[R-390] Theory Question - RF Transformer Alignment

[David Wise]

The coil info comes from the R-390 Final Engineering Report,
a fascinating read all around, but they were doing the
same thing at least back to the 75A/51J.

The complex cam is the one in the coil-winding machine.
You can bet there was some trial and error to compensate
for distributed capacitance and edge effects.  But they
only had to do it once, that's the beauty of it.

I follow your inductance arguments, but if I tried
it myself I'd err; I can hang on better through the
frequency reasoning.

Dave Wise

> -----Original Message-----
> From: Dan Merz [mailto:mdmerz at verizon.net]
> Sent: Monday, September 15, 2008 1:12 PM
> To: David Wise; 'Mike Hardie'; 'R-390 at mailman.qth.net'
> Subject: RE: [R-390] Theory Question - RF Transformer Alignment
>
>
> Dave,  thanks for coming in with specific info about the coil
> design in the
> 390.  It all makes sense.  I didn't realize the cams were spirals and
> thought they were trial and error shaped  to linearize the
> inductance change
> to a linear frequency change.  Makes much more sense that the
> coil would be
> designed to be frequency linear with displacement and the cam
> a spiral to
> couple core displacement linearly with the dial rotation. The linear