On Sat, Mar 5, 2022 at 02:57 AM, David Wilcox K8WPE wrote:
Can someone explain why my YouKits FG 01 and RigExpert A600 (and even my old
MJF 269) analyzers don¡¯t need calibration every time I use them compared to
the NanoVNA? What is the difference in the operating firmware or actual
operation?
In the ¡°old days¡± I never had to calibrate anything when tuning my
antennas with my GDO or noise bridge? Ha!
The NanoVNA is a two port Vector Network Analyzer that is capable of much better accuracy than any of the other devices you mentioned. It is also a more complicated instrument with more features. The best results are obtained when you calibrate for the range of interest because this creates a good reference plane and the best instrument calibration. However you could use the NanoVNA out-of-the box or by calibrating once for the widest frequency range and storing that in slot 0 for future measurements. You could then zoom to the frequency range of interest and get as good or better SWR and RL measurements than the other instruments you mentioned. For complex impedance measurements calibration is required for the best accuracy.
The devices you mentioned were calibrated at the factory and this is sufficient for making RL and SWR measurements. For complex impedance measurements they are not that accurate out-of-the box.
The MFJ 269 has a difficult calibration procedure that the user can perform and this will give better performance than the usual poor factory calibration. I know because I did my MFJ-259B which is an earlier version of the 269. Unfortunately the calibration is only done on the RF drivel level and the bridge resistors and does not do anything about the other sources of error in the device. The RL and SWR are acceptable on this device but the complex impedance is not great and you don't know the sign of the reactance.
I don't know about the YouKits FG 01 but I can tell you about the RigExpert RigExpert A600. It is a one port VNA and comes factory calibrated for the full frequency range and has this cal data stored in the instrument. However the device is capable of SOL calibration by the user and the manual states than this should be used for precise measurements. You can save the user cal data and switch between it and the factory default.
In this group we often see people questioning why the operation of the NanoVNA requires more effort and knowledge than Antenna Analyzers, GDO's and noise bridges that are also used for tuning antennas. The reason is that A VNA is a much more powerful instrument and requires more training and care in its use. Entry level VNA products cost thousand of $$ only a few years ago but the price has dropped to where hobbyists can purchase one. But just because it is low-cost does not mean that the skill level to use one properly has dropped as well.
These handy devices are handy to own, fun to use and worth the effort to learn how to use in my opinion.
Roger
Roger Need