When I look at consumer wireless devices, I ask myself: does any actual 'design' go into the antenna?
Look at the antennas, they are just a length of wire, or sometimes a loop of wire. I recall my days studying EM theory, and RF design, it's complex stuff. (though I had only rudimentary exposure to antenna design) Then I observe what's in use, and I scratch my head. Are there any formulae, principles, optimizations, involved in these devices?
If you look at the hobbyist literature, you see much the same: a circuit diagram, with that little 'antenna' thigamajig. It's just given that way, with no information. Like manna from heaven, or what?
In aerospace, with their big $$, of course they do sophisticated antenna development. But what about your cell phone?
Oh yes. Considerable design. With antennas, it's called "antenna modeling" using NEC2 or NEC4. See shopping list of suitable programs at:
If you want to play, I suggest 4NEC2, which comes with a large collection of sample antennas:
Some of my tinkering with 4NEC2 and antennas: Look at the antennas, they are just a length of wire,
Or radiating surfaces. However, their simplicity is deceiving. It's very easy to design a marginal and inefficient radiator, one that is optimized within the required constraints is far more difficult.
Naw... All RF is magic.
Oh yes. Even the simple antennas follow the rules. The basics are simple. You're responsible for delivering RF from perhaps a 50 ohm source and matching it to the impedance of free space (377 ohms), in the desired direction, and without losing any in the process.
I don't see a problem. What antenna information were you expecting on the schematic diagram?
Your cell phone antenna system is the nightmare of antenna design. My phone PDA has internal antennas for 900/1800MHz, 2.4GHz Wi-Fi, 2.4GHz Bluetooth, and 1.5GHz GPS. Some new handsets will be arriving with
2.5GHz Wi-Max. All that works simultaneously, without mutual interference, maintaining FCC Part 15 radiation requirements, SAR (specific absorption rate) safety requirements, while delivering the bulk of the RF in the general direction of the cell site. Oh, I forgot that it also has to work with varying body, hand, head, and car kit capacitance and blockage. All this within an insanely small package. The final result may look simplistic, but are invariably the end result of substantial modeling, cursing, and compromise.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Absolutely! For any receiver antenna design, you have to take care of opertating frequency and bandwidth (even multiband operation), then "Q", then efficiency issues - such as anticipted detuning if worn on the body (i.e. Walkman type radio, etc..) It's not as simple as it might appear at first.
A colleague of mine just finished work on a "simple" loop antenna for a major manufacturer of new portable HD Radio receivers. So you can conclude that even "simple" antenna design work is still in demand....
I recommend: Weeks, W.L. "Antenna Engineering" New York, McGraw Hill, 1968 among others as a resonable start. (non-hobbyist)
Choke, cough, sputter, etc... I need a rant. I've done cleanup jobs on products that never saw the benefits of a calculation. Many were reverse engineered or cloned, with only a minimum understanding of the original design[1]. The rush to market has created some truly amazing implementations that border on butchery. In the broad sense, I agree that most things eventually are designed, calculated, re-designed, re-calculated, optimized, cost reduced, cost reduced some more, butchered, and delivered. Many products are a basically good idea, badly implemented, and held together by a mess of band aids. Touch anything, and the house of cards falls over. Fortunately, it was fixing such butchery that kept me in business for a long time.
My business card still reads "If this stuff worked, you wouldn't need me".
Since we're talking about antennas, has anyone ever tried to model the typical Radio Shack yagi TV antenna? One would expect that with such a long product lifetime, years of evolutionary development, the availability of sophisticated modeling tools, and the need for more sensitivity with OTA digital TV, that such antennas would be a superior design. No so. I've reverse engineered two of these (that I have on my roof) and found them to be abysmal. On some channels, there's more gain in the reverse direction than in the forward. The herringbone log periodic attempt is really quite omni directional with the added detriment of lousy gain. From my numbers, it would seem that these are designed on the basis of aesthetics and manufacturing costs (using identical length elements) rather than performance.
