Saturday, July 30, 2011



Definitely gonna open up a can of worms here but after seeing so many ill-conceived   antenna questions and articles on various internet sites, I wanted to revisit a few concepts that seem to be written in stone and have become internet folklore myths propagated, so to speak, on your first google search.

Antennas are extremely subjective, even the most advanced phased array or that 700 ft  multiband loop you got up at 100 ft. can fool us into thinking it’s the best idea since Marconi. If you are using a slinky in your attic then build a magnet wire, invisible dipole, strung out to an available tree it’s gonna make your day.
It’s all relative to your experience.
I do not claim to be an expert, just coming from the knowledge gained from building at least 40 wire antennas from 160 to 2 meters over 30 years in multiple locations from stateside to Bahamas, Kuwait and many qth’s in-between.


Sure, if you have a tight space and only one decent support it will do a credible job. HOWEVER, the whole low angle, better DX thing attributed to the inverted vee is hogwash ! UNLESS you can get the center up at least a 1/2WL and maintain a 90 degree angle at the feedpoint wires and keep the ends off the ground 1/4wl, you will be better off with a flat top dipole at half the height 90% of the time. There is one website out there that claims that you are better off with the ends at 2ft off the ground, amazing bad info!


Better than what? The hardest antenna to build in the ham world is an efficient vertical. To achieve the low angle take off is no easy undertaking.
Too much is beyond our control unless you live on an out island in the Caribbean.
Near field reflection, ground loss, and current path return can be maximized by an extensive radial field be it buried or raised. BUT; the far field reflection is gonna determine your reinforced take off angle and signal out there. Problem is most of the time that is beyond our control. Vertical polarization is a worthy goal, I achieved a 20 degree take off angle with 20db of front to back with phased ground mounted shrunken quads but still can only get 5dbi of gain due to low height and  ground losses.


Yep it is a good way to get multiband capabilities with a single antenna, definitely better than coax, BUT, ladderline is far from lossless when used in extreme multiband mismatched conditions, see Tom’s, W8JI, excellent findings on this subject on his website.
Do not assume you are getting your signal, ERP, effectively on all the bands your tuner might be happy with because of the prevailing myth that ladderline will somehow ignore a gigantic mismatch and perform lossless miracles. Does anyone really believe that a 450 ohm feedline facing a 20 ohm or 5000 ohm antenna is lossless?


Somehow this military variation has become the antenna de jour for folks looking for instant reliable close in QSO’s on 40 and 80 meters. Get over it, 90% of wire antennas are already low enough to qualify for this NVIS thing. I for one cannot think of any reason to put an 80 meter dipole at 12ft. to achieve a dependable 20 or 200 mile daily contact. If the propagation is working that day then that will be the paradigm of performance, be it at 10 ft or 40ft. Stick anything you can as high and flat as possible. If you are lucky enough to have supports at 1/2wl high on your band of choice, you might not be able to work your neighbor everyday but that’s why somebody invented skype.


Let’s pop this bubble, so to speak. The wide bandwidth, amazingly efficient myth is everywhere on the internet. It is probably the most over rated extremely heavy monoband wire out there.
Studies have shown, VK1OD and others, what a piece of junk this thing really is. The bandwidth is expanded around 15 KHZ, and actually has loss attributed to that miniscule bandwidth stretch! Seems like a lot of work and extra weight for an antenna less efficient than a dipole at the same height.


I am assuming most people understand that these designs are all variations of wire vertical antennas, some closed loops less dependant on ground conditions but in the case of the 1/2 square, it is nothing more than a two element vertical, low gain, broadside array in desperate need of an excellent ground plane at near and far field to do anything equal to or better than a dipole at the same height. Occasionally it just might outperform a dipole if you have optimum ground conditions and achieve the lower angle takeoff often written of as gospel for any ground conditions.


That big heavy 9 to 1 balun is there to provide a relatively close match on multiple bands by selective compromise placement on the radiator. Nothing wrong with that concept except a lot of wasted power up there, but still better than on the feedline or the tuner in the shack. Sometimes it is nice to have the feedline closer to the shack entry due to available supports. It would probably be my choice if conditions dictated the need and I had 3 strong supports to hold this heavy sucker up the air.


Not really, forget worrying about the orientation unless you get the sucker up in the air around a 1/2wl. Most of the time they will work perfectly fine in all directions if the prop is on your side. The beauty of the good old monoband dipole is it is about 90% efficient when fed correctly and cut to correct length.
Would I put up a rotatable aluminum dipole on an 80 ft tower for 40 meters, absolutely! That’s when it does the directional thing, more a signal to noise advantage in a non gain antenna but worth the investment at the right height.


A little esoteric but my experience on this dictates the sharing of my experience.
This probably is the first and last time I will ever disagree with the master, ON4UN.
IF you are after maximum gain AND front to back the only way to go, at least on thin wire antennas on the lower bands is to correctly phase them into a two element array.
Remember I mentioned antenna evaluation is based on relative experience?
My very first antenna article on Eham many moons ago was about a two element reversible 40 meter parasitic reversible quad. Wow was I impressed with myself until I built a smaller one phased and really saw the dramatic improvement, now I’m hooked on being the first one heard in DX pileups!


I know this one has been beat to death but still annoying and frustrating when a manufacturer or article writer espouses a flat SWR as the paradigm of antenna performance.  Of course beam antenna manufacturers are aware their antenna is not naturally resonant, that’s why there are mucho matching systems at the feedpoint.
SWR means nothing, nada, as far as antenna performance unless it suddenly rises while the wind blew your antenna down.
The only resonant antenna at 50/72 coax feedline ohms is a true 1/2wl dipole up at least 1/4wl. I will leave it to others to better explain what standing waves are, better yet read a few books! EVERY other antenna is gonna be above or below that 50 ohm coax at its feedpoint. How we choose to match this situation separates the signals from the noisemakers.
If you are building your own design, and I suggest you do, have a clue what the impedance should be at the feedpoint. A perfectly built vertical is around 38 ohm, dipole 50/70 ohms, a full size loop around 100 ohms, an EDZ around 5000ohms, 2 element beams around 27ohms.
None of these excellent antennas besides the dipole will have a 1 to 1 swr.
Before the day of 50 ohm transceivers the SWR issue was not the make or break thing it has become today with the modern radios.
Study the facts about standing waves and it will become clear to you that is but one aspect of antenna evaluation and in a lot of situations means a heck of a lot less than what you are actually trying to transmit a decent signal from.


The true test of any antenna is CONSISTANCY and expectations thru many days, months, solar cycles etc. We all do the best we can and face multiple reasons for choosing what antennas we use. I only hope that some of my comments will help some newer hams take the time to study some real antenna theory, not the amazing amount of crummy ideas out there on internet antenna sites that promise impossible results.

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