Once upon a time, when I was very young, I travelled to a faraway island with an antenna in my bag that I had put together myself. Everything I knew about antennas I had learned in a single evening from an elderly retired naval engineer, a no nonsense expert in his field, shaped by lifetime in the military, we sat in his den - a clean office with medals and oil paintings of grey steel warships hung square and level. His serious visage beamed with love and delight when his partner - whose projected persona was the polar opposite of his own reserve - a flamboyantly camp man in trailing colorful silks who brought us cups of tea and exquisite little cakes, and would look at the the notes I was taking an theatrically shudder, swooning with the the back of hand to his forehead that ‘he never would never understand all that stuff’<p>I wasn’t entirely sure I did either - the retired engineer was able to explain things in the lingo of his trade, but couldnt confirm my attempts to connect the terms he was using to my first year university physics concepts.<p>But a month later I was sending an email from the jungle via length of unspooled cable
Antenna theory is a pet peeve of mine. The problem is that it is universally taught with the "Path Loss Equation" and that equation leads to a very poor understanding of how antennas work.<p>Almost every technically trained person understands that electromagnetic radiation energy dissipates according to the inverse square law in the far field. But the Path Loss Equation jumps through hoops to shoe horn in a frequency term that clearly, if you think about it, has no reason to be there. The distance term is necessary of course but the frequency term scientifically illiterate.<p>This all comes down to the fact that at some point someone decided they would deem the gain transmitting and receiving antennas as "equal and reciprocal" if they are physically the same. In order to make this delusion work out mathematically a phantom frequency term has to forced into the equation to make the maths work out.<p>For those who care (not many I expect) the way things really work is that the gain of the transmitter can be function of frequency (geometry and all that) but the receiver has no gain, the energy it traps depends only on its area.<p>Ok I'm stepping of my soap box, thanks for listening.
Antennas are weird beasts. Their behavior and performance can be predicted and measured in very technical ways but, at the end of the day, throwing a random length of wire over a tree branch, cut to 1/2 or 1/4 of the operating frequency wavelength can be all one needs to communicate with another station, even a very lower transmit power. This applies primarily to HF and VHF. Frequencies reaching up into the microwave range is where antenna design starts becoming a dark art, practiced by wizards and neuromancers.
Vector Network Analyzers have come down in price to the $100 range, which is amazing in and of itself, so the home experimenter, likely a Ham radio operator, has a lot more capability to precisely measure things that were pure guesswork in the past.<p>Of course, the anechoic chamber is a nice thing to have. I once got to see the Anechoic chamber at Northrup Grumman near Chicago during a open house... a theater size room they used for various measurements. I'll never forget it.<p>This is a nice collection of information. The other place to get this type of data in the past was the Amateur Radio Handbook from the ARRL.
Also, here's a good place for design theory and construction practice of consumer-grade TV and FM radio antennae:<p><a href="https://www.digitalhome.ca/forums/antenna-research-development.186/" rel="nofollow">https://www.digitalhome.ca/forums/antenna-research-developme...</a>
Antennas are super fun, they still feel like magic to me every time I see one. In college I took a microwaves theory course where we had to design antennas for some problem sets, and we gave them to some dude in a basement lab who then fabbed them in like an hour for us to test. Kind of mind boggling that with a few tools and handiwork you could produce real electronics with reasonable characteristics!
A very interesting site full of downloadable papers on various subjects including antennas. <a href="https://www.jpier.org/PIER/pier.php" rel="nofollow">https://www.jpier.org/PIER/pier.php</a><p>This one for example may turn useful if one needs to build a WiFi multiband planar internal antenna. <a href="https://www.jpier.org/PIERL/pier.php?paper=11073004" rel="nofollow">https://www.jpier.org/PIERL/pier.php?paper=11073004</a><p>...yes, that stuff is black magic/voodoo
Excellent stuff, surprised I’ve never stumbled upon the site before. It’s not just about antennas, it also offers concise yet intuitive explanations of related concepts such as Fourier analysis.
I may be mistaken, but this site is by a former Apple antenna engineer, isn't it? If he's who I seem to recall he is, he must have some incredible Steve Jobs war stories.