[1] Incidentally, what is the one thing that you can't determine by reverse engineering a product? Answer: design and production tolerances. That's where things usually go awry and why industrial espionage is still popular.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Cute, true, and getting worse. However, the above article is about software abominations, which is quite different from hardware and antennas. Software can be fixed, which is it's own punishment as the fixes are arriving much faster than the products. There isn't anything I've bought with software or firmware, that didn't require an update on arrival.
Not so with hardware. They're not called patches, updates, or fixes. They're called recalls, rebuilds, or warranty replacements, with all the detrimental implications. Software is easy to fix, but not hardware.
So, one would expect that there would be more care applied to hardware design, to avoid the warranty recall experience. That's generally true, but there were enough exceptions to have kept me in business. The generally higher level of quality is probably due to the minor fact that anyone can see if the hardware is malfunctioning. However, software bugs and oddities are not so easy to see or identify. Hardware also requires considerable time and effort to add features, while in software, feature bloat is epidemic. Features and functions get added faster than bugs get fixed, so the inevitable result is a bloated and bug infested product. If that were true for hardware, civilization would have collapsed long ago.
Antenna design has other important advantages. You can't see it work. You can't tell how it works. Product comparisons are almost impossible. Nobody understands the numbers. RF and antennas are indistinguishable from magic. I've often considered going into the antenna business, where the basic plan would be to design maximally weird looking antennas, with marginal performance. If I have time, maybe I'll do some calculations to see how badly it works.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Sorry. I didn't want to reveal the entire business plan. Yes, there will be the requisite inflated claims, contrived testing, invented techy-like terminology, irrelevant testimonials, and insane prices (shipping and handling extra). I'll also try to make sure that my antennas self deteriorate, include an unfathomable warranty, and are delivered from a factory in China that can't easily be located or sued.
Nope. They're dull and ordinary products. My antennas will in colors not found in nature, aerodynamically styled, eco friendly, and sufficiently ostentatious to attract attention, so that everyone knows that the owner overpaid for the antenna. I may even throw in a manual written in proof read English. For a business model, methinks something based on the $1,200 AC power cords might be profitable:
When the market is saturated, I'll recycle the business plan on midnight television. Get rich replacing all your friends and neighbors antennas.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Those stupid little stick-on "antennas" that are supposed to boost coverage to your cell phone. All you do is take out the battery and stick this metalized sticker underneath it to "enhance" the phone's performance. I mean, this baby doesn't even have wires!!
And of course, they do absolutely nothing.
-But people buy em by truckload.
Maybe the business plan here screams designing stickers in the shape of "rabbit ears" for new video cell phone services such as V-Cast, MediaFLO and the like...??
Ummm, no. My crystal ball is at the sorcerers being repaired. My abilities to read minds and predict the future are temporarily limited.
RF is magic. It doesn't matter if it works or not. It just "feels" or "looks" like it's working. Perception is everything.
I don't know about anyone actually paying for one, but every cell phone battery I purchase from Hong Kong, seems to get shipped with one. My guess is they have a surplus and are just unloading them.
Don't forget the little wire screen stickons that go over the earpiece and allegedly protect against RF induced brain rot. Judging by the average persons inability to operate a vehicle while yacking on a cell phone, these don't work either.
It's interesting to note that my first adventure into radio was when I was about 10 years old, and I read an advertisement in Popular Electronics that proclaimed "Turn your house wiring into a giant
1000ft TV antenna". Seemed reasonable to me, so I arranged to obtain one to play with. That resulted in a nasty electrical shock as the TV was of the AC/DC type (no xformer), and the box consisted solely of a "capacitator". Despite my rather violent introduction to electricity, I assumed that anything that powerful was worthy of study. It's been downhill ever since.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
And sometimes it is the final daft last minute cost reductions that contribute to the most annoying product defects and excessive infant mortality. Don't you just love beancounters...
