Hi Bill,
The MFJ seems to be the outlier. Consider that a man with a clock always knows what time it is. A man with two or three clocks can never be sure:) Other replies to your post point at other factors so I won't go over those.
73,
Bill? KU8H
t'uther Bill
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On 2/5/21 5:34 PM, Bill AA6BD wrote:
I measured my 40M OCF Dipole with my NanoVNA-H4 and it shows that the minimum SWR of 1.68 is at 6.975 MHz. I had the loan of an MFJ-259C, and it shows the minimum SWR of 1.6 is at 7.14 MHz. I also have an Arduino based SWR analyzer designed by K6BEZ and it shows the minimum SWR of 1.7 is at 6.92 MHz. The SWR figures align nicely, but the center frequency is not very close. In the 40M band, this difference represents about half of the band. I calibrated the NanoVNA, and scanned from 6.5 to 7.5 MHz so precision of the 101 steps should not be an issue. Which device(s) do I believe? How can I resolve this difference?
