[Elecraft] keying ration control

[dw]

Thanks Vic,
I should take a look at the Idiom Press devices.
Can't hurt to have one more keyer ;^D

On Fri, 17 Apr 2009 12:26 -0700, "Vic K2VCO" <vic at rakefet.com> wrote:
> dw wrote:
> 
> > Before rolling my own, I talked to one designer who provides updates for
> > his keyer device.
> > And he got all holier-than-thou on me when he understood that I wanted
> > width control for all three elements.
> > 
> > My last cw rig utilizes the Curtis weighting schema and the dits were
> > too short and the dahs too long.
> > So with this adjustment schema, it was just not possible to get a
> > satisfactory product.
> 
> In perfect CW, spaces and dits should be the same length. Dahs are
> supposed to be 3 times 
> the length of a dit.
> 
> A weight control varies the dit:sapce ratio. Since most keyers base the
> length of dahs on 
> the dits, it also varies the dah:space ratio.
> 
> It's not too hard to get a keyer to close a circuit with the proper
> ratios. The 
> complexities crop up when you connect it to a transmitter.
> 
> Some transmitters shorten all keyed elements by a fixed amount, say 3 ms.
> If your keyer 
> produces perfect code, then you will have two problems: both the dits and
> dahs will be a 
> bit short (insufficient weight) and the ratio between the dits and dahs
> will not be 3:1, 
> because the shortening is a greater percentage of a dit than of a dah.
> 
> The problem will get worse as speed increase because the shortening will
> be a greater 
> percentage of both dits and dahs.
> 
> If you only have a weight control, you can't fix this. If you adjust it
> so that the dits 
> are right, the dahs will be a bit long. Say the dit was supposed to 50 ms
> lon but the 
> transmitter shortened them to 47. Then you adjust the weight control for
> 50 ms dits again. 
> That means the circuit is actually closed for 53 ms on a dit, and 159 ms
> for a dah. When 
> the transmitter shortens the dahs by 3 ms., they come out 156 instead of
> 150!
> 
> You could solve this by having separate adjustments for dit:space ratio
> (weight) and 
> dit:dah ratio. But this would only work for a single speed.
> 
> The simplest solution is to implement keying compensation, where you can
> have the keyer 
> add a fixed amount to each keyed element -- in this case 3 ms --
> regardless of speed.
> 
> This is what the Idiom Press keyers do. In addition to a weight setting
> there is a 
> compensation setting. You set the compensation to undo whatever your
> transmitter does, and 
> then set the weight according to your personal preferences.
> 
> -- 
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco
-- 
 Bw_dw at fastmail.net