Contact us
 Install Instructions:

Home page  -  Contact us  - Products

Understanding the Cap-L design Theory
The future of Antenna Technology   About gain

 Over the years history has shown that man does not like to have his theories challenged.  He doesn't want to know or hear about change. This is only natural to a certain extent.  Even today, after many users with my antenna's talking all over the world, there is skepticism.  The proof is in the operation, not calculated figures.  At some point, I'm sure someone with a larger budget than mine will setup an antenna range and prove once and for all that these antennas work as well if not better than a half wave dipole.  People with 1st Class FCC Commercial Licensees have compared them to dipoles and G5RV's.  My antenna has proven to match their signal strength transmitting from the same location at the same time with the same contact and power levels.  And my antenna was providing a 2 S unit lower noise figure at one location. They are typically 1 or 2 S units quieter than a dipole despite being vertically polarized. (They can also be noisy if you have a lot of vertically polarized noise in your area.)  The quiet feature is a normal function of a high Q antenna resonant on the band of operation.

No one ever stops to think about current antenna technology.  They simply read it from a book and assume those are the rules.  Today physics can come up with a pretty good explanation of what electricity is, but they still don't know for sure. Imagine that.  Physics doesn't have all the answers.  Today people are discovering things that go against all textbook thinking.  It's all over the internet.  Google the word "captret capacitor" and read about one.  Gravity can, and is, being defied by people making devices from toothpicks and high voltage in their own home without a physics degree or even an engineering degree. Google "lifter project" if you don't believe me.

I accept that its hard to believe a 2.5 foot long antenna on 40 meters can do so well against antennas much larger.  But the fact is, it is true.  Believe it. One customer has worked Israel, Italy, Australia, Philippines, and other parts of Europe with only 100 watts on 40 meters (including Russia) with a Survivor 1SM40-2 only 20 feet off the ground.  Others are checking into daily traffic nets every day with solid contacts repeatable each and every day.

Is This REAL?
  Many questions and statements are being made about these antennas being fake or a hoax.  Lets update things a little. Current antenna technology is based upon apeture or size in relation to the speed of light.  That is, the length of the antenna is based upon how fast electricity travels down a wire at the frequency of operation.  This is old school thinking. 
Where does it say that you have to have an antenna of a certain size?  The antenna books say you do...

Keep in mind that with very few exceptions, we are still making antennas based on 100 year old technology.

This design cannot be modeled with current antenna modeling software because it is not designed using any of the equations those programs use to determine performance.

1st rule of antenna design is: All antennas must have a return path, similar to a magnet with both a north and south pole, same thing for an antenna, no exceptions, period..
2nd rule of antenna design: All antennas must be an electrical 1/2 (one half) wavelength in order to perform well...
These rules exist based upon 100 year old technology and experimentation.  Decades of experimentation and trial and error have gone into these rules and many attempts to break them have failed.... with the exception of...
Only two designs ....
The so called 'magnetic loop',... and the design I call the Cap-L
The loop has been well documented so I won't go into that here.

 Some say "Its Just a T2LT antenna" aka coaxial vertical dipole.
The Primary complaint I here others say about this design is that its not radiating from the 'little stub' on the end of the coax, but the coax itself! AKA the delay line... That is what they say, simply because they've never seen one and it Looks like my design, a little...  But, the calculations used to make Survivor antennas, are NOT based upon conventional antenna design formulas, the T2LT is.  The coaxial dipole is simply a piece of coax with the top 1/4 wave of the jacket stripped and the lower 1/4 wave jacket is the other side of the dipole.  You need a choke at the bottom to terminate the lower length, and that is similar to my 1SM series, But.....

I have proof that the coax is NOT the Primary radiator.  I have successfully built and tested a version of the Cap-L that does NOT HAVE A DELAY LINE..... and it works equally well as its older brother...  So now we know  that it works as advertised and not as some people assume.   There are simple tests you can do with the basic antenna to prove that its not radiating from the delay line too.  You can bury the delay line,  or you can change orientation of the antenna and watch the signal vary because of the polarization shift, all the while the delay line is in a fixed position.  It's too bad that people become educated beyond thier ability to understand.  When you see performance right in front of your  eyes and deny it,  well I believe its called some form of insanity.
All I can say is don't let your knowledge get in the way of learning.

