[CQ-Contest] CW keying interface (reed relays)
w9sz at prairienet.org
Thu Aug 2 23:55:56 EDT 2007
Back in my Novice days I used a Hallicrafters HT-40, which used cathode
keying. I tried a reed relay in a keyer (remember the Accu-Keyer?) and
after a short time the contacts became welded together. I built a keyer
using a PNP transistor, which worked fine with that rig. I think the
transistor I used was a common HO transistor used in TV sets back then.
I later acquired an FT101E which also did fine with that keyer. I found
out later that it would also work OK with rigs like the TS-440 which
didn't use cathode keyiong (no cathode to key!)
I figured no one was using cathode-keyed rigs anymore, as solid-state rigs
had become the order of the day. So I never bothered to tell anyone that
So you're not alone ...
73, Zack W9SZ
On Thu, 2 Aug 2007, Art Boyars wrote:
> K8CC mentions: "I think I remember N6TR saying that he is now using reed relays ..."
> I think I disdained reed relays back in the 1970's when I saw that they were rated (as I recall) on the order 1-mega-operations mean before failure, and I calculated that a single 48 hour DX contest gave roughly one mega-operation of the relay. Maybe I was also concerned about the pull-in and drop-out times for QRQ (perhaps a prophetic vision of computer-generated E-E-N-A-4 at 60 WPM). But I could be wrong, and maybe the relays are better now, and I would surely yield to the superior knowledge, wisdom, and skills of Tree and Dave.
> But it really is neat that the well-known two-transistor "negative keying interface" would actually work for positive, too ... and nobody seems to have discovered it by accident.
> 73, Art K3KU
> (If K3KU is poking his head out, then SS CW must be getting close.)
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