to the amplifier.  
The Hallicrafters Dual Diversity receiver, model DD1 differs from the usual commercial 
installation in that instead of using separately tuned receivers with individual high frequency 
oscillators, a common oscillator is used which feeds the first detectors of each of the two 
receivers. This eliminates the expensive...

wave length apart. Suffice to say, regardless of the type of antenna system you should choose 
to use, diversity action will be better when the two antennas are separated by as great a 
distance as possible.  
At this point it might be well to bear in mind that no one aerial, regardless of type, will work 
at peak efficiency throughout the tuning range of the DD1 receiver. The most practical 
antenna system for general coverage reception will be that consisting of two inverted L 
antennas approximately...

OPERATING SUGGESTION 
(General)  
The receiver has reached you in a sturdily constructed container. The packing case was 
designed to give maximum protection to the instrument while in transit. If the case bears 
visible evidence of having been damaged in shipment it is suggested that you get in touch 
with the carrier at once.  
The power amplifier and power supply are packed separately. The cables which will connect 
these units to the receiver are packed in the same container. The A. C. cord to...

FREQUENCY COVERAGE  
The Hallicrafters Model DD1 Receiving System tunes from 545 KC to 46 mc. This frequency 
range is covered by 6 bands. They are as follows: 
1 - 540 KC to 1500 KC 
2 - 1.5 MC to 4.2 MC  
3 - 4 MC to 10 MC  
4 - 10 MC to 20 MC  
5 - 20 MC to 36 MC  
6 - 34 MC to 46 MC 
When switching from one band to another, pressing the button that is identified by the 
frequency marking on its front will switch all seven coils for that range, There are a total of 42 
coils in the coil and switch...

because of it having an injector grid into which can be fed the output of the 6J5 Heterotone 
oscillator. The Heterotone oscillator modulates the signal flowing in the I.F. amplifier. The 
electron stream in the 6L7 is already modulated by the signal in the normal operation of the 
tube. When the voltage at the heterotone frequency is applied to the injector grid, the electron 
stream is further modulated at this frequency. The product of these two modulating voltages 
appears in the plate circuit of the...

the wanted frequency. The band-spread control will be of great help in tuning in short-wave 
stations by virtue of the fact that they can be more accurately resonated due to the capacity 
change with this control being but a small fraction of the change experienced should the 
coverage control be used and moved through the same number of degrees. Directly below 
each of the large dials will be seen an aperture through which is visible an indirectly lighted 
vernier dial, Using the markings on this 100...

stage. It is recommended that the heterotone be used for the copying of code signals when it is 
desired to use the receiver in the dual position. The Heterotone gives either 500 or 1000 cycle 
output. The Hi-Low switch in back of the panel near the Heterotone oscillator tube will 
allow the choice of either of those two modulating frequencies. 
In the down position of this switch, the Heterodyne oscillator is connected in the circuit. The 
pitch of the beat note can be varied by the knob marked Pitch...