Hello,
Actually it has been longer than 10 years...in the 80s with yagimax..boy was that fun and stupid, but we didnt knew better at that time, and in the 90s over towards Nec.
I truly have great faith in programms like enzec pro 4etc. (nec 2 will do in most situations).
The reason for that is that we have tested quite some antennas especially for confirmation in VHF/UHF region.
By doing (testing high in frequency) so you illuminate the near by obstacles as there futhere away in reference to wavelength as it is on HF.
Here comes the clue...antennas are spot on.
We have had difficulties where the resonance frequency wasnt where it supposed to be,
That was with using nec2 and LFA antennas. But thats know for NEC2, if you do those calculations in Nec4 they are spot on again.. (nec 2 has difficulties with for example LFA antennas).
The best reason why i have faith in it is cause it is modeled in "freespace".
No where on earth you will always have the same circumstances.
A model made in freespace will always be really close to a real life antenna if it is clear of obstacles, again..it can be spot on as has been proven with those VHF antennas...
But those are at least 10 wavelengths away of anything...
But one needs to be precise. A finger nail on UHF will have influence.
Another beautifull thing is there is no debat with modeling...the debate here on cluster is always about one having a slightly different setup as the other..and though thats really true and something t bare in mind...modelling has no issues with it. simple as that.
Personally as a antenna manufacturer i always supply dimensions.
There are "non-critical" antennas where you can add a bit or so...
But just take a look at MACO and there manual they specify for each frequency different dimensions.
Now take a look at the tapes...how can one be sure there are no faults when putting them on. Or perhaps they are not straigth on..wich side of the tape are you gonna use? what if a tape has come off ?
There are actually many many antennas who do chang if added just a inch.
Manufacturers have always got away with lack of gain/fb simple cause no one measures them. The only thing a guy wants to see is a flat SWR.
Sadly though SWR is nice as a indication, a flat swr doesnt indicate the antenna is doing his upmost.
Faults easily come in play when for example not using the rigth shorting factor of a wire.
If seen guys complaining cause they made a quad with 2,5mm copperwire insulated!
Now thats at least a couple procent.
Another beautifull example is the 2el quad where people use 1/4 wave 75ohm stub.
and think the velocity factor is correct given by the manufacuter of the cable.
You need to measure it...i have had already many times that the factor changed over a new rol.
Other faults are for example not the correct amount of segmentation applied.
but there are more "booby traps" in moddeling, just to name one:
There are well known manufacturers who have moddeld without boom/mast etc.
And there are those who design a yagi but have no "feeling" for a antenna.
One should consider the Q of the anetnna aswell, for EME work the antenna temperature is important etc.
Now, to be honest when i started off i didnt know "shXt" either, I thougth i did!
But now i know i probarbly still dont, thats why you need to have "guru's" giving a helping hand from time to time as they do with me too.
keep learning every day...reading..reading..reading
And the best thing is there are good guys will to share informations !
Write everyting carefull down, wire diameter/spacing/length/distance on boom insert the boom and the possible rest of the mechanical structure.
Have fun!
Henry
11 meter Dx antenna systemx
