Tuned Circuits; Transmitter Output - Shure T1 Service Manual

L209, diode D201, capacitor C214, and capacitor divider C224 and
C230.
bility despite changes in the battery voltage, regulated 5 Vdc bias is ap-
plied to the varactor diode and to the base of Q201. Temperature com-
pensation is provided by C224, C230, and C214.

Tuned Circuits

of the oscillator frequency (approximately 60
L202, C217, and C233. (The latter components also form a capacitively-
tapped voltage divider for matching the signal to the base of Q203.) The
output is double-tuned to provide high-spectral purity. Regulated dc bias
is again employed to minimize changes in loading on the oscillator stage
and to stabilize the drive levels.
cuit tuned to the output frequency (for example, 180
L204, C215, C237, C236, L207, C235, and C222 perform tuning and
impedance-matching functions. As in the preceding stage, regulated dc
bias is applied to the base circuit to stabilize the drive level, and the
output is double-tuned to provide spectral purity.
the input provides stability. The output circuit consists of a resonant tank
circuit (L203 and C213) capacitively coupled to a low-pass filter (C219,
L206, and C218). C213 and C219 provide a capacitively tapped voltage
divider for matching into the low-pass filter.

Transmitter Output

tenna. No user adjustment permits this value to be exceeded. The unit
should be powered exclusively by a 9 Vdc dry battery (an alkaline type,
such as a Duracell
lowing voltages should appear at the terminals of the output transistor;
quency of 169.445
6 Vdc, the final collector current drops to 15 mAdc and the output power
declines to +13.9 dBm (24.4 mW).
25C1016 (CC)
Frequency and Temperature Stability: To ensure frequency sta-
Stage 1: The collector circuit of Q201 is tuned to the third harmonic
Stage 2: Q203 operates as a frequency tripler, with its collector cir-
Stage 3: Q204 operates as a tuned amplifier. Resistive loading on
Transmitter: This can deliver up to +17 dBm (50 mW) to the an-
1604, is recommended).
MN
Voltage Measurements: With 9 Vdc applied to the unit, the fol-
S
Vc = 8.88 Vdc
S
Vb = .450 Vdc
S
Ve = .473 Vdc.
S
Base current = .29 mAdc
S
Emitter current = 21.5 mAdc
S
Collector current = 21.8 mAdc
S
Power input = 183 mW
The output power is +16.5 dBm (44.7 mW) into a 50 Ω load, at a fre-
z. At the minimum acceptable battery voltage of
MH
3
Shure T1 Body-Pack Transmitters
z) by L205, C225, C234,
MH
MH
z). In this case,
Characteristics