Network Analyser's and MIFARE antenna tuning - Page 1
Forum section: electronics / beginners

author: mc
author_rank: Regular Contributor
timestamp: January 26, 2014, 07:49:22 pm
content: First up, I'll admit I never even knew what a VNA was until a few weeks ago.I'm currently desiging a system based on MIFARE classic tags (13.56MHz), and for prototyping have been using the Elechouse NFC modules, however the cost of the modules is quite substantial, so I'm looking at creating my own antenna board based around the same NXP PN532 chip.Which brings me to tuning the antenna. I've had a read through NXPs relevant App Note (AN1445), and although I could just copy an existing design, and hope it works well enough for what I need, I'd rather do it properly using a Impedance/Network Analyser.Now that's where I've become stuck, as I have no idea what kind of analyser would actually do what I'd need it to.Would something such as theSDR-Kits VNWA 3do?Or is it really on a job for analysers that cost a substantial amount more?

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: January 26, 2014, 08:29:07 pm
content: My answers are from the ham radio hobby 1.8 MHz - 400MHz and want to add at least up to 2GHz - 5GHz for wifi testing .My list of antenna stuff ,MFJ-259B bought used needing repair , not finished yet .MFJ-269 bought used repaired & using .Timewave TZ-900 bought use working , now getting repaired - they are local here .MiniVNA Pro just recently bought used with Nexus 7 and working , except having issues getting all functions working on Macbook , many more functions on computer .Depending on how deep you want to get into , or how many aspects of measurement you want to get into , the VNA's may be more than needed ?With something like a used MFJ-259 around $125 - $150 , then most measurements not directly read from screens & meters of the 259 can be figured from those 259 readings , as an example finding weather your reactance is positive or negative is indicated by adjusting frequency .Also what is your familiarization with antenna theory ?

author: mc
author_rank: Regular Contributor
timestamp: January 27, 2014, 06:35:08 pm
content: Quote from: KD0CAC John on January 26, 2014, 08:29:07 pmSomewhere between nothing and not much!I think I understand the principle/theory of the tuning, however it's not something I've ever needed to know about before.At the moment, I'm trying to decide if it's worth buying the equipment to tune my own antennas, and I'm struggling to understand what exactly I need to do that.I know that I ideally need something that can display the results on a smith chart, which is why I mentioned the VNWA above.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: January 27, 2014, 09:50:36 pm
content: Then it depends on several other issues , 1st off getting some learning / training on antenna use , tuning , building & theory .You can narrow that down some by limiting to a frequency range of expected future use - which also would help you get the equipment / test gear specific to your needs , they have frequency ranges that at the higher end , become newer & raise the price quickly .At longer HF - high freq. 1.8MHz - 30MHz ham radio freq. measuring wire for antennas can be within 1 - 3 ft.But at higher freq. like wifi 2.3 - 2.5GHz & 5GHz , you need to be in fractions of an inch.So for your project measuring within a inch will be good .It can be much more complicated than that , its just a mater of what accuracy's that are required ?So unless you have money burning a hole in your pocket and just want measuring equipment to aid to the learning process , I would suggest not spending big bucks , especially when it comes to picking up some used HP , Tektronix etc. gear that can run $1,000 - $1,500 +++ .

author: on8vq
author_rank: Newbie
timestamp: January 27, 2014, 10:47:08 pm
content: Like you, I didn't even know what a VNA does until recently. I then built a N2PK VNA, and it's really a nice instrument. I already learned a lot from using it, and I still am.If RF interests you, getting a VNA is really worth it. The VNWA is a nice product, if it fits your budget. If you want to build one yourself, consider a N2PK VNA (if you have SMT soldering experience).BTW, I just found a nice tutorial for VNA measurements, it might interest you:http://www.pa4tim.nl/?p=1594

author: PA4TIM
author_rank: Super Contributor
timestamp: January 27, 2014, 10:54:45 pm
content: I have two VNWA's and a HP VNA. The VNWA is a very capable VNA. If you want to learn more about measuring antennas and see measure results and application about the VNWA you can download VNA tutorials from my site.http://www.pa4tim.nl/?p=1594The VNWA is a real VNA and a good one too, but it is not a 200k dollar R&S or Agilent where you need a cal kit that cost tripple the price of the VNWA including a calkit

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: January 28, 2014, 02:56:34 am
content: Thanks for you site , bookmarked and will be reading to learn more thanks ,JohnKD0CAC

author: mc
author_rank: Regular Contributor
timestamp: January 28, 2014, 10:35:54 pm
content: P4TIM, thanks for that link.I've read the first chapter, and it's already made things a lot clearer, with my main question being answered.A VNWA looks like the best option, as I'd rather just buy something that works, instead of building something that might not.