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Author Topic: MiniVNA or AIM4170 analyser?  (Read 25624 times)
W4WGA
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« on: May 17, 2007, 04:31:14 PM »

I have to confess to having more fun building antennas than actually using them.  I have one of the original MFJ 259s and I am about to throw it off the tower.  Just not stable enough and limited measurements.  Looking at PC based antenna analysers so it will be easier to record the effect of changes.  I think I am down to a choice between the MiniVNA and the AIM4170 but open to other suggestions.  The 4170 is just past the top of my price range but it looks like it might be worth a little sacrifice.  Has anyone done a side by side comparison for accuracy, features and ease of use?  Is the 4170 worth the extra $100?  Is there a better choice under $400?

(Actually I think I will keep the 259 for tuning the 137.5 QFHs.  :-) )
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K6AER
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« Reply #1 on: May 17, 2007, 07:06:03 PM »

I bought the AIM-4170 at the Visalia DX convention about a month ago. It is an excellent single port analyzer. Here are some of the items you can do with the unit;

Phase and complex phase are easily measured along with VSWR, reflection coefficient, inductive and capacitive reactance. The plot output is displayed in a Microsoft format on an excel format along with a color plot of all parameters. Some of the actual uses others have mentioned are listed below

•   Determine a balun’s resonate frequency and its common mode impedance vs. frequency (effective band-width).

•   Check to see what impedances my tuner is matching for my tune fed dipole for the various bands.

•   Measuring and adjusting traps.

•   Measure an antenna’s feed point impedance from the transmitter’s end of the feed-line.

•   Change the reference impedance for SWR measurements to something other than 50-ohms.

•   Measure the antenna systems common mode impedance at shack end of the transmission line (useful for determining if and where a choke may be required).

•   Quickly measure and/or calibrate transmission lines without doing any calculations.

•   Be able to recall the information from files for future analysis.

•   Impedance fault measurements of transmission lines. Both short and open lines.

•   Build accurate filter networks and understand the reactive application of various components.

•   Look at the performance inductors, capacitors and resistors and their real world interaction.

•   The unit can be used as a signal generator with a very stable frequency and level output. You will need a precision attenuator for level output control.

The unit is small and easily transported for field test work. Cable hookup is via a serial cable. Power supply is via an AC wall wart or a 9 volt battery. Unlike the MFJ unit the current requirement is small.

Bottom line is the unit is definitely worth the $420 cost. I have a lot of expensive HP test equipment but this little box is impressive and duplicates the function of test equipment costing 100 times as much.
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PY2JF
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« Reply #2 on: January 01, 2012, 06:29:01 PM »

Now they have the Minivna Pro. In the following link they state the results are just like an Anritsu VNA.

http://www.miniradiosolutions.com/miniVNA_PRO.php

By the way, anyone already tried to tune a duplexer using one of this VNA?

Any feedback will be welcomed.

73 from PY2JF
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KA4POL
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« Reply #3 on: January 01, 2012, 10:05:01 PM »

May I draw your attention to http://sdr-kits.net/VNWA3_Description.html

This is a real excellent solution for hams. Tuning a duplexer is fun with that unit. It is definitely worth the money. There is a Yahoo Group as well.

Be aware that using any VNWA is not just like measuring voltage. It always requires very accurate calibration for each measurement. Worst case even bending a cable can influence your setup.
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G8JNJ
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« Reply #4 on: January 02, 2012, 03:17:55 AM »

Hi All,

I'm in the fortunate position of having access to several of these devices, and I'd rate them in this order.

VNA 2180 - Excellent accuracy - very reliable, easy to use, stable software - Second port permits through loss measurements. Limited frequency range.

AIM 4170B - Excellent accuracy - very reliable, easy to use, stable software. Limited frequency range but AIM UHF is better.

SDR Kits VNWA3 - Very good accuracy up to 500MHz (less so beyond 500MHz), needs good calibration before tests commence. Usability of software fairly good. More suited to shack workbench than antenna farm.

MiniVNA - Moderate accuracy up to about 1K Ohm impedance measurement. Limited calibration method. Accuracy not good when connected to large antennas due to external RF swamping test source. VNA/J software from Dietmar DL2SBA is good. Second port permits through loss measurements. Limited frequency range.

However all of these will tell you a lot more than the various handheld analysers that are available. The downside is that they need to be connected to a PC.

Note that with all antenna measurements. Make sure you understand the contribution of any connecting cables to the overall system.

Regards,

Martin - G8JNJ

www.g8jnj.webs.com
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KA4POL
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« Reply #5 on: January 02, 2012, 06:54:26 AM »

What do you understand by 'excellent' or 'very good' accuracy? Usually accuracy is given by tolerances. Do you have any values characterizing such?
Unfortunately many people think it is trivial to use a VNWA. Before getting one I'd collect as much information as possible. Then I'd decide if this is the way to go. Not that I'm against these VNWAs but they require a lot of knowledge for efficient use.
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AD5X
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« Reply #6 on: January 02, 2012, 09:22:29 AM »

...Unfortunately many people think it is trivial to use a VNWA. Before getting one I'd collect as much information as possible. Then I'd decide if this is the way to go. Not that I'm against these VNWAs but they require a lot of knowledge for efficient use.

My only experiences are with the AIM4170C, AIMuhf and VNA2180.  Not sure what you mean by "a lot of knowledge for efficient use".  The software is extremely user-friendly. 

