Dave-
Well said. My experiences have been exactly as yours. Before I learned how to
model I felt like I was just spinning wheels, never knowing whether I was
proceeding backward or forward.
In his book N6BT stated thay any antenna will work. At a radio club meeting
once we hooked up a light bulb to the antenna port on a transceiver and worked
a couple stations across the country. Does that prove it's a good antenna?
Tom H
K0SN
> On Sep 11, 2019, at 10:45 PM, David Gilbert <xdavid@cis-broadband.com> wrote:
>
>
> I think most of that is fairly misguided advice when it comes to antennas.
>
> Here's what I don't understand. Of all the things we as hams have under our
> control to improve our ability to communicate, antennas are at or near the
> top of the list. Up to a certain point (as was discussed here recently), the
> effectiveness of an antenna has more bang for the buck than pretty much
> anything else we have a handle on. So why on earth do some hams relegate it
> to "just put something up and see if it works"? That can certainly be fun,
> and I have personally built multiple dozens of different antennas just for
> grins, especially over the several decades I've operated Field Day or gone
> camping. But if you aren't trying to optimize your results just admit that
> you don't really care. Which is fine, of course. There are lots of aspects
> of ham radio I have zero interest in, but antennas isn't one of them and I
> would have thought that anyone subscribed to this list was here to learn how
> to make better ones.
>
> If you are indeed trying to optimize your antenna(s) , trial and error is a
> terrible way to learn how to do it because you can't control enough of the
> variables and some variables are even pretty hard to measure. Multiple
> iterations are slow, as well as being imprecise (because of the variables) if
> you're trying to improve things like gain or pattern or the ability to be
> heard in general.
>
> It used to be that we were either stuck experimenting with antennas or doing
> laborious mathematical calculations by hand, but even basic modeling programs
> have turned that completely around. It isn't that the models are infallible
> (they are not) .... it's our ability to quickly and easily learn from them
> that is important. As I said above, I have built many, many antennas over
> the years and I played around with most of them to see what would happen, but
> I've learned far more from looking at the current distributions along the
> elements in EZNEC and observing the effects on gain bandwidth, pattern, and
> SWR than I ever did with various experiments. The rest of what I've learned
> came from smarter folks than I here on TowerTalk who either understand
> antenna theory better than I do or were better at modeling that I am. I can
> honestly say I haven't learned much of anything worthwhile from somebody who
> put up something and claimed "it worked."
>
> You say no one doubts the results of the experimenter. That maybe true of
> the chemist or circuit designer who can control his environment, but I ALWAYS
> doubt the results of the antenna experimenter who can't explain his results
> with either theory or a suitable model, or both, because I know in most cases
> he wasn't able to control or allow for important variables (propagation,
> proximity effects, noise variability, etc) and probably didn't even
> understand enough to do so if he relied only on his experimentation to teach
> himself about antennas. I have a few of my own examples of this, the most
> notable being an antenna I tried for Field Day one year. I wasn't able to do
> my normal preparation so I modeled a flat elongated vertical wire rectangular
> loop fed in the middle of one of the short vertical segments. The model said
> it would perform marginally at best, but it was easy to put up and could be
> fed on both 20m and 40m, so I went with it anyway. The night before Field
> Day I gave
it a try and worked an FR5 (FR5DN, I think) first try using 5 watts from here
in Arizona with Q5 CW signals both ways (somewhere I have the QSL card to prove
it). I thought hey, maybe this thing is better than I thought. It wasn't. I
didn't work a single other DX station that night and the antenna turned out to
be one of the worst I ever built for Field Day as well.
>
> The bottom line is NOT that antenna modeling will always give you the right
> answer, but it will make you a heck of a lot smarter more quickly than simple
> experimentation will, and in most cases you will at least know in which
> direction to make changes if you're trying to make improvements.
>
> One last example. I recently built a 5 element 6m yagi using dimensions
> posted by DK7ZB on his website, and he came up with those dimensions using
> modeling software. Most 5 element yagis have a feedpoint impedance down
> between 12 and 15 ohms, but his design (others have done the same) natively
> gives a 50 ohm feedpoint at a very small sacrifice of forward gain. It does
> so by making the first director actually longer than the driven element. How
> much time and how many iterations do you think it would take an experimenter
> to stumble across that?
>
> By the way, modeling has given me FAR more "eureka" moments than any antenna
> I ever built.
>
> 73,
> Dave AB7E
>
>
>
>
>> On 9/11/2019 6:45 PM, Don wrote:
>> Well put by Mr Fox, Shawn. Reminds me of a little picture frame with the
>> following which hung on the wall of one of our top engineers in the test and
>> instruments company I worked for. Smart, learned, well educated and a
>> dedicated experimenter, determined to defy the 'it has to be so' crowd.
>> Quite successful.
>>
>> "No one believes the results of the computational modeler except the
>> modeler, for only he understands the premises. No one doubts the
>> experimenter's results except the experimenter, for only he knows his
>> mistakes'. Beneath was two handwrittenlines on a strip of paper. "Modeling
>> is not as exciting as experimenting where the outcome can be an Eureka
>> moment".
>>
>> I had copied that and tucked it away in my old company history files I left
>> with.
>>
>> Don T W7WLL
>>
>>> On 9/11/2019 2:08 PM, Shawn Donley wrote:
>>> I occasionally teach a class on modeling certain mechanical systems using
>>> Simulink. The second slide is a quote from the British mathematician
>>> George E.P Box. I think it may apply to this discussion as well.
>>>
>>>
>>> "All models are approximations. Essentially, all models are wrong, but some
>>> are useful."
>>> _______________________________________________
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>>>
>>
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