Wednesday, March 25, 2020

NanoVNA Antenna Testing - VSWR and Cable Loss

 I have some time on my hands so I finally got up to speed on the NanaoVNA.  It was actually pretty easy to figure out and quite allot of bang for the BUC.

The initial test will be to go through all my Antennas from 160m to 70cm and get VSWR measurements in the pass band they are dedicated too.   Initial setup is a 20' chunk of RG59 between the Nano and my rack where all the antennas terminate.   Then I will move to the rack and test again just to see if there is much of a difference.

Band     Antenna Type             Initial Test                2nd test @rack with 1'Cable
160m   Inv  L/8 radials            1.884 / 1.1                 1.1.807 / 1.1
80m     Inv L/8 radials             3.819 / 1.1                 3.5 / 1.1
40m     1/4 Vert/8 Radials        7.0 / 1.1                    7.3 / 1.1
30m     1/4 Vert/8 Radials        10.5/ 1.1                   10.15 / 1
20m     1/4 Vert/8 Radials        14.0 1.1                    14.1 / 1.1
17m     1/4 Vert/8 Radials        18.0 / 1.2                  18.3 /1.0
15m     Fan Dipole                   21.0 / 1.9                  21.5 / 1.9
10m     Fan Dipole                   28.0 / 1.5                  28.9 / 1.4
6m       Fan Dipole                   51.6 / 1.1                  51.1 / 3.0
2m       5/8 Vert                        146.7 / 1.1                146.2 / 1.0
2m       Vert*                            145.3 / 1.2                144.6 / 1.1
70 cm  Vert*                            430.0 1 / 1.0             431.1 / 1.0


* some sort of commercial dual band vertical at the top of the hill


To measure cable loss and length ideally you would have an open cable... all reflected back.  Plan B,  choose a freq with an SWR > 3 the higher the better!   Best for measuring length as well as cable loss...not perfect but a good ballpark.

Band                                    worse swr             cable loss
160m   Inv  L/8 radials       1.136 / 4.3                 2db
80m     Inv  L/8 radials       2.5  / 3.0                    3db
40m     Inv  L/8 radials       3.5 / 3.1                     2.8db

The 160m inv l works very good on 6m























The IFL is about 500' of LDF4.  The worse SWR close to 50MHz was @ 66.963 MHz and was 2.6.  I ran the test here and the loss measured was 3.5 db.

LDF4 is listed at 50.0 MHz 0.46 db / 100 ft and at 85 MHz its 0.60 db / 100ft.  As you can see the Nano measurement is pretty close to theroretical.