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TABLE OF CONTENTS |
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General |
Specifications |
3 |
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I |
General Description |
5 |
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II |
Installation |
Instructions |
6 |
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A. |
Unpacking |
6 |
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B. |
Location |
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6 |
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C. |
Power |
Requirements |
6 |
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D. |
Antenna |
Requirements |
6 |
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E. |
Speaker |
Requirements |
7 |
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F . Anti-VOX |
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7 |
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G . Muting |
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7 |
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III |
Control Functions |
9 |
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A. |
Front |
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9 |
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B. |
Rear |
Jacks |
11 |
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c . |
Side |
Controls & Jacks |
12 |
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IV |
Operation |
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13 |
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A. |
Preliminary Control Settings |
13 |
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B.Single Sideband or Double Sideband Suppressed
c. |
Carrier |
Reception |
13 |
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C. W. Reception |
13 |
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D . |
AM Reception |
14 |
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E. |
RTTY |
Reception |
14 |
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F . |
Adjusting |
Dial Calibration |
15 |
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G . Noise Blanker Operation |
15 |
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H. |
Operation |
of Notch Control |
16 |
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I . |
Accessory |
Frequency Coverage |
17 |
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J. |
Fixed |
Frequency Operation |
20 |
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V Theory of Operation |
21 |
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A* |
R. F. Amplifier |
21 |
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B. |
First Mixer and Premixer System |
21 |
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c . |
Second |
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Converter |
22 |
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D. |
50 KC I. F. System |
22 |
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E. |
Detector |
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Systems |
22 |
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F . |
Audio |
Output |
24 |
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G . |
AVC System |
24 |
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H. |
S Meter |
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24 |
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I . |
Noise |
Blanker |
25 |
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J. |
Crystal |
Calibrator |
25 |
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K. |
Power |
Supply |
25 |
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-l-
VI |
Service |
Data |
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27 |
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A, |
Removing |
Top Cover |
27 |
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B. |
Removing |
Bottom Cover |
27 |
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C. Tube Replacement |
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27 |
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D. Troubleshooting |
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27 |
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VII |
Alignment |
Instructions |
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32 |
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A. |
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50KC |
Oscillator Alignment |
32 |
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B. |
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50KC |
I. F. Alignment |
32 |
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c . |
Crystal Filter and |
Filter Match Transformer |
33 |
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Alignment |
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D . |
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5595 |
KC |
Oscillator |
Alignment |
33 |
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E. |
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Antenna |
RF, and |
Injection Circuit Alignment |
34 |
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F . |
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100 KC Calibrator |
Alignment |
35 |
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G . |
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V.F.O. Adjustment |
35 |
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H. |
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Notch Filter Alignment |
35 |
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I . |
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Passband Tuner Alignment |
35 |
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J. |
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Bias |
and |
S-meter |
adjustment |
36 |
CHARTS AND ILLUSTRATIONS
Fig. # 1
Fig . # 2
Fig. # 3
Fig. # 4
Fig. # 5
Fig . # 6
Fig. # 7
Fig. # 8
Fig . # 9
Fig. # 10
Fig. # 11
Fig., # 12
Fig . # 13
Connecting R-4A to TR-4 Transceiver |
8 |
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Viewing Angle |
Option |
8 |
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Rear View |
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12 |
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Crystal Freg. |
Chart |
18 |
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Pre selector |
Chart |
19 |
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Selectivity |
C |
urve s |
23 |
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Notch |
Curves |
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23 |
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Block |
Dia |
gram |
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26 |
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Voltage Chart |
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28 |
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Resistance |
Chart |
29 |
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Top View |
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30 |
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Bottom View |
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31 |
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Schematic |
Diagram |
37 |
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-2-
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GENERAL SPECIFICATIONS |
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FREQUENCY |
COVERAGE: |
3 . 5 - 4 . 0 MC , 7.0-7.5Mc, 1 4 . 0 - 1 4 |
. 5 , 21.0-21.5, |
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and |
28.5-29.0 MC with |
crystals |
supplied. Ten accessory crystal sockets |
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are |
provided |
for coverage |
of any |
10 additional 500 KC ranges |
between 1.5 |
and 30 MC with the exception of 5.0-6.0 MC .
