On Sun, 2009-03-29 at 18:12 -0400, John Graves wrote:
>
>
> Dr. Gerald N. Johnson wrote:
> > On Sun, 2009-03-29 at 16:36 -0400, John Graves wrote:
> >> If I may jump in with a question. I have a jupiter but my Drake 2B rcvr
> >> might need this, after I recap it.
> >>
> >> I have a MFJ 259B antenna tester, which will work as a frequency counter
> >> that does resolve to 1 Hz.
> >
> > Resolution is distinct from accuracy. What is the precision of the
> > counter's clock? It can be as bad as 100 ppm which is a 100 Hz error at
> > 1 MHz or 900 Hz at 9 MHz which is disastrous when aligning a BFO to a
> > filter.
>
> Jerry,
>
> The manual claims 1 ppm at room temperature. It is an old (or at least
> semi-old) MFJ piece of equipment. But if it is 10 times worse than
> spec, it sounds as though it is close enough to bring the adjustment in.
> >
> John Graves
> WA1JG
> jh.graves@verizon.net
10 ppm at 9 MHz is 90 Hz. I thought the object of the task was to
resolve the difference between 200 and 300 Hz from the filter corner. A
potential error of 90 Hz is nearly all of that.
1 ppm takes care and annual calibration against a better standard. And
to do that at HF WWV takes a month of quiet propagation days to achieve
1 ppm.
73, Jerry, K0CQ
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