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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Wireless and Communications => Topic started by: Gian Luca Cavalliini on February 16, 2019, 04:11:24 am

Title: affordable USB VNA
Post by: Gian Luca Cavalliini on February 16, 2019, 04:11:24 am
Hi all,
long time searching for an affordable VNA.
Any thoughts about this one? Or maybe you know others in similar price range?
Thanx in advance!

Gian Luca
Title: Re: affordable USB VNA
Post by: Henry Cohen on February 16, 2019, 07:33:13 am
Hi all,
long time searching for an affordable VNA.
Any thoughts about this one? Or maybe you know others in similar price range?
Thanx in advance!

Link or device details?
Title: Re: affordable USB VNA
Post by: Lyle Williams on February 16, 2019, 05:09:05 pm
These units certainly hit a low price point.

Measurements can be a bit slow compared to proper instruments.  Eg 2 minutes for a set of S parameters over a wide frequency range vs 2 seconds for a proper VNA.

Make sure the unit you order covers the frequencies you care about at full resolution.

Most of these units only measure from one side. You get S21 and S11, if you want S12 and S22 you need to re-plug and measure from the other side.  Some will allow an external transfer relay to be attached and controlled to overcome this directionality issue.
Title: Re: affordable USB VNA
Post by: Gian Luca Cavalliini on February 17, 2019, 05:52:50 am
oops... sorry for missing link...

http://pocketvna.com/product/
Title: Re: affordable USB VNA
Post by: Lyle Williams on February 17, 2019, 01:39:18 pm
As this is a live sound forum, I'm guessing you care about wireless mic frequencies.

You need to research this unit to find out how it performs at those frequencies.  It is unclear what the performance of this unit is above 350MHz.  Does the resolution fall of a cliff to 40dB, or does it slowly taper away up to 4GHz?
Title: Re: affordable USB VNA
Post by: Henry Cohen on February 17, 2019, 01:40:51 pm
oops... sorry for missing link...

http://pocketvna.com/product/

You might want to look at the TinyVNA (http://miniradiosolutions.com/54-2/) as well.  In either case, I recommend using some low loss jumpers for adapting the VNA connectors to your connector of choice to avoid strain on the SMA's.
Title: Re: affordable USB VNA
Post by: Lyle Williams on February 17, 2019, 01:56:05 pm
Don't forget to get a calibration kit.  The VNA just shows how your tested item performs relative to the calibration kit.

For this kind of work you don't need a zillion dollar one.  Generally as part of the calibration you measure a short circuit, an open circuit, a 50ohm load, and a through connect.
Title: Re: affordable USB VNA
Post by: Russell Ault on February 17, 2019, 03:38:45 pm
http://pocketvna.com/product/

I picked up one of those to try out. Haven't had the time to do much with it yet (and, to be honest, it's not like I have another VNA to compare it against), but what I will say is that if you do go that route you should check out the beta software. If nothing else, the calibration process was much more intuitive, especially for someone (like me) with no previous VNA experience.

In either case, I recommend using some low loss jumpers for adapting the VNA connectors to your connector of choice to avoid strain on the SMA's.

Henry, when using the jumpers, do you calibrate at the end of the jumper or at the SMA?

-Russ
Title: Re: affordable USB VNA
Post by: Henry Cohen on February 17, 2019, 03:45:43 pm
Henry, when using the jumpers, do you calibrate at the end of the jumper or at the SMA?

Always at the end of the jumper, or whatever other coax cables, adapters nd/or jumpers needed to test, but not part of the circuit/device under test.
Title: Re: affordable USB VNA
Post by: Russell Ault on February 17, 2019, 04:29:40 pm
Always at the end of the jumper, or whatever other coax cables, adapters nd/or jumpers needed to test, but not part of the circuit/device under test.

That makes a lot of sense. That raises the next question: what are people using for BNC calibration kits? There has to be something out there that's "good enough" and costs less than $1000 (or, ideally, less than $100)?

-Russ
Title: Re: affordable USB VNA
Post by: John Sulek on February 17, 2019, 04:50:55 pm
That makes a lot of sense. That raises the next question: what are people using for BNC calibration kits? There has to be something out there that's "good enough" and costs less than $1000 (or, ideally, less than $100)?

-Russ

Look at the Array Solutions web site. They have BNC calibration kits for their VNA's in the UHF frequency range.
Complete male/female kit is $120.
Title: Re: affordable USB VNA
Post by: Russell Ault on February 18, 2019, 01:37:04 am
Look at the Array Solutions web site. They have BNC calibration kits for their VNA's in the UHF frequency range.
Complete male/female kit is $120.

Ordered. Gotta love the amateur community.

-Russ