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[TRLog] Universal CW Keying Circuit

Subject: [TRLog] Universal CW Keying Circuit
From: (Jack Trampler)
Date: Sun, 4 Jul 1999 16:06:41 -0400
Recently my FT-1000MP took ill and I had to return it to Yaesu.  I inquired
on this reflector about keying the Drake T4XC with the keying circuit that
appears in the TR manual.  I received many replies (thank you to all) and
there were two routes to choose from.

Since the Drake uses grid block keying, the first option was to change the
transistor to a PNP type capable of handling the keying voltage.  This
measured -34.5 volts at the key.  The problem with this option is when my MP
comes back I will have to change the transistor again.

The second option was to use the existing circuit to key a relay.  Pete,
N4ZR said:

>I believe the C-line uses -60 to -70 volts DC for grid block keying.  As
>such the polarity is wrong, and the voltage rating would be exceeded.  The
>simplest fix probably is to put a dip relay in the collector, provide 5
>volts to operate it, and use the relay contacts to key the C-line.

I decided to go the route of the relay as it will be compatible with all
rigs.  I used a Radio Shack 5VDC reed relay (part #275-232) with the coil
connected between the transistor collector and the junction of pin 17 and
the 1K ohm resistor that goes the  emitter.  Pin 17 supplies 5 VDC.  I
tested this relay up to 50 WPM and it works very well.

The only question I have now is the relay draws 20ma.  Will this additional
current damage the computer or serial port?  I would think not, but I don't
have any specs on this.  If anyone know for sure, I would appreciate hearing
from you.

Jack - N2JT

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