Phil - AD5X
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KA4POL
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« Reply #7 on: January 02, 2012, 10:43:20 AM »

Software is of course part of the business. What I mean is the knowledge about calibration. You need to put together  the correct measuring setup. If you don't do this your results are unusable. Even a cheap connector may degrade your findings.
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G8JNJ
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« Reply #8 on: January 03, 2012, 02:20:17 AM »

Hi Dieter,

WRT your question >What do you understand by 'excellent' or 'very good' accuracy? Usually accuracy is given by tolerances. Do you have any values characterizing such?<

The point I was trying to make is that the AIM and VNWA are all capable of providing accurate results, comparable to that of much more expensive lab grade equipment. However the AIM (once calibrated) is very stable. I feel that I can rely upon it to provide accurate results without having to repeat the calibration procedure each time I power it up. My experience of the VNWA is that I find it necessary to re-calibrate it before I make any serious measurements.

The MiniVNA (I have no experience of the Pro) is useful for a quick 'look see' but the calibration method and measurement resolution is not comparable to the other instruments.

Regards,

Martin - G8JNJ

www.g8jnj.webs.com
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KA4POL
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« Reply #9 on: January 03, 2012, 04:44:24 AM »

With any VNWA you need to recalibrate as soon as your setup is changed, i.e. a longer cable or a different connector or else.
Does the AIM support a DTFM (distance to fault measurement)? This would be helpful in measuring an antenna via the cable from within the shack. The VNWA does support that. I do not know about the others.
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G8JNJ
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« Reply #10 on: January 03, 2012, 06:51:02 AM »

Yes both AIM's have a TDR function (impedance vs. distance) and a cable length extension function. This permits quick measurements at the end of standard cable types, without having to do a full calibration.

Obviously with any VNA you have to recal if you change cables etc. But with the VNWA I find that you have to do this if you alter the measurement frequency range (or similar minor changes). The AIM uses interpolation between calibration points to minimise the need to do this every time (Unless you wish to make a really accurate measurement).

I'm not disputing the accuracy, just the ease of usability. I can plug the AIM into the laptop and make measurements almost immediately. With the VNWA I always have to calibrate it first, before I have full confidence in the measurements.

This is just my experience – your mileage may vary.

Regards,

Martin - G8JNJ

www.g8jnj.webs.com
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K9FV
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« Reply #11 on: January 03, 2012, 09:40:10 AM »

I agree with the AIM4170 as being easy to use - I have been VERY happy with it, I only wish the UHF version had been out when I purchased.  The hold up with me buying a VNA is having the knowledge to use it effectively.  The AIM4170 (and UHF) pushes my level of knowledge, but I'm always learning with it. I'm not ready to chunk my 259B, but it does get a LOT less use these days.

73 de Ken H>
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SP4SKR
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« Reply #12 on: January 07, 2013, 08:20:38 AM »

Obviously with any VNA you have to recal if you change cables etc. But with the VNWA I find that you have to do this if you alter the measurement frequency range (or similar minor changes).
It is not true I am afraid. You should use master calibration feature in VNWA software. More details can be found in http://sdr-kits.net/DG8SAQ/VNWA/VNWA_HELP.pdf - search for master calibration.

The AIM uses interpolation between calibration points to minimise the need to do this every time (Unless you wish to make a really accurate measurement).
That is also how master calibration in VNWA works.

And now my $0.02 :

I've never used AIM analyzers, so it is hard for me to judge their capabilities. However I am using expensive professional VNAs from HP and R&S at work. So I can only say that VNWA (especially its software) reaches to that professional range. Of course VNWA lacks the dynamic range and power sweeps available in professional equipment, however from my personal experience they are very rarely needed by hams.

Best regards,
Adam - SP4SKR
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G8JNJ
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« Reply #13 on: January 08, 2013, 12:40:55 AM »

Hi Adam,

You commented

> You should use master calibration feature in VNWA software.<

When was this implemented ? I see the note in the latest guide. But I don't remember it being in there about a year ago. Prior to that the comment >When you modify the number of data points or the frequency span, the calibration will be invalidated and is thus lost< Was applicable.

From a user perspective, my observation is that due to ease of use. My VNA2180 gets used nearly very day and the AIM4170 about once a month. The SDR Kits VNWA3 get used about 3 or 4 times a year. The mini VNA hasn't been used for over a year.

But as I said before, your milage may vary.

Regards,

Martin - G8JNJ

www.g8jnj.webs.com

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SP4SKR
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« Reply #14 on: January 08, 2013, 03:23:28 AM »

Hi Martin,
> You should use master calibration feature in VNWA software.<

When was this implemented ? I see the note in the latest guide. But I don't remember it being in there about a year ago.
I don't know when it was implemented and I am using VNWA software only for last month. So you may be right that master calibration was implemented recently. The important point is that it is implemented Grin
From a user perspective, my observation is that due to ease of use. My VNA2180 gets used nearly very day and the AIM4170 about once a month. The SDR Kits VNWA3 get used about 3 or 4 times a year. The mini VNA hasn't been used for over a year.
Can you elaborate a little bit more about why it is so easy to use VNA2180 and AIM4170 please? Can you also tell me what exactly are you doing with them?

As I said before I am using big and expensive VNAs at work for RF and microwave circuit design at the professional level. I can see that VNWA software capabilities is are not far away from what these big guys offer. I especially like custom expressions calculator in VNWA. On the other hand I do realize that my use cases may be quite different from what an average ham needs.

Best regards,
Adam - SP4SKR
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