selected manually prior to transmission, but not essential).
Manual band filter selection can only be made when the amplifier is in ‘Standby’
mode. When the Amplifier is switched to ‘OPR’ (Operate) no manual band change
can be made, the amplifier will automatically switch bands as soon as the radio
begins to transmit after a band change.
Default from the factory the standard ‘Standby’ parameters are Pin (Input Power)
and T1 (Transistor temperature). Pin maybe used when adjusting the input power to
the amplifier, but for the first transmission we recommend that the transceiver power
be set to minimum output power. (Pin in Standby will only be accurate if the output
load is 50 Ohms resistive).
Now switch to ‘OPR’ Operate, by pressing the ‘STB / OPR button
d
.
Begin a transmission and you will see that the amplifier is functional, The TX LED
c
will illuminate to indicate the PTT input is working and that the amplifier has
switched to transmit.
If there are no alarms adjust the drive power until a maximum
of 500W is displayed on the power meter. This is best carried out either in a constant
carrier mode, CW or FM to provide a constant output level. You can then see what
input power is required to drive the amplifier to 500W. So long as you are operating
into a 50 ohm resistive load / antenna there is no problem to remain in TX whilst
doing this procedure for some time, if your dummy load is suitably rated. (if doing
this into a radiating antenna, transmissions should be made as brief as possible to
avoid unnecessary interference).
The amplifier on most bands is capable of more than 500W output, however 500W
is the point 1dB compression, driving the amplifier harder will cause increasing
compression with the increase in distortion in linear modes such as SSB etc. The
extra power in the output will make little difference at the receiving station and may
even reduce the quality of the signal if the amplifier is being driven too hard into
compression.
(As an example let’s look at the difference between 500W and 560W output.
Assuming 20W drive for both conditions, (in reality more power would be required
for the higher output, so the difference would be lower, but this will suffice to
explain the concept). 10*Log(10) 500/20 =13.98dB Gain. 10*Log(10) 560/20 =
14.47dB gain.
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