Rebuilt the antenna analyzer as a scalar network analyzer

Some time back I built the k6bez antenna analyzer which utilized a cheap eBay DDS and and resistive bridge. It served it’s purpose though accuracy was questionable with no compensation of the diode voltage drop and lacking in power. My build being cheap and nasty lacked a case so it was fragile.

With an pressing need to build and tune some filters and wanting to put the thing in a box, it seemed like a good idea to rebuild it but as a Simple Scalar Network Analyzer allowing for more flexibility in measurements. I just happened to have a couple of AD8307 log detectors in the junk box having snapped them up at a good price a while back. The enclosures were also really well priced on eBay.

I’m fairly happy the way it turned out.   

I’ve set the amp so output power is 0dBm. The AD8307 log power detector is in a soon to be covered shielded enclosure, buffer amp below and the blue box contains a return loss bridge, thereby getting me back to where I started.  
  

The calibration results don’t seem too bad. The roll off at the lower end is likely due to either the 0.01uF cap on the detector input or the use of 43 material for the toroid in the bridge. It will do until the solar activity forces us onto 160m… Testing with a variety of different non-50ohm loads results in the expected return losses within fractions of a dB. The AD8307 is worth the cost.

Back to multibanding the skimmer and the hf amp…

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