The width of the radiation lobe of the antenna is one of the important parameters of any directional antenna. The data that we can learn in the descriptions of the antennas always apply to a certain environment, which will not be 99% identical to ours. Almost every antenna calculation program will draw you a directional diagram (for vertical and horizontal plane) - again in an ideal space, preferably in a model space (at a certain height above the ground).
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Like the directional diagram of your antenna?
The way to measure the radiation pattern is known - but demanding on patience. What would you say to the fact that you can measure the directional diagram of your antenna in the comfort of a hamschack?
The principle of measurement
And this is exactly what the PolarPlot program from Bob Freeth offers you. You will need: a measured antenna with a rotator, a QRPP transmitter, a receiver (preferably with a switchable AGC) with a friend and a PC with the PolarPlot program.
To draw the directional characteristic, the fact is used that when receiving an unmodulated carrier CW/SSB signal in the area when the AGC is not active (possibly switched off) there is a very close relationship between the strength of the HF and LF signal. Today's receivers are almost linear in the range of about 40 dB (which I guess is enough for any antenna).
In order to be able to measure the characteristics of your antenna, you must transmit with a constant power to the rotating antenna. A friend (better friends, more directions) will receive your signal. It will then measure the antenna's directional characteristics from the NF signal.
PolarPlot setup
PolarPlot má bohaté možnosti Settings. Nikto sa nevyhne dvom nastaveniam: kalibrácii a času na otočenie antény o 360°. Ostatné Settings sa väčšinou týkajú úpravy grafu (odstránenie špičiek, zaoblenie, lin/log mierka) či úschovy dát (tlač, uloženie na disk).
Limitations of PolarPlot
Given that the program can be run 30 times in 15 days, I definitely recommend at least a brief look at the help file (RTF in the program directory) before running the program itself. Everything is explained there to make your measurement successful. Otherwise, you will probably be disappointed and the radiation diagram will not correspond to your ideas at all.
Evaluation
I tried the program a year ago when testing a three-element OWA (own design). Estimated gain, lobe width and F/B ratio matched my estimates.
You can find the program among the programs in the "Download" section of this portal. I would welcome it if you share the results of your measurements with others, for example here.