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Re: Saving
Thanks!
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Now does this recall all the stuff including the calibration etc.? Joe WB9SBD On 9/12/2021 11:33 AM, DiSlord wrote:
Recall menu |
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Re: Measuring crystal parameters with classic NanoVNA?
I add this feature for all H/H4/V2/V2Plus in my last v1.0.69
See Marker->Measure menu Unpack and use firmware for your device variant /g/nanovna-users/files/Dislord%27s%20Nanovna%20-H%20Firmware/NanoVNA%20v1.0.69%20fw%20pack.zip |
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Re: Saving
Joe,
The prior save-1 action will keep 1 as you set it up. That is all cals, freq range, display etc... But, if you decide that you do not like some item in 1... as long as you do not significantly change the freq range... no issue. However, if for some reason you wish to change details that impact CAL. Then you will have to recal. |
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Re: Saving
Ok,
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Good, Now if I was to save to Save-1, how does one use save 1 in the future? Joe WB9SBD On 9/12/2021 10:41 AM, Maurizio IZ1MDJ wrote:
Hi Joe , you have to save 0 . |
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Measuring crystal parameters with classic NanoVNA?
I recently joined the club and bought a NanoVNA, which I think is a "classic" version clone (no case, no shielding). It is currently running NanoVNA-H firmware 0.4.5-1-efbbceca. My current goal is to measure crystal parameters for building crystal filters.
For NanoVNA-V2, there is a special "ojisan" firmware that has easy-to-use menu options for measuring crystal parameters; see , section "LC, Crystal series resonant measurement". Through a series of measurements, the firmware then computes and displays the crystal parameters as shown in the below sample: Fs= 7.997345 MHz Fp= 8.0130 MHz Ls= 13.5 mH Cs= 29.3 fF Cp= 7.47 pF Rs= 17.5 ¦¸ Q= 38791 Unfortunately, this firmware does not work on my classic NanoVNA. Is there a similar firmware for the classic NanoVNA or NanoVNA-H that allows easy measurement of crystal parameters? |
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Saving
When you do a calibrate.
Open Short Load, And then Save, I usually save 1 What is this saving actually doing? Can you retrieve this Save for future use? Speaking of a save. say you make changes to the traces, One I never ever use, so I have to shut it off every time.? and one I have to change from port 2 to 1 and then make it be a SWR trace. Can this be saved and made like a new default? So i don't have to make all those changes every time I want to make a SWR measurement? Joe WB9SBD |
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Re: Measuring Inductance.
Interesting how a little DX35 with its small output tube would provide a similar set of L taps
for the pi net as a pair of big bottle 3-500 Z's. Apparently the ratio of plate V to plate I and the fact that 2 tubes in the SB220 are in parallel provide nearly the same plate Z. |
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Re: Measuring Inductance.
I took my old DX35 tank coil that has multiple taps and my Mosley traps and they pretty match your Now is values.
Here is your now is: 10 = 1.1uH 15 = 1.8uH 20= 2.94uH 40= 6.46uH 80= 12.46uH Ps I used multiple stimulus from 500khc to 32 mhz? ranges were 1-8, 10-25 etc to get better detail. Also, tried without recalibration still had good enough results De K8HTB Joe |
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Re: Measuring Inductance.
If you¡¯re looking to refine your measurement repeatability, do a fresh recal, repeat the sweeps of both induntors under as near exact conditions possible, then recheck your cal to confirm measurement integrity was maintained between cals.
Switches can frustrate repeatability, so its important to have a handle on tolerances in your measurements. It¡¯s always good practice to do end of test cal checks, and to quantify the variability between duplicate measurements. Its an easy method for determining the boundaries of uncertainty that are attributable to the quality of your test equipment and processes, while also validating the integrity of your results. -- 73 Gary, N3GO |
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Re: Measuring Inductance.
Joe,
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Once you have measured and installed the coil and capacitors in the RF Amplifier you can tweak the settings to compensate for stray capacitance and inductance by measuring the 50 ohm output impedance in the amplifier by simulating the RF Plate resistance. BEFORE YOU DO THIS MEASUREMENT VERIFY THE AMPLIFIER IS POWERED DOWN AND PLACE A SHORT ACROSS THE POWER FILTER CAPACITORS TO DISCHARGE THE CAPACITORS! - Place the RF Tube in it's socket. This will simulate the tube capacitance. The ARRL handbook gives the following approximation formula for calculating the load resistance of a vacuum tube power amplifier: Vp Rl = ---- KIp where K is 1.5 for class AB, 1.57 for class B, and 2 for class C. Calculate and install a non-inductive resistor from tube late to ground to simulate the Plate load. - Install the NanoVNA on the RF Output connector - Set the PI Network Capacitors and Coil for each band and adjust the capacitors (and coil tap if necessary) to get the output impedance close to 50 +j0 ohms. The plate formula is an approximation but these measurements will get you into the ballpark. - Remove the resistor before operating the amplifier. BEFORE YOU DO THIS MEASUREMENT VERIFY THE AMPLIFIER IS POWERED DOWN AND PLACE A SHORT ACROSS THE POWER FILTER CAPACITORS TO DISCHARGE THE CAPACITORS! I used to repair and install Marine MF (2 to 4 Mhz) radios on boats when I was in college 45 years ago. I had to adjust the output series coil to resonate the 20 foot whip antenna. I was I had the NanoVNA back in those days! 73 Mike N2MS On 09/11/2021 1:22 PM Joe WB9SBD <nss@...> wrote: |
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Re: Measuring Inductance.
