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Author Topic: PocketVNA Any idea what its like?  (Read 13194 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?
 

Online 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?
 

Online 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
 

Offline 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.
 

Online 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
 

Online 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.
 

Online 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.
 
The following users thanked this post: deephaven, hendorog

Offline 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.

 

Online 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.

 

Online 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 »
 

Online 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.
 


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