Dipole with different diameter legs adjusting?

I am looking into the T2LT design and was wondering how to adjust SWR. Some say just to adjust the top section, but as it is a dipole both legs should be of equal electrical length (also including velocity factor). Both legs are also different in diameter. What is the influence of this and how could i measure/check/adjust this for an optimal antenna performance? 

73
Karel
19CT024

You probably should alter them equally allowing for the VF of the lower part. Will it matter? I don't know for sure, I'm not very familiar with that type of antenna.

Maybe someone understands the T2LT will be along in a while?

I found https://www.translatorscafe.com/unit-converter/en-US/calculator/dipole-antenna/ which speaks of a K-factor in the relation between diameter and wavelength. The graph shown there will get me about the difference between 0.982 and 0.983(rudely reading the graph) as a K-factor. So it matters about 1/1000 of 5.5m. I just can't work that precise when building an antenna, so just making the bottom section 2.6m, 95%(reasonable guess of velocity factor of insulated copper wire) of 2.77m would seem to work just fine.

Still i'm wondering if there is some reading on the nanoVNA to confirm both sections of a dipole are electrically the same length.

Hi Karel. It is true, dipole legs should be adjusted equally to keep it balanced. I have found though just adjusting the tip of a t2lt type dipole for best swr is fine when adjusting. RG58 is often used to make them and the diameter difference of the centre conductor and outer shield of that coax is not big.

Have made one with no choke previously and it worked fine using very low power. You might think this strange, but if you imagine a coax/sleeve dipole is really only a 1/4 wave ground plane with its leg radials bent all the way down until flush with around the coax, then it helps to understand what is happening. As long as there is at least a 1/4 wave of coax under the radiating / inner core top part it will work. A choke of some sort, coax wound or snap on beads does help to stop common mode current back in the shack, might help with radiation pattern, and can help get a truer swr reading.