PORTABLE TRANSMITTING AND
TYPE 3 MK II
DESCRIPTION AND OPERATING
For Set Serial No ...78336...
2. Installation Instructions
3. Operating Instructions
4. The Aerial Systen=m
5. Battery Charging
6. Fault Tracing and Maintenance
c. Combination Power Pack for A.C. Mains and 6V Battery operation.
d. Instruction Manual
e. Spares Box containing:
1. 60 ft. Aerial wire.
2. 10 ft. Earth wire.
3. Transmitting key.
4. Telephone headset (L.R.).
5. 12 fuses 5 x 10 amp; 2 x 1 amp; 5 x 500m/amp.
6. 1 Spare Valve 7Q7, 7R7, EL32, 6L6.
8. 2 brass pins to convert Mains plug to Continental fitting.
9. ES.BC Adaptor.
10. BC/2 pin Adaptor.
11. 4 Tank Coils L1 3,0 - 5,5 Mc/s
L2 4,5 - 7,5 Mc/s
L3 6,5 - 10,0 Mc/s
L4 9,0 - 16,0 Mc/s
The above apparatus (a) to (e) is packed into two water-tight containers and in addition the following items are provided:
f. 2,6 V batteries, type 3SAF15 each in a water-tight container.
g. Hand Generator 6V 5 Amp, with cables in water-tight container.
h. Webbing carrying equipment
Crystals are supplied separately.
I. COMBENATION POWER PACK for AC and Battery Operation.
Size: 10¾ x ??? x 5" Weight: 12lbs 80zs.
A. Mains Supply: A.C. only 97-140 Volt, 190-250Volt. 40-60c/s
Consumption: a. Transmit 70 watts
b. Receive 40 watts
B. Battery Supply: 6 Volt accumulator, automobile type of largest available ampere-hour. capacity.
Maximum drain 10 Amps. This battery is only provided with Packing B
Consumption: a. Transmit 9,5 Amps (key down) 3,5 Amps (Key up).
b. Receive 4,5 Amps.
A spare vibrator, 6-Volt, non-synchronous, is fixed inside.
Size: 9½ x 6 x 4¾, Weight: 7lbs 80zs.
Supply: From the Power Pack - a. 500V at 60mA
b. 230V at 18 mA
c. 6,3V at 1,1 Amp
Circuit: oscillator-doubler driving Class C amplifier, crystal controlled. Provision for frequency doubling. Plug-in tank coils to cover 3.0 tp 16 Mc/sec. "Tune-Send-Receive" switch. Multi-range meter to read voltages and currents on transmitter and receiver. Plug-in Transmitting key.
A on AC Mains
a. Average fundamental power is 20 watts
b. The second harmonic power is 20 watts
c. The third harmonic power is 16-20 watts
B On Batteries
a. Average fundamental power is 20 watts
b. The second harmonic power is 18-20 watts
c. The third harmonic power is 15-18 watts.
Size: 9½ x 4¼ x 4¼, Weight: 6lbs 12ozs
Supply: From Power Pack a. 230V at 28 mA
b. 6,3 V at 1,2 Amps
c. 14V ± 10%
Circuit: 4 valve seven stage superheterodyne receiver essentially designed for CW reception. 3 wave band switch selector 3.1 to 15.5 Mc/sec total coverage. 50-1 slow motion vernier dial. BFO pitch control incorporating ON/OFF switch. Volume control and 'phone' socket.
Valves: Frequency changer - 7Q7 Loctal pentagrid . IF Amplifier - 7R7 Loctal double diode pentode. 2nd IF Amplifier and BFO - 7Q7 Loctal pentagrid. 2nd Detector and LF Amplifier - 7R7 Loctal double diode pentode.
Intermediate Frequency: 470Kc/sec. BFO 470 Kc ± 3 kC/s.
Sensitivity: 1 - 3 microvolts for 10 milliwatts output at 1000 cps (CW input and BFO on).
