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Author Topic: PocketVNA Any idea what its like?  (Read 13319 times)

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Offline mohala

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PocketVNA Any idea what its like?
« on: March 29, 2016, 08:26:20 AM »
Hiya everyone,

Long time reader of EEVblog but a short time writer.

I have been on a mission to find a low cost VNA for antenna design for the 2.4Ghz bluetooth and wifi band, but the results have been quite limited, with those in MiniVNA Tiny, MegiQ or LA Techniques.

Seeing the last two go for over £4000 (or copper mountain which is around $3000 1 port VNA) seam to be a lot of money to let go for a beginner.

I eventually found these guys called Pocket VNA, costing $430 or 390 Euros the guys are from what I see are Germany, It looks really interesting from a money point of view.

But I was wondering has anyone tested their VNA's before and if you would like to give your opinion on accuracy, build and reliability.

It would be really appreciated.

The link is http://pocketvna.com/

Best regards

Mo
 

Online TheSteve

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Re: PocketVNA Any idea what its like?
« Reply #1 on: March 29, 2016, 09:03:49 AM »
I think I'd prefer a used HP 8714C or similar(yes shipping them is expensive...)
VE7FM
 

Offline Koen

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Re: PocketVNA Any idea what its like?
« Reply #2 on: March 29, 2016, 09:08:44 AM »
Over a similar frequency range and similar price, I own a MiniVNA Tiny and would appreciate it if someone more knowledgeable could compare the two. Thank you !
 

Offline mohala

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Re: PocketVNA Any idea what its like?
« Reply #3 on: March 29, 2016, 09:42:14 AM »
Over a similar frequency range and similar price, I own a MiniVNA Tiny and would appreciate it if someone more knowledgeable could compare the two. Thank you !

I agree I had noticed the MiniVNA Tiny when connected to a tablet you have to press a button to start a single sweep, from the looks of the software on the PocketVNA they have something called "Live Measurement" I'm guessing  its a continuous sweep.

That maybe an advantage I'n not sure?
 

Offline Bud

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Re: PocketVNA Any idea what its like?
« Reply #4 on: March 29, 2016, 10:23:41 AM »
They (cheap ones) all use broadband power detectors at their input, therefore detecting all rf energy at the point of measurement which may cause skewed readings. I'd think they are in a same leage in terms of accuracy.
 

Offline mohala

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Re: PocketVNA Any idea what its like?
« Reply #5 on: March 29, 2016, 11:06:52 AM »
I guess its a nice way to start learning antenna design and matching. With a cheap VNA than spending thousands on one, maybe when you build up the experience and looking to go to do work professionally, you could go to the R&S, Aglient or Arintsu VNA's.

What you guys think?
 

Offline Bud

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Re: PocketVNA Any idea what its like?
« Reply #6 on: March 29, 2016, 01:04:12 PM »
It certainly is.
 

Offline Theobald

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Re: PocketVNA Any idea what its like?
« Reply #7 on: March 31, 2016, 01:31:06 AM »
Hi,
I use a miniVNA Tiny at work for PCB antenna matching and SAW filter amplitude response in the ISM 868 band. It does the job. The Java application on PC is correct, a good product (at least @ 868MHz).
A minor point, it can get very hot, not so good for the reliability, unplug it when unused.

Add a Smith chart freeware and you're ready.

In the other hand, I've never use a 4000€ VNA, I can't compare.
Theo
 

Offline Koen

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Re: PocketVNA Any idea what its like?
« Reply #8 on: March 31, 2016, 07:23:32 AM »
Hello, I used to let it warm up for half an hour before calibrating and measuring anything. Usually, it then stays close to 50°C.
Is disconnecting/reconnecting it to use it cold better ?
 

Offline Theobald

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Re: PocketVNA Any idea what its like?
« Reply #9 on: March 31, 2016, 06:38:44 PM »
Hello,
no, you're right and that's the point: don't make calibration (open, short, 50ohms trilogy) at room temperature, let it warm up. Again, it's a minor issue, even 4000€ instruments need a warm up !

Theo
 

Online Neganur

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Re: PocketVNA Any idea what its like?
« Reply #10 on: March 31, 2016, 08:56:03 PM »
Anritsu has a 1-port USB NVA for antenna measurements, it's fairly affordable and, judging by trying it on a trade show, pretty good too!

