[Elecraft] Vibroplex Bug

[Ron D'Eau Claire]

The problem I dealt with is not contact bounce, but contacts that do not
make a low enough resistance connection to trigger the logic properly. It
sounded like that was Werner's problem too.

It's easy to see the contact resistance issue using a scope on the key line.
The key voltage simply isn't being pulled down far enough to reliably key
the rig unless the contacts are *very* clean, and without adequate current
flowing through them to maintain a self-cleaning action, they quickly
oxidize again without help - or some other way to key the rig like Vic's
clever relay circuit. 

The K3 is much more forgiving in that respect, but I haven't investigated to
see why. IF it works, I'm happy :-) 

I've never experienced significant contact bounce with a bug. The full
weight of the pendulum mechanism is mashing the contacts together as long as
the dit interval lasts. The only possible problem can occur on break as the
contacts separate, but the "U" shaped spring will prevent that if it's
working correctly. As the pendulum moves away from the stationary dit
contact, the spring pushes against the contacts, smoothly holding them
together until the spring reaches the end of its travel and the contact
moves away. If the spring vibrates at all at the moment of break, it will be
moving in the direction to further separate the contacts as they part. By
the time the "U" spring might swing the contact back back toward the
stationary dit contact, the pendulum has separated the whole assembly far
enough to avoid the contacts touching. 

Some fellows dampen that "U" shaped spring so it doesn't move freely. I'd
expect them to experience contact bounce since they've defeated the
mechanical "de-bouncer". 

Ron AC7AC 

-----Original Message-----
All you need is a 1uf capacitor across the bug contacts. Radio Shack has 
some that are small enough to fit in an RCA plug! Actually .5 UF is enough 
so I have 2 ea. 1UF in series. These eliminate the mushy and double dit 
symptom. Cleaning doesn't always work. Some modern rigs such as the K3 and 
Omni 7 are overly sensitive to switch noise and the cap will clear it up.
Radio Shack PN is:  272-1434
Steve
N4LQ
N4LQ at carolina.rr.com