Selectivity: Bandwidth 1 Kc/sec 3dB down from peak.
9 Kc/sec 20 dB down from peak.
Max Output: 50 milliwatts into 120 ohm telephones (Impedance 800 ohm at 800cps).
Before setting up to establish communication, the proposed site should be examined as to its suitability for the installation of an efficient Aerial and Earth system, and the question of a power supply considered. Where possible AC Mains should be used and a 6Volt large capacity accumulator obtained for emergency use.
The operator should study Appendix A on Aerials and make himself familiar with the methode of adjusting the voltage selector on the Power pack and Tuning the receiver and Transmitter.
Aerials: 60 ft of aerial wire is provided as much of which as possible should be suspended as high as possible and not too close to earthed objects in order to obtain maximum efficiency. One end will, when operating, be connected to the Aerial terminal on the transmitter. See Appendix A.
Earth: A good electrical connection must be made to an existing earth tube, a main waterpipe or central heating system. If these are not available a wire of the same length as the aerial should be suspended underneath it, preferable two or three feet above the ground. The earth wire or this counterpoise will be connected to the Earth terminal on the transmitter.
1. POWER PACK.
A. If mains are available ascertain whether they are AC or DC, this apparatus must NOT be used on DC Mains. If AC is available ascertain the voltage by reference to the electric light meter, electrical apparatus in use, or the markings on electric light bulbs. Note the type of plug or connection required and prepare your lead for future use.
B. To adjust the Power Pack to a known voltage: Insert the "Mains-Battery" plug to read "MAINS" as in Fig. 1 The selection is made by inserting 4 small 2-pin plugs into the holes provided on PANEL A (see Fig. 1). The plugs must be pushed well in and cover the numbers which add together to the voltage required. Two plugs must always cover either the "205V" or "102V". the other two plugs are used to cover "+0V", "+10V" or "+20V" (see figs 1 to 9). Thus in Fig.1, plugs (A) and (A) cover "205V", plug (C) covers "+20V" and plug (D) covers "+0V". The power pack is now adjusted for a main voltage of 205+20+0=225 Volts. In practice this setting is used for any voltage between 220 and 234 Volts. Similarly in Fig. 9 the voltage is 102+20+10=132Volts. This setting is used for any voltage between 127V and 140Volts.
C. To adjust the Power Pack when Mains voltage is not known. If the mains are known to be AC, but the voltage is not known, proceed as follows:
a. See that the "RX" 6 pin plug is not connected to the Power Pack.
b. Plug the "TX" 6-pin plug into the Power Pack and set the "TSR" (Tune-Send-Receive) switch to "R" and the meter
selection on position 2.
c. Set the "Battery-Mains" plug to "Mains" and adjust the voltage selector to the highest setting (235V-250V) Fig. 5.
d. Switch on and the meter will give a reading.
e. If this reading is less than ½ scale (300) switch off and reset the voltage selector to the next lower setting Fig. 4 and
recheck the meter reading.
f. Proceed thus until a voltage setting is found in which the meter reads as nearly ½ scale (300) as possible.
g. Always use this voltage setting when working these mains.
NOTE: If the first meter reading (c) is only about 150 the mains are in the 100 Volt range, in this case, replace the 500 mAmp fuse by a 1 Amp fuse, then, adjust the selector to 127-140 Volts. Fig. 9 and make checks progressively as above.
D. To adjust Power Pack for Battery Operation. If Mains are not available or are unsuitable, a 6 Volt accumulator must be procured. It is essential for satisfactory working that, in view of the heavy drain on the battery, up to 10 Amps when transmitting and 4 Amps when receiving, it should be of the automobile type, fully charged and in good condition. Two such batteries may, with advantage, be used in parallel.
a. With the "ON-OFF" switch on the Power Pack in the "OFF" position connect the lead provided to the battery terminals, polarity will not affect performance, and plug on to the large pins marked "B" (see Fig. 10).
b. Set the "Battery-Mains" plug to "Battery" (see Fig. 10).
c. Switch to "ON". A voltage will be shown on the transmitter meter, in position 2 and a faint hum heard in the Pack.