There's two bandwidth models, 40MHz...4GHz and 150kHz...6GHz

Datasheet (3MB):
https://www.anritsu.com/en-US/test-measurement/support/downloads/brochures-datasheets-and-catalogs/dwl010872

EDIT: found the email with the list price for the 4GHz model, it was 2.8k EUR (price is a year old). Of course that's much more that 400-500 for the PocketVNA.
« Last Edit: March 31, 2016, 09:07:39 PM by Neganur »
 

Offline jeffsf

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Re: PocketVNA Any idea what its like?
« Reply #11 on: April 06, 2016, 04:47:55 AM »
I think I'd prefer a used HP 8714C or similar

I would too...
...except that the asking price is generally out of my budget.

One option to consider is a VSWR bridge which will give you magnitude, but not phase. For tuning antennas, you often just need the magnitude.

If you've got 40 dB of directivity you can probably measure return loss down to about 20-30 dB
See, for example, http://www.anritsu.com/en-us/test-measurement/solutions/en-us/Understanding-directivity

Wiltron (now Anritsu) makes several models. The higher directivity ones (40 dB) covering up to a couple GHz can be had for $200 with patience.
An "SWR Autotester" includes a detector, while an "SWR Bridge" does not.
http://exodus.poly.edu/~kurt/manuals/manuals/Other/WILTRON%20SWR%20Autotesters%20&%20Bridges%20Operation%20&%20Maintenance.pdf
https://www.valuetronics.com/Manuals/ANRITSU-60N50.pdf

You'll also need a signal generator that covers the frequencies of interest, if you don't have one already. Sweep isn't really necessary as you can step through the frequencies of interest.

If you've got an RF detector for the range, another option would be a directional coupler. Check Narda, for example. The directivity generally isn't as good as the Wiltron bridges/autotesters, but they can be found for $50 or so, with patience.
 

Offline RadioDude

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Re: PocketVNA Any idea what its like?
« Reply #12 on: June 19, 2016, 02:04:51 AM »
I saw a demonstration of a MegiQ VNA-0440. It works nice and professional and it has UFL calibration also. There is review comparing with Rohde & Schwarz ZVL and MiniVNA: http://www.gsm-modem.de/M2M/wp-content/uploads/2014/04/IoT-M2M-Cookbook-Harald_excerpt.pdf

Price is about €2800.
 

Offline D3f1ant

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Re: PocketVNA Any idea what its like?
« Reply #13 on: August 06, 2016, 06:18:06 AM »
Anybody end up buying/testing a pocketvna?
 

Offline German_EE

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Re: PocketVNA Any idea what its like?
« Reply #14 on: August 06, 2016, 11:18:58 PM »
There is some confusion here about the different VNA names and brands.

The MiniVNA only works from 1 MHz to 180 MHz and due to internal limitations in the circuitry cannot indicate the sign of a reactive impedance, you therefore cannot determine if a device is inductive, resistive or capacitive and cannot plot it on a Smith Chart. RF connections are BNC and the computer connection is USB 2

The MiniVNA Pro is an upgraded version of the MiniVNA with SMA connectors and it can interface using Bluetooth. This VNA CAN measure the sign of a complex impedance and therefore can display a Smith Chart. Frequency range is 100 KHz to 180 MHz.

The MiniVNA Tiny can work from 1 MHz to 3 GHz and has SMA connectors. This VNA can also measure the sign of a complex impedance and Smith Chart software is included. Computer connection is via USB using a Mini-USB connector.

Disclaimer: I am a happy MiniVNA owner.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

Warren Buffett
 

Offline D3f1ant

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Re: PocketVNA Any idea what its like?
« Reply #15 on: August 07, 2016, 09:06:39 AM »
Could some of you guys with experience with usb vna's please chime in over at a similar thread in test equipment  :-+
http://www.eevblog.com/forum/testgear/vna-recommendations/
 

Offline rfbroadband

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Re: PocketVNA Any idea what its like?
« Reply #16 on: August 07, 2016, 09:11:56 AM »
I would buy a used VNA with better specs. 40dB of dynamic range above 1GHz is simply not acceptable for many cases.
 

