Measuring a LZ1AQ like DIY loop amplifier with NanoVNA

[Dirk_SDR]

I've built a LZ1AQ loop amplifier similar to that:

LZ1AQ Boards (Have a new batch of boards)

groups.io

Now my question is:
I want to measure frequency range and gain of this amp only (without a loop wire) with my NanoVNA.
For S21 I would have to connect the 2 amplifier loop inputs to the 50 Ohm coax output of the NanoVNA.
But how?
What is the best way to test this low impedance loop amp with a standard VNA?

 

[prcguy]

I've built a LZ1AQ loop amplifier similar to that:

LZ1AQ Boards (Have a new batch of boards)

groups.io

Now my question is:
I want to measure frequency range and gain of this amp only (without a loop wire) with my NanoVNA.
For S21 I would have to connect the 2 amplifier loop inputs to the 50 Ohm coax output of the NanoVNA.
But how?
What is the best way to test this low impedance loop amp with a standard VNA?

A typical small non resonant loop about 1m dia is about 160 ohms across most of the HF range so I would use a 4:1 balun connected to the balanced input of the amplifier fed from the output of the VNA. You could use two 4:1 baluns back to back for cal then remove one for the measurement then subtract the small loss of one balun from the final outcome. The balun loss should be very small across 3-30MHz so maybe you don't need to have a balun in circuit for cal.

 

[Dirk_SDR]

Thank you. I'll try with a 1:4 balun.