NOTE: The position of the voltage selector plugs on Panel A is quite immaterial and has no effect when "Battery-Mains" plug is set to "Battery".
E. To change from Battery to Mains operation and vice-versa. If a rapid change-over from Mains to Battery operation in likely to be required, it is advisable to connect up as specified in sections D and B, both battery and mains leads being connected to the Power Pack. Assuming AC mains are in use, should they fail then:
a. Move Power Pack switch to "OFF".
b. Reverse "Battery-Mains" plug to read "Battery".
c. Switch to "ON".
I. If the apparatus is to be used with with the battery still connected up to the electrical system of a car, the BLACK battery clip should be connected to the terminal which is earthed to the car chassis, irrespective of whether it is Positive or Negative.
II. It is absolutely essential that the voltage of the accumulator used should not exceed 6.3 Volts, since otherwise the set may be damaged. The accumulator must not be charged whilst connected to the set.
III. If, when on battery operation no hum is heard from the Power Pack and the battery and the fuse are in order, the vibrator may be faulty. Disconnect and withdraw the Power Pack from the suitcase. take out the 2 screws in each side of the metal case and remove the lid. Insert the spare vibrator into the red clip in place of the faulty vibrator.
F. Transmitter and Receiver Connections. Normally the 6-pin "TX" cable plug is fitted in the upper row of sockets on the Power Pack, marked "TX" or "RX". The 6-pin "RX" cable plug is fitted in the lower sockets marked "RX only". In this position the receiver is automatically switched off when the Transmitter "TSR" switch is at "S" (Send). If it is required to operate the receiver alone, the cable must be fitted in the upper sockets "TX or RX".
The Aerial and Earth terminals are on the Transmitter Panel. The plug on the short coloured lead on the Transmitter should be inserted in the Aerial socket on the Receiver. If the receiver alone is to be used, the Aerial wire maybe removed from the Transmitter aerial terminal and used in the receiver aerial socket. (see B2 overview)
G. Fuses. Two fuse holders are provided on the Power Pack panel. On e marked "LT" is fitted with a 10-Amp fuse of the cartridge type, the other marked "AC" is sent out with a 500 mA fuse as is normally used on 200-250 Volt mains. For use on 100-120 Volt mains 1 Amp fuses are provided for use in this position. A fuse may be replaced readily by unscrewing the plug of the appropriate fuse holder (see diagram), withdrawing the plug and fitting another cartridge fuse of the correct rating.
The operator should make himself familiar with the functions of the following controls.
A. "Crystal Selector". This switch adjust the transmitter to suit different crystal frequencies and not the operating frequency. One position of the switch is for use on fundamental operation irrespective of crystal frequency.
B. "Wave Band". This switch sets the frequency of the oscillator valve to the band required. This will usually be the transmitting frequency, e.g. Using a 6.0 Mc/s crystal fundamental set the "Wave Band" to "5-7" and the transmission is on 6.0 Mc/s. With the "Crystal Selector" set to "Harmonic 5.2-6" and the same crystal, the "Wave Band" would be set to 9-12 Mc/s and the transmitted frequency would be 12.0 Mc/s.
C. "TSR". This "Tune-Send-Receive" switch performs the following functions:
I. Position "T". In this position the transmitter is ready for tuning. The key is short circuited. The power to PA (Power
Amplifier) is reduced to protect the valve. The aerial is disconnected so that no signal is transmitted until required.
The receiver HT is switched off. Receiver heaters are still on.
II. Position "S". The receiver HT is still switched off. The aerial is in circuit. When the key is depressed, the PA valve will
transmit at full power. This is the operating position.
III. Position "R". The transmitter HT is now off and receiver HT on. The aerial is now connected to the receiver. No other
transmitter controls should be altered in going from "Send" to "Receive".