SELECTIVITY: Drake tunable passband filter provides:
.4 KC at 6 DB down and 2.6 KC at 60 DB down
1.2KC at 6 DB down and 4.8 KC at 60 DB down
2.4KC at 6 DB down and 8.2 KC at 60 DB down
4.8KC at 6 DB down and 20 KC at 60 DB down
Selectivity switching is independent of detector and AVC switching.
I. F . FREQUENCIES: |
First I. F. - 5645 KC crystal lattice filter; second I.F. |
50 KC tunable L/C |
filter. |
STABILITY: Less than 100 cycles after warm up. Less than 100 cycles for 10% line voltage change.
SENSITIVITY: Less than .5 uv for 10 DB signal plus noise to noise on all amateur bands.
MODES OF OPERATION: SSB, CW, AM, RTTY |
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DIAL CALIBRATION: Main dial calibrated 0 to 500 |
KC and 500 to 1000 |
KC in |
5 KC divisions. Vernier dial calibrated 0 to 25 KC |
in 1 KC divisions. |
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CALIBRATION ACCURACY: Better than 1 KC when calibrated at nearest |
100 |
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KC point. |
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AVC: Amplified delayed AVC having slow (. 75 sec .) or fast (. 025 sec.) discharge; less than 100 microsecond charge. AVC can also be switched off . 3 DB change in AF output with 60 DB change in RF input.
AUDIO OUTPUT: 1.4 watts max. and .5 watts at AVC threshold.
AUDIO OUTPUT IMPEDANCE: 4 ohms and hi impedance for anti-vox.
ANTENNA INPUT: Nominal 52 ohms.
SPURIOUS RESPONSES: Image rejection more than 60 DB. I. F. rejection more than 60 DB on ham ranges. Internal spurious responses in ham ranges less than the equivalent 1 uv signal on the antenna.
-3-
TUBES AND SEMICONDUCTORS: |
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TUBE |
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FUNCTION |
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12BZ6 |
R.F. amp. |
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12BA6 |
100 KC calibrator |
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6HS6 |
1st mixer |
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6HS6 |
Premixer |
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12BE6 |
2nd mixer and xtal oscillator |
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12BA6 |
50 KC I.F. |
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12BA6 |
50 KC I.F. |
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2N3394 |
AVC amp./AVC det. |
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2 - 2N3394 |
Audio amp. |
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6EH5 |
Audio output |
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12BA6 |
Noise |
blanker |
amp. |
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12AX 7A |
Noise |
blanker |
amp. /shaper |
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2N706 |
VFO |
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2N3858 |
VFO buffer |
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2N3394 |
Xtal |
oscillator |
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lN714 |
Voltage |
regulator |
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0B2 and lN483A |
Voltage |
regulator |
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2 - lN3194 |
Power |
supply |
rectifiers |
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lN3194 |
Bias |
rectifier |
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lN270 and 2N3394 |
AM detector |
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2 - lN483A |
Noise |
blanker |
pulse clippers |
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lN483A |
Noise |
blanker |
gate |
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lN483A |
Switching |
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2 - lN270 |
Prod. det. |
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FRONT PANEL CONTROLS: Main tuning, AF gain, RF gain, SSB/CW-AM with slow AVC, fast AVC, or AVC off, function switch, band switch,xtal switch, passband tuning and selectivity, preselector, notch, and headphone jack.
REAR AND SIDE JACKS AND CONTROLS: S-meter zero, notch adjust, antenna jack, speaker jack, mute jack, anti-vox jack, T4/T4X injection jack, accessory power socket, crystal lock socket, xtal/VFO switch, ground post , and fuse post.
POWER CONSUMPTION: 60 watts, 120/240 VAC, 50/60 cycles.
DIMENSIONS: 5-l/2” high, l0-3/4” wide, cabinet depth ll-5/8”, overall length 12-l/4”, weight 16 lbs.
-4-
I GENERAL DESCRIPTION
The DRAKE R-4A is an extremely versatile communication receiver designed to bring you every feature desirable for the ultimate in the reception of all modes of amateur communications.
