This is a Brand-New, Unused Ameritron model # ARB-704 Transceiver to Linear Amplifier keying interface. It came from the Estate of a local Amateur Radio Operator, who ordered it and never put it in service. It's still in the original shipping box, and includes the manual and four cables, as shown in the pictures.

This interface allows a Ham Radio Transceiver to safely key a Linear Amplifier, such as vintage units made by Heathkit, Collins, Drake, Henry, Swan, etc. that have a keying voltage that's too high for modern radios' keying relays to safely handle.

The instruction manual is also available for free on-line download. I've taken a few pictures of it that you can probably zoom in on for more information.

Here's some ARB-704 Info from the Ameritron site:

Ameritron Amplifier-to-Transceiver Interface

The ARB-704 will work with almost any transceiver without the need for a plug-and-play pre-wired cable.

The ARB-704 advanced interface is compatible with all common radios and amplifiers even though radios and amplifiers do not have standardized voltages, accessory plugs, or wiring. This interface is designed to work with any amplifier/radio combination.

The input is designed to be compatible with any transmitter or transceiver, and the output is compatible with AC control lines or DC positive or negative amplifier control lines having up to 200 Volts peak open circuit voltage and 300 mA of operating current.

Why you need the ARB-704 Amplifiers can damage radios if the amplifier has too much relay control voltage, voltage spikes, or excessive current on the relay control line. Such damage often appears as "stuck" or "sticky" transmit relays in exciters or shorted transistors on transmit control lines. In most cases where the radio is damaged, the system transmits normally but the external amplifier stays locked in a "transmit" mode. This prevents receive signals from coming through the amplifier with normal levels whenever the amplifier is in the "ON" or "OPERATE" position.

The ARB-704 has many electrical advantages over conventional relay buffer systems. The ARB-704 has no moving parts, switches almost instantaneously. It is noiseless, has very long life, and will not develop dirty contacts. It operates with negative, AC, or positive amplifier relay control lines.

It works with any relay voltage(AC, positive or negative) up to 200 peak volts and any relay current up to 300 mA. The ARB-704 is fully compatible with conventional amplifier relay systems. It is especially suited for buffering vacuum relay QSK amplifiers, since the ARB-704 does not affect attack or release times in a deleterious manner.

The ARB-704 operates with transmitters or transceivers that pull amplifier control lines to ground, or output a wide range of positive or negative control voltages. The transmitter only switches currents under .35 milliamperes and very low voltages when using the ARB-704. Measures a super compact 4 ¼" x 1 ¾" x 2 ¼".

The ARB-704 is supplied with the following:

1. One power connector cord and plug with red wire (+12 Volts) and black wire (negative and ground).

2. Three phono (RCA) cords with connectors on each end. These cables are for relay, ALC and amplifier control lines.

Plug-and-Play Cables for the ARB-704 (A plug-and-play cable is not needed if your radio is not listed)
Model # Transceivers
PNP-8D FT-1000/2000, (MP), 767GX, 920, 990, 747GX
PNP-8M FT-890, 840, 817, 857, 897, FT450, 950, 900
PNP-35 FT-100, (D)
PNP-5M FT-847
PNP-7D TS-440, 690, 450, 180, 140, 950, 130, 870, 2000,
50, 120, 530, 430, 830, 850, 940, 570
PNP-13D All models of the IC-706 series, 718, 7000
PNP-7DK TS-930 (serial numbers below 309)
PNP-8MK TS-480
PNP-5D FT-980
PNP-8DI ICOM ACC JACK
PNP-7DI ICOM ACC 2 JACK



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