LESSON THIRTY-THREE. RECEIVING UNDAMPED WAVES. THE TICKER.A decided difference is encountered between damped and undamped oscillations when receiving signals. The ordinary detector cannot be used for receiving undamped oscillations without first being properly modified.When telegraphing the dots and dashes of the code by undamped oscillations the change taking place in the detector circuit would merely move the telephone receiver diaphragm from its normal position at the beginning of each dot or dash, causing a click to be heard and nothing more. The telephone receiver diaphragm would remain in a fixed position just as long as the waves from the transmitter kept coming in during each signal. Both dots and dashes would be heard simply as clicks and not appear distinguishable from one another.The most common and perhaps also the best method is to employ a device called a "ticker" in place of the detector for receiving undamped oscillations.This arrangement is illustrated in Fig. 63. The left hand part of the illustration is the circuit diagram. A detail of the "ticker" wheel is shown at the right.The condenser F C is of comparatively large capacity and is fixed. The condenser C is also fixed but is of much smaller capacity. F C is usually a condenser having a capacity of several tenths of a microfarad while C has only a few thousands of a microfarad capacity.FIG. 63. The Poulsen Ticker for receiving undamped Waves.FIG. 63. The Poulsen Ticker for receiving undamped Waves.T is the ticker wheel and consists of a small brass wheel having a groove in the periphery like a pulley. This wheel is mounted on the shaft of a small motor so that it can be revolved at high speed.A fine wire is arranged to rub against the groove in the wheel and make contact with the latter.When the wheel is revolving at high speed, the wire does not make perfect contact at all points but tends to vibrate and to act as the equivalent of a very high speed interrupter by rapidly opening and closing the circuit.The basic idea in employing a device and a circuit of this sort in receiving undamped waves is as follows:When the contact is broken at the ticker wheel and the condenser F C is disconnected from the oscillating circuit formed by the condenser C and the secondary of the receiving transformer, the condenser C accumulates a relatively large amount of energy.Then when the ticker connects the condenser F C in parallel with C, F C takes the major part of the stored energy and discharges it through the telephones P, causing a click to be heard in the latter.The interruptions of the "ticker" are very rapid, a great many taking place during the duration of a dot or a dash, so that the resultant clicks occur very close together and the dots and dashes sound very similar to the spark signals of a transmitter sending forth damped waves.The sensitiveness of the ticker arrangement is very great, in fact much greater than that of any detector.
LESSON THIRTY-THREE. RECEIVING UNDAMPED WAVES. THE TICKER.A decided difference is encountered between damped and undamped oscillations when receiving signals. The ordinary detector cannot be used for receiving undamped oscillations without first being properly modified.When telegraphing the dots and dashes of the code by undamped oscillations the change taking place in the detector circuit would merely move the telephone receiver diaphragm from its normal position at the beginning of each dot or dash, causing a click to be heard and nothing more. The telephone receiver diaphragm would remain in a fixed position just as long as the waves from the transmitter kept coming in during each signal. Both dots and dashes would be heard simply as clicks and not appear distinguishable from one another.The most common and perhaps also the best method is to employ a device called a "ticker" in place of the detector for receiving undamped oscillations.This arrangement is illustrated in Fig. 63. The left hand part of the illustration is the circuit diagram. A detail of the "ticker" wheel is shown at the right.The condenser F C is of comparatively large capacity and is fixed. The condenser C is also fixed but is of much smaller capacity. F C is usually a condenser having a capacity of several tenths of a microfarad while C has only a few thousands of a microfarad capacity.FIG. 63. The Poulsen Ticker for receiving undamped Waves.FIG. 63. The Poulsen Ticker for receiving undamped Waves.T is the ticker wheel and consists of a small brass wheel having a groove in the periphery like a pulley. This wheel is mounted on the shaft of a small motor so that it can be revolved at high speed.A fine wire is arranged to rub against the groove in the wheel and make contact with the latter.When the wheel is revolving at high speed, the wire does not make perfect contact at all points but tends to vibrate and to act as the equivalent of a very high speed interrupter by rapidly opening and closing the circuit.The basic idea in employing a device and a circuit of this sort in receiving undamped waves is as follows:When the contact is broken at the ticker wheel and the condenser F C is disconnected from the oscillating circuit formed by the condenser C and the secondary of the receiving transformer, the condenser C accumulates a relatively large amount of energy.Then when the ticker connects the condenser F C in parallel with C, F C takes the major part of the stored energy and discharges it through the telephones P, causing a click to be heard in the latter.The interruptions of the "ticker" are very rapid, a great many taking place during the duration of a dot or a dash, so that the resultant clicks occur very close together and the dots and dashes sound very similar to the spark signals of a transmitter sending forth damped waves.The sensitiveness of the ticker arrangement is very great, in fact much greater than that of any detector.
