This is the Help file for Quisk VNA, a program that turns the Quisk2010 and HiQSDR transceiver and the Hermes-Lite transceiver into a Vector Network Analyzer (VNA). This Help appears when you press the Help button. Quisk is written by Jim Ahlstrom, N2ADR, www.james.ahlstrom.name. Mail to jahlstr at gmail.com. To run the Quisk VNA program, use "python quisk_vna.py" or set up a shortcut. This program only works with hardware that is based on UDP. It does not work with SoftRock hardware.
For HiQSDR you need to update your firmware to Version 1.3 or later. For Hermes-Lite update to 32 or later. The new firmware locks the phase of the RF output to the phase of the RF detector. There is a time delay in the path, but this is removed by the calibration procedure. The calibration graphs will show a linear phase change with frequency due to this delay.
There are two ways to use your hardware. You could connect the RF output through attenuators, through a device under test and then back to the RF input. This is called transmission mode. It is used to plot the response of filters and to measure the electrical length of cables. Or you could connect the RF input and output through attenuators to a resistive return loss bridge. This is called reflection mode. It is used to measure SWR and impedance. You must choose a mode and calibrate for that mode and hardware before you take any data. The calibration is saved and will be restored the next time the program starts. This is convenient when making repeated measurements, but you should calibrate frequently for best accuracy. Hermes-Lite requires a power on/off and a calibration before taking data, but the calibration is good until it is powered down.
The hardware generates RF output only when one of the "Calibrate" buttons or the "Run" button is turned on. The calibration routines save data every 15 kHz from zero to sixty megahertz (thirty for Hermes-Lite). You can change the measurement frequency span at any time without recalibration. Although you can set a frequency span up to sixty (thirty) megahertz, my original hardware has a low pass filter cutoff of 35 megahertz, so the