NOTE: So long as the "TX" and "RX" plugs are in the Power Pack sockets and the Power Pack switch ON, the heaters of both transmitter and receiver are on. (heaters = gloeispanning)
D. "Meter Selector". This switches the moving coil meter into different circuits of the transmitter or receiver to measure either voltage or current. The positions of the switch are as tabulated on page 5.
E. "PA Grid Tuning". This knob controls a variable condenser which is a fine adjustment to the setting of the "Wave Band" switch. With the "Meter Selector" in position 3 tuning is accomplished by observing the deflection given by the PA Grid Current.
F. "Anode Tuning". This knob controls the tuning condenser for the PA valve. It is always adjusted for minimum PA total current.
G. "Aerial Matching". This knob controls a variable condenser and is used to adjust or match the transmitter to suit any particular aerial. It may be considered as a "load increasing" control.
The two sockets above the "Crystal Selector" are 2-pin quartz crystals (3.000-8.000 Mc/s) and those below, for the 2-pin plug on the key lead. The aerial terminal is above the "TSR" switch and the Earth below it. See B2 overview.
With an AC power supply, aerial and earth system installed and if possible a 6V accumulator for emergency use available, proceed as follows:
a. Open the suitcase and examine the apparatus.
b. Plug the 6-pins marked "TX" and "RX" which will be found lying on the panel into the sockets on the Power Pack
marked "TX" and "RX" and "RX only" respectively.
c. Open spares box, remove the mains and battery leads, plug them on to their appropriate pins (see Figs. 1 and 3).
See that the "ON-OFF" switch on the Power Pack is to "OFF" then connect the Battery clips to the Battery terminals and
plug in and switch on the mains.
d. Plug the key into the transmitter and the telephones into the receiver.
e. The "Meter-Selector" switch should be in position 2.
f. Adjust the Power Pack voltage to the voltage of the mains (previously determined) and set the "Battery-Mains" plug tp
g. Insert the Aerial Plug on the Transmitter into the socket on the receiver (see B2 overview).
h. Attach the Aerial and Earth wires to the appropriate terminals (see B2 overview).
i. Select your crystal and the appropriate coil, plug them in.
j. Set the "Crystal Selector" and "Wave Band" switches to the correct frequency.
II. TO TUNE THE RECEIVER.
a. Turn the "TSR" switch to "R" and switch on the Power Pack. There should be a deflection of about half a scale on the
meter (indicating anode volts) and in a few moments a faint hum heard in the telephones.
b. Set the "Wave Band" switch to the desired band.
c. If CW is to be received, set the BFO knob on the "ON" position at "0".
d. Consult the chart or graph relating to frequency and dial settings and move the tuning control over the setting indicated
for the frequency desired and advance the volume control towards maximum until a comfortable volume is reached.
e. Should the station not be received at once, check the "TSR" and "Wave Band" switch and Graph reading and then again
search around the setting indicated by moving the tuning control slowly to and from on either side of the number given
on the chart.
f. Beat Frequency Control. Attention to the following points will ensure best reception. the beat oscillator is provided with a
control for varying the pitch of the note received. This control is normally set to "0". When a station is received the
main tuning knob should be adjusted to give the lowest pitch possible and then the "BFO" control set to give the desired
note for morse reception. Setting the "BFO" control on either side of zero will provide the required note . If interference
from another station is experienced, setting the control to the same number on the other side of the zero should be
tried. This will give the same pitched note for the wanted station but a different note for the interfering station, thus
permitting the operator to recognise easily his own station. When searching for a station, the BFO control should always
be on "0" The receiver is designed to give maximum volume for a note of 1000 cycles per second and the BFO control
should always be adjusted for this frequency.
III. TO TUNE THE TRANSMITTER.
a. Transmitting on fundamental.
For the purpose of this example it is assumed that a crystal of a frequency of 3.775 Mc/s is to be used.
