[CQ-Contest] CW keying interface (reed relays)

Zack Widup 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 
it worked.

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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