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Second Zoom talk by Barry K3EUI on the NanoVNA
Monday, 12. July 2021, 19:30 - 22:00
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Contact Dave G8PGO

LRS Online Club Night Topic: NanoVNA: An Antenna Stethoscope Part 2

Please join me tonight to take another look at the Nano VNA.
What exactly does it measure?  What is calculated?

Are we able to interpret what each of the following graphs are showing about an antenna's performance?

Reflection Coefficient (magnitude)
Return Loss (dB)
SWR

Question:
Which impedance has the largest SWR value with  50 ohm coax feed line:
    25+jo,  100+j0,  40+j30,  40-j30

What level of attenuation (dB) in our feed line is "acceptable" ?

Then Resistance, Reactance, and Impedance:  what do these mean?
When operating off the resonant frequency, which changes faster: resistance or reactance?

How can we correct a reactance (at the antenna)?
How can we correct a reactance from our shack?

The Smith Chart - we have to spend more time on this graph
The POLAR graph has some real benefits over a rectilinear X,Y graph.

Resonance again -  is it always the "lowest SWR" point?  
Don't confuse resonance (no reactance) with the best match.
My  130 ft  long 80m dipole 25 ft above ground has a much lower impedance than 50 ohms so without a matching coil I get a fairly large SWR on  50 ohm coax.  Now what?

Bring quesions and comments to this Zoom talk.

 

12thJuly 2021 19.30 BST 18.30 UTC

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