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Can the nanoVNA be used as a scalar spectrum analyzer ?
Maybe, or better, surely, something is escaping me....
I connected CH1 of the nanoVNA to a calibrated generator, set to -20 dBm, 10 MHz output. I set the nanoVNA for a Center Frequency of 10 MHz. The Stop Frequency automatically did set at 19.9 MHz. What I saw on the nano screen was what I expected, a peak just at 10 MHz, albeit the cursor indicated an amplitude of slightly less than - 6dBm, but my concern is another.. At this point I set the frequency output of the generator at 9.9 MHz. What I did expect was to see the peak on the nano moving a bit to the left, to 9.9 MHz... No... the peak disappeared completely... a flat blue trace at the bottom of the screen.... There is surely something escaping me, but what ? TNX for any clarifications, -- /*73 Alberto I2PHD* <<< >>>/ |
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Re: errors of "error" models
#95.1 : On a Sufficient Condition for Identical Measurements Using Two Different VNAs
Hello, Well, we think that this "phenomenon", that may looking as a rather unexpected one, but in fact we searched for something like it in the last few months, has to do with the many, very interesting all, properties of M?bius transformation: Sincerely, gin&pez@arg :#95.1 |
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Re: errors of "error" models
#95: On a Sufficient Condition for Identical Measurements Using Two Different VNAs
Hello, - - - - - - (c) gin&pez@arg (cc-by-4.0) 2019 : start - - - - - - Allow us, please, to announce that we just verified experimentally one of the theoretically sufficient conditions we found, in order to take identical measurements using two different VNAs, e.g. our [HP8505A] and our [NanoVNA]. Specifically, the theoretically sufficient condition, that we found and verified, concerns the most common case of using a [LeastVNA] for measuring Nominal Values without Uncertainties with the loads S, L, O having Nominal values of ( -1 , 0 , +1 ), respectively and obeying our G-mini equation: G = (g - l) (o - s) / [ (g - o) (s - l) - (g - s) (l - o) ] Well, if the following relation holds: (g"2 - g"1) = k (g'2 - g'1) where (g"1 , g"2) , (g'1, g'2) are pairs of measurements using a [VNA"] and a [VNA'] respectively, resulting from the same pair of loads (G1, G2), then we have immediately: G" = (g" - l") (o" - s") / [ (g" - o") (s" - l") - (g" - s") (l" - o") ] = = k (g' - l') k (o' - s') / [ k (g' - o') k (s' - l') - k (g' - s') k (l' - o') ] = = k^2 (g' - l') (o' - s') / [k^2 { (g' - o') (s' - l') - (g' - s') (l' - o') } ] = = (g' - l') (o' - s') / [ (g' - o') (s' - l') - (g' - s') (l' - o') ] = = G' Thus, using as [VNA"] our [HP 8505A] and as [VNA'] our [NanoVNA] with our three 3 HP Standards S, L, O, as well as our -repeatedly mentioned- One-Port Standard of 50 Ohm DC, we just found at 405 MHz, in ordered pairs (modulus, argument in degrees) the following almost identical results: (g" - l") / (g' - l') = ~( 12 , - 137 ) (o" - s") / (o' - s') = ~( 12 , -136 ) (s" - l") / (s' - l') = ~( 12 , -135 ) (g" - o") / (g' - o') = ~( 12 , - 138 ) (l" - o") / (l' - o') = ~( 12 , - 138 ) (g" - s") / (g' - s ') = ~( 12 , - 135 ) which results in a mean value of k = ~( 12 , 136.5 ), and thus verifies experimentally at 405 MHz, our above sufficient condition. We repeated the same procedure at 639 MHz and we concluded that * m o s t * o f * a n y * o t h e r * c h e c k * these results may explain fully: #30 : our final report 1 - 4 Oct 2019 /g/nanovna-users/message/3989 - - - finish : (c) gin&pez@arg (cc-by-4.0) 2019 - - - - - - - - - - Sincerely, gin&pez@arg :#95 |
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Re: New version of NanoVNA-Saver: 0.2.1
Hi, Rune!
Thanks for your answer in NanoVNA-Saver0.2.0 thread. I will continue here. There was a task to find out an impedance of unknown teflon coax cable, which looks like 75 Ohm. I did it with the help of NanoVNA TDR measurements. A 500 mm piece of 50 Ohm teflon coax cable with SMA connector was plugged into the device and a piece of unknown cable was soldered to its other end and left open. The results are on the device screen photo. Then I decided to do the same with the help of the built in TDR function of NanoVNA-Saver, as you suggested. What I saw in TDR window, looks correctly, but when I put marker on the curve, only distance was displayed, but not an impedance value. See the next screenshort. The impedance value can only be read approximately from the impedance axis. I think that it would be very useful to display an impedance under marker. After that I put device in TDR mode again, menu item - TRANSFORM/LOW PASS STEP and run Sweep in NanoVNA-Saver. The results were very interesting. TDR window displays something wrong. But ¡°S11R+jX¡± window seems to be alike device screen. See the next screenshort. The markers shows true values of impedance of two pieces of cables. Only horizontal axis is in MHz. :) I think, that it is one of the ways to measure transmission line impedance with NanoVNA-Saver. Thank you very much! Merry Christmas! 73! Andy, UA3RAW |
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Re: First PCB pictures of the V2
The design is to be finalized (last prototype verification) in a week. After that it depends on the manufacturer, but I'm guessing a month or so. However I may have a few excess prototypes that I can offer to software/firmware developers early for free (I'm not authorized to sell it).
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Re: errors of "error" models
#92 ' : Our General Picture of [TheLeastVNA] - Update
Hello, Allow us, please, to update our General Picture of [TheLeastVNA] [1] by * c o r r e c t i n g * its its very part referenced to Erik's, PD0EK arrows, in such a way that our new rephrasing to not be affected by any possible new look of his picture [2], that is as follows: " however, * A N Y * O T H E R * VNA operating in a similar way as a [LeastVNA], can be effectively considered as this 4-port [LeastVNA] above : e.g. the schematic one in the picture by Erik, PD0EK at [2]: where, the 4 Graphic Symbols shown at the whole upper half of it: (1) [Sinusoidal Generator] (2) [a0] (3) [b0] (4) [couple of opposite arrows a1 and b1, just before the DUT] also consist such a 4-port [LeastVNA]. Sincerely, gin&pez@arg REFERENCES: [1] #92: Our General Picture of [TheLeastVNA]: 24 December 2019 - /g/nanovna-users/message/8612 [2] Will do: 24 December 2019 - /g/nanovna-users/message/8635 :#92' |
gin&pez@arg
Alberto I2PHD
Andy UA3RAW
OwO
Pablo E. Untroib