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If I calibrate 3.5 MHz-7.4MHz and then want to narrow down the start and stop freqs, do I have to calibrate again if I change w/in the freqs calibrated


Walter Egenmaier 2022/01/13 07:23

If I calibrate a wider range, such as 3.5MHz-7.4MHz and then want to narrow down to just 3.5MHz-3.9 MHz, do I have to recalibrate since I changed the START STOP freqs to a narrower width, but still w/in the original calibration?
Walt

Jim Lux 2022/01/13 08:04

That depends on your accuracy requirements.  But in general, that's fine.  The firmware interpolates between cal points. So your original cal spanned 3.9 MHz with 101 (or more) points, so the cal points are 39 kHz apart.  I doubt the behavior of the bridges and detectors in the VNA change much over 39 kHz.

Lou W7HV 2022/01/13 08:27

What's worked for me in the HF range using a V2Plus4 is to do one 401 point cal from 3.5MHz to 29 MHz, save it, and use that for all subsequent narrower measurements within that range.  I probably could have gone to 1.8MHz but I don't operate down there.  If the measurement system is well behaved and varies slowly and smoothly within that range, that's more than good enough.

Walter Egenmaier 2022/01/13 10:47

That helps me understand better...I was trying to eliminate an unneeded
calibration, but it looks like it is truly needed to be accurate. Your
explanation tells me to do the extra calibration to get the most accurate
readings.
I appreciate it,
Walt/WB4ZUT

On Thu, Jan 13, 2022 at 10:04 AM Jim Lux <jim@luxfamily.com> wrote:

> That depends on your accuracy requirements. But in general, that's fine.
> The firmware interpolates between cal points. So your original cal spanned
> 3.9 MHz with 101 (or more) points, so the cal points are 39 kHz apart. I
> doubt the behavior of the bridges and detectors in the VNA change much over
> 39 kHz.
>
>
>
>
>

--
Walter H. Egenmaier, O.D
EyeCare Consultants
Evansville, IN 47708
(812) 426-2020 Phone
(812) 426-2828 Fax
WB4ZUT
wegenmaier@gmail.com
http://www.eyecare-consultants.net

Vladimir Lebedev 2022/01/13 09:43

Walt,
please see picture - all calibrations with start-and-stop frequencies. Wouldn't it be for You?
(it's a screenshot of my sold SAA-2)
Best regards

Vladimir
DL7PGA

Walter Egenmaier 2022/01/13 11:58

I believe you are saying to create smaller ranges of Start and Stop and
just save them.
My question was more of should I recalibrate EVERY time I change the Start
Stop frequencies.
Another user explained that it would be better to calibrate the range I
want, for instance, 3.5MHz to 4.0 MHz, rather than calibrate from
3.5MHz-7.4MHz and then change the start stop frequencies so I could check
both 80 and 40 meters. I was just trying to do one less calibration, but it
would be better to do 2 separate calibrations for the specific range I am
interested in. Thank you,
Walt

On Thu, Jan 13, 2022 at 11:43 AM Vladimir Lebedev <dl7pga@yandex.com> wrote:

> Walt,
> please see picture - all calibrations with start-and-stop frequencies.
> Wouldn't it be for You?
> (it's a screenshot of my sold SAA-2)
> Best regards
>
> Vladimir
> DL7PGA
>
>
>

--
Walter H. Egenmaier, O.D
EyeCare Consultants
Evansville, IN 47708
(812) 426-2020 Phone
(812) 426-2828 Fax
WB4ZUT
wegenmaier@gmail.com
http://www.eyecare-consultants.net

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