开云体育

One of the bugaboos is what happens when something goes wrong in the VNA?? Take a second harmonic out of range for example......? The SOL will not tell you that you have a problem.? BUT the measurements will be invalid.? SO, I built up a reactive load to test the linearity of the device at 10 MHz.? How about a simple test like confirming the linearity?? ?I built up a serial network of a SMD 50 ohm resistor in series with a selected SMD 318.5 pF cap to ground on a PCB male plug.? Well, at 10 MHz, that reads 50-j50. Scale up and down 5 MHz and see -j100 and at 20 MHz -j25 and the j better track, if not you have a problem.........? Try it some time.??

Mel, K6KBE

Good one, Mel. I would just like to point out that such tests may work fine at lower HF frequencies where we may be able to neglect effects of non-ideal components and effects caused by connections between components, etc. However, at higher frequencies, what we measure will certainly also be affected by non-ideal component behaviour and by hidden realisation dependent effects.

73
Dieter, VK3FFB

Another question, when you set the Z range to 200 and sweep it, the range is limited to 200 ohms, why doesn't it stay there when you sweep SWR?? Like why isn't the limit 4:1 SWR?

Mel, K6KBE

Mel,
it is always difficult to design an analyzer like the FA-VA4/5 according to all user requirements. Simply, different people like different behaviours, menus, arrangments. What you currently see is a compromize to serve most common needs. Some people like SWR and Z modes connected, others would like to have it as independend modes. Making everything adjustable is also not an option as it would require hundreds of settings... again a compromize.
I suggest that you take a look at the PC software VNWA. This very professional software is extremly customizable. Taking a sweep locally outside and analyzing the data after importing to VNWA is also very powerful.
Regards

Michael