FS: An Ameritron Amplifier Interface Relay Buffer unit, model #
ARB-702K. It is a linear amplifier keying circuit interface unit to go
between an HF transceiver and an older linear amplifier, such as
Heathkit SB-200/220 series, Collins 30L1/30S1, Swan, Henry amplifiers,
etc. that have a keying relay that has up to 200 volts on the
amplifier keying line. Most modern HF transceivers are only capable of
keying linear amplifiers that have a keying voltage of no more than 30
to 50 volts maximum. If you try to key one of these older linear
amplifiers directly with your later model Icom, Kenwood, Yaesu, etc.
transceiver, you will probably weld the T/R relay contacts together.
This unit lowers the voltage and current that the radio has to key to
a very low, safe value. It has a handshaking line that can be used
with QSK (full break-in) transceivers, and an input for ALC. This
ARB-702 is currently wired up with a DIN plug that is setup for use
with most Kenwood HF transceivers - it had been used with a Kenwood
TS-450S/AT and a Heathkit SB-220 Amplifier. Jumpers can be moved on
the internal circuit board so that it can be used with other HF
transceivers. $25 plus postage.