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-------- Original message --------From: Peter Gottlieb <hpnpilot@...> Date: 07/08/2019 18:36 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements I will perform some more measurements. One issue is that I only have a N male OSL (on a 7mm to N adapter on the VNA) so the BNC and SMA loads have to be via adapters.? They are precision ones but are bound to have some effect, if only phase, at 900 MHz. Peter> On Aug 7, 2019, at 11:56 AM, tuckvk3cca <tuckvk3cca@...> wrote:> > For one port it should be sufficient. When you get a good match the return loss is low so adequate dynamic range is necessary. I would also check both the RL and it's phase. The latter is most tricky . I wish there is such a thing as a standard zero degree phase dummy. I often find I get good RL : 40dB or so but very lousy phases. Sent from my Samsung Galaxy smartphone.> -------- Original message --------From: Peter Gottlieb <hpnpilot@...> Date: 07/08/2019? 17:29? (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements Is the basic OSL calibration sufficient?? Or do I need to do something special?Peter> On Aug 7, 2019, at 11:18 AM, tuckvk3cca <tuckvk3cca@...> wrote:> > I don't understand you Peter, the 8753 is a network analyzer, which will> give you S11 the reflection coefficient.? The log of its magnitude will be> the return loss.? It should be able to convert your readings into complex> impedance R+jX too. I have the equivalent of the minivNA which only> calibrates with one point, an open load. I still get 38 to 40 dB return loss> at HF for some of my better 50ohm loads.? I use the j-VNA software which> converts all magnitudes and phase measurements to S parameters of R+jX etc.> Most of the time I just live with this simple calibration procedure. On> transmission just a through pass for baseline calibration works for most> applications.? For a full S parameter set measurement one does need to work> much harder in terms of calibration.?? > > -----Original Message-----> From: [email protected] <[email protected]> On Behalf Of Peter> Gottlieb> Sent: Wednesday, August 7, 2019 4:29 PM> To: [email protected]> Subject: Re: [nanovna-users] Some basic load measurements> > 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>> >> > > > > > > > > >