[1000mp] ARB-704 and Yaesu Mark V

[Win]

The easy and cheep way to key almost any amplifier is to use a MPSA42 
transistor to switch the amp.  It is in turn switched by a low current 
switching transistor (2n3906, 2n3904 etc.)  Voltage for the transistors can 
be taken from the same Din connector. Using the switching voltages from the 
Din connector allows you to bypass the relay in the transceiver (turn it off 
if you wish).  This type of circuit is also satisfactory for QSK in 
amplifiers that have that feature. An NPN transistors will switch a positive 
key voltage while a PNP transistor will switch a negative key voltage. The 
MPSA42 will switch up to 300v at 500 ma.

I interface both my Mark 5 and IC-746 to the same amplifier this way.  My 
Amp is cathode bias keyed with about 150 V open circuit and 200 ma keyed. 
My circuits are built into the cable Din connector and potted with epoxy. 
One uses a pos key voltage while the other uses a negative key voltage (two 
different cables).

I added a second RCA port and have both radios going to the same AMP in 
parallel. Now there is no cable switching when going from one rig to 
another.

I have seen several of these circuits depicted on the internet, and on this 
list, over the years. It is best to breadboard the circuit and test it 
before before putting it into the cable.

Win