[hpsdr] VNA calibration loads

[radio at netins.net]

Hi Larry,

First, I really enjoy watching your SimSmith videos on Utube.  My wife 
bought a "Smart TV" which makes them much easier to follow than on my 
computer screen.

My "VNA" is a Hermes SDR radio and a circuit from an old ARRL handbook 
meant to isolate two RF generators. It uses female BNC connectors.  The 
software was written by VK6PH.  The loads are made with male BNC 
bulkhead connectors.  The "50 Ohm" load was made using just a small 
leaded part that measures close to 50 Ohms on my multimeter.  It is 
mounted from the center of the connector to a small copper tube soldered 
to the BNC connector (a bit like inside a coax).

After watching several of your videos and running SimSmith myself, it is 
pretty obvious my calibration loads can be improved.  One of the videos 
showed calibration loads you made with copper clad board for use with a 
dual banana to BNC adapter.  I would like to duplicate them.

Did you make a layout and then etch the board material or did you cut 
the board with an Exacto blade to remove the copper?

The mating surface of the copper looks as if it had been tinned.  Is 
there a reason for this?

John,  W0GN