[R-390] Slide rule calculations

[Bill Hawkins]

George,

You can't do it with a slide rule, because you can't read it to one
part in a thousand. For ten times the cost, you might be able to
read it to one part in 10,000 with a magnifier.

Four beats per second means your generator is 4 Hz either above or
below WWV's 2.5 MHz. On the plus side, that's 2.500004. Multiply
that by 4 and get 10.000016 MHz, or 1.6 parts in 10 to the sixth
power (which is 1 millionth or 1E-6, where E is exponent of ten).
You'll get the same answer if you divide 4 by 2.5, but it'll take
longer.

So your accuracy is 1.6E-6 or 1.6E-4 percent, or 0.00016%. This is
very good for something set by a dial. But you get 2.5000005 or
2.5E-7 when you move 10 Hz on the dial. You were only off 4 Hz
before, so I'd guess that you went from being below to being above,
and made a tiny error in setting the dial.

WWV on a bad propagation day is good to 1E-7.

Was that what you're looking for?

Bill Hawkins


-----Original Message-----
From: george stringe
Sent: Thursday, December 04, 2008 12:47 PM

OK so here is a test for all the slide rule junkies: I have my Wavetek
sig gen all warmed up and my BA Hallicrafter SX-71 tuned to WWV at
2.5Mhz.
When the generator is set at  2.50000 Mhz, I am guessing that I get 4
beats/second,  if I set the gen at 2.50001, I get 2 seconds per beat.
So, what is my generator accuracy percentage?