You can buy or build a keying relay to put between the radio and the AMP or
you can just order a Heil Dual Footswitch that will key the radio and the
amp at the same time. If you click on this link
http://www.k5joe.com/page3.html and go to the AL-82 Amp, click on that
picture and you will see the little Ameritron Amplifier Relay Buffer switch
that you can buy. You do not want the voltage of the amp to get into the
746.
K5JOE
Happy Hammin/


"Jim McDermott" wrote in message
...
Just picked up an Icom 746 to give my TR-4 some time off. This 746 doc
isn't too clear on connecting it to an old amp like the L-4B. How do I
handle the keying voltage difference? Are there any other things I need
to
mod to drive this old beast?

Thanks!

Jim

Jim : Go to Radio shack. Get a small 12V relay with external contacts
that close when relay energized. Use the 7 pin DIN connector and put
pin 1 (12v) and pin 3 (ground on xmit)to the relay coil. On xmit you
will be keying the relay which in turn keys the linear. The relay
output of the RS relays will tell you what amp capable of handling.
Most are good for up to 2-3 amps and up to 24 volts from a linear, in
fact can key 110v linear relays OK too if about 200ma or so.. These
relays are cheap. Do NOT buy the Icom device, you will pay $25-30..
San

Jim : Go to Radio shack. Get a small 12V relay with external contacts
that close when relay energized. Use the 7 pin DIN connector and put
pin 1 (12v) and pin 3 (ground on xmit)to the relay coil. On xmit you
will be keying the relay which in turn keys the linear. The relay
output of the RS relays will tell you what amp capable of handling.
Most are good for up to 2-3 amps and up to 24 volts from a linear, in
fact can key 110v linear relays OK too if about 200ma or so.. These
relays are cheap. Do NOT buy the Icom device, you will pay $25-30..
San