Return Loss of GNSS Antenna

[Sbilf]

Hi guys,

I need help on a GNSS antenna. My board is a lap timer whit ceramic antenna   GPS/BEIDOU/GLONASS. The datasheet explain best layout for to have best performance but I can't respect them.
In  the frequency 1561 / 1575 /  1602 MHz  I should have low return loss. If I don't follow the  suggestions of datasheet I think Frequency Range of antenna and curve of Return loss change. How can I measure these curves in my situation and understood how worsened have I gotten?

I' m thinking by  vector network analyzer for example "NanoVNA". But I don't sure is correct.

Thanks a lot.

[WPXS472]

I am a bit puzzled as to why return loss is important with a GNSS antenna. They are receive antennas. If the specs for the antenna say it is for a given frequency, or range of frequencies, I think you would assume it works for those frequencies. Since most GNSS antennas have a built in preamplifier, it would be difficult to measure the return loss of the antenna from the end of the coax feed line anyway. Placement of the antenna is important because of the effects of nearby objects. They can cause reflections and multipath, reducing the accuracy of the GPS.

[uski]

I see the value of checking the antenna. A lot of sellers have no clue about what they are selling and I bet that single frequency, L1 GPS antennas, can very quickly be relabeled, by mistake or intentionally, as GNSS multi-band antennas.
Similarly, some antennas will be better than others...

I do agree that because of the LNA, it will be hard ot measure. But it makes sense to discuss how one could compare there antennas, so they can be compared, and their specs verified.

Sbilf, the issue you are going to face if you do not respect the specifications of the antenna is that you might shift the antenna out of frequency. I would suggest working with the antenna manufacturer, I have been in similar situations before, and often they have useful guidelines for these situations (from "do this XXX and it will fix everything" to "we have no idea" with "if you do what you want to do it will not work" in between)