Dave,
Please educate me.? Suppose I build a product that has a SMA-F connector on it and you and I are going to measure S11 for my product.? The only way we are able to get the same answer is if there is an agreed upon definition as to where within the mated SMA connectors we are going to call the reference plane.? Agreed?
The most accurate way to calibrate my measuring equipment is to connect a cable to it that is terminated in an SMA-M connector and then calibrate it with calibration O/S/L standards that have SMA-F connectors.? This eliminates any adapters being needed.? Agreed?
Since my O/S/L standards have some physical length I will need to move the reference plane closer to the measuring equipment by some small amount.? To my way of thinking this can be done either by the measuring equipment automatically of manually by doing some line extension.
Is this incorrect?
Larry, W0QE
toggle quoted message
Show quoted text
On 10/11/2019 10:07 PM, Dr. David Kirkby from Kirkby Microwave Ltd wrote:
On Sat, 12 Oct 2019 at 03:13, Larry Benko <xxw0qe@...> wrote:
Alan,
I understand what you are saying well. Since any calibration standards
will have some physical length you or the analyzer needs to subtract
this length before you can make accurate measurements.
No, neither the user nor the analyzer has to subtract any physical length.
Doing that would give reasonable results, but certainly not as accurate as
the 8753 is capable of.
In fact, with proper support in the firmware, and correct use, the NanoVNA
might outperform the 8753 in some measurements if one just subtracted a
delay on the 8753.
Just considering the open, there are 3 parameters that need to be taken
into account. In order of decreasing importance these are
1) Offset length
2) Capacitance, which is frequency dependant
3) Loss, which is frequency dependant.
The 8753
analyzer family does this length correction automatically which is why
the open and short cal. standards show as arcs. I have never seen any
small hobby type VNAs do this automatic correction.
I don¡¯t know what you mean by ¡°automatically¡±. The 8753 has no way to
automatically determine the offset length, capacitance or loss of the
standards.
The VNWA will show arcs for the calibration standards, and so will some
Deepace products. They are all aimed at the amateur market
Larry, W0QE
Dave, G8WRB
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
Telephone 01621-680100./ +44 1621 680100
Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom
