Antenna tuning method

[XXL]

Looking for some advice on tuning antennas with a nanovna, as there are many variables involved.

I’m currently using the swr and ohms trace to tune it. But soon as you move the antenna or place it somewhere else, everything changes. Is this just what happens in the real world or is there a way to tune without objects changing it value ?

Also are there any other settings on the VNA I could be using to tune it ?

[Albert H]

Part of the problem is proximity to other objects. I usually put my antenna under test on my small test tower. The nearest object to the aerial is then about 16m away and has no measurable effect on most aerials I work on.

Putting aerials in actual site locations can give rise to all sorts of problems. The most important thing is to get the aerial high and clear of everything else!

[rigmo]

Yes Can be very difficult and can take a lot of time... I compere measurements between nanoVNA-F and Antena Analyser https://www.qrz.ru/classifieds/detail/a ... 1ky_292595, and get the same values....

[rigmo]

sorry for this I offering my
NanoVNA - F for sale.
reason: I wouldn’t if I didn’t have a need. - there is no hidden flaw.

[sinus trouble]

The antenna is probably the most important part of any transmission system which is often disregarded!

And yes unfortunately, You are correct! There are many variables! This is the main reason why the Dipole is the antenna of choice!

As Albert mentioned? Testing is different to actual installation!

I dont think your method of testing is the problem (VNA) Which will tell if the system is heavily loaded inductively or capacitive? (As a Smith Chart will show)

Not only does the Antenna dimensions play a role, The Transmission line (Coax) is part of the tuned circuit and needs to be consistent to wavelength!

[Albert H]

Every part of the antenna needs to be taken into account - even the mast that's supporting it. The coax, the connectors, everything affects how the aerial works.

Some people complain about the loss in a few metres of RG58, and then use PL259 / SO239 connectors (horrible discontinuity and dreadful match).

You need to use the right connectors, and the right coax. If you're doing anything up to 10 Watts or so, and want to use a dipole, use TV "low-loss" coax (the brown sleeved stuff) and Belling-Lee connectors. The dipole will be around 72Ω and the match - with a Pawsey Stub will be damn near perfect.

It's easy enough to dimension the output stage of your rig to match into 75 / 72Ω. You're going to need a 75Ω dummy load, though and an SWR bridge built for the different impedance.

All my old link gear used 75Ω connectors, coax and aerials. Most frequently, I'd use ordinary cheap (B&Q) TV Yagis for Band IV and V links.