Offline cncjerry

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Re: PocketVNA Any idea what its like?
« Reply #17 on: August 08, 2016, 05:27:55 AM »
The problem I had with simple VNA circuits as I tried to build my own before settling on the N2PK VNA, was that they were very broad-band and if you had any local broadcast stations (and I do) then it was worthless.  Trying to plot my off center fed dipole and I had peaks and dips and all kinds of problems.

So no mater what you buy, I suggest you find something that does precise power measurements with some type of filtering.  Many of the low cost VNA units use a signal generator with a directional coupler and an AD8307 for the returned power measurement. In a perfect world, this setup would work fine but the 8307 is reading not only the reflected power from the signal generator, but all the harmonics as well as any broadcast stations, amateurs, etc.

The bottom line is I would check any of the VNA units you are considering for problems with broadcast stations.  A good indicator of a problem is if they offer a broadcast band filter as an option.

One other thing I can add is if you have a sweep generator (any cheap DDS off eBay will work) a directional coupler or resistive bridge, and an RTLSDR dongle, you can get pretty close results to many of the low cost VNA units out there.
 

Offline D3f1ant

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Re: PocketVNA Any idea what its like?
« Reply #18 on: August 18, 2016, 06:19:01 AM »
This is whats inside a pocket VNA  if anybody was curious.
 
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Online borjam

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Re: PocketVNA Any idea what its like?
« Reply #19 on: August 18, 2016, 04:40:45 PM »
I would buy a used VNA with better specs. 40dB of dynamic range above 1GHz is simply not acceptable for many cases.
Correct me if I'm wrong please. If you are designing filters and other microwave circuitry you will need better specs. If you are checking antennas 40 dB should be rather adequate.

 

Offline hendorog

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Re: PocketVNA Any idea what its like?
« Reply #20 on: August 19, 2016, 09:35:57 AM »
This is whats inside a pocket VNA  if anybody was curious.

Thats cool, thanks for posting it. I just spent some time figuring out how I think it works.
Maybe this is all wrong, but here are some things I noticed:

RFFC5071 mixer 1 output is 30MHz minimum but goes directly into a 4.8kHz max ADC.
http://www.rfmd.com/store/downloads/dl/file/id/27381/rffc5071/5072_data_sheet.pdf
http://www.analog.com/media/en/technical-documentation/data-sheets/AD7192.pdf

The unbalanced side of several of the GH marked Minicircuits baluns seem to be connected inconsistently compared to the datasheet.
Pin 1 & 2 should be ground and pin 3 is the unbalanced signal. I don't know if/how much this matters...
http://www.minicircuits.com/pdfs/TCM1-43X+.pdf

I can't work out how the bridge circuit works - I think it is R28, R29, R30 and U15 but it doesn't seem to be connected in the way I would expect.

I haven't worked out what U2 is doing. My first thought was it was the reference path, but it should be connected to the other switch output of U36 - then switching U36 one way measures the DUT and the other way measures the reference. Instead it is connected to the DUT port.

 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #21 on: January 12, 2017, 05:47:13 PM »
So - what would be the general consensus?
The PocketVNA or the MiniVNA Tiny?

I'm looking at building some antennas (1GHz <> 2.4GHz), amateur level, but I do want to have some repeatability and measurements. Big irons are too expensive overhere.

Specs are pretty similar for both of them from what I can see..

The MiniVNA Tiny has a bit more output power, dynamic range seems to be on par..
"to remain static is to lose ground"
 

Offline julianhigginson

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Re: PocketVNA Any idea what its like?
« Reply #22 on: January 20, 2017, 05:32:49 PM »
I think for the money the miniVNA tiny and the pocketVNA are both pretty amazing!

I'd pick the pocketVNA, because it's about 100 EUR less than the miniVNA tiny, has a metal case, and specs seem kind of similar... possibly slightly better on the pocketVNA (and miniVNA doesn't have a lot of specs published on the site which I find offputting.

