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Stan, here's Rudy's answer to your question: "Yes, I always reset before a new calibration and then check afterwards with Smith Chart OSL." Brian

The "scale/div" menu item does not use those other range keys on the keyboard, like some other items do (at least for the traces with dB values and phase angles, I didn't try all trace types).

i don't think so, but it runs fine on my Win 10 64 bit machine. It also runs in parallels on Mac OSX, Win 10 64 bit R85

That's more like it, although it sure doesn't look like a *30 MHz* LPF. More like 10 MHz. You might zoom in on 1-21 MHz. OTOH those ceramic filters are not necessarily 50 ohms in and out, Try the

Definitely Log mag is what you want.

Well, it sure looks like a low pass filter - the cutoff looks a bit high for a filter described as a 30 MHz Low Pass. I'd set the span to something like 0.1 to 100.1 (that makes the divisions on the

Is there a 64 bit version? Thanks, larry

Not an issue - you pressed the Scale button and you need to enter a new scale reference then click ENT Press the <- key to return to the main display. It's normal for the keyboard to cover part of

Set it to LOGMAG. Freq. range was 1 - 100 Mhz.

I can tell it was wrong setting. It is showing resistance? I should have set it for LOGMAG? Will try again later.

This is what I got.

The menu display containing k M G is cut off. It happens in certain occasions, not all the time. Is this faulty? Or is it because something else?

Sorry to ask, but is he resetting the calibration each time before calibrating? Missing that requirement was my problem last time I had a similar issue.

I put less emphasis on the 25-ohm measurement after calibrating with 50 ohms because then the load accuracy matters. I think he used a pair of highly accurate HP loads, but who knows the exact values.

Here it is. Same resistance offset (looks like same percentage, too). The reactance slope now extends throughout the frequency span. Brian

That is weird. The reflection coefficient (raw) is going to be (50-25)/(50+25) or 0.333 That's not getting anywhere near the noise floor. It would be interesting to see what he gets if he

Yes. N6LF calibrated with a 25-ohm load and then immediately measured it. That's why I don't understand the result. The resistance offset looks like a numerical bias issue. I don't know what to make

The actual limitation is the SNR into the detectors. That's driven more by circuit noise within the 5 kHz measurement bandwidth. In round numbers, each measurement is about 50-60 dB SNR. 60 dB SNR

Thanks, Jim. I'll read the analysis. I didn't realize the ADC was 16 bits. That's a lot. Now I feel even less forgiving about the observed performance. I don't understand why the possible

The measurements are made by integrating over 1 millisecond, after a I/Q conversion to 5kHz. It's a 16 bit ADC, but the noise floor isn't quite that good, and there's system noise too. I started a