RM Italy BLA600 User Manual page 12

The difference between the two values is approximately 0.5dB. Now consider that 1
'S' Point on your receiver is usually approximately 6dB you can immediately see
that 0.5dB difference really will be unnoticeable on his 'S' meter, if the amplifier is
now well into compression the linearity is lower and the distortion will increase
probably making your signal actually slightly less intelligible).
The amplifier is fully protected for input overdrive even accidental 100W on the
input has not been found to cause damage as the protection is extremely quick but
this should obviously be avoided.
*Important note regarding ATU's and non resonant antennas*
It is very important to understand when using a non resonant antenna in
conjunction with an Antenna Matching Unit (ATU, Tuner etc.), that the
antenna is only tuned under low power, ie with the amplifier in Standby.
Usually the ATU requires only a few watts <10W in order to tune the antenna to
resonance. If you find that that when the amplifier is outputting high power
that there is a significant difference in the VSWR this usually means that there
is a problem. Either that the ATU cannot support the increased power, or
maybe the Balun if used , is not sufficiently rated, or a problem with the
antenna itself not being able to support high power. Antennas that have
matching networks or baluns at the feed point or trapped antennas where
maybe an ATU is used to cover both CW and SSB sections of the band. Make
sure that these components are rated for the power being used. Sudden
increases in VSWR can also indicate arcing on variable capacitors or
component failure. Special attention must also be given to Automatic ATU's.
These must ABSOLUTELY not be used to tune the antenna at high power,
(with the amplifier in 'Operate'). As generally they use relays to switch between
banks of fixed inductors and capacitors, at high power the relays can be
damaged almost immediately if they have break before make contacts. Also
depending on the tuning algorithm used they can present very high / low
impedances to the internal components that may cause voltages and current
beyond safe limits. Auto tuners should be disabled such that another tuning
cycle cannot be made during TX periods at high power, after the initial low
power tuning. It is of course possible to make a final adjustment manually so
long as the adjustments are small. The BLA600 is protected against high
VSWR loads but it is very bad practice to tune the antenna at high power and
there is always the risk of damage to both the amplifier and ATU as well as
creating unneccessary interference on the bands.
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