LESSON THIRTY-THREE. RECEIVING UNDAMPED WAVES. THE TICKER.A decided difference is encountered between damped and undamped oscillations when receiving signals. The ordinary detector cannot be used for receiving undamped oscillations without first being properly modified.When telegraphing the dots and dashes of the code by undamped oscillations the change taking place in the detector circuit would merely move the telephone receiver diaphragm from its normal position at the beginning of each dot or dash, causing a click to be heard and nothing more. The telephone receiver diaphragm would remain in a fixed position just as long as the waves from the transmitter kept coming in during each signal. Both dots and dashes would be heard simply as clicks and not appear distinguishable from one another.The most common and perhaps also the best method is to employ a device called a "ticker" in place of the detector for receiving undamped oscillations.This arrangement is illustrated in Fig. 63. The left hand part of the illustration is the circuit diagram. A detail of the "ticker" wheel is shown at the right.The condenser F C is of comparatively large capacity and is fixed. The condenser C is also fixed but is of much smaller capacity. F C is usually a condenser having a capacity of several tenths of a microfarad while C has only a few thousands of a microfarad capacity.FIG. 63. The Poulsen Ticker for receiving undamped Waves.FIG. 63. The Poulsen Ticker for receiving undamped Waves.T is the ticker wheel and consists of a small brass wheel having a groove in the periphery like a pulley. This wheel is mounted on the shaft of a small motor so that it can be revolved at high speed.A fine wire is arranged to rub against the groove in the wheel and make contact with the latter.When the wheel is revolving at high speed, the wire does not make perfect contact at all points but tends to vibrate and to act as the equivalent of a very high speed interrupter by rapidly opening and closing the circuit.The basic idea in employing a device and a circuit of this sort in receiving undamped waves is as follows:When the contact is broken at the ticker wheel and the condenser F C is disconnected from the oscillating circuit formed by the condenser C and the secondary of the receiving transformer, the condenser C accumulates a relatively large amount of energy.Then when the ticker connects the condenser F C in parallel with C, F C takes the major part of the stored energy and discharges it through the telephones P, causing a click to be heard in the latter.The interruptions of the "ticker" are very rapid, a great many taking place during the duration of a dot or a dash, so that the resultant clicks occur very close together and the dots and dashes sound very similar to the spark signals of a transmitter sending forth damped waves.The sensitiveness of the ticker arrangement is very great, in fact much greater than that of any detector.
A decided difference is encountered between damped and undamped oscillations when receiving signals. The ordinary detector cannot be used for receiving undamped oscillations without first being properly modified.
When telegraphing the dots and dashes of the code by undamped oscillations the change taking place in the detector circuit would merely move the telephone receiver diaphragm from its normal position at the beginning of each dot or dash, causing a click to be heard and nothing more. The telephone receiver diaphragm would remain in a fixed position just as long as the waves from the transmitter kept coming in during each signal. Both dots and dashes would be heard simply as clicks and not appear distinguishable from one another.
The most common and perhaps also the best method is to employ a device called a "ticker" in place of the detector for receiving undamped oscillations.
This arrangement is illustrated in Fig. 63. The left hand part of the illustration is the circuit diagram. A detail of the "ticker" wheel is shown at the right.
The condenser F C is of comparatively large capacity and is fixed. The condenser C is also fixed but is of much smaller capacity. F C is usually a condenser having a capacity of several tenths of a microfarad while C has only a few thousands of a microfarad capacity.
FIG. 63. The Poulsen Ticker for receiving undamped Waves.FIG. 63. The Poulsen Ticker for receiving undamped Waves.
FIG. 63. The Poulsen Ticker for receiving undamped Waves.
T is the ticker wheel and consists of a small brass wheel having a groove in the periphery like a pulley. This wheel is mounted on the shaft of a small motor so that it can be revolved at high speed.
A fine wire is arranged to rub against the groove in the wheel and make contact with the latter.
When the wheel is revolving at high speed, the wire does not make perfect contact at all points but tends to vibrate and to act as the equivalent of a very high speed interrupter by rapidly opening and closing the circuit.
The basic idea in employing a device and a circuit of this sort in receiving undamped waves is as follows:
When the contact is broken at the ticker wheel and the condenser F C is disconnected from the oscillating circuit formed by the condenser C and the secondary of the receiving transformer, the condenser C accumulates a relatively large amount of energy.
Then when the ticker connects the condenser F C in parallel with C, F C takes the major part of the stored energy and discharges it through the telephones P, causing a click to be heard in the latter.
The interruptions of the "ticker" are very rapid, a great many taking place during the duration of a dot or a dash, so that the resultant clicks occur very close together and the dots and dashes sound very similar to the spark signals of a transmitter sending forth damped waves.
The sensitiveness of the ticker arrangement is very great, in fact much greater than that of any detector.