Surely, as I recall, it is not the accuracy of the dc resistance of the load that is most important, but the ac impedance of the whole device as the frequency increases. Inductance of the resistor(s) in the load, capacitance across them, poor connector dimensions are FAR more important if you want good results above hf frequencies. Construction of these reference loads is critical, which is why the professional ones useable above 6 ghz cost many times the cost of the nano. Making a good short and open is a walk in the park by comparison.
There are several sites on the internet which show how to make your own sma standards which can be quite good up to several ghz. I have made several sets which are almost as good as some cheap ¡°professional¡± ones I have, but I have not managed to get them assessed on a professional vna. Unfortunately, owners and users of really good kit do not like ¡° foreign¡± stuff to come near their gear in case dodgy connectors damage the ones on their ?20,000 plus vna. Likewise they never loan their standard out.
Steve L. G7PSZ
