High Z ant(enna) connector on SDRplay RSPduo.

From: A. C.
Sent: 06 October 2025.

Andrew, I was going to mention but I forgot, in the after RTOP meeting yesterday you asked what the High Z antenna connectors in the duo were for. It’s the connection to use for long wire antennas such as what you would use to listen to SW shortwave or even to VLF multiple loop type antennas as these are not 50 ohm compliant and  are normally of much higher impedance. 500 – 1000 ohms.

So connections would go the P or positive connection going to the near end of a long wire antenna and the N can float or be grounded. If a long wire dipole is used one side goes to P and the other side of the dipole goes to the N. If a multiturn VLF loop (such as for 30 – 60 KHz) is used, the loop ends go to P and N and ground is of course obvious.  A cold water pipe or ground rod are the usual culprits. In some cases intermediate impedance antennas such as single loops still require a balun matching transformer to bring up the impedance for the best High Z matching signal reception.  For all the microwave radio astronomy stuff everything hundreds or GHz and up the High Z connector can just be ignored since we only work with 50 ohm matching antennas.

  Anyway I am really excited about your great success with the duo now being able to run on GNU  radio, in Windows no less. A real advancement in being able to expand to a wider bandwidth and as you mentioned with the ability to synchronize receiver clocks for multiple units simultaneously for interferometry, great stuff.

Adrian