Any antenna is a transducer, or coupler to its medium.  In this case the medium is what I refer to as 'space' or 'either' for lack of a better term.   Therefor all antennas 'couple' your transmitters energy into space. (And the reverse is true for your reciever)

How efficiently the antennas do that (radiate), is subject to a lot of debate.  The most commonly accepted idea is straight from the engineering books covering coupling power from the load to source.  It says that the most efficient coupling occurs when the most power can be delivered to the load.  This condition is usually met when the source and load impedances are an exact match. 

Trouble is, what is the exact impedance of 'space'?
For many, the commonly accepted answer is aproximately 377 ohms.  Wiki Link here  This number is based upon choosen values in some of the equations. (see bottom of wiki) These numbers represent, I'm sure, be best guess based on available data at the time.  I suspect that these values are in error because the equations are based upon a little understood principal of radiating electromagnetic fields.  Sure there are many formulas that chart time, intensity and direction of these fields but these formulas are also based upon observations of waves traveling in other mediums like water and light in a vacuum.  The truth is, NO One Knows Why this radiation radiates!  Ask anyone you know, professor or engineer "What causes electromagnetic radiation to travel from one place to another?"   They don't know.  The point is, we are dealing with, on a daily basis, communications based upon a radiation that is poorly understood.  So, based upon "choosen" numbers for equations and the lack of knowledge of why this form of radiation even travels,  I suggest to you that there is a huge area of learning yet to be discovered.  After all, we are all still driving cars based on 100 year old technology.

So if we take another look at the coupler idea, then maximum energy transfer should be when an antennas impedance matches 'space'.   Without making this too confusing, even the antenna designers will tell you that antennas like a dipole have a varying impedance all up and down its length.  It just depends on where you connect to it as to what impedance you get.  So the center fed dipole of 72 ohms or the vertical with 38 ohms, are only representations of "Feed Point" impedances and have nothing to do with the coupling to space.  With one exception,... They must be coupling to it poorly, but at least coupled, because the impendance of these antennas is a constantly varying value all along its length..
One Last Thing:  Technology has documented the "Feeding" of an antenna extremely well.  But that has very little to do with the actual  energy transfer to space.  Why?  Because this impedance matching issue (to space) is totally ignored (in basic antenna designs), thats why.

But what if you can connect to space with a coupler that is more closely matched to the impedance of space?  By the way, couplers are simply designed to 'couple' the signal, and size is not usually considered as important in the design.
This is what the Survivor Antenna does, it couples to space.
And the proof is in the performance:  Measuring gain of slightly more than 2dbD over a conventional ground plane antenna made with 1/4 elements tuned to resonance, my  antennas have consistantly shown more signal a.k.a. gain.  As measured on a Motorola commercial service monitor with tracking generator and spectrum analyzer.  Same distance, same coax, same elevation, same surroundings, same power level for both antennas.
I didn't say I knew what the exact impedance of space is.
I just know that the Cap-L works, and it works well.

So basically, the Cap-L functions like a coupler, just like any small transformer with fields radiating from it, and orientation is important. [Even an iron core transformer has fields radiating from it] I build them to operate as verticals in thier basic configuration, but they can be mounted horizontally for NVIS or EMMCOMM work.  That is,  high angle sky wave comms for close in contacts.  It's been done.

The 1SM versions for sale here are capable of high performance for thier size.
If you're wanting a design that renders high performance in a small package, this is it.

Reference:  Note that this design could not have been possible without the help of my good friend Arthur Wentz, DL7AHW who has freely contributed to my design by providing base calculations and dimensions.  Arthur consulted two physicists for help in the design. You can google his site and find information on how he builds a version of this design.  Arthur has spent many hours on these antennas and has been copied many times.  The microvert and roomcap designs are modifications of his design.

Tom Brent

Home - Contact me  - Products - Photo's