Well,
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I left the coils in place in the amp, BUT.... I lifted all the taps, so the coil is floating free but inside the amp. And all readings are normal now. Interesting. So OK we planned on leaving the taps on 80, 40, 20, as they are, just add the extra "L" using the tubing coil. So thats what I just did, I found suitable and convenient taps for 10 = 1.1uH and for 15= 1.8uH. So original was 80= 11.6 40= 5.6 20= 2.06 15= .936 10= .448 Now is, 10 = 1.1uH 15 = 1.8uH 20= 2.94uH 40= 6.46uH 80= 12.46uH The switch must be messing with the readings when all connected. So next step is now the reverse matching thing. wish me luck. Joe WB9SBD On 9/11/2021 12:15 PM, Gary O'Neil wrote:
The rotations on the Smith chart generally imply of resonance. The resonant frequency is where the trace crosses the real axis. It sounds like you may have moved the SRF inband. |
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Re: Measuring Inductance.
The rotations on the Smith chart generally imply of resonance. The resonant frequency is where the trace crosses the real axis. It sounds like you may have moved the SRF inband.
Don¡¯t change your setup, but remeasure the first coil. If you repeat your original result, you can conclude that your test configuration is probably correct and sound. Beyond that, trust the measurements. For collateral confirmation, enter the coil dimensions into one of the online solenoid coil calculators, and compare the predicted inductance values for ballpark agreement with your measurements. -- 73 Gary, N3GO |
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Re: Measuring Inductance.
Not identical coil.
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I needed slightly more "L" on every band. so I made the 10/15 meter coil slightly bigger. You see the coil. 3/16" tubing, 7 turns, 1.75 diameter 2.25 long. New coil, 3/16" tubing also 7 turns, BUT 2.25 diameter, and 2.25 long. So it should have slightly more "L". I don't understand why now I am getting the 2 rotations on the smith chart. Joe WB9SBD On 9/11/2021 10:25 AM, Gary O'Neil wrote:
Identical coil identical set up identical results. Not true? Something not identical. Check set up. |
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Re: Basic Output Definitions
ward harriman
Allow me to take a stab at this and try not to introduce too many new issues.
1) The 'phase' can be viewed as the 'delay' between the input signal and the output signal. When considering scattering parameters, the signal being measured is usually a 'voltage'. Any 'delay' indicates the presence of reactance in the circuit. (OK, I have to complicate this a bit. For one port devices where there is only one electrical node one can measure, one can still think of an 'input signal' and an 'output signal' which are simply 'added' to produce the measured signal.) 2) The terms 'real part' and 'imaginary part' are meaningless if no 'of' is included. For example, I may report a measurement has a "real part of .1". The question is, are we talking about the 'real part of the reflection coefficient' or the 'real part of the impedance'. Stated simply, "No 'of', no meaning". As for the Smith chart, the plot is one of the 'real/imaginary parts of the voltage reflection coefficient' but the circles are the 'real and imaginary parts' of the impedance. Usually, a marker reports the 'real/imag' part of the impedance but that is wholly product dependent. 3) They MAY be the same, it depends on the 'of'...... If the real/imag refer to the voltage reflection coefficient then they will be different than the impedance. But... if real/imag is 'of' the impedance, they would be the same (by definition). 4) Spp parameters are ratios and are therefore unitless. The vast majority of Scattering Parameter papers discuss the ratios of VOLTAGES. A few use the term to refer to Power Ratios. ( I implore people to avoid the trap of arguing the 'proper' definition. I understand there are two camps. I have found it to be a fruitless discussion as it generally devolves into a 'Holy War'.) For the newly initiated, one can safely assume Spp refers to a voltage ratio. Hope that helps. |
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Re: Basic Output Definitions
Andrew Kurtz
That reference (below) is excellent, and clarifies everything! Thanks, Roger.
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Here is a link to an excellent paper by Olivier Pilloud HB9CEM which describes the relationship between the reflection coefficient Gamma (¦£). complex impedance (R+jX), Return Loss and VSWR. He also shows how the rectangular plot, polar plot and Smith chart are overlaid. He finishes up with an example and plots the results. |
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