It provides a linear permeability-tuned solid state VFO with 1 KC readability, and premixed injection with crystal controlled high frequency
oscillator for |
stability |
on all bands. |
A |
100 KC crystal calibrator is built-in. |
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An |
improved |
passband |
tuner/filter with |
four selectivity positions, and |
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a built-in notch filter are incorporated |
to provide the desired selectivity |
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and |
interference rejection, and a noise |
blanker |
is |
built-in for elimination |
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of most noise on CW, SSB and AM. |
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As supplied, the unit gives complete coverage of |
80, |
40, 20, and |
15 |
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meter bands as well as the 28.5 MC to 29 .O MC portion of 10 meters. |
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Ten |
accessory crystal sockets are provided for coverage of other |
500 |
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KC |
frequency |
ranges between 1.5 and |
30 |
MC such as 160 Meters, |
MARS |
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frequencies, WWV, short wave broadcast, etc. These sockets can be programed to give up to 5 MC of continuous coverage for convenient use with V. H. F. converters.
The R-4A also includes time proven DRAKE AVC with fast-attack/slow-
release for SSB or AM and fast-attach |
fast-release for CW. If desired, |
the AVC can be completely disabled for |
CW reception. |
Complete AVC action and accurate S-meter indication can be obtained, on all modes. A crystal-lattice filter following the first mixer provides excellent overload characteristics by providing selectivity before gain producing stages.
When used with our T-4 Reciter, transceive operation may be obtained, and when used with the T-4X transmitter, either transceive or independent receive and transmit functions are possible.
-5-
II INSTALLATION INSTRUCTIONS
A . UNPACKING
Carefully remove your R-4A from the packing carton and examine it closely for signs of shipping damage. Should any be apparent, notify the delivering carrier immediately, stating the full extent of the damage.
Fill out and mail the enclosed warranty registration card so that your warranty will be effective.
Save the packing material. You may need it later for reshipment or storage.
Inspect the packing material closely before putting it away to be sure that you have not overlooked any accessory hardware.
B.LOCATION
In general the location of the R-4A is not critical. However, care should be taken to insure that space is allowed around the unit for adequate air circulation. Extremely hot locations, such as near radiators or heating units, should be avoided. Do not cover the top of the R-4A with books, papers, or pieces of equipment, as overheating may result.
c.POWER REQUIREMENTS
The R-4A is supplied with a dual-primary power transformer and can be
operated from |
120 or 240 volt 5 0 / 6 0 |
cycle |
AC. |
As supplied from the factory, |
it is wired for |
120 volt operation. If |
240 |
volt |
operation is desired, it will |
be necessary to remove the black/yellow and black/green power transformer primary wires from the terminals to which they are now connected and
connect |
them |
together at |
the unused terminal on the same terminal strip. |
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It will |
also |
be necessary |
to replace the . 75 amp fuse supplied with the |
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unit with a .4 amp Slo-Blo fuse for adequate protection at the increased |
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voltage |
(see |
schematic diagram). |
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D. |
ANTENNA REQUIREMENTS |
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The R-4A is |
designed to |
give best results when used with an antenna resonant |
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on the operating frequency and having |
an impedance from 50 to 75 ohms. |
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This |
requirement is most |
easily met |
using a center-fed dipole antenna cut |
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to the desired frequency and fed with RG58A/U cable. However, there are |
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many |
other |
antennas which will fulfill this requirement. For a more detailed |
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de scription on antennas , we suggest you refer to the ARRL Antenna Book or The Radio Amateur’s Handbook.
-6-
Antenna connection to the R-4A is provided at the jack on the rear of the chassis marked ANT.
It is recommended that when the R-4A is used with a transmitter, the transmitting antenna be used; change-over being accomplished by an antenna relay. This function is provided internally in our model T-4 and T-4X Transmitters.
E.SPEAKER REQUIREMENTS
A good quality 4 ohm speaker should be connected to the jack on the rear of the chassis marked SPKR. If one lead of the speaker is grounded to its cabinet, its connection should be to the chassis of the R-4A.
Our accessory speaker model MS-4 provides the correct match, correct tonality for good communications audio, correct connector, and is c o m - patible in appearance with the R-4A. It will also house our model AC-4 power supply which is needed in conjunction with our model T-4 and T-4X Transmitters.
