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December 31, 1967
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sov/lo6-59-5-3/13 Amplitude and Frequency Distortions in Oacillators with Frequency- Keying the oscillator. For an oscillator having an inductive "soft" feedback, the equation has the form (Ref 5) x =- A(-r)cos (.r-V(T)] (1) where the amplitude of the oscillation A(T) and the phase v(T) are determined by Eq (2) and (3). Solution of Eq (2) has the forin A(-r) -Acm1 (4) V cm I + Ce where Acm is the steady-state amplitude and C is an integration constant given by A2 AM 2 C cm - (6) A(0)2 Card 3/8 where u is a parameter of the oscillator and is much sov/io6-59-5-3/13 Amplitude and Frequency Distortions in oscillators with Frequency- Keying smaller than 1. Finally C is transformed into C 1 - CX2 cx2 + x(0)2 1 2 Q X(O) (17) i PAc A4 - x(OF2 M b A2 - X(O cm _x )2 c c m where x is the ratio of the grid-voltage to the cut-off voltage of the,oscillator valve and Cx =W 0 2 Cj 0.1 C30l is the natural frequency of the oscillator tuned circuit without the keyed capacItancePop the frequency with the capacitance connected. Because C depends on the value of x(O), the oscillation amplitude (after connection of the capacitance)will change from a value Acm to a value A(O) given by Acm Card 4/8 AM 'r 4 + C (18) sov/lo6-59-5-3/13 Amplitude and Frequency Distortions in Oscillators with Frequency- Keying As time progresses, the value A given by Eq 18 tends to Acm* Thus, parasitic amplitude modulation will be produced. The maximum depth of modulation is found by considering the two extreme values of C which the author shows to be 1 - a2 w Cmax (21) d2 2 02 and Cm'ax -1 (X W02 - W01- (22) az W 2 01 For C = 0, there is no amplitude modulation. The relative maximum and minimum ?'throws" in amplitude Card 5/8 corresponding to the extreme values of C are SOV/106-59-5-3/13 Amplitude and Frequency Distortions in Oscillators with Frequency- Keying ,AA(O)min __ A(O)min - Acm Acm Arm AA(O)max Acm Card 6/8 A(O)jna3c -Acm Acm .._101 - 002 (23) W 01 WOl - w02 (21k) w02 Thus, the depth of the amplitude modulation does not depend on the oscillator parameters but only on the ratio of the frequency change to the generated frequency. This conclusion is only valid ift (a) the capacitor is fully discharged when it is connected to the circuit; (b) the duration of the transients is small compared with the duration of the elementary "frequency-pulBell. Finally, the author investigates the frequency distortion introduced by the keying. Ideally, the oscillation frequency should switch Instantaneously from one steady-state value to the other but, in fact, sov/io6-59-5-3/13 Amplitude and Frequency Distortions in OncillatorE with Frequency- Keying the instantaneous frequency change differs from the difference between the two steady-state frequencies by an amount depending on the value of C. For C = 0, the step change of frequency is ACO = WI - W2 (27) and the difference between the instantaneous step change of frequency and the ideal change is zero. For C = C,,,,,, the difference between the actual step frequency change and the ideal Is shown to be 81OW = 3 2 (w0.2 w202 max Acmllp(wol - W02) _ + - wo UTI (30) This is illustrated in Fig 4 which shows an oscillogram Card 7/8 which would be obtained if the oscillator output were sov/lo6-59-5-3/13 Amplitude and Frequency Distortions in Oscillators with Frequency- Keying passed through an ideal discriminator. There are 4 figures and 5 Soviet references. SUBMITTED: 25th July 1958 Card 8/8 7//0 2 AUMOR: Nakhmanovich, V. E. 28794 S/106/61/000/010/006/OC6 A055/A127 TITLE: Some possibilities of increasing the frequency stability of radio transmitters operating in frequency telegraphy PERIODICAL: Elektrosvyazt, no. 10, 1961, 67 - 69 TEXT: One of the methods of increasing the frequency stability of radio transmitters in frequency telegraphy is based on the simultaneous existence of two sia-ble frequencies in the exciter; to effect frequency keying, these two frequen- cies are applied alternately to the output. Phase Jumps (up to 1800) occur how- ever at the moments of switching and cause a widening of the spectrum of the ra-- diated frequencies. The author proves analytically that the width of this sDec-. trum can be reduced considerably by an adequate control of the phase Jump. Let us assume that the phase jump at the passage from one of the frequencies to the_of~her is 4-66 and -W respectively. Fig. 1 shows the varilLtion of the frequency and phase of the oscillations in the case of keying by IL sequence of dots. Analytical- ly, these variations can be expressed as: a(t) - Aosin[&)ot+e(t)] - Ao[sinabt cos 0(t)+cosujot sin 0(t)],(1) Card 1,6 28794 3/106/61/000/010/006/006 Some possibilities of increasing the... A055/A127 G(t) =Mat -2) ato