QSK CW: TX DLY vs CW WGHT with internal keyer

[Bill VanAlstyne W5WVO]

Just thinking out loud here, having recently upgraded my 3-500Z amplifier with fast vacuum T-R relays...

The default (and fastest) QSK transmit delay setting (TX DLY) is 8 ms. At 20 WPM, this shortens the length of a nominal 60 ms dit element to 52 ms long. To regain this lost "dit time" when using QSK, the default setting for the CW WGHT element-to-space ratio is 1.15. (52 ms X 1.15 = 60 ms approximately.) So the 1.15 default weight factor was seemingly arrived at by using 20 WPM as a nominal QSK code speed.

Assuming this reasoning is correct (Wayne/Eric, please enlighten me if it isn't), two things come to mind:

First, since amplifier T-R speeds below 4 ms are readily achievable using vacuum RF relays, and faster than that using PIN diodes, it might make sense to make TX DLY settings of less than 8 ms available -- say, down to 2 ms, while still leaving the default at 8 ms.

Second, as QSK code speed is increased, the TX DLY factor (whatever it is, currently 8 ms by default) becomes a larger and larger proportion of the element time, requiring a larger weight ratio to correct for the TX DLY shortening. For example, at 25 WPM (48 ms element) and TX DLY = 8 ms, a CW WGHT setting of 1.20 would be correct; at 30 WPM (40 ms element), again with TX DLY = 8 ms, a CW WGHT setting of 1.25 would be correct; and so on. Might it make sense to optionally have CW WGHT track with the user's code speed setting during QSK operation? (You wouldn't want to do this in non-QSK CW mode, of course.) The tracking formula would be based on the user's TX DLY setting, whether 8 ms or something faster/slower.

Of course, this would only apply if the internal CW keyer were being used; if using an external key or keyer, you'd be stuck with a fixed CW WGHT setting...

Comments?

Bill W5WVO
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[Hank Garretson]

I think what we are really talking about is Keying Compensation, not Code
Weight.  I use a K1EL WinKeyer with Keying Compensation set to 06 ms with my
K3.  See pages 15 and 16 here for good discussion of Keying Compensation,
http://k1el.tripod.com/files/WKUSB_QuickStart.pdf .  My twenty-plus-year old
CMOS Super Keyer II also has Keying Compensation option.

73,

Hank, W6SX

Mammoth Lakes, California

Elevation 8083 feet in John Muir's Range of Light


On Thu, Mar 25, 2010 at 10:22 PM, Bill VanAlstyne W5WVO <[hidden email]
> wrote:

Just thinking out loud here, having recently upgraded my 3-500Z amplifier

> with fast vacuum T-R relays...
>
> The default (and fastest) QSK transmit delay setting (TX DLY) is 8 ms. At
> 20 WPM, this shortens the length of a nominal 60 ms dit element to 52 ms
> long. To regain this lost "dit time" when using QSK, the default setting for
> the CW WGHT element-to-space ratio is 1.15. (52 ms X 1.15 = 60 ms
> approximately.) So the 1.15 default weight factor was seemingly arrived at
> by using 20 WPM as a nominal QSK code speed.
>
> Assuming this reasoning is correct (Wayne/Eric, please enlighten me if it
> isn't), two things come to mind:
>
> First, since amplifier T-R speeds below 4 ms are readily achievable using
> vacuum RF relays, and faster than that using PIN diodes, it might make sense
> to make TX DLY settings of less than 8 ms available -- say, down to 2 ms,
> while still leaving the default at 8 ms.
>
> Second, as QSK code speed is increased, the TX DLY factor (whatever it is,
> currently 8 ms by default) becomes a larger and larger proportion of the
> element time, requiring a larger weight ratio to correct for the TX DLY
> shortening. For example, at 25 WPM (48 ms element) and TX DLY = 8 ms, a CW
> WGHT setting of 1.20 would be correct; at 30 WPM (40 ms element), again with
> TX DLY = 8 ms, a CW WGHT setting of 1.25 would be correct; and so on. Might
> it make sense to optionally have CW WGHT track with the user's code speed
> setting during QSK operation? (You wouldn't want to do this in non-QSK CW
> mode, of course.) The tracking formula would be based on the user's TX DLY
> setting, whether 8 ms or something faster/slower.
>
> Of course, this would only apply if the internal CW keyer were being used;
> if using an external key or keyer, you'd be stuck with a fixed CW WGHT
> setting...
>
> Comments?
>
> Bill W5WVO
>

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