Foundations of Amateur Radio Empirical evidence and the scientific method The hobby of amateur radio is a curious animal. It sits at the junction between empirical evidence and the scientific method. On the one hand it's all about physics, electricity, magnetism and the science behind those. On the other hand it's about trying something out and seeing what happens. When I started in this hobby, I was all about the science. I wanted to know "Why is it so?" "What evidence is there to support that?", all the typical questions you might ask if you're coming at this from that direction. As is often the case, the more you know, the less you know. That is, the more you understand a topic, the more you understand that you know nothing. The deeper you dig, the more variables become apparent, the deeper the hole goes, the further away from absolute you travel. That's not to say that our hobby is unknowable or non-deterministic, far from it. It's often so complex as to defy immediate explanation using high-school physics. You'll get to a certain point with that knowledge, then from one moment to the next you'll open a door into a world where that knowledge is just not enough. Interestingly when you look at for example the standard way of determining the length of a dipole, a fixed number divided by the frequency, that number we use, what ever the value, is an example of an empirical evidence based number and as observations go, it's not a particularly good one, which is why when you start using it you'll find all manner of exceptions, alterations, modifiers, etc. If there was a formula for a dipole, it would not just have that fixed number and the frequency. Nor would it be a simple division, since the number of variables is likely to head to infinity by the time you actually approach something that can model the real world. Between those two extremes, the quick-and-dirty empirical calculation and the intricate model at the scientific end lies a point of "good enough". The point of "good enough" is where what you're calculating is likely to end up with something that works most of the time. It's not 100% accurate, nor is it trivial, but it gives you a level of confidence that the thing you're calculating is useful and reproducible in many circumstances. I've been told by those who have told me that they know, that the fixed number divided by the frequency is on that "good enough" point, but my experience and the evidence says otherwise. Oh, that's ok, just add 5% to that number, or just cut it long, or insert some or other correction factor to account for the variation, that will give you "good enough". Ok, I'll bite. If that's "good enough", why are we teaching our new amateurs that this is how you create a dipole, no explanation about the variations, the effects of the environment, the material used, just: "Here's a number that you divide by the frequency and you'll have a dipole." My point is that it's time to revisit some of the things we think are "good enough" and look for something "better". I'm not advocating that we all need to become theoretical physicists, though for some that might be just the ticket, but I am saying that we should not just state that making a dipole, or calculating anything associated with our hobby, should be done without context. Here's some context for the magic number 468. Ward N0AX did the research almost a decade ago. It's a fascinating read, look it up! Turns out that the first occurrence of the magic of 468 comes in the form of 438. Yes, that's correct, 438 was the first attempt at making a magic number and it was based on measurements by G. William Lang in 1926 and it was based on averaging measurements for several antennas. In the 1929 ARRL handbook the number 468 first appeared and has been repeated ever since. Apparently as it turns out, the more you repeat something the more it's right. To the point of being ridiculed if you dare question the validity of such a notion. So, what is it, scientific, or empirical, or is it a little of both? I'm Onno VK6FLAB To listen to the podcast, visit the website: http://podcasts.vk6flab.com/. You can also use your podcast tool of choice and search for my callsign, VK6FLAB. Full instructions on how to listen are here: https://podcasts.vk6flab.com/about/help All podcast transcripts are collated and edited in an annual volume which you can find by searching for my callsign on your local Amazon store, or visit my author page: http://amazon.com/author/owh. Volume 7 is out now. Feel free to get in touch directly via email: cq@vk6flab.com, follow on twitter: @VK6FLAB (http://twitter.com/vk6flab/) or check the website for more: http://vk6flab.com/ If you'd like to join a weekly net for new and returning amateurs, check out the details at http://ftroop.vk6flab.com/, the net runs every week on Saturday, from 00:00 to 01:00 UTC on Echolink, IRLP, AllStar Link and 2m FM via various repeaters.
You described my ham radio experience over the past week. At some point, the rules of thumb fail, and you are forced to see what's actually happening and accept that it doesn't fit those rules.
"It sits at the junction between empirical evidence and the scientific method." First of all empirical evidence in ham radio is sometimes claimed by those who have never known what it is. And, because we typically do not know those that claiming having such evidence we can't be sure. Sometime those making the claims do not understand, "just because you can rationalize something, doesn't mean it is rational." Coming down off my high horse I'll introduce the term engineered. Engineering is applied science. A design may start with a rule or rule of thumb but is generally assumed to only be close. Sometimes close is good enough. Sometimes that "good enough" is in the eye of the beholder and they want better. For instance, can it be better that 1.8:1 SWR? I want better! Or, 3:1 SWR?!?! What the heck? Then you get to dig into those rules of thumb(s) discovering their limitations ... or where you f-d up. There always limitations and boundary conditions that can be tricky to discover. Isn't this really the fun or one of the fun aspects of ham radio? Yes, it is also very satisfying to build something that works good enough the 1st time and would be quite discouraging if nothing ever worked without requiring one having to be an engineer everytime.
