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Antenna Considerations:
The amplifier is designed to work into a 50 ohms resistive load and any antenna outside
of this requirement must use an antenna tuning unit between the output of the amplifier
and antenna.
It is recommended to check that the antenna to be used is sufficiently rated for at least
500W power handling before connecting this product. It is also recommended to check
that the VSWR does not change considerably with increased power as this would indicate
that the antenna was not suitable for high power use.
Cable losses particularly increase with increasing frequency. Always use a good quality
50 Ohm feeder and keep the length as short as possible. Not only will this allow more
power to reach the antenna but will also increase the signal strength at the receiver.
This amplifier should not be operated into mismatched loads, (high VSWR), An accept-
able level should be less than 1.5:1. Less than 2.0:1 is also acceptable but some reduction
in power may be seen and the amplifier will work less efficiently and generate more heat.
There is no protection for excessive VSWR so it is advised that the antenna is tuned cor-
rectly for the frequency it is to used on to avoid damage to the amplifier.
Mode:
The KL405 may be used for all of the common narrow band transmission modes such as
SSB, CW,AM,FM, SSTV and data modes etc.
RX Preamplifier:
The KL405 is fitted with an RX preamplifier, that when activated can help to increase
the received signal level. This can be used when the signal level is low to help improve
intelligibility of the received signal. The RX preamp can be used independently of the
amplifier however when the amplifier and preamp are both activated the preamp is auto-
[
matically switched out of line when the amplifier is in transmission. Switch
is used to
_
switch the preamp on and off. LED
is illuminated when the preamp is switched on.
Warning: Transmit Time.
Hi Duty cycle modes such as FM and Data modes etc. operate the amplifier at full power
all of the time unlike modes like SSB and CW that are either intermittent or only reach
peak output for very short times, these high duty cycle modes will run the amplifier much
harder and generate more heat in the same amount of time. It should be noted that the
amplifier although capable of being used with these modes should not be operated con-
tinuously. A transmission time of more than a few minutes should be avoided to avoid
excessive transistor junction temperature. The exact time for transmission in these modes
will depend on numerous factors such as, how good the ventilation around the amplifier
is if there is sufficient space for freely flowing air to circulate, etc. If the ambient tem-
perature is high this will reduce the total time in transmission. Common sense should be
exercised, if the heat sink is becoming too hot then sufficient time should be allowed to
let it cool down before reuse.
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