Hello to all
I can agree that cable length has a certain influence on VSWR. I experienced that already, when installing 3&4G GSM-antennas in a previous life, VSWR could be worsened or improved notably by leaving or cutting a few millimeters of the coax length. I was lucky enough to be working with Anritsu sitemasters then, but actually for LoRa development activities, I only use an N1201SA and it shows similar results for cable length influence.
I tested a cheap waterproof antenna like pe1mew in The BIG and SMALL ANTENNA topic part 1 , but also 2 long whip antennas from RAK Wireless and 4 short whip antennas from TTGO and Heltec, all for 868 MHz.
The waterproof antenna got about half a meter of cable fixed on it, so I had to use that anyway. But since this cable length is about 3 times the half-wavelength @868MHz, it should have only little influence on VSWR (but minus a few gain so not really ignored, Costo!). On testing indoors, I found very high VSWR’s due to reflexions of the walls. Once mounted outdoors on the roof, it showed quite good VSWR lower than 1.3,so I think this antenna is not so bad at all (@pe1mew: maybe this confirms BoRRoZ’s good results?).
Then I went for the whip antennas, and found that the fact of testing them indoors had little influence on any of them, as they all gave about the same VSWR indoors and outdoors. Two of them (a long RAK and a short TTGO whip) gave the lowest VSWR of 1.0 over a large band in the 868 range.
So I decided to test those two antennas, once mounted directly on the vector analyzer standing on a desk, then lying horizontally on the desk, and finally mounted on a stand and sequencially tested with cable extenders of 25, 17 ,16 and 15 cm. You have to add about 2x1 cm to the cable length if you count it strictly from pin to pin, so only the 15 cm extender cable got around the half wave length of 17,27 cm… and this makes sense, as all cables gave VSWR between 2,3 to 6 and more when using the extensions, except the 15 cm extension which got 1.7 VSWR !