Time to market and first mover advantage is viewed as far more important than stable or fully functional software. Excel 2007 is a fabulous example right now. It can barely chart a few thousand points without keeling over or grinding to a standstill. Its predecessor 2003 is happy with charts containing tens of thousands of points and is an order of magnitude faster for complex graphs. But so long as consumers accept having defective new products shoved down their throats that is what will happen.
There is an interesting corollary to the software game. Unlike hardware, software does not wear out with age. Your requirements may change until it no longer does the required job, but so long as it does what you need you are much better off with an established trustworthy application than the newest gee whiz flash bang premature release.
Same for software development. People get into very strange scrapes that need external skilled resource to sort out very late in the day.
Some are. I have met a few antenna designers who really know what they are doing. Large phased arrays have to be exactly right or they don't perform anything like to specification.
There's much more to the problem than just rush to market. Product life cycles have decreased sufficiently that often several generations of future replacement products are being designed when a product hits the market. The incentive to fix any defects in the current product is lost if someone decides that "we'll just give them the new version, which will be out next month". Why put time and money into fixing a product that obsolete on introduction? (I've seen this happen several times).
Note: I am not a programmist.
Nope. Bad example. Excel is a classic example of my software axiom "Functions and features get added faster than bugs get fixed". The inevitable result is a bloated monster, burdened by useless features, and full of bugs. I haven't actually tried Excel 2007, but if it's as bad as you suggest, I'm sure it qualifies.
The effect is understandable. Functions and features sell products. Bug fixes do not. I haven't seen any retail software package display on the box "Fewer bugs than previous version" as a product feature. Well, actually MS did that when Windoze 2000 was introduced and proudly proclaimed that "it crashes less often". Anyway, if you have limited time and resource, and you have to choose whether to allocate them to new features or old bugs, the choice is obvious. Bugs can always be fixed after product release.
Mediocrity sells. What I find fascinating is that buyers often cite the vain hope that the new version may have fixed some of the bugs as a reason for upgrading. That's also my main reason for upgrading. However, when I find something I like, I stay with it. I'm still running Office 2000 and not having any major issues as compared to those running later versions.
Ah, but there is also "software rot":
Old software just looks old. The surplus stores are full of perfectly adequate, shrink wrapped software, that would totally functional were it kept up to date with bug fixes. However, that's rarely the case, so toss the old bugs, and replace them with new bugs. It's so bad, that at least one company had released new product disguised as an older product in order to convince consumers that perhaps the long history might yield fewer bugs. Free Lotus Symphony:
I haven't tried it but I smell a wolf in sheep's clothing.
Agreed. I'm a mediocre antenna designer and have great respect for those that understand the technology. I read some of the IEEE Antenna and Propagation Proceedings and am often lost in the math and models. However, I was referring to the average consumer of antennas. TV antennas are again a good example. Look at the variety offered and try to distinguish by either observation or specification, which are the best antennas for OTA TV reception. Most consumers can't do that, so they purchase the biggest, weirdest looking, and most gold plated yagi, that's really a fairly rotten antenna compared to a simple bow tie array, backed by a large barbeque grill. Same with the rabbit ears, with the tiny parabolic dish in between, that sits on the TV. The dish does absolutely nothing and is there strictly for looks.
The problem is that sometimes, such weirdness goes too far. I once designed (on paper) a TV antenna consisting of a helical spiral array. Lots of gain, lots of bandwidth, polarization insensitive, but really, really, really big and ugly. It looked like a giant conical ziggurat on its side with a giant barbeque grill base. I didn't have to build one as it was obvious that nobody would want one on their roof. Ugly and fancy sell, but there's a limit.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Also the hours of standby time / airtime is influenced heavily by the efficiency of the antenna. So unless marketing dares to lie, it pays to put some attention to the engineering of the antenna.