1. Connect up the aerial, Earth, Key , Telephones and Power Pack as already described.
2. Take coil L1 and plug it into its socket with the figures L1A to the front.
3. Plug the crystal into its socket and set the "Crystal Selector" knob to "Fundamental all Crystals".
4. Set "Wave Band" knob to Position "3-4".
5. Set "Meter Selector" to Position 2-PA Voltage.
6. Set the "TSR" switch to "T" (Tune).
7. Set "Anode Tuning" and "Aerial Matching" knobs to "10".
8. Switch on the Power Pack. The meter should read about 300.
9. Switch "Meter Selection" to 3. Adjust "PA Grid Tuning" for maximum meter reading.
10. Switch "Meter Selector" to 6 (PA total current, meter reads about half scale).
11. Turn the "Anode Tuning" knob until the meter reading dips to a minimum value, this is usually about 100 with the
"Anode Tuning" knob at about 2. The transmitter is now in tune and ready to be matched to the aerial.
12. Turn the "TSR" switch to "S". the meter will now cease to read until the key is pressed.
13. Press the key. The meter reading is now greater (about 200) as the aerial is beginning to take power from the
Matching the Aerial. The key must be held down whilst matching.
14. Readjust the "Anode Tuning" for DIP (minimum reading on meter).
15. Turn "Aerial Tuning" knob from "10" towards "0" until the meter reads 320 (one division more than half-scale).
16. Readjust "Anode Tuning" for dip.
17. Repeat 15 and 16 until when "Anode Tuning" is to "dip", the meter reading is exactly half-scale (300).
1. The meter MUST DIP to the final reading. This is proof that the transmitter is tuning.
The valve will take more current when off tune, but give out much less power
2. With a bad earth or a too short aerial, it may not be possible to load up fully the transmitter.
In this case the 'dip' will be below 320 on the scale (65 m/a)
b. Transmitting on Harmonic.
It is assumed that the same crystal (3.755 mc/s) is to be used (in daylight) and that the signal is to be sent out on 7510
mc/s, which is the second harmonic or double the crystal frequency. The transmitter is set up as above (1) to (17)
except for the following details:
1. The tank coil will now be L3A as given in the coil table.
2. The "Crystal Selector" knob is now set to "Harmonic 3 6 - 4 6" since the crystal frequency falls between these numbers.
3. The "Wave band" knob is now set tp "7-9" since the harmonic is between 7 and 9 Mc/s.
4. Everything else is done in the same order, and the meter readings will be the same. the aerial is matched in the same
way and the "Anode Tuning" control adjusted to give the dip between 300 and 320. The power radiated is the same on
harmonic as on fundamental frequency. With the "Meter Selector" switch at Position 5, the meter measures the oscillator
grid current and proves whether or not the crystal is working. It need only be used if there is any doubt that the
transmitter is working properly. It normally reads 2½-7½ on the 15 scale, that is 25 to 75m/a.
c. Transmitting on Third and Fourth Harmonics.
The transmitter may be used to send on third and fourth harmonics if necessary. the tuning up is again as above,
1. The tank coil must be chosen for 3 or 4 times the crystal frequency (3rd or 4th harmonic) as required.
2. The "Crystal Selector" is set for second harmonic.
3. The "Wave Band" knob should be set to correspond with the tank coil. This would be "9.3 - 12.2" for the third harmonic of the crystal frequency used in the above example (3.755 Mc/s) sending out on 11.265 Mc/s. On the 4th harmonic of the same crystal the output frequency would be 15.020 Mc/s, and the "Wave Band" setting would be "12.2 - 16.0".
1. The power of the transmitter will be less as higher harmonics are used. This is usually more than compensated for
by the increased aerial efficiency at higher frequencies.
2. It may not be possible to 'load" the transmitter to as high as a meter reading as on fundamental, and it is recommended
that the reading 280 and 260 be substituted for 320 and 300 (15) and (17) above on fourth harmonic, and on third
also if the transmitter will not "tune up".
MAINTENANCE & FAULT TRACING.