Its a pity the SDR-kits website is such an uncomprehensible pile of words. I tried to look for the kit, a simple explaination on how to use it or specs but they don't seem to exist. If it can be tricked into going over 3GHz at reasonable sweep speeds I might consider buying one. I just have to get my head around to read those Smith charts.
The website is indeed pretty confused and messy ("Documents" links to some random data sheets ,but not to the VNA) then the "webshop", sometimes referred to the the "e-shop" on the site will bring you to buy the thing.
But the Help file (which is just a PDF version of the Windows Help) is filled with references to the Version 3, the 3E, expansion boards etc. Page two then shows a board with a serial connector and a USB interface board. Talks about LPT interfaces (parallel).
I've just gone back to the webshite now - Apart from a couple of sets with cal kits, you can buy the VNWA3 or the 3E, which is referred to as a 3+ with expansion board. Finally on page 11 of the help file:
"VNWA3E was formerly named VNWA3+ but both are the same product. The DG8SAQ VNWA3E is the VNWA3 fitted with the VNWA3 Expansion Board which provides additional functionality as follows:..."
I wish they just had a line on the webshop description that said: "1kHz-500MHz (1300MHz with reduced performance) 2-port VNA with integrated Transmission/Reflection test set"
Anyway after I figured out which one to buy, I received it and promptly had lots of issues getting the thing to work at all. Admittedly with a Win7 VM. The problem is that the Setup routine was very un-polished, with a confusing (IMO) method of calling the items e.g. there is a Window area called "Auxiliary Audio Settings"
with text that says "Aux. Audio measure THRU", but then a pulldown for "Aux. reference = right channel")
The software has some quirky UI, that is definitely not according to any UI guidelines - something like a utility you might get from a motherboard maker.
I was rather chagrined when I initially received the item after the poor purchasing experience due to the confusing website. Which was then promptly followed by the audio setup that had to be done each time I plug it in, a VMware issue, but still the setup was just strange - requiring me to follow the precise procedures in the manual each time, because the names and placement of the controls (choice between left/right, main/aux and thru/reflect). Afterwards I was rather vocal on the Yahoo site, complaining about the interface* and that for 500 quid it should be a bit more polished, I ended up giving some constructive criticism and Tom Baier (DG8SAQ) incorporated my suggestion of an auto-setup for the mapping of thru, reflect, left, right, main and aux. Therefore for most people they just have to disconnect cables and press "auto setup".
*I have used VNAs, programmed them and written cal routines for them since 1998, so I consider myself fairly au-fait with the concepts. Moreoever, I had lent the VNWA to a university professor, who is also a practical engineer running a successful radar company, and he had problems following the setup as well.
So the conclusion is that yes, it's pretty good for what it does. I don't consider it a wonder box. I really wish that the interface was open source, because there are a number of dialog boxes I want to change, the calibration is not what I'm used to (HP VNA background), but probably no worse than the R&S analyzers I have fought with. The thing is not very good as a spectrum analyzer, it's very rudimentary for that. Tom Baier is responsive and helpful for those that are experiencing problems.
It's certainly lighter than any other VNA!
I'm in the process of making an S-parameter set for it, and maybe swapping out the mixers, to give better performance at the higher frequencies.
I've not been able to do any real comparisons to Agilent VNAs. Much of the accuracy comes down to the cal kit, but as most people don't have 3 grand to spend on a real cal kit, I wouldn't worry too much about it. Above 500MHz the lack of DR will play a role. I assume there will be a few spurs as well due to the use of the DDS aliases.