Re: RFIV vs bridge
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Hi Kerry,
Impressive! I don't achieve that level. I tried a 5.1k resistor just now too, the charts are set to 10 ohms per division (same as yours), with 1-60MHz range total. I am using ADC speed:9, and ADC Avg:5. The blue trace is a single sweep, and the red trace is average of 36 sweeps. There's a chance it could be improved by changing my power supply (I'm using just an average AC/DC converter 5V barrel-plug output brick (Meanwell GST25B05-P1J<>), and inside the N2PK enclosure I created the 10V rail with an ADM660 switched-capacitor voltage doubler chip. That can't be too wise, I should try swapping it out one day. I might also try with a linear 5V PSU at some point, but nevertheless the results seem acceptable for now, just a few tens of ohms noise at such a high DUT resistance. [cid:6e197815-ba88-496f-92e2-5f27e245fc02] [cid:48575797-959d-4f89-9a17-76fe560a4bda] ________________________________ From: [email protected] <[email protected]> on behalf of Kerry via groups.io <planningpower@...> Sent: 28 January 2024 21:07 To: [email protected] <[email protected]> Subject: Re: [N2PK-VNA] RFIV vs bridge Check that Instrument Mode is set to Reflection and RF I-V; Transmission mode should not be used with RF I-V mode. Also check that calibration mode is set to Response Calibration. These settings should be applied automatically when RF I-V mode is selected but they may have been inadvertently changed. Also check that the two co-axial cables are not transposed; I once did this when I first used the fixture with my VNWA. As I recall, the results were incorrect but, surprisingly, "in the ballpark", probably due to the awesome power of calibration. There was a discussion of the RF I-V fixture some years ago on the old N2PK Yahoo group; Bill Carver was having a problem with his, I think. To assist, I did some measurements of a 5k1 0805 resistor and obtained results as seen in the attachment; Paul opined that this was very good, the kind of result that might be expected. Kerry VK2TIL. |
