开云体育

Good questions; unfortunately the answers can get involved.
Yes, real and imaginary are resistance and reactance.? Usually in Ohms.? Reactance is Z sin(phase angle) and resistance is Z cos(phase angle).? The display may only give the angle; I'm not sure.
You can use the phase angle plot to locate resonance; it jumps sharply at that frequency, more sensitive than trying to sweep around to find where it crosses the resistance axis (Smith chart).
Much can be learned by fiddling with it.
Bob K6DDX

So I'm a ham and I usually just use the NanoVNA for analyzing "1 port networks" otherwise known as antennas. But I do try to learn other stuff, and I ran into something that doesn't make sense to me.

I thought that REAL and IMAG would be the same as resistance and reactance, but it seems like they're the sin/cos of the phase angle or something? Which step in the math are these values?

Also I'm just curious as to what PHASE is useful for. I'm guessing it's probably most useful for a DUT that is an amplifier or filter. (More stuff that I have yet to learn much about.)
--
KV0A - Robert

Interesting... this new jig seems to be working better than I had thought.

I just swept all four of the filters I have. The filter I had chosen for my first test, turns to be the one with the greatest asymmetry in its group-delay curve. The other 180 kHz filter also has a lower peak on the high-frequency side but the asymmetry is less. The two 280 khz filters have even less asymmetry, and the lower group-delay peak is on the low-frequency side.

So, I may actually be seeing actual variations between the filters with less bias than I had thought.

So, here's Junkbox Jig #2.

I took a different approach with this one. Instead of using an L-match, I dug through my junkbox and found a bag of little ferrite-toroid transformers which have a 2:1 winding ratio. I used these to step up the 50-ohm NanoVNA impedance to around 200 ohms, and added 130 ohms in series on each side of the filter to reach 330 ohms. For this board I kept the pad sizes for the filter to a minimum, and hogged away the copper around them to minimize parasitic capacitance.

I took a measurement of one of the same 180 kHz filters I used in the previous tests. The results... not very much different than I saw with the L-match. There's still a significant asymmetry in the amplitude group-delay curves, although to the eye it appears less (I haven't graphed out the two sets of numbers on the same scale for comparison, yet).

The transformers I'm using here are probably less than ideal for the application. The primary measures out at about 350 uH, the secondary at around 1350 mH. If I short the secondary, the primary drops to under 2 uH... the inter-winding coupling is good but not perfect. So, there's probably some left-over inductance for the filter to see.

What I may do, is take a couple more of these transformers, strip them down, and rewind them - twist the wires together to form a bifilar pair, and then wind a few turns of this. This should give tighter coupling and less residual inductance. I don''t think I need as many turns as I have at the moment, either.

It's also possible that the group-delay asymmetry indicates that the source/load R values are too high for the filter... it may "want" to see less than 330R due to manufacturing variations.

The next big step will be to figure out some sort of active/buffered jig, with precise and/or adjustable source and load resistances. I think I've got a couple of video op amps around here somewhere...

Thank you very much for the information - it was just what I was looking for.

I will directly connect the NanoVNA to my input circuit to see how it looks now I know that I will not damage the IC by applying too much power - I am mainly wanting to do an S11 measurement so I can try to get a good match on the RF input.

Currently my circuit shows a 15dB gain when I apply a -30dB signal to the RF input.

My current test circuit (set up on a breadboard until I get a rough design in place) is in balanced mode and I was wondering about the 1.5k and 3k input impedance as I had read about this a few times. I think I will need to re-work my toroids as currently they do a 50 to 1.5k ohm transformation but I may also try redesigning this section and use the method described on page 10 of AN1994 (I will need to change a few details in the calculations as the PDF is for an SA605 which appears to have a higher input impedance at around 5k ohm):



Thanks again for the suggestions - they are really helpful.

Please be aware the stated input impedance is per input so if you use the NE602 in balanced input mode (and you should) it's twice the resistance and half the capacity.
The impedance is fairly stable till above 100MHz so you better connect the transformer to a 3k resistor

Even better is to search for NXP AN1994 where the formula for calculating the optimal matching network is explained

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

The input of the 602 can take more RF but the output circuits are in overload.
That would make gain compression if you were doing S21, for S11 it should
be fine.

