On Fri, Jul 12, 2024 at 08:41 PM, Everett N4CY wrote:
When Sweeping a LZ1AQ amp you need to use a 1:1 transformer between the VNA and the amplifier.
Ideally, but when using a stand alone VNA, that is not connected to anything, it is so small in terms of wavelength, that it is effectively "floating" and balanced without the need for an extra transformer.
This is the big advantage of the battery powered, pocket sized VNA's. You don't need to worry about the influence of the test gear adding stray circuit paths.
But you do need to make the input Z and gain measurements separately, to avoid unbalancing the input during the Z measurements. If the output is connected to VNA port 2, it will ground one of the amplifier inputs.
As an experiment, I just tried adding a 1:1 transformer on the input, and it made practically no difference to the measurements.
Regards,
Martin
