Every transceiver has a keying output for an amplifier – but not all those outputs are capable of keying the high voltages or currents of an amplifier. High voltages or voltage peaks can destroy the keying stage of the transceiver. To prevent this an additional buffer relay like the ARB-704 is used.
The Ameritron ARB-704 is a semiconductor keying buffer to control the PTT line of nearly any amplifier. It handles voltages up to 200V and currents up to 300mA. This covers nearly all power amplifiers available on the market today. The idle voltage of the amp can be either positive or begative or even AC. The keying buffer keys against ground, works absolutely without noise and is fast enough to handle QSK keying without changing the shape of the key pulse.
The input can be configured by internal jumpers for various voltage levels, either positive or negative. This makes the ARB-704 useable with nearly any transceiver. The input current is below 1mA. Even very sensitive keying outputs liket those of the IC-706 can be handled.
The wiring and setup of the ARB-704 is very simple. The device has both, RCA (Cinch) sockets and a 5pin DIN socket for ready-made cables (see below). The RCA sockets are used with standard RCA cable for PTT from TRx to ARB-704 and on to the amplifier. If ALC is used this connections bypasses the ARB-704, TRx and PA are connected directly on the ALC line.
Optionally WiMo offers ready-made cables for many transceivers. These cables use in most cases the ACC sockets on the rear of the radio. The ARB-704 must be supplied with 9 to 18V DC power, a separate DC cable is supplied. Some ready-made cables take the power directly from the transceiver.
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