[TowerTalk] Suggestions -- VNA, Smith Chart Software

[Grant Saviers]

Re your original question - having both the DG8SAQ VNWA (sdr-kits.net) 
and original AIM4170 here are some of my thoughts -

Of course the VNWA can do much more as a two port VNA, has an attractive 
price, better RF range, an extremely active yahoogroup, and very 
frequent updates to the code, both enhancements and bug fixes.  There 
are lots of links to helpful references and much discussion about 
calibration esoterica way above my pay grade.  Kits are no longer 
offered.  Mine is V2.6 and V3 is current production and various options 
are available if getting at the insides are of interest.  So, for bench 
work it wins for me, partly because the SMA connectors always seem on 
the fragile side or require calibrated adapters to RG8 like stuff.

So, for HF antenna measurements, usually I go with the AIM4170, although 
I need 12v power for it.  OTOH, the VNWA needs USB power and if or 
enough power is available from a laptop on battery power is a crap 
shoot.  The AIM folks have released several updates with bug fixes and 
function upgrades.  Then again, few laptop screens can be read in 
sunlight on a roof or at the top of the tower.

Of course neither can do what a recently "retired" Rhode or Agilent unit 
can do, but the weight is about 1/100 and the cost far less than the 
simplest repair to either brand.  However, as one blogger noted, "the 
VNWA should scare the c**p out of Agilent for how well it works".

Keeping a standard coax cable with the calibration plane at the antenna 
end helps accurate antenna measurements.  In fact, one could calibrate 
each coax at time of installation, while still on the ground, and save 
the specific cal files (works for either unit).

Last time I wanted to buy MatLab (for some servo work) the cheapest 
license was over $1K and I'm not sure for how long.  There are ~$100 
student versions, but they are tied tightly to courses, proof of 
enrollment, and have date expirations, IIRC.  There is an open source 
competitor SciLab, but I have no experience with it.

Grant KZ1W

On 5/9/2012 8:33 AM, Jim Brown wrote:
> On 5/8/2012 9:01 PM, Jim Lux wrote:
>> what do you want to do with the software?  Design matching networks, or
>> just display stuff?
> Design matching networks, primarily with transmission lines.
>
>> Do you have experience with Matlab?
> No.
>
>> There's a bunch of nice Smith chart manipulation stuff with Matlab (and most of it seems to work with Octave, too)
> Last I heard, Matlab was pricy.
>
> Thanks and 73, Jim
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