Personally I had a pleasant surprise lately. I bought a miniVNA
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After it arrived I started to hook up all kind of stuff in my house. Including the rubber duck antenna of my HAM Standard porto. Initially I thought it was way off in frequency.
Until I put it straight up and held the miniVNA in my hand as if it was a portofone. Suddenly it was exactly on frequency (obtimum in the middle of the band) and very close to 50 Ohm. Wow. This thing must have been engineered, tested and tuned.
"Jeff Liebermann" skrev i en meddelelse news: snipped-for-privacy@4ax.com...
Yes so; My dishwasher made a lot of pretty colours with a circuit board carrying 380V so I went to the spare parts shoppe to get a New One.
What I got handed was a fixpack: A cardboard box with instructions, replacement hoses, cable ties, a small injection pump and some rubber gaskets to be fittes in specified locations to stop water from dripping onto the board and make colours. The new board was coated too with some red-ish thick varnish ;-)
The description and price on the MiniVNA are very attractive. Have you had any unexpected results or problems? Are there any limitations on R and X values, especially for HF antennas? Have you noticed any interference from broadcast signals? Thanks.
No problems. The only thing is that at low levels there can be some small spikes traveling on top of the curves. Keeping it further from my PC improves that. Perhaps due to the plastic housing.
Further it does not measure full 360 degree phase, but 180. This is because an AD8302 is used. But then I find absolute phase reading not that helpful. A bit of cable adds phase as well. Perhaps when the software might progress and tries to compensate it might be more important.
I am not sure on what you mean with limitations on R/X. Anything way off 50 ohm gets inaccurate. Whether this is worse than other simple VNA's I cannot judge. In the Yahoo group
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this pops up every now and then. Different software versions seems to behave a bit different in this respect as well. I am simply hoping it evolves in the right direction over time. I did help a friend with his antenna though. He had some difficulty finding the right settings of his antenna tuner. Partly because his homebrew PA had a tendency to oscillate. We hooked up the miniVNA an within a few minutes we found optimum settings for all bands of interest. Minor adjustments were needed with the PA hooked up (we know the PA is not 50 ohm itself).
With my type of measurements I did not experience broadcast issues. But then it is not as sensitive as e.g. a spectrum analyzer. Also my antenna tests were not in broadcast frequency range (or no strong signals nearby). Do not think of it as the perfect network analyzer. Having said that it suits me fine. Measuring crystals (Q, Rs, frequency), cable length / velocity factor, resonance points, bandpass curves, return loss (range about 0-40dB), having a 1-180 MHz stable signal generator and such make it a very nice device. The software can export data to spreadsheet or a smith chart tool written by another party. Screenshots can be saved for documentation etc. The only thing is you need a computer to use it (laptop will do). A simple PDA program does exist, but I have not yet seen screenshots. Else it might tempt me to buy a PDA.
I guess an advantage is that the software improves over time. Calibration (output/sensitivity curves and DDS frequency) is made a lot easier in the latest version. But still I use several versions depending on what I want to do. Installation can be a bit dodgy as well, but usually people succeed and users are happy. Note I only use the windows software. The linux version seems to be made by more skilled software developers, but I have not used it. So I do not know if it has similar calibration features as the windows stuff.
Thanks for the assessment of the MiniVNA. My reason for inquiring about R and X accuracy is because I want to measure impedance versus frequency at the antenna terminals and use the R and X values to calculate the necessary network C and L for low VSWR. Broadcast station rejection is important when
The design does start with the frequency and the speed of light fro there beyond consumer goods (whom use the shit antennas they can get for .10 cents) there is design. controlling the beam pointing and providing and efficent conversion of EM energy t a voltage you can use to process.
And there is still room for innovation!
go to
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here the typical frequency and size rule of thumb...is broken and 1/8 sized volume is now possible, ad with gain and controlled impedance and beam charactetisitcs, too!
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