Vox Operation - Kenwood TS-430S Instruction Manual

5.2.6. FINAL STAGE PROTECTION
The TS-430S features a VSWR protection circuit to pro-
tect the final-amplifier transistors.
Three different protection circuits are used.
1. The final-stage transistors are protected by detecting
VSWR of the antenna system and automatically low-
ering transmitter output power if the VSWR is too
high.
2. When the heat-sink temperature rises, a detection cir-
cuit activates a cooling fan. Under normal conditions,
this cooling fan sufficiently cools the heat sink.
3. The heat-sink temperature could rise abnormally dur-
ing long transmissions, if the area adjacent to the
heat-sink is blocked. In this case, the transmission is
inhibited until the heat-sink cools to the proper tem-
perature.
NOTES:
1. If transmitter output decreases due to activation of the
protection circuit caused by high VSWR, carefully re-
check and retune the antenna system.
2. When the cooling fan starts to operate, determine that
adequate air flow is possible in the heat-sink area.
@ Operation of the Cooling Fan
The cooling fan operates when the heat-sink temperature
rises to approximately 50°C (122°f) and ceases to operate
when the temperature decreases to normal, approximately
40°C (104°F). The heat-sink is made of die-cast aluminum
and is actually the rear panel. It must be kept clear of sur-
rounding objects to allow heat to dissipate easily.
The cooling fan is designed to operate when the heat-sink
temperature is at a specific level, regardless of whether
the unit is in transmit or receive mode.
5.2.7. MIC GAIN CONTROL (Fig. 5-5)
This control adjusts the microphone input level. When us-
ing the TS-430S in a voice mode, connect a microphone
and set the STANDBY switch to SEND (an antenna or
dummy load must be connected).
For SSB operation, set the meter switch to ALC and speak
into the microphone. Adjust the MIC GAIN control so the
meter does not deflect out of the ALC zone at signal
peaks.
The TS-430S accepts either a low or high impedance mic-
rophone (500 2 to 50 kQ). When using a low impedance
microphone (500 ) the MIC GAIN control should be ad-
vanced slightly higher than when a high impedance micro-
phone is used, while observing the ALC meter.
12
@ ALC (Automatic Level Control)
The ALC monitors the transmitter final stage output to
minimize distortion in your transmitted signal. It automati-
cally adjusts output to an optimum level.
Pointer should not deflect beyond ALC zone at signal peaks.
Fig. 5-5 ALC Adjustment
5.3 VOX OPERATION
5.3.1. VOX SWITCH
VOX (voice operated transmit) is used to switch the
TS-430S into transmit mode by your voice. Place the
VOX switch ON and speak into the microphone. The
transceiver automatically switches to transmit mode (the
MIC control should be adjusted in advance as explained in
Item 5.2.7), Both the SEND switch and the MIC P.T.T.
switch are left in the REC position.
5.3.2. VOX GAIN CONTROL
This adjusts the VOX circuit sensitivity. Speak into the mi-
crophone at a normal voice level and adjust the control.
Increased sensitivity allows transmission with a lower
voice level. Transceiver operating condition (receive or
transmit) can be checked by the ON AIR LED.
Note that if the control is advanced too far, the VOX circuit
may be "tripped" by ambient noise.
5.3.3. ANTI-VOX CONTROL
This prevents the VOX circuit from being false-tripped by
sound from the speaker.
Adjust the control so the VOX will not operate at the de-
sired speaker volume level.