I guess, from here, I would speak with the pocketVNA manufacturer about what sort of deal they have for returns, and if that seems OK to you, buy it, run it through its paces in your lab, and see if you think it's worth the money yourself!
« Last Edit: January 23, 2017, 08:10:46 PM by julianhigginson »
 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #23 on: March 03, 2017, 06:55:56 AM »
Got the PocketVNA, it's awesome.. The software is fast and easy to use, doesn't install crap, calibration works well, doesn't get too hot,... You can tune antennae in a jiffy  :-+ great product  :-DMM
"to remain static is to lose ground"
 

Offline julianhigginson

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Re: PocketVNA Any idea what its like?
« Reply #24 on: March 03, 2017, 10:56:09 AM »
awesome to hear! I pulled the trigger the other week, and mine is due in a few days, too.

He did say via email that I could return it (postage at my cost) if it's not right for me, but glad to hear someone else really loves theirs already.
 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #25 on: March 04, 2017, 12:32:30 AM »
Yep, works great. Initially made a "general" calibration file to do a quick check over a broad range; and then a couple precision, application specifics.

Here's an ADS-B antenna before and after tuning (1090MHz). 1/4wave GP antenne. It was a bit too long initially. Now well tuned.
"to remain static is to lose ground"
 
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Offline julianhigginson

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Re: PocketVNA Any idea what its like?
« Reply #26 on: March 08, 2017, 05:31:38 PM »
I had some interesting introduction to my pocketVNA, but quite happy with how it's going now.
Here's the calibration phase of 2-3G, and then a measurement of a detachable wifi antenna (plus 1.5cm or so of RP-SMA adapter.. maybe I should have compensated that??)


 

Offline rfspezi

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Re: PocketVNA Any idea what its like?
« Reply #27 on: March 16, 2017, 09:04:44 PM »
I have analyzed the miniVNA in this thread here: https://www.mikrocontroller.net/topic/351273
The implementation of the pocketVNA is almost identical.
In the block-diagram you can see how the the resistive broadband bridge works.

« Last Edit: March 16, 2017, 09:26:57 PM by rfspezi »
 

Offline cncjerry

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Offline michael2

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Re: PocketVNA Any idea what its like?
« Reply #29 on: March 24, 2017, 09:36:06 AM »
I'm owning a 2.0 pocketVNA and I'm disappointed.

On its web site is claimed:
Quote
fully functional 2-port 4 GHz VNA
 

This is overdrawn to the limits in my opinion. The problems are significant temperature drift and insufficient calibration options, especially the S21 calibration is useless in my opinion.

Up to 100 MHz this VNA works good. Up to 1 GHz you have to control the ambient temperature to say 2°C to get repeatable readings.

For the range up to 2 Ghz you have to be very nitpicking. Additionally to control the ambient temperature very close you have to set up your desired measuring parameters (which should be equal to the calibration procedure) and make continuous measurements for about 20 minutes. Then you can use the accumulating function to get some nice readings.

But the range starting at about 2 GHz and exceptionally above 3 GHz is useless in my opinion. Even about 10 minutes after a fresh calibration the readings are drifting like an off-road car in the dessert... Repeatability is not achievable.

Another thing is the software. There are a some issues. But software can be fixed and I think the software gets fixed in the future. But it is annoying to live with the issues in the meantime. Maybe I'm a little bit huffy regarding the software...

My conclusion? Compared to other products in this area the pocketVNA is currently no better. Other products claim a range to 1 GHz for example and support the claimed range very well. I think with more investments into the software pocketVNA can outperform in the range up to 1GHz in the future. But the range 2 GHZ and above will never work reliably, I think. At least with the actual hardware version.

 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #30 on: March 24, 2017, 07:04:31 PM »
Did you make sure to let the device warm up before calibrating? As with any VNA, you need to let it warm up before calibrating. Otherwise it will drift...
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Offline michael2

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Re: PocketVNA Any idea what its like?
« Reply #31 on: March 25, 2017, 08:04:00 AM »
Did you make sure to let the device warm up before calibrating? As with any VNA, you need to let it warm up before calibrating. Otherwise it will drift...

Of course, without warm up for an hour even the 100 MHz range is bad. Stabilization starts about 30 minutes after power up.



 

Offline michael2

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Re: PocketVNA Any idea what its like?
« Reply #32 on: March 28, 2017, 06:42:02 AM »
1 GHz to 4 GHZ, some scans the last 24 hours. The problems are clearly visible, I think.

I wonder, if someone else have this issues too?
 

