May be it's a new version in program, that you must enter the velocity factor as .66 and not in percent. Your measured data are ok, but the 2m RG174 has a loss of 2dB @ 900 Mhz. So the real mismatch at your antenna is -2.34 dB. (You must add 2 x 2 dB). That is very bad for an antenna. A better way will be to use the 2m RG174 with a connector at the end and make a calibration at this end. Thn use a very short cable from that connector to your PCB.
Am 23.02.2025 um 04:46 schrieb Nico via groups.io:
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Hi,
Is my setup ok ? Is there any monstrous mistakes in my montage ? I'm quite new to the nanoVNA. Well, I am totally new on VNAs themselves. I did not know their exitance 2 months ago ! Well, I want to match my antenna because so far, it is pretty horrible. But, before ordering some matching network component and then screwing everything because I am missing something obvious, I would like someone to point me to the rookie mistakes I could have made.
The project is a LoRa module (902-928MHz) connected to a small antenna mounted on a pcb. The pcb is inside a small polycarbonate box. I have followed the design rules for this antenna from the manufacturer. I have calibrated my nanoVNA-F V2 (from sysjoint) using the supplied calibration set, straight at the S11 connector. My board is inside its final box and mounted on a wood plank that mimic the final location. My board is hooked up to the vna through an RG-174 I had laying around. It is 2 meters exactly. I have added an E-Delay of 10.1ns as per a calculator I found on the Times microwave website. I don't know if there is a bug in the vna's firmware but I had to put 0.66 as the velocity factor in order to make it display 2.00 meters as the cable length. If I put 66 as in 66%, it shows 200 meters. Anyways, I'm not sure if that part is that relevant.
So, by looking at the pictures, does anyone can see some obvious mistakes ?
Thank you so much
schweppe