FUNCTION GENERATOR LCE NR WITH MODULATION

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Gervase Lester
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1 FUNCTION GENERATOR LCE NR WITH MODULATION IMPO Electronic A/S Svovlhatten 3 DK-5220 Odense SØ Tel Fax mail@impo.dk

Function generator type LCE 1 2 3 4 5 6 7 8 9 10 11 Continuously variable fine adjustment of the frequency (1 to 10 times the adjustment on the decade switch) 12 Waveform selector (,, ) 13

3 Function generator type LCE Continuously variable fine adjustment of the frequency (1 to 10 times the adjustment on the decade switch) 12 Waveform selector (,, ) 13 Continuously variable adjustment of the output voltage from Vp for and from 0-20 Vpp for and on output bush ➆ 14 Mains switch 15 Adjustment of voltage amplifier, A v = U out U in 16 Decade switch for selecting range of frequency adjustment 17 Output from function generator 18 Button for 20 db attenuation of output signal 19 Output for DC-amplifier (Connection of loudspeaker, tele-loop, student desks or amplification of signal from output terminal ➆. Amplification 0-10 times +/-12.5 V, 2.5 A 10 Input DC amplifier - 10 kohm input impedance

4 Function generator type LCE Function generator with frequency range 0.1 Hz khz divided into 6 decades with linear scale for fine adjustment of the frequency within the individual decades. A switch is provided for selection of the waveforms sine, triangle and square. The output voltage for the waveforms sine and triangle is continuously variable adjustable from 0 - +/-10 Vp, and the waveform square can be adjusted from V. Attenuator switch with 20 db damping. Type LCE is provided with a 20 Watt DC output amplifier. FREQUENCY MODULATION On receiving radio signals the main interest is centred around the audio frequencies as a rule (say from 20 to 20,000 Hz). In theory there is nothing to stop a radio transmitter transmit this order of frequency, only the result would be that the receiver would receive signals simultaneously from several stations. It is therefore essential that each station is distinguishable from the others, so that the receiver is in a position to choose one of them. Consequently each radio station has its own transmitting frequency (carrier frequency) with the corresponding wavelenght (carrier wave) containing the actual transmission. To make room for the desired number of transmitters, the carrier frequency must be located in the high frequency area (over 150 khz). When the transmitter is open without sending any programme, the only thing being transmitted is the carrier frequency. The programme itself is low frequency signals that modulate the carrier frequency. If there is a need to convert the modulated signal back to an audible and intelligible sound, the low frequency must be separated out from the high frequency, which incidentally is called "demodulating". Generator LCE can via a 2-beam oscilloscope display frequency modulation. A backup generator to the LCE generator is needed (for instance the LCE). The object is to demonstrate how an LF signal (modulation signal) can be transported by an HF signal (carrier frequency) as is the case in all FM broadcasting.

DC-AMPLIFIER Adjustment of voltage amplification, A v = U out U in Input for DC amplifier (galvanically separated from the generator part) DC amplifier output The DC output amplifier is protected

5 DC-AMPLIFIER Adjustment of voltage amplification, A v = U out U in Input for DC amplifier (galvanically separated from the generator part) DC amplifier output The DC output amplifier is protected against short-circuit and galvanically separated from the generator part. The amplifier will produce +/-12.5 V voltage oscillation at an output current of +/-2.5 A with an amplitude stability of +/-1%. Frequency range with 100% load, DC to 20 khz. The harmonic distortion at 1 khz is typically less than 0.1%. The amplifier is suitable for providing the student desks with a frequency for experimental purposes for instance with filters or amplifiers. The amplifier can also be used for a teleloop. DATA Inputs: DC connected Input impedance: 10 kohm Voltage amplification: 0-10 times continuously variably calibrated Amplitude stability: +/-1% Output: DC connected. Protected against shortcircuit Range, output: DC to 20 khz Voltage max.: +/ V Current max.: +/- 2.5 A (R L = > 4 ohm) 20 khz-100 khz Voltage max.: +/ V Current max.: +/- 2.5 A (R L = > 4 ohm) Harmonic distortion at 1 khz: 0.1% IMPORTANT! Turn the amplification control Av to zero (counterclockweise) before connection/disconnection of anything to the amplifier output. This is also the case before turning off/on the unit.

6 LOUDSPEAKER Whenever the loudspeaker is connected to the output, the input signal to the amplifier should be carefully watched, as no DC voltage can be tolerated, since the amplifier is bound to amplify it and send a DC current through the loudspeaker, which thereby may be damaged. Do not turn up the volume control so as to damage the loudspeaker coil connected to it. Excess current is all too easily generated to the extent that the coil burns out or the membrane movement gets excessive resulting in the membrane becoming dislodged. Extra care is advised in case of amplifying the square signals from the generator part, as these squares go from zero to a positive voltage. This means that the loudspeaker moves in one direction only - which in turn places an enormous strain on the loudspeaker and its membrane. The input impedance is 10 kohm, and the amplification is calibrated from 0 to 10 times, continuously variable.

7 FUNCTION GENERATOR TYPE LCE TECHNICAL DATA Mains voltage: 230 VAC +/-10%, Hz Frequency range: 0.1 Hz to 100 khz in 6 decade ranges with linear scale Accuracy: Better than +/-2% Distortion: 0.5% max. Output voltage sine: 0 to 20 V pp Output voltage triangle: 0 to 20 V pp Output voltage square: Positive 0 to +10 V Output impedance: 600 Max. charging current: 25 ma Rise time: 1.5 usek. at V Attenuator: -20 db

Electronics II. 3. measurement : Tuned circuits

Electronics II. 3. measurement : Tuned circuits This laboratory session involves circuits which contain a double-t (or TT), a passive RC circuit: Figure 1. Double T passive RC circuit module The upper