F.ANTI -VOX
A high impedance output is provided at the ANTI-VOX jack on the rear of the R-4A chassis for use with our T-4 and T-4X transmitters and other transmitters having voice control capabilities. The impedance at this terminal is approximately 5000 ohms. If the transmitting equipment requires a lower impedance it may be necessary to attach a matching transformer between the ANTI-VOX terminal on the R-4A and the ANTI-
VOX |
input terminal of the transmitter, or to use the speaker output. |
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G . |
MUTING |
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The Mute jack on the rear of the R-4A is connected so that when the |
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function switch is in EXT-MUTE position the receiver will operate only |
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when the |
inner-conductor of this jack |
is shorted |
to ground, |
and the R-4A |
will mute |
when the inner-conductor is |
open with |
respect to |
ground. |
The inner-conductor should, therefore, |
be |
connected to a relay contact in |
the transmitter or antenna relay which |
is |
normally open when transmitting |
and grounded when receiving. It is recommended that a shielded wire be used between the mute terminal and the relay such as is provided with our model T-4 and T-4X Transmitters.
If external muting is not desired, the STBY and ON positions of the function
switch can |
be used. It is necessary to |
insert a shorted plug in the Mute |
Jack to obtain N. B. and CAL functions. |
Such a plug is installed in each |
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R-4A when |
shipped. |
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-7-
III CONTROL FUNCTIONS
A.FRONT
1.MAIN TUNING - The MAIN TUNING knob of the R-4A determines the
frequency on which you are receiving. The vernier skirt around this
knob is |
calibrated in |
KC’s from 0 to 25. |
The main dial is calibrated |
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in five KC divisions |
and has two scale S . |
Use the 0 to .500 scale |
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for bands 7.000-7.500, 14.000-14.500, |
21.000-21.500, etc.; use |
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the .500 |
to 1.000 scale for bands 1.500-2.000, 3.500-4.000, |
28.500- |
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29.000, |
etc . The small red knob just to |
the right of the dial |
scale |
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is for adjusting the position of the indicator line for calibrating the main dial. The knob skirt is also adjustable by pushing it in slightly and rotating it in the desired direction while holding the main tuning knob stationary.
2. BAND - The BAND control is a six position switch used to select the amateur band desired or to switch the RF circuits to the correct tuning range when tuning accessory frequency ranges. The frequency range which may be tuned for each setting of the band switch control is given on the chart on page 16.
3. XTAL - The XTAL switch is an eleven position switch used to determine which crystal socket will be inserted in the circuit. When it is in the
normal position, |
crystal selection is |
accomplished by means of the |
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band |
switch (with the exception of |
the 1.5 setting). |
When this switch |
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is set |
on any of |
the other positions |
1 through 10, the |
crystal inserted |
in the corresponding crystal socket will be inserted in the circuit |
for |
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accessory band |
operation. The BAND |
switch must |
then be set in |
ac- |
cordance with the information given on |
the crystal |
frequency chart |
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for reception of |
the frequency desired. |
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4. PRESELECTOR - The PRESELECTOR control permeability-tunes the antenna, RF, and premixer coupling coils to the desired frequency. The logging
scale on this control is |
calibrated from 0 to 10 with markings showing |
the correct settings for |
the 160 through 10 meter amateur bands. |
5. FUNCTION - The FUNCTION switch is a six position switch used to select the method of operating the R-4A.
When in the OFF position the power transformer primary is |
opened, |
thus turning the unit off. When in the STBY position, the |
power |
is connected, thus allowing the filament and B+ to operate but the |
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receiver is muted regardless of external connection. When |
in the |
ON position, the receiver is unmuted regardless of external muting
connection. |
When in the EXT-MUTE POSITION, the receiver is |
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muted or unmuted depending upon whether or |
not the mute connection |
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on the rear |
of the chassis is grounded, thus |
permitting external control |
-9-
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by |
the transmitter. |
When in the N. B. position the noise |
blanker |
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is |
energized, |
and when in the CAL position, the noise blanker is |
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switched off and the calibrator is switched on. In these last two |
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positions the muting function is the same as if the switch |
were in |
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the EXT-MUTE position, so |
if external muting is not used, a shorted |
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plug must be |
inserted in the Mute jack to obtain these functions. |
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6. |
SSB/CW-AM - |
This switch determines the detector which is used and |
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the AVC mode. When in the AM position, a diode detector is incorpor- |
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ated, the |
BFO |
is switched off, and the AVC with a slow time constant |
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is |
used. |
The |
other |
three positions under the heading SSB/CW employ |
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a product detector with the BFO. In the SLOW AVC position the AVC |
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delay time is about .7 5 seconds. In the FAST AVC position it is approx- |
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imately |
.025 |
seconds. |
In |
the AVC OFF position no AVC |
is generated. |
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The SLOW AVC position should normally be used with single sideband |
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and CW and the fast position should normally be used for break-in |
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CW and RTTY. The AVC OFF position should be used only on CW |
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under difficult |
conditions |
in |
conjunction with the RF gain |
control. |
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7. |
AF GAIN - The |
A. F. GAIN |
knob controls the audio output |
level of |
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the |
receiver. |
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8.RF GAIN - The R.F. GAIN knob varies the bias applied to the AVC -
controlled tubes thus controlling the R. F. gain of the unit.
