George,
I'll give it a try... What does the 87A manual say about the keying
input to the amp? Is it a relay coil? So many volts at what current?
The idea for direct relay coil switching that use DC voltage as a source
is to put a diode across the coil in the reverse direction. This is to
reduce the "back emf" voltage when the relay contact or FET opens in the
transceiver. Same type of voltage as was created in the old car
ignition system using points in the distributor. The back voltage can
be above 400 volts peak for a 24 volt DC relay coil.
What the SDR-1000 manual says is "we are providing the diode, you need
to hook it to the hot, + side of the relay coil in the amp." This means
you have to have a separate connection back into the amp. Some amps may
have that connection offered as a auxiliary DC voltage. Otherwise
you'll have to open the case and run a new wire for the diode.
Actually, its easier to just install a 1N4007 reverse diode across the
relay coil in the amp and be done with it. No need for the wire to pin 8.
Tell me what your manual says and I can give you a better line of moose
poop about the care and feeding of relay coils.
73, Larry K2LT
PS: Boil the eggs before you decorate them!
George Bennett wrote:
I want to connect my SDR-1000 to an Alpha 87A amplifier. Page 15 of the manual states
"The Common Protection Diode (pin-8) should be connected to the positive lead of the
relay power supply. This will shunt the reverse voltage from the relay coil as it is
turned off, thereby protecting the control transistors from transient voltages."
I'm afraid I don't know what that means. Can someone help me with this?
Thanks,
George Bennett
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