开云体育

If you can tell me a simple way to set up to measure return loss I can do
that for the various loads. I can do the smith chart but it is very hard to
see in a photo as the loads are all just tiny dots near the center on the
horizontal line. Perhaps easier to see if I change display colors or save
onto the floppy instead. What I call the cheap BNC is an old mil spec
terminator probably designed for HF and it gives a nice little spiral
around the center.


Peter

On Aug 7, 2019, at 5:48 AM, tuckvk3cca <tuckvk3cca@...> wrote:

That is expected Peter. Have you got the imaginary parts or phases? Best

to plot on a Smith chart too and see how your samples rotate from low to
high frequency. 1.02 swr corresponds to about 40dB return loss which is
very respectable at 900MHz.Sent from my Samsung Galaxy smartphone.

-------- Original message --------From: Peter Gottlieb <

hpnpilot@...> Date: 07/08/2019 04:43 (GMT+01:00) To:
[email protected] Subject: [nanovna-users] Some basic load
measurements Resending from website as it didn't seem to go through as a
message. Also my pasted table from Excel lost formatting so I tried to fix
it to be more readable.I just did some very simple resistance and SWR
measurements using a HP 8753ES with 85046A, resistance was measured using a
calibrated Agilent 34401A in 4 wire mode.I did a very basic one port 3
point cal using a Anritsu OSL which is specified to over 3 GHz.I took
measurements at 900 MHz.Load R ohms SWR
SWR notesOSL 50.052 1.001 FlatCheap
BNC 51.104 1.908 Sloping up with freqNano load
49.044 1.019 FlatNarda 12.4 GHz 49.536
1.018 FlatTiny SMA 50.787 1.009
FlatI am guessing there is some significant reactive component in the BNC
terminator. All three of the SMA loads showed a flat SWR with frequency so
I'm thinking they all have a minimal reactive component.The difference in
resistances while keeping SWR low was a bit of a surprise to me. The load
that came with the Nano is over an ohm off of the load I used to calibrate
yet the SWR remains at a low 1.019. Why is this? I did the math and
surprisingly this is indeed correct, per calculation the SWR should be
1.021 vs my measured 1.019. I'd say this is darn close seeing one
measurement is DC resistance and the other is at 900 MHz.So my conclusion
is that SWR is not a sensitive number to see resistance differences.Once I
read some of the references cited I can do some more advanced
measurements.Peter