[Elecraft] Antenna Musings (was EH antenna...)

[Larry Weaver]

At 09:59 AM 2/23/2003, you wrote:
>.....
>I am NOT suggesting that people who hook up a new antenna and work
>fantastic DX with it are lying, but I am saying that the "real world" is
>too variable to collect valid data about one antenna being better
>without carefully-controlled conditions where antennas can be compared.

During my working life, I dealt with antennas at frequencies where testing 
in an anechoic chamber was possible. Even in such a highly controlled 
environment results were sometimes questionable. When the antenna was put 
in its real environment, it usually performed differently. We can approach 
that kind of test with field strength measurements much like those 
performed by the HFPack group (http://www.hfpack.com) who seem to be using 
a good method although I haven't looked at it in detail as yet.

Most amateur radio antenna comparison is anecdotal (especially in ads), not 
scientific, which is OK so long as it's not confused with a definitive 
answer. "I worked the world on my Gotham vertical." (Remember the Gotham 
vertical?)

An example of anecdotal performance is my experience in the ARRL 160 meter 
contest in December. I live on a small lot which makes a 160m antenna 
problematic. Fully subscribing to the idea that "any antenna is better than 
no antenna," I put up an inverted-vee, of sorts, which was 30 feet high in 
the center with most of it wrapped around the house at eave level. I was 
able to work the east coast and Hawaii from Southern California. Sunday 
morning, I got up and made several more QSOs, one in Texas. Being a 
temporary installation, I went out to take the antenna down only to find it 
had fallen down during the night. Those final QSO"s were made with the wire 
laying on the ground. I suppose I could sell it as a stealth 160 meter 
antenna at a huge price since I have confirmed QSOs saying it 
works--"works" being a relative term.

The antenna's environment is an important factor. Many of us probably dream 
of huge Yagis on tall towers. Yet the experience of Team 
Vertical  http://www.k2kw.com/  says a vertical in a salt water environment 
beats a Yagi. Is a vertical better than a Yagi? Not at my location on a big 
chunk of limestone in So Cal but it is on Palmyra Island or the right 
location in Jamaica.

Another variable is what you want to accomplish with the antenna. Until new 
laws of physics are discovered, the bigger and higher the better, as Ron 
said--up to a point. For antennas small relative to a half wave (or 
quarter-wave for a monopole vertical), that is definitely true. The low 
radiation resistance combined with losses in the matching system leaves 
little power radiated. A 20 meter ham stick is consistently better than the 
Yaesu ATAS on my vehicle. On 15  & 10, they are comparable but not as good 
as a longer antenna.

An antenna can be too long. When an antenna reaches multiple half-waves in 
length, nulls appear in directions that may be important to you. Oriented 
properly, however, it can have gain. Although it has the reputation of 
being a multi-band antenna, the G5RV was designed to provide gain on 20 
meters (see G5RV's article in ARRL Antenna Compendium One) where it is 1.5 
wavelengths long. It's multi-band character is a result of the low loss in 
the open wire feedline used for matching on 20.

An antenna can be too high, depending on ionospheric conditions--that's why 
the "big guns" have stacks of Yagis that can be switched into different 
configurations. Sometimes the lower Yagi works better than the higher ones. 
NVIS antennas are an example of a low antenna (10 - 20 ft) which will 
perform better than a very high antenna out to 500-1000 miles.

A "best" antenna doesn't exist in a global sense; what is best depends on 
your QTH and what you want to accomplish. The best antenna is the one that 
radiates the high percentage of the power you put into it in the directions 
you want it to go. This is especially important when you are operating QRP.

Take a look at "Rules of Thumb for Beginners" 
http://www.fix.net/~jparker/norcal/features/bgnsant.html  and L. B. Cebik's 
pages http://www.cebik.com/radio.html  (especially "Antennas from the 
Ground Up" near the bottom of the page) which is filled with antenna 
comparisons using NEC analysis.

In most cases a Home Depot special will outperform many very expensive 
commercial antennas using gimmicks to attract customers, small size, and 
claims without proof. My favorite portable antenna is a 20 meter dipole 
made from a piece of 300 ohm twinlead that I saw in QST several months ago. 
By adding pieces of wire to the ends I'm on 40 or 80 meters. It rolls up 
easily and away I go. It works better than a commercial product I own and 
its price was one-hundredth the cost of the commercial antenna.

73...Larry N6TW