Antenna analyzer with Si5351 #si5351a #antennas


Hi everyone! I did an antenna analyzer with pic18f250, si5351 and sa612(Ne612). I have a hardware problem. It seems to work fine if I test for example with a impedance about 50 ohms. But when I test with a impedance like 100 ohms or 18 ohms the instrument lose accuracy. Anyone of the group that made some similar antenna analyzer could have a similar issue?  I will add some picture of the circuit just for show you how is the circuit diagram. Im using two outputs of the Si5351. One to test the impedance value and the other as "local oscillator" for feed the mixers. Any advice will be greatful for me! Thank you all for your help!

Steve in Okinawa

Try it without the diodes that are across the antenna input.

Evan Hand

Hi Nahuel,

I am not sure about this but will go ahead and throw it out as a possibility.

The voltage sensor is using a divider that is too close to the impedance of the circuit being measured.  Maybe try to get the total higher than 10x the impedance that you expect to see on the antenna.

Again, just a thought.