Offline hendorog

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Re: PocketVNA Any idea what its like?
« Reply #33 on: March 28, 2017, 07:38:27 AM »
1 GHz to 4 GHZ, some scans the last 24 hours. The problems are clearly visible, I think.

I wonder, if someone else have this issues too?

Perhaps there is no Reference path in these instruments?  i.e. Where the Source is measured directly separately to the DUT and then the ratio calculated and put through the calibration.
That should minimise the drift.

I thought that the green switch in the block diagram posted was for that purpose but it seems not - i.e. alternating between measuring the DUT and the reflection. There is a corresponding switch on the PocketVNA PCB image posted earlier in the thread too.
 

Offline YO5EB

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Re: PocketVNA Any idea what its like?
« Reply #34 on: May 12, 2017, 06:20:28 PM »
I have this device. I try to write here yesterday but my message did not reach the Forum. If I can post now, I come back with technical details.
 

Offline eb4fbz

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Re: PocketVNA Any idea what its like?
« Reply #35 on: May 29, 2017, 08:14:45 PM »
It has a serious design flaw: the Port 2 return loss is horrible, so the DUT is mismatched and huge ripple can be observed when measuring a coaxial cable loss (S21). How are you supposed to be able to tune a cavity filter with one port so badly terminated?

You can find there are two rf paths in parallel, so 25ohm at low frequency and whatever above 1GHz where transmission lines matters. Those RFSW6024 SPDT switches are non-reflective, so ports allways present 50ohm. Look at C128, C118, U2 and U36.

Mismatch could be alleviated placing an attenuator at port 2, but it will reduce the measurement dynamic range.

« Last Edit: May 29, 2017, 08:16:16 PM by eb4fbz »
 

Offline michael2

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Re: PocketVNA Any idea what its like?
« Reply #36 on: May 30, 2017, 01:11:23 AM »
It has a serious design flaw: the Port 2 return loss is horrible, so the DUT is mismatched and huge ripple can be observed when measuring a coaxial cable loss (S21). How are you supposed to be able to tune a cavity filter with one port so badly terminated?

You can find there are two rf paths in parallel, so 25ohm at low frequency and whatever above 1GHz where transmission lines matters.

I can confirm this. I contacted the Pocket-VNA owner early this year and provided him an measurement which I now attached to this posting. The answer was disappointing and the problem not understood. I refrained from further discussion because I lost the confidence in Pocket VNA.

 

Offline hendorog

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Re: PocketVNA Any idea what its like?
« Reply #37 on: May 30, 2017, 04:22:07 AM »
You can find there are two rf paths in parallel, so 25ohm at low frequency and whatever above 1GHz where transmission lines matters. Those RFSW6024 SPDT switches are non-reflective, so ports allways present 50ohm. Look at C128, C118, U2 and U36.


Yeah I noticed that in the earlier image too. You can see in the diagram of the miniVNA posted by rfspezi how it should be connected.
http://www.eevblog.com/forum/rf-microwave/pocketvna-any-idea-what-its-like/?action=dlattach;attach=299771;image

Maybe worth trying to mod it, it should work better as long as that U36 switch is actually being flipped.

Edited to fix the link to the image
« Last Edit: May 30, 2017, 05:20:06 PM by hendorog »
 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #38 on: May 31, 2017, 03:11:17 PM »
Curious as to what hardware version you guys have - I have a "version 2" (February 2017)

edit: here's what I get when verifying a 3 months old calibration. No issues like the above where values wildly drift.
« Last Edit: May 31, 2017, 03:19:21 PM by Wirehead »
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Offline michael2

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Re: PocketVNA Any idea what its like?
« Reply #39 on: June 01, 2017, 01:03:29 AM »
Curious as to what hardware version you guys have - I have a "version 2" (February 2017)

edit: here's what I get when verifying a 3 months old calibration. No issues like the above where values wildly drift.

This looks like a totally different product!

What was the frequency span of your measurement?
 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #40 on: June 01, 2017, 03:13:57 AM »
Ok, here's some more.. First of all, some HF bands (80meter, 40meter, 20meter). Then VHF (2meter) and UHF (70cm) and finally ADS-B (+- 1090MHz) and 2.4GHz Wifi.

