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Thanks for the book page image - this is essentially what I have currently breadboarded up although my toroids are wound for 1.5k rather than 3k. I am going to try removing a turn off the primary side and adding a turn on the secondary side initially as this will give me a 50 to 3k ohm match (well 50 to 2938 ohm).

The other difference is that the output transformer in the image uses an FT-50B-43 and I am using an FT37-43 for both input and output transformers as these are the ones I have plenty of.

Once I have made a few measurements I will then wind new toroids using the Wes Hayward numbers and see how they compare, this should be a 50 to 3828 ohm match. It will be interesting to see what difference the two windings make to the return loss / VSWR and output.

Thanks again for this suggestion.

Kerr,

Wes Hayward (W7ZOI) did some tests on the NE602 (lower temp range than SA602) and published them in his book Experimental Methods in RF Design. The balance input configuration will give you better performance. Here is an excerpt from his book showing the test results and how to wind the transformers....

ground loop or pcb residual capacitance?

I put it online in pdf because that can be read/viewed by anyone.
The pptx format is not compatible with e.g. OpenOffice, and the file is also quite large.

If you want the original pptx file, no problem, send me a mail on my qrz.com email address.
(This also gives me some feedback about who is interested or using my work, hi)

If you want to make a translation into your language, please post it here, so that maybe you can collaborate with others on it.
(and hopefully agree on the fact if the Return Loss is negative or positive ... hi)

73 - Luc ON7DQ

...maybe.

Since last I posted, I've experimented with a variety of possibilities; none of which worked...8^(

But, I reverted back to a message where I mentioned building a filter with half of the circuit on each side of a common copper substrate that didn't have the anomaly.

That construction gave me the idea that maybe there was a ground loop; I'd read about that sort of thing but not for HF. Anyway, I reworked one of the LPF PCBs to put all the RF ground connections on one common plane. Via's were added to connect the planes physically otherwise. The attachment shows an ExpressPCB model.

This corrected the effects for 20m, don't know about 30 yet.



--
Chuck, W5USJ

On Mon, Mar 9, 2020 at 07:31 AM, <mcebokli@...> wrote:

"... I have the cables and standards from the old one, so no problem there."
=================================================================

Marko,
The RG-174 cables and SOL standards delivered with the original NanoVNA are only rated up to 1 GHz. If you intend to use the V2 (SSA-2) to its full 3 GHz capability then you should consider the cost of adding 3 GHz rated cables and standards, in addition to the 3.7V battery.

If you only intend to use SAA-2 at your desktop connected to a PC then a battery is not needed. For portable use I believe either a 3.7V Lion or LiPo battery can be installed. A battery from an unused cellphone would probably work fine.

- Herb

This is great, just what I wanted: the same device, but with wider frequency and dynamic ranges.
I love the smallness of it, same display as before is OK for me.
I have the cables and standards from the old one, so no problem there.
The only thing that hurts is - no battery?
Is there any recommendations for an exact battery type (and link to buy..?)
For what kind of battery is the internal charging circuit designed? I wouldn't dare to put in a different chemistry,
especially as LiPo is famous for caching fire?

Marko Cebokli

I have been reading a bit more about these matching networks and have found another one I think I will try as well.



Starting on page 15 there is a worked example of how to create a 'bandpass matching network to transform 50 ohms to the input of an SA602 mixer'.

Noting the suggestion from the previous posts about balanced inputs I think this particular circuit is unbalanced as all the components are grounded just before the input. I think using this circuit I would put its output to pin 1 of the NE602 and ground pin 2 via a 47nF capacitor (I have seen this configuration in several other examples).

Initially I have modelled this network in SimSmith and adjusted the components to create a match at a frequency of 7.15MHz (as I think this is unbalanced I have used 1.5k ohm and 3pF for the load), the simulation looks good and will be a great starting point for building the circuit for real. I will now test these new ideas out in practise and see which one I think works the best for me.

My reason for doing these experiments is that I find it a great way to learn and I also really enjoy making radio circuits.

If anyone has any additional comments or suggestions I would be extremely happy to receive them.

Resistance (REAL) is a value (at al freqs) and can be plotted on an XY graph on the horizontal axe

IMAG is an? reactance value? (L or C) at a specific frequency and can be plotted on an XY graph on the vertical axe

For any Z there is a REAL+IMAG value at a specific frequency. If you put the IMAG value on top of the REAL value

(as two vectors) you can draw a new vector from (0,0) to (REAL,IMAG)

The length of that vector? corresponds to the impedance at a specific frequency , the angle to the hor axe

is what we call PHASE (Phi)

Below X= REAL? Y=IMAG? r=Z

When writing IMAG values, to distinct them from REALS, we put an"i " in front of it.

The length of z = sqr(x^2+y^2)? y =Z*sin(Phi)? and y= Z*cos(Phi)??? i*i= -1

Want to learn more :? Google "complex numbers"


Afbeeldingsresultaat voor real imag vector som

--
Independent Expert on CE marking
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From: jafinch78 .

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?
===========================

The bandwidth extension and dual-core modifications have been around for a long time, done by many, and on both my Plutos. Yes, the current firmware is required, but it's been some time since it was released. I must confess to preferring information from the source rather than 3rd party videos.



Calibration is included, and seems pretty good. A 10 dB attenuator is added on both TX and RX ports "to improve matching". I don't see any means of receiver calibration. Peak hold is included, but not smoothing or averaging, although I would expect these to be added as the software develops. Would be helpful as can be seen from the attached!

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

My recommendation:

For any ham newby in rf calculating, who is seriously willing to learn,
or who simply wants to optimize his antennas (by using his NanoVNA, or not)
the fastest and (to my knowledge) so far best way is by:

1. downloading Ward Harriman, AE6TY's freeware SimSmith and
2. watching Larry Benko, W0QE's SimSmith Basics videos.

Free download is available here:



Some of Larry's videos may be found here (and after that you can google for many more):



SimSmith probably is the most advanced rf design Smith Diagram software available today.
It is not yet finished though, not 100% free of errors, but in the process of constant improvement.
For any serious ham or RF Engineering student it is a "must have".

73, Hans
DJ7BA





-----Ursprüngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von Bob Albert via Groups.Io
Gesendet: Montag, 9. M?rz 2020 04:07
An: [email protected]
Betreff: Re: [nanovna-users] Dumb question: What are REAL, IMAG, and PHASE good for? #general_vna

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

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