Radio Link S.R. Mark II Colin Guy, G4DDI
Contents
1. must be provided between each microphone post and H Q where gun sounds are recorded Principle of Radio Link S R Mk II At the microphone a single set serves for both speech and gun sounds When transmitting the latter the sender frequency is automatically altered by a predetermined amount depending on the channel being used There are five channels see table 1 At H Q a special set is used having a multi channel receiver consisting of a single local oscillator and five I F amplifiers which are tuned 10kc s apart in frequency The centre channel is used for speech The outputs from these channels are connected to the Recorder In this way the off frequency transmissions from the microphone senders are selected without mutual interference and are directed to the corresponding galvanometer strings of the recorder Table 1 Channel 1 Speech Frequency plus 20kc s Channel 2 Speech Frequency plus 10kc s Channel 3 No alteration in frequency Channel 4 Speech Frequency minus 10 kc s Channel 5 Speech Frequency minus 20 kc s Construction In construction and external appearance the sets resemble the Wireless Sets No 22 in that the same C J Guy cases are used to house the set proper and the power supply unit The vehicle carrier and pack carrying arrangements are identical The bulk of the components used are common to those used in either the W S No 18 No 19 or No 22 Frequency The sets operate on t2. to give the signal Use of Remote Operating Units No I The unit is carried inside the power supply unit and is intended to be employed at Advanced Posts where it would be difficult to conceal the wireless station with its aerial The unit is used at the observer s position and is connected to the set by one or more lengths of 6 conductor rubber covered cable When the station is set up and netted the cable is plugged into the REMOTE CONTROL socket on the panel The microphone and headphones are disconnected from the set and plugged into the remote control unit at the Advanced Post Send Receive switching is done by the pressel switch as before and no operator is required at the set except to check the tuning or to change frequency A remote operating unit is also carried in the H Q set to serve as a spare Circuit Details The outstation fig 3 receiver consists of R F amplifier V1A ARP12 local oscillator V1B ARP12 mixer V1C ARP12 IF amplifier ViD ARP12 and detector avc output V2A AR8 The sender consists of M O V3B ARP34 buffer V4A ATP4 P A V4B and V4C ATP4 and ranging microphone amplifier V3A VMARS S R Mk 2 R F AMPLIFIER MIXER LF AMPLIFIER DETECTOR ARP 12 ARP 12 ARP OUTPUT AR 8 LOCAL OSCILLATOR A R P 34 i i i V2C 1 1 PES 1 4 4 1 Ai RECORDER POWER AMPLIFIER BUFFER A T P 4 A R P 34 VLA R F AMPLIFIER
3. A R P 12 HOT WIRE MIC POWER AMPLIFIER AMPLIFIER 2 X ATP 4 A R P 34 C J Guy 4 ARP34 The H Q station fig 4 receiver consists of R F amplifier VSA ARP12 local oscillator V2C ARP34 and five I F amplifiers each consisting of a mixer V3B ARP12 LF amplifier V3C ARP12 and detector output V4A AR8 The I F amplifiers are tuned to freguencies spaced 10 kc s apart The H Q sender consists of M O V2B ARP34 buffer V2A ARP34 and P A V3A ATP4 Six spare valves are carried in unwired holders inside the outstation sets It will be seen from the above that this eguipment shares much in common with the WS22 and WS62 and anyone familiar with these sets would have no difficulty in making an example of this eguipment operational Final have never come across an example of this eguipment in the flesh my understanding is that as it doesn t cover any amateur bands most of those examples that did find their way onto the surplus market were broken for spares However if anyone does have one tucked away or has a technical manual for it would be pleased to hear from them Also the manual gives no information about the recording equipment except a reference to film which implies that it would be an optical recorder If anyone knows anything about this or how the resulting recordings were used to determine gun positions an article would be most welcome DETECTOR A V C OUTPUT AR 8 SP
4. EECH MICROPHONE VALVE USED ON RECEIVER ONLY VALVE USED ON SENDER ONLY
5. VMARS S R Mk 2 Radio Link S R Mark IT colin Guy Gap In last year s members survey we asked if there were any specific eguipments about which members would like to see an article one member mentioned the above eguipment Earlier this year the eguipment was mentioned again in conversation with Howard Aspinall G3RXH and it is from a user manual kindly loaned to me by Howard that this article has been compiled Purpose and Facilities This is a specialised wireless apparatus for use in Gun Sound Ranging both for R T communications and for transmission of gun sound impulses from the special microphone used to the recording eguipment at Headquarters It replaces wire connections during mobile operations enabling the sound ranging Base to be deployed more quickly The Radio Link consists of nine sets eight of which are outstations and one Headquarters The outstations can be remote controlled from a point up to half a mile distant and a self contained Loudspeaker Unit is provided for use with the HQ set to enable plotting centre personnel to monitor all speech communications An S R Troop in action consists of a Headguarters where gun sound recording is done five microphone posts to detect the gun sounds and two advanced posts to control the recording when once the base station is established R T communications are reguired between H Q and all the outstations In addition an independent one way channel
