Hi Paul... Totally agree about antenna theory/ sizes etc, when I worked at J-Beam in Northampton
we designed most stuff from HF to UHF, the top genius there was Corrie Webster... used a slide rule
No Computers or simulation programs about in them old days!

One method used for testing a design, was to build a scale model at Twice the frequency say, obviously
length diameter ratio messed it up a bit, but you could get a pretty good idea, if it was going to work
Thing is, same as circuit design, so many variables, you had to actually build it, and see what happens

They did an Amateur radio antenna, called the Triple Three, a Three Element on 28 MHz, 21 MHz, and 14 MHz
Testing the prototype, started off with a KW Atlanta, then a KW 1000 watt Linear amplifier was used
to make sure the Balun and trap coils, would stand the sort of power the Americans would throw at it
But, we had forgot to swop the TV Coax used, and found it getting "a Little Warm" at 1Kw pep

We sold some VHF 2 Metre Yagis to America, where their band is 144-148 mhz they managed to cook
the wound Balun coils, so we had to get hold of, some Red PTFE Silver plated wire to replace them

Test equipment was quite basic, a Rohde & Schwarz Polyscop Mostly valve, with a tracking generator unit
https://www.radiomuseum.org/r/rohde_polyskop_ii_swob.html

It was in the days, when TV programs were Not just on, in the Evenings, (with a test card on during the day)
and we had complaints from a nearby Housing estate, that our UHF testing, was wiping their daytime TV's out !

Talking of Interference, Locally we have the Weetabix Factory in Kettering....In the 60's they had several
RF Dryers that caused huge problems, They only got a visit, when harmonics interfered with Police VHF comms
Reason was, they were a self-oscillating PA stage around 27mhz ish, and depending on temperature, humidity etc
you could hear the frequency shift, as the trays of Weetabix went through
And by bad luck, an outside metal chimney radiated well enough, for signal to be picked up in Europe !

Why do we make a habit,over the years, of doing things totally Backwards, and the wrong way in the UK ?
Look at the crap made by Clive Sinclair, using our money, (calculators and ZX Spectrum only things OK at the time)
The Flatscreen CRT, and the electric Bike called the Zike, where its rubber drivebelt, would have been
more at home, on a vinyl record turntable, as for the Sinclair C5.. https://en.wikipedia.org/wiki/Sinclair_C5
Oh Well, better do some work, (PCB assembly today)

Rod Watts