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
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