6. d Dimensions Weight Dimensions ins Ibs os HA Long Deep High 1 Sender 32 35 17 13 12 2 Power unit 21 21 7 13 8 Sender receiver and A 3 power unit on 67 70 24 13 14 carrier No 1 Units i 4 Loudspeaking 16 6 12 10 Erecting the Aerial Before you can operate the station a suitable aerial must be erected and connected to the set See Figs 1 and 2 Operation It doesn t matter how good the wireless sets you are using may be you will not have good signals or good recordings at H Q unless they are all accurately tuned to the same frequency This point is emphasised with all communication equipment but must be very strongly emphasised with respect to the Radio Link S R Bringing a group of stations on to the same frequency is called Netting and to do it successfully all the operators in the group must i Know exactly how to tune the wireless set quickly and with confidence This has been described in the last two sections ALWAYS NET TO H Q STATION ii Understand and carry out the netting drill accurately remembering that the H Q station is always right and his instructions must always be obeyed immediately When all stations have been netted H Q calls each microphone station in turn to Press for S R using pre arranged code Before calling a given station the H Q METER SWITCH must be set to the correspondi
7. he range from 9 to 10 5 Mc s in one band Bandwidth required is 50 kc s 20 kc s above and below the allotted frequency plus an allowance of 10 kc s for drift and various errors Power Supply The power supply unit is operated from a 6 volt accumulator HT and bias supplies are obtained from a three commutator rotary transformer which supplies 60mA at 150 volts and 40mA at 40 volts The unit also contains the necessary R F and A F filtering The valve heaters are supplied from the 6 volt accumulator The battery drain whether sending or receiving is 6 5 amps Layout of Stations Figs 1 and 2 show the layout of the stations Tuning Systems The outstation has a 2 gang condenser which tunes the M O circuit 1 section tunes the M O the other section is a compensator for the channel spreading and a 2 gang condenser which tunes the receiver R F circuit and local oscillator 2 single section condensers tune the Buffer stage and Aerial circuit independently The H Q set has 2 single section condensers which tune the L O and Aerial circuits independently The Buffer stage is fixed tuned using a Band pass coil The receiver has a 2 gang condenser which tunes the R F circuit and local oscillator Aerials The set is designed primarily for use with rod aerials 34 in length Aerials shorter than this can be used when working at close range or where the 34 aerial would be too conspicuous It must however be stressed that successf
8. ng channel As each station s S R carrier is received the corresponding CHANNEL SENSITIVITY control is adjusted to give a dip of 50 on the meter For Channel 3 the SPEECH S R switch must be pressed to throw the Channel 3 control into circuit Operation when Sound Ranging After establishing the net and adjusting channel sensitivities the system is ready to record gun sounds It is assumed that the Recorder S R is ready and that the recorder operator has set the appropriate attenuators or switches to the R L position 1 Location Shoots H Q turns over control of the net to one of the Advanced Posts which then proceeds to give the group call to find out if he is heard clearly by all other stations When a record is to be made control sends SHOT or other pre arranged code word which is the signal for all microphone stations to PRESS FOR S R and for H Q to operate SPEECH S R switch to S R The switches will be held operated for a pre arranged time say 30 seconds to allow records to be received from all channels On releasing the switches the net returns to normal speech operation 2 Ranging Shoots In this case control remains with H Q station and the Advanced Posts stand by The instant of firing the ranging gun is reported to H Q by telephone or otherwise the time delay before sending SHOT can be calculated from available data and H Q operator will be told when
9. ul film recording necessitates as high a signal to noise ratio as possible much more so than in the case of ordinary R T communications The longest aerial possible up to 34 should therefore be used consistent with the tactical situation when working at distances over one mile At ranges less than one mile the absence of A V C on the H Q receivers renders it liable to overloading from the near station VMARS S R Mk 2 LAYOUT OF COMPLETE O S STATION S R MICROPHONE S AERIAL OF COMPLETE Q STATION CONNECT TO RECORDER SR AERIAL UNIT LOUDSPEAKING CONNECT TO RECORDER S R C J Guy 2 VMARS S R Mk 2 The offending Outstation may have to use a reduced aerial in these circumstances Reduce by one section at a time until the H Q is satisfied Units Loudspeaking No 1 This is provided for use at S R Troop headguarters to enable the Plotting Centre personnel to monitor the communication system without wearing headphones Also the officer in charge can talk to the HQ set operator who is wearing headphones by means of a hand microphone No 4 plugged into the loudspeaker unit The loudspeaker unit is plugged into the telephone jack on the Recorder S R which is in turn connected through the 14 wire connecting cable to the intercommunications systrem in the H Q set The loudspeaker unit is completely self contained requiring only a 6 volt accumulator and hand microphone for working Weights an
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