Which schematic and values did you use? That amplitude curve is weird.
Also, VSWR is very high on marker 3 (30 m)
Jos¨¦, CO2JA
toggle quoted message
Show quoted text
On 6/4/20, GM7 <geeemmseven@...> wrote:
Hi All,
I'm trying to test a set of Low Pass Filters for 40m, 30m, 20m & 10m. I'm
getting consistent results for each of them but not the results I expected.
I'm struggling to establish whether the problem is with the filters or with
my test setup / calibration or even with the NanoVNA.
I've repeated this with and without a test fixture and got essentially the
same results. I attach the test fixture (see photo) and then calibrate
(reset, followed by open, short, isolation, thru). I then check the smith
chart with short, open and 50ohm loads to sanity check the calibration.
The attached image shows the 30m LPF. It doesn't have the passband I would
expect or the roll-off I would expect. Instead it's almost a linear
roll-off over the range under test.
Can anyone help? For example by either correcting my test methodology or
offering any advice. Thanks in advance.
Jose Amador