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 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 300mA of operating current.

The ARB-704 RADIO input currrent and voltage requirements are minimal.  Only a few volts and much less than one milliampere is required for normal operation.  Virtually any radio can directly operate the ARB-704.

The ARB-704 allows the use of many older amplifiers without expensive modifications to them.  You can use the SB-200, SB-220, 30L-1 and others with your modern transceiver by just plugging them into the buffer.

Ameritron offers several plug-and-play cables that interface more common radios to the ARB-704.  Plug-and-play cables for various radios are listed under "Suggested Parts" above.

Ameritron ARB-704 Amplifier Interface Instructions (113K pdf)

One protection or buffering system requires installation of a low-current isolation relay between the radio and amplifier. Unfortunately an isolation relay’s field coil can still draw appreciable current, and relay coils produce a voltage spike when unkeyed. If a back-pulse canceling diode is installed to suppress back EMF or coil back-pulse voltage, relay release time increases.

The ARB-704 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. Your transmitter is only required to switch current under .35 milliamperes and very low voltages when using the ARB-704.  Measures a super compact 4-1/4W x 1-3/4H x 2-1/4D inches

Ameritron products are warranted by the manufacturer to be free from defects in materials and workmanship for a period of one year from the date of purchase.

Warranty of the amplifier vacuum tubes also involves the manufacturer's date code.

Contact Ameritron for further details of their warranty policy and procedures.

Ameritron
116 Willow Road
Starkville, MS 39759

General Information: (662) 323-8211
Technical Support: (662) 323-8211
Fax Number: (662) 323-6551

Part #	Part Name	Ship By	Price	Add to Cart
AMR-PNP-13D	Ameritron Interface Cable, 704 to IC-706/7000	Ship Tuesday	$ 16.95
AMR-PNP-5M	Ameritron Interface Cable, 704 to FT-847 Yaesu	Ship Tuesday	$ 16.95
AMR-PNP-7DI	Ameritron Interface Cable, 704 to Icom ACC2 Jack	Ship Tuesday	$ 16.95
AMR-PNP-7D	Ameritron Interface Cable, 704 to TS-440/690/450/180/140/950/130/870+ Kenwood	Ship Tuesday	$ 16.95
AMR-PNP-8D	Ameritron Interface Cable, 704 to FT-1000/900/767/920/990/747 Yaesu	Ship Tuesday	$ 16.95
AMR-PNP-8M	Ameritron Interface Cable, 704 to Yaesu 450/840/817/857/897/950	Ship Tuesday	$ 16.95
AMR-PNP-8MK	Ameritron Interface Cable, 704 to 8-pin mini, TS-480 Kenwood	Ship Tuesday	$ 16.95