[WT-support] Rotors

[Bob Wilson, N6TV]

On Tue, Aug 11, 2009 at 7:13 AM, w7upf <donsay2 at cox.net> wrote:

> I am still waiting for resolution of the "bug" in <wtRotator.exe> so I
> can use the degree "offset" feature.


An attempt was made to fix this in version 4.1.0.  Unfortunately, it still
doesn't work right.

I also tried wt_dev 4.2.0-dev and wtRotators_dev 1.4.0-dev.  The "wtRotators
dialogs go blank" problem present in wtRotators veresion 1.3 is fixed in
1.4.0-dev, but the offset calculation still has problems:

Example:

   1. Enter offset 20° in wtRotators, on the 20m antenna
   2. Put Win-test on 20m
   3. Enter beam heading 35 and press Ctrl-F12.  Rotator turns to 15° (OK).
   4. Enter beam heading 20 and press Ctrl-F12.  Rotator turns to 0° (OK).
   5. Enter beam heading 19 and press Ctrl-F12.
   6. Bug:  rotator does not turn at all.

In sum, wtRotators is still broken.

The logic seems to be:

moveRotatorTo = Heading - Offset;

and if the result is a negative number, it doesn't turn.  Oops.

Personally I'd like to see the dialog made more intuitive.  Entering an
offset of 350° when your beam is 10° off seems somewhat counterintuitive.

Suggestion:  allow wtRotators to accept any offset from -180° to +180° (or
-360° to +360°).  If your beam is twisted to the right, enter a positive
(clockwise) offset.  If your beam is twisted to the left, enter a negative
(counterclockwise) offset.

Then in C code we could write something like:

unsigned short Heading;       /* 0° - 359°      */
signed   short Offset;        /* -180° to +180° */
unsigned short moveRotatorTo  /* 0° to 359°     */

moveRotatorTo = (unsigned short)
  ( ( (signed short)Heading - Offset + 360 ) // 360 );

For those more familiar with math than programming languages, the "//"
operator means "modulo", the remainder after dividing by 360 in this
example.  This ensures that the result is always between 0 and 359 no matter
what value you enter in Heading and Offset.

73,
Bob, N6TV
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