When calibrating, I always do 10 average, 10 adc average, no smoothing (smoothing is cheating  ;) )

When measuring: 10ADC average.
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Offline michael2

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Re: PocketVNA Any idea what its like?
« Reply #41 on: June 02, 2017, 06:08:37 AM »
This is the type label of my PocketVNA. Please could you provide your label for comparison?

 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #42 on: June 02, 2017, 06:16:16 AM »
Yep, same version. Do remember, that whenever you want to do a representative measurement on a vna, you have to calibrate it, with test leads and such. Every time. No exceptions. Also variation in lab temp has a great impact. Such is life with any vna. My calibration checks above are done in semi stable conditions, but above 2 GHz, things get critical.
"to remain static is to lose ground"
 

Offline eb4fbz

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Re: PocketVNA Any idea what its like?
« Reply #43 on: June 02, 2017, 07:07:46 AM »
Curious as to what hardware version you guys have - I have a "version 2" (February 2017)

edit: here's what I get when verifying a 3 months old calibration. No issues like the above where values wildly drift.

That's not the issue: you have just checked the calibration accuracy by placing the OSL kit at the Port 1 after calibration, that should be fine even with a 25ohm source impedance if the maths are done properly, that's what the calibration is for (+/- temperature drift). The problem is that having a ~25ohm port 1 impedance will affect the DUT behaviour because of the mismatch, and this can't be corrected by calibration (these things are what makes the professional VNAs expensive). Even measuring a coax cable loss will be error prone because of the S21 ripple generated by the reflections.

Unfortunatelly, you can't check the port 1 impedance without another VNA, because port 2 doesn't have reflection measurement capability (it's not a bidirectional VNA, so only S11 and S21 measurements). But it's clear by looking at the PCB that the design arround port 1 (CN2 connector!) is far from ideal.

You can check the effect of port 1 matching by measuring a couple of meters long coaxial cable. First calibrate the VNA and measure the coax S21 as usual, save the trace. Then place a 10dB attenuator at port 1, calibrate the VNA again and remeasure the same coax. You will see that measurements doesn't match, and the first one will show a huge ripple. You can use the 10dB pad technique to improve this behaviour, but you will reduce the VNA dynamic range by 10dB.

Now imagine trying to adjust or optimize a high Q circuit, like a band pass cavity or duplexer: it will not be possible because it's behaviour will be very different when connected to the VNA. Resonances will change, loss, rejection... You could be able to get the desired response, but it will not work the same way when attached to a 50&50ohm system.

If your VNA behaves differently, please take a photo of the PCB to look for the differences.
« Last Edit: June 02, 2017, 07:23:50 AM by eb4fbz »
 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #44 on: June 02, 2017, 07:23:08 AM »
Curious as to what hardware version you guys have - I have a "version 2" (February 2017)

edit: here's what I get when verifying a 3 months old calibration. No issues like the above where values wildly drift.

If your VNA behaves differently, please take a photo of the PCB to look for the differences.

I'll try to take a picture tomorrow. Bit hesitant to open it up, but hey, for the good cause :)
"to remain static is to lose ground"
 
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Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #45 on: June 02, 2017, 07:36:28 AM »
By the way - here's the effect of the VNA warming up.

1GHz - 4GHz - 1001 step sweep - 10adc avg - 10 avg cal.

Initial calibration was made after warm-up of 4 hours. Then I've let the device settle unpowered, and then let it warm up again. Last measurement is after 4 hours again in exact conditions (yes, nitpicking. Same usb port, cable orientation, connector cleaning, ...) of the load calibration standard. You can see it slowly creeps to the correct value once the device is warmed up.

No through measurement yet, and I'll need to get that 10dB pad eb4fbz is suggesting  :-+
"to remain static is to lose ground"
 

Offline pete463251

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Re: PocketVNA Any idea what its like?
« Reply #46 on: June 20, 2017, 11:49:33 AM »
Hi Everyone,

Great thread, first time poster here.  I wrote antennatheory.com and also launched a kickstarter this month of a 400MHz-2.7GHz 2 port VNA, I'd be thrilled if you checked it out:
https://www.kickstarter.com/projects/1913839854/chazwazza-a-low-cost-2-port-400mhz-27ghz-vna

People send me the miniVNA and pocketVNA a few times and ask why the one I developed, called the Chazwazza is better.  I really liked the comparison referenced earlier (http://www.gsm-modem.de/M2M/wp-content/uploads/2014/04/IoT-M2M-Cookbook-Harald_excerpt.pdf) on page 74, which shows the comparison of the miniVNA to a high end VNA and it doesn't stack up too well.

