I did my call from 1-15Mhz I believe. I tried to call for the range
that I was going to be using, but my cals don't seem to be "sticking"
anyhow. Not sure what I am doing wrong.
Chris KQ6UP
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On Mon, Jul 12, 2021 at 6:25 AM Jim Lux <jim@...> wrote:
On 7/12/21 5:55 AM, Christopher Maness wrote:
Hello, Chris KQ6UP in SoCal.
I wanted to do a calibration with some short coax going to a test fixture for a LPF. I was surprised that calibration did not zero out the capacitance as the short open coax (stub) acts like a little capacitor. I found that I was better off just measuring the components 1 by 1 directly at the SMA and trusting the calculations. The LPF did end up working nicely in situ, but I would have rather tuned it in the text fixture. This could be pilot error, or maybe the calibration will not zero out that much capacitance. The lead was short and the frequency was low (14Mhz) though, so I was surprised.
That *is* odd - I've done cals with 25 or 100 ft of coax (as well as a
foot) and it seems to work ok. One thing I did get caught, by, though,
was when the cal frequency range didn't match the measurement frequency
range. The firmware tries to interpolate, but with a long coax, and big
frequency steps (say you did your cal 0-300 MHz with 101 steps, so the
steps are 3 MHz), I think the interpolation algorithm doesn't always
work, if your measurement range is narrower (say, 10-30 MHz, with 200
kHz steps).
But with a short cable, it should work just fine.
Another question. When I initially calibrated and stored in 1 of the possible setting memories, it retained my desired frequency range. However, I am not sure how to save a new frequency range so that is what comes up when I first turn on the unit. Do I have to clear out that memory and its saved calibrations in order to retain the frequency settings?
Thanks,
Chris KQ6UP
