[CQ-Contest] CW keying interface

Art Boyars art.boyars at verizon.net
Thu Aug 2 10:18:34 EDT 2007

I have already responded directly to Chris, saying that I do not know why the "K3KU" circuit is not working for his FT-101E with its minus-8V grid-block keying.  I noted that the circuit has worked for myself and other people, but that I expected the negative key line would be around -70V, so maybe the circuits key-down voltage was not good enough for -8V.

Upon further thought, that circuit has been published several times as an interface for keying grid block transmitters.  (Often, the published circuit has a reverse diode across the key line.  Obviously, you cannot have that diode in the K3KU implementation -- it would short a positive key line.)  Now, the FT-101 series is a pretty popular rig, and I would expect that somebody has tried the "negative keying interface" circuit.  Has anybody experienced a problem like Chris: keys TX, but not sidetone?  If not, maybe the problem is in Chris' rig, and not in the interface circuit.

If anybody in my area (zip 20902) has an FT 101 (would it have to be the E version??), I'd be happy bring over my keyer and see if it keys your rig.

73, Art K3KU

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