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 n...@carolina.rr.com ----- Original Message ----- From: "Vic K2VCO" <v...@rakefet.com> To: "'Elecraft List'" <Elecraft@mailman.qth.net> Sent: Sunday, August 23, 2009 3:19 PM Subject: Re: [Elecraft] Vibroplex Bug
> Ron D'Eau Claire wrote: >> I suspect you're experiencing "scratchy" or intermittent dits, not chirp. >> ("Chirp" is when your frequency shifts up or down during the initial >> milliseconds after the key closes) >> >> As others pointed out, a good low resistance contact is *required* by >> modern >> rigs that key a low voltage/low current line, which is a problem with >> mechanical contacts, especially contacts that just "bump" with little >> pressure like the dit contacts on a bug. > > Deoxit helps, as Ron says. Also intermittent cleaning with a business > card. But the real > solution for bug keying of modern rigs -- even the K3, which *is* better > than the K2 at > this -- is a simple circuit composed of a reed relay with a capacitor > across the coil to > soak up the contact bounce. > > Here is a description and schematic. You will need to use a fixed-width > font to see it > properly: > > Get a radio shack 12 volt SPST reed relay (275-233) or similar. One side > of the relay coil > goes to the positive terminal of a 9v battery and the other side goes to > your bug's > ungrounded contacts. In parallel with the coil put a 4.7 to 10uf 25v > electrolytic > capacitor (also from Radio Shack) and any silicon diode. Orient the > capactitor so that > the positive side goes to the coil terminal that is connected to the > battery. The diode > is reverse-connected; its CATHODE goes to the coil terminal that is > connected to the > battery. Finally, connect the negative side of the battery to the bug's > grounded side. > If you want to run the circuit from a 12v supply instead of a battery, put > an 820 ohm 1/4w > resistor in series with the 12v. > > coil > |------------+@@@@@@@+--------> to bug > | | | > - + +--| (--+ 4.7 to 10 uf capacitor > --- - 9v | | > | +--|<---+ diode > |------------------------------> > /// > > Here's a photo of such a circuit attached to a bug: > <http://www.qsl.net/k2vco/Bug640.jpg> > > The value of the capacitor should be the smallest necessary clean up the > bounce. The large > it is, the more it will stretch the dots and you will have to adjust the > dwell time of the > dot contact on your bug to compensate. > > Yes, I have tried various electronic debouncing circuits, and none of them > proved as > satisfactory to me as this simple one. The relay is almost silent (the > slight tick is > drowned out by the noise of the bug). > -- > 73, > Vic, K2VCO > Fresno CA > http://www.qsl.net/k2vco > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html