10
8. Transmit operation
The RX/TX-switching is activated by applying zero volts or ground to the
“PTT” or pin 6 of the “CONTROL”-jack on the rear panel. This will be
indicated by the illuminated green “PTT”-LED. On most transceivers, a ground
on transmit will be supplied separately by an accessory output on their rear
panel.
Both of the two internal coaxial relays are controlled with different time delays
to allow for their specific switching times and to achieve zero power switching.
The PTT line is also used to generate the bias voltage to run the MOSFETs in
class AB. Without RF input the total idle current is 5 A, equivalent to dissipating
250 watts. An internal generated and delayed PTT- function is available at the
inner contact of the rear sided “AUX“- jack to reliably control a connected
transceiver. Any potential at the inner conductor is switched to ground.
In essence, your amplifier provides a built-in multi-level sequencer which
provides an alternate means to key your radio last.
When the amplifier PTT is activated usually via a foot switch, the preamp
voltage is dropped first, internal relays are switched, the RF amplifier section is
turned on and finally via the AUX jack a ground on transmit is available to key
your radio.
When using SSB you should not exceed 80% watts of input power to achieve
best spectral purity with low inter-modulation distortion. A red LED indicator
integrated in the front panel power meter indicates the 1 dB compression point
limit at 1950 watts. Exceeding this limit will cause harmonic distortions to be
transmitted. An integrated peak-hold function provides a more effective
indication of the output power.