Here we go again, complete with an enticing fresh beating of a very unfresh, dead horse - all 17 pages of comments worth of unfresh. Why, it's like deja vu all over again! http://forums.qrz.com/index.php?thr...now-about-dipole-calculators-is-wrong.630800/ Out with the axe handles and baseball bats. It's time to get medieval. Microwave popcorn optional, but suggested. This is going to be a l-o-n-g show...
How about just calling it what it is, an approximation. Usually non engineers are the persons who don't understand approximations and want something that is exact. 468 is an approximation. If you use 492 you can always cut off the excess while making measurements. Mark N5RFX
I remember asking what "EIF" meant on a engineering drawing and being told: "to be Engineered in Field - a variation of FIF - Fit in Field." Worked back then, works now.
The fact that we have these points of view showcased --here and in several other 'top page' threads--is indicative of the very sorry state of ham radio in 2019, IMO. This is a 'hobby' that includes some of the very best people in telecommunications and radio science, many more than willing to share their expertise and help. Thanks for insulting us. 468 divided by feet is an exact formula for a thin wire dipole in free space with no dielectrics, assuming the effective speed of light is , well the speed of light. No 'velocity factor'. It comes from the formula that US hams have to learn to study for their ham licensees-- wavelength times frequency =c divide wavelength in this by two to get half a wave. Your 'dipole' propagates a half wave. WHY...DON'T ...YOU...KNOW...THIS...?????? This is not a *&^(^ 'rule of thumb'. Its an exact formula utilizing reasonable assumptions. Simple. When a distinction is made between the evidence and the scientific method---its just appalling. When a distinction is made between 'scientific' and 'empirical'--its just appalling. Its a real turn off for those who try to help. These showcased attitudes are reminiscent of CB and Freeband from years ago. Not for me. Science is NOT 'like magic but real' as the poster happily advertises. What we are seeing is a bunch of interesting words juxtaposed together to induce happy time endorphins---with no concession to reality. MO. It's all BS. It says nothing. But it feels good! I'm out.
Who does that? I sure don't. What I do is to say "This is the starting point. It applies to an idealized wire dipole in free space using a perfect conductor whose diameter is very small compared to a wavelength. Other real-world factors may affect the length - but this is where you start."
I use 470, not 468 or 492. And then I arbitrarily add a couple of feet for typing off at the insulators, because "empirically" or otherwise, 468/f doesn't actually tell me how much wire I really need. So do I have to turn in my Physics PhD now ?
It's not like we are publishing peer-reviewed papers in Nature magazine here, Chip. Edison once asked an engineer to calculate the volume of a light bulb. After much work with paper and pencil, the engineer produced his answer. Edison said, "You're off by at least 5%". Edison then filled the bulb with water and poured it into a measuring cup. AF4RK
Must have been a day off from his gig of publicly electrocuting innocent animals for ole Tom... ...scientifically, empirically, or otherwise.
Not picking on you OM; my following comments are generally addressed-- This is not a case of snobbery. Empiricism is not separate from the scientific method. There is a core of understanding that ALL ham operators know--because they are ham operators. And they need it to get their US ham licensees--I can't speak for other countries. We (some) seem to think it is not only proper, but COOL to abandon that core body of knowledge. We (some)seem to think, in 2019, that ANY ALLUSION to technical assumption somehow DISSES and DEGRADES those who say its all BS --and that those who call us out on it are ELITISTS and (&(&)&)_'s. Really: ham radio wasn't started to be a plea to ignorance. It wasn't that way for 80 years. Why should we be making a transition away from our core culture? Why are many offended by being reminded WHO WE ARE, and WHY WE EXIST (at least in the US under Part 97 service)? Please tell me why there is this TRANSITION, WHY it is happening, and WHY its a 'good thing'? You don't NEED to be an engineer; a Ph.D. in physics; you can sell bread to celiac patients, for all I care. But I do want to know WHO we see ourselves as being in 2019. What's driving it? How is it in tune with the mission--in the US--of Part 97? How do we justify the US amateur radio service if it lacks the skills of technical knowledge? Example: freq x wavelength = c, and a dipole(1/2 wave) is 1/2 of that inferred wavelength (with stated assumptions.) HENCE-- length (dipole in feet ) =468 / freq in MHz Its not..... 'empirical and separate from the scientific method' If , for example, you cut your 40M dipole and hang it 20 feet off the ground, this formula won't be exact for you. Ask why.
That's the beauty of this hobby. It becomes whatever you make of it. It can be engineering, like the meticulously-planned installation of the free-standing tower that has supported the TH7DX tribander for over 30 years at my ex's QTH (separate story) . Or it can be "let's see what happens" when I threw some wire up in the mature maple trees at my new QTH. Both installations have generated ATNO's on the path that gave me an Honor Roll plaque for the shack wall. The young man who built his first SSB exciter from old television parts grew up to install a television transmitter that serves a city. All made possible by this intersection of science and creativity.
