Think of it in golfing terms. It's like trying to putt with a 'mashie'. (personally I prefer a #2 wood to putt)
Mike C.
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On 12/20/2021 1:48 PM, Dave Daniel wrote:
Remember, the difference between ¡°accuracy¡± and ¡°precision¡± is important.
Accuracy has to do with the degree to which an instrument can determine a measured value compared to the actual value, independent of the method of measurement.
Precision is the degree to which an instrument can display the actual value.
For precision, think about measuring a length; does the scale read in 10ths of an inch, 100ths of an inch? And how accurate are those markings on the scale?
DaveD
On Dec 20, 2021, at 13:18, Earle Wilkinson <earle.wilkinson@...> wrote:
?Thanks for the response will let you know the outcome
Earle D Wilkinson
(6Y5EW)
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Email address: earle.wilkinson@...
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On Mon, Dec 20, 2021, 10:21 AM Jim Lux <jim@...> wrote:
On 12/20/21 12:27 AM, Earle Wilkinson wrote:
Earle D Wilkinson
(6Y5EW)
Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA
On Mon, Dec 20, 2021, 3:18 AM Earle Wilkinson <earle.wilkinson@...
wrote:
New at this.
I got myself an NanoVNA 2 version 4.
Everyone says best thing ever happened.
Better than sliced cheese.
My problem is that I a sticular when it comes to accuracy.
I would like to check my club stations duplexer accuracy on 147.960 high
pass filter with 147.360 as the split on the low pass filter, that is
minus
600 kc split.
Now her is my problem I can only set my markers at 147.300 and 147.900.
Not the exact repeater frequency.
Will the difference of 60 hz make a difference in the accuracy of the
tuning insertion loss etc.
I realise that I need to be accurate at least with the 50 ohms
impedance.
Thanks for your response.
Earle D Wilkinson
(6Y5EW)
Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA
Two issues that arise:
#1 The NanoVNA only has a limited number of frequency steps
(101,201,401, depending on which firmware and model) unless you're using
software on an external computer that does multiple scans. So, if you
set your span to, say, 147 to 148 MHz, then you'll get a measurement
every 10 kHz (with 101 points). Solution here is to use one of the many
software packages that will talk to the NanoVNA and make multiple scans
and combine them.
#2 The 28 MHz oscillator in the NanoVNA isn't necessarily accurate
enough. I don't recall the spec, but let's say it's on the order of 10
ppm (good for a TCXO) - at 147 MHz, that means it could be off by 1470 Hz.
Mike C.