The reason I developed mine was to have a low cost (and accurate!) stand alone device - which means no software to install.  I also found I could do integrated automatic calibration, which was a side benefit. 

My kickstarter will probably fail, so I'm trying to decide if there is enough demand for VNAs out there to do another spin, cost down and wider frequency range but with continued solid accuracy.  Feel free to ping me on any of this stuff!

Thanks
Pete

p.s. 40 dB of range is more than enough for tuning antennas.  It is a rookie move to care if your s11 is less than -20 dB, the effects of the cable and installation in any real environment will alter the antenna.  So if your target is s11<-40 dB, your wasting your time!   source: me    :-DD
 
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Offline eb4fbz

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Re: PocketVNA Any idea what its like?
« Reply #47 on: June 26, 2017, 08:42:20 PM »
p.s. 40 dB of range is more than enough for tuning antennas.  It is a rookie move to care if your s11 is less than -20 dB, the effects of the cable and installation in any real environment will alter the antenna.  So if your target is s11<-40 dB, your wasting your time!   source: me    :-DD

You are right, but i would expect much more from 2-Port VNA than just a VSWR antenna analyzer. For filters and duplexers adjustment you absolutely need >80dB S21 dynamic range, and none of these "amateur" VNAs is able to do so at 1GHz. Besides that, accurate and repeatable calibration is a must, and test ports impedance should be perfectly matched to 50ohm or performance will be severely degraded. I know this is not cheap to achieve at >500MHz, but an inaccurate VNA is a no sense.
 

Offline fcb

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Re: PocketVNA Any idea what its like?
« Reply #48 on: June 26, 2017, 08:59:01 PM »
Everyone seems to be building 2 port VNA's.  My personal view is that this is just because there are now some really nice RF IC's available at low cost, and engineers are thinking "great IC, lets build a 2 port VNA).

Even Pico Technology have just built one.  They certainly have their uses, but most seem to be destined to become posh VSWR meters.

What would be really useful is a USB connected (powered via mains!) 4 port VNA that goes from 300KHz to 6GHz (to replace my aging 8753C).....
 

Offline fcb

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Re: PocketVNA Any idea what its like?
« Reply #49 on: June 26, 2017, 09:05:58 PM »
And just to add insult to injury. I really don't see why the chazwazza has a crappy display on it, why not just USB it into a PC - better chance of accessing the pretty good performance so far, or at least a USB port.
 

Online Kalvin

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Re: PocketVNA Any idea what its like?
« Reply #50 on: June 26, 2017, 10:07:31 PM »
Everyone seems to be building 2 port VNA's.  My personal view is that this is just because there are now some really nice RF IC's available at low cost, and engineers are thinking "great IC, lets build a 2 port VNA).

Even Pico Technology have just built one.  They certainly have their uses, but most seem to be destined to become posh VSWR meters.

What would be really useful is a USB connected (powered via mains!) 4 port VNA that goes from 300KHz to 6GHz (to replace my aging 8753C).....

This doesn't go down to 300 kHz but nevertheless inexpensive and nice design with detailed explanation:

http://hforsten.com/cheap-homemade-30-mhz-6-ghz-vector-network-analyzer.html

With some improvements:

http://hforsten.com/improved-homemade-vna.html

The design files can be found in the Github.
 

Offline fcb

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Re: PocketVNA Any idea what its like?
« Reply #51 on: June 27, 2017, 05:57:14 AM »
That's a really impressive project - might be very interesting if he does a third version.

300KHz is overkill - but 30MHz still very usable as the bottom end.
 

Offline Wirehead

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Re: PocketVNA Any idea what its like?
« Reply #52 on: August 10, 2017, 06:55:19 AM »
It seems Martin quietly released a beta version of the new pocketVNA software. Much improved calibration screens and methods.. I'll give it a go tomorrow :)
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