3
OPERATION
14
This linear amplifier has various protection circuits.

DALC circuit

The ALC (Automatic Level Control) circuit automati-
cally limits RF output power by controlling the input
level of the exciter.This prevents transmission of dis-
torted signals when the input signal level exceeds the
allowable level.
The ALC activates under the following conditions:
- Output power of the linear amplifier exceeds 1 kW
- Antenna SWR becomes 2:1 or more
- Output power of the exciter exceeds 100 W

DCooling fans

•The power supply cooling fans activate when the lin-
ear amplifier is activated and while transmitting.
•The antenna tuner cooling fans activate when the
antenna tuner is activated and while transmitting.
•All cooling fans activate when the heatsink tempera-
ture of the final FETs reaches 50 °C (122 °F) or
more.

DCircuit breaker

If the circuit breaker activates or the linear amplifier
stops functioning, try to find the source of the prob-
lem, then push the circuit breaker button to fill the
white parts.
- Circuit breaker capacity: 20 A (U.S.A. version)
15 A (Europe version)

DLinear amplifier protection circuit

When a protection circuit is activated, a band indicator
blinks to show a problem as described below.
➥[AMP/PROTECT] lights red when a protection cir-
cuit is activated.
- Push [AMP/PROTECT] to cancel the protection circuit.
The built-in automatic antenna tuner can match the
antenna feed line impedance to 50 Ωwhen the feed
line impedance is within 16.7 to 150 Ωfor HF bands
(VSWR 3:1) or within 20 to 125 Ωfor 50 MHz bands
(VSWR 2.5:1).
Once the tuner matches an antenna, the tuning cir-
cuit condition is memorized as a preset point for each
frequency range (100 kHz steps, 70 ranges).There-
fore, when you change the frequency range, the tun-
ing circuit is automatically preset to the memorized
point.
This antenna tuner is also used when the linear am-
plifier is turned OFF.
➥Push [TUNER] for 2 sec. to start manual antenna
tuning.
•When the tuner cannot tune the antenna (SWR 1.5:1 or
greater), the tuning circuit is bypassed automatically
after 20 sec.
While operating in the 50 MHz band, the antenna
tuner does not start automatically. Push [TUNER]
for 2 sec. to tune the antenna manually.
■Protection circuit■Antenna tuner operation
Item Indication Possible cause
1[TEMP] The heatsink temperature of the
final FETs exceeds 100 °C (212
°F).
2[AUTO] Power level of the 4 PA units be-
comes unbalanced.
3[ALC] ALC control level exceeds the
control range.
4[VD]Output voltage of the internal
power supply exceeds 55 V DC.
5[ID]Current of the final FETs (I
D
) ex-
ceeds 50 A.
6Current band’s
indicator Gain of the final FETs drops.
7Selected and
current band’s
indicator
When transmitting with different
band selections between the lin-
ear amplifier and exciter.
8
[AMP/PROTECT]
The power supply has a malfunc-
tion.