9 . NOTCH - The NOTCH control tunes a highly selective notch across
the receiver’s passband |
for |
the purpose of eliminating interfering |
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carriers . When turned to the OFF position, the Notch is moved out- |
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side the receiver’ s pa ssband. Rotation of this control is in the same |
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direction from |
the center as |
PASSBAND control; i. e. If PASSBAND is |
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set to the left side (lower sideband) then heterodynes will be removed |
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with NOTCH set left of center. |
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10 ?) PASSBAND - The PASSBAND |
control is |
composed of two parts; the pass- |
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band selector lever and |
the |
passband |
tuning knob. The selector lever |
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is calibrated in numbers representing the band widths in KC’s at 6 DB |
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down(.4, 1 . 2 , |
2 . 4 , |
and 4.8KC). |
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The length and |
position |
of the |
lines which make up the passband tuning |
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calibration indicate the relative band widths and their positions with |
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respect to each |
other. |
The |
pointer on |
the Passband tuning knob repre- |
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sents the relative position of the fixed 50 KC BFO with respect to the |
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movable passbands. |
The dots |
at the |
ends of the lines indicate the cor- |
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rect settings of |
the PASSBAND |
tuning |
knob for single sideband reception. |
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All of the left hand dots are for lower |
sideband and all of the right hand |
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dots are for upper sideband. |
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-lO-
For CW reception on the . 4 position the signal is tuned for most pleasing note with the frequency knob and is then peaked with the PASSBAND tuning knob. You can then tune other stations without changing the PASSBAND tuning knob setting. The audio frequency at maximum signal strength will be correct.
11.PHONE JACK - A PHONE JACK is provided on the front of the R-4A for private listening when desired. The jack automatically mutes the speaker output when headphones are plugged in. While the headphone impedance is not critical (adequate output is available for most commercially available phones) more output is obtained on lower impedance phones . We recommend a good set of 600 ohm phones, such as the Trimm type 56 - 06.
12.S - M E T E R - The S-METER indicates relative signal strength of the re-
ceived |
signal. It is calibrated in S-units |
from S-l to |
S-9 |
and DB over |
S-9. Each S-unit equals about 5 DB and |
S-9 is about |
30 |
microvolts |
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at the |
ANT terminal. |
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B. REAR CONTROLS & JACKS
1.INJ. JACK - The INJ. jack provides a means of coupling the premixer system of the R-4A to the T4 or T4X transmitters so that transceive
operation with these units can be obtained.
2 . SPEAKER JACK - The SPEAKER JACK on the rear of the chassis is for the connection of a 4 ohm speaker such as our MS-4.
3 . MUTE JACK - The MUTE JACK is for externally muting and unmuting the r e c e i v e r . The receiver is muted when the FUNCTION switch is in the EXT-MUTE, N. B., and CAL positions and when the center conductor of this jack is open from ground. Shorting the center conductor to ground returns the receiver to the receive condition.
4 . ANTI-VOX JACK - High impedance audio is brought out the ANTI-VOX JACK for use in energizing the ANTI-VOX circuit of a transmitter used with the unit such as our T-4 and T-4X.
5 . ANTENNA JACK - The ANTENNA JACK provides a means for connecting the R-4A to an antenna. The input impedance at this point is approximately 52 ohms and can be used with antennas having impedances between 50 and 75 ohms.
6 . POWER SOCKET - A POWER SOCKET is provided on the rear of the R-4A for operating external accessories. This plug mates with a Cinch Type 5AB2 connector. Maximum load is 6.3 VAC @ .75 amp and +150 VDC
@ 30 ma.
-11-
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