The problem is there is a level where the base to base resistance may go
out of range but I believe its greater than 0dbm than suspected without damage.
Either way you will not break it at any level under 0DBM, why are we sure?
The nano VNA has several of them in there! Look at the schematic.

An aside the 602 is more gain than needed at 40M and input coupling loss
will help not hinder that. Most 40M 602 designs do not lack for sensitivity with
even with obvious input loss.

Allison
-----------------
No direct email, it goes to bit bucket due address harvesting in groups.IO

On Sun, Mar 8, 2020 at 04:43 AM, David J Taylor wrote:

Anyone played with this software?

Looks like Signals Everywhere did an overview of mods in his "Adalm Pluto SDR Tutorial: 70Mhz to 6Ghz and Dual Core CPU Modification":

Looks like he has another firmware update video also:

Not sure about normalization and whatever performance verification like calibration pre-processing or smoothing can be done... to improve performance maybe?

Hack RF is single duplex so no tracking generator and no SNA
There is a SA application for the Hack RF.


--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

I'm also interested in that for Hack RF

Jos

Peter Loron schreef op 8-3-2020 18:57:

Is this the Ron Boyk that I know and have worked with in the past?
*Clyde K. Spencer*

Very interesting! Any idea if there is something similar for the Hack RF One? It has a similar TX/RX range…

-Pete

Hello,

May I suggest to publish the presentation in Power Point format? This
will allow more easy translations to other languages.

I mention Power Point because I think that it is the original format.

Best regards,

Ignacio EB4APL


--
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.

Sorry, I'm a little late, but no, I cannot personally confirm it. The friend who got one is very impressed with it, but is a thousand miles away, so I can't examine it. The seller is a very large supplier of radio/electronics equipment and I feel "should" be reliable. But hey may not know of the variations. The employees there would be hams, but not likely RF network engineers. A potential buyer could ask them directly, and should. Also ask about return privilege if it's unsatisfactory.

Doug

The AirSpy R1 and R1 also enable a spiff spectrum analyzer that covers
roughly 20 MHz through 1.8 GHz. The necessary SW, SpectrumSpy, comes free
as a part of the SDR# download. It will do as little as a 10 MHz span or
as much as 20 MHz to 1.8 GHz in one screen presentation.

No connection to AirSpy other than using a number of their products.

Dave - W?LEV

<>
Virus-free.
www.avast.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Sun, Mar 8, 2020 at 11:43 AM David J Taylor via Groups.Io <david-taylor=
[email protected]> wrote:

For those of you with an ADALM Pluto SDR, here's a 70 MHz - 6 GHz spectrum
analyser & tracking generator:



Looks very interesting. Anyone played with this software?

Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

--

*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*

Figured it out -- download mode requires a simultaneous downward press of the jog wheel while powering on. After that, flashing the new firmware was easy.

Paul, W9AC

I recently purchased a nanoVNA-H4 model from R&L Electronics. I am attempting to place the VNA in download mode to flash new firmware. The Config menu shows no such "DFU" option. As such, I'm assuming this model requires a two-pin header jumper on the main PC board. Questions:

1) Am I correct in assuming this model requires me to jumper the header pins on the PC board?

2) Once the new firmware is downloaded and functioning, will the latest firmware have a "DFU" menu option under Config so that a hardware jumper won’t be necessary in the future?

Paul, W9AC

Would a 50 ohm pad between the VNA and the input (50 ohm) to the transformer?

I am currently designing a receiver for the 40 meter band and will be using an NE602 for my mixer. I have most of the individual circuits built (pre-amp, bandpass filter, crystal filter etc) and they are all 50 ohm impedance.

As the NE602 has around 1.5k ohm input impedance I have have wound a 4:22 toroid for the RF input to convert from 50 ohm to 1.5k ohm.

Using my NanoVNA I want to measure the impedance (and return loss / VSWR) of my RF input circuit so I can adjust the windings to get a good match but the NanoVNA outputs around -13 to -9 dBm, this is too high for the NE602 RF input which has a maximum input of about -25dBm.

How would I go about attaching the NanoVNA to the RF input of the NE602 without causing an overload?

Thanks in advance for any suggestions or advise,

Kerr