[time-nuts] DIY VNA design

[Bob kb8tq]

Hi

One option in the "1 GHz and down" range is to team up a surplus HP S-Parameter test set with your own electronics. That way you let HP do all of the fancy directional coupler stuff and relays. They don't sell well on the auction sites. The result is that a bit of time making lowball offers can generally get you one or more of them for not a whole lot of money. 

Bob

> On Aug 21, 2016, at 12:46 AM, Bob Albert via time-nuts <time-nuts at febo.com> wrote:
> 
> I was interested in this, but my needs are mostly below 100 MHz.  I wonder what could be done similarly for this lower range...
> Bob
> 
> 
>    On Saturday, August 20, 2016 8:54 PM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:
> 
> 
> Another great posting, Attila.
> 
> When I was with Agilent, we looked at all kinds of
> simplified network analyzer architectures, and I
> would have to say the author is really well informed.
> One issue he doesn't seem to be aware of is that the
> ADL5801, when driven single ended, has some quirks
> below 100 MHz that I discovered experimentally.
> (The data sheet is silent on this).  IMHO, it
> would be worth 7 Euro's to use a balun, however,
> I would like to know the part number of this
> supposed component.  I am not so sure about MCL
> actually covering 30 MHz to 6 GHz in the same
> balun.  Sometimes their advertising is confusing,
> and when they say .03-6 GHz baluns, they mean
> that the range can be covered in several bands
> by several model numbers.
> 
> Still, quite impressive work by an individual
> practitioner.
> 
> Rick
> 
>> On 8/20/2016 7:19 PM, Attila Kinali wrote:
>> Moin,
>> 
>> I stumbled over a new open hardware/source VNA design:
>> http://hforsten.com/cheap-homemade-30-mhz-6-ghz-vector-network-analyzer.html
>> 
>> Unlike other designs out there, this one is very well done and has very
>> little room for improvement, without increasing the price considerably.
>> 
>> About the only things i would do different is to use two receiver
>> channels, one fix connected at the TX source to be able to do a
>> difference measurement between TX and the RX channels and thus
>> improving precision. And the other would be to use a dual ADC
>> with an FPGA for the data processing, again in order to increase
>> performance.
>> 
>> But as I wrote, both changes would increase complexity and price.
>> 
>> Other than being a well thought through design, the website also
>> explains all the big design choices and why this or that has been
>> done instead of one of the many alternatives. That alone makes it
>> worth reading, IMHO.
>> 
>>             Attila Kinali
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