I bought a 23cm transverter from SG-Lab and Hristiyan (LZ5HP) added a small PCB antenna.

Time for a LiteVNA sweep!

Almost perfect! VSWR of 1.1 at 1296 MHz! It should easy to fix it by shortening it to reach a VSWR of 1.

For further Investigation you can have a look at the S1P files:

• 23cm 2-El SG-Lab sweep from 1200 - 1300MHz

This files can be investigated using NanoVNASaver.