Mobile HF Antenna Shootout at Oakdale Radio Club 19 /20 Feb 2011.

Compiled by ZS1JHG

HF Mobile Antenna shootout

Uncountable different opinions, numbers of different types and manufacturers.

“Screw driver antenna”, “base loaded”, “centre loaded”, “top loaded”, all has

their pro’s and con’s.

A mobile antenna always is a compromise between mobility and efficiency.

Which mobile antenna and setup on a vehicle is best performing?

This to find out surely is of great interest for many hams. Such evaluations are

only possible under test conditions not easily to prepare. E.g. all tests must be

done at the same ambient environmental conditions (site) using certified HF

signals fed to the antenna via always the same signal source and coax feeding

cable, a certified omni-directional receiving antenna and a professional test

receiver recording the received signal strength of all participating mobile units.

On the end all hams could compare their type of antenna and installation with all

the others tested.

Using a “Rohde & Schwarz Exciter Type RK043” generating stabilized 20mW HF

output on all frequencies between 1.6 and 30MHz, fed to your antenna, a “Rohde

& Schwarz Test Receiver Type ESH3” with readouts in uV, dBuV, and dBm and a

certified calibrated broadband omni directional antenna type SAS-1D made by

ANTENNA RESEARCH ASSOCIATES, INC in Beltsville/USA with a constant gain

factor of 15dB over the frequency range from 300KHz to 1,000 MHz, allows to

compare the efficiency of all mobile antennae installations under scrutiny.

All test results will be recorded and after all tests concluded the best performing

setup will be published on the SARL Forum and the winner will receive an 8.5m

telescopic glass fiber polyester mast of the design recently delivered to 142

ham’s.

A dedicated test site marked “Test Plot” at the grounds of the Oakdal Club, far

from all other vehicles and moving structures and the shack of the Oakdal

Amateur Radio Station ZS1OAK providing best conditions for such an event

which even could be a social gathering for interested hams and their families,

the latter exploring the fantastic facilities of the club, like swimming pool and

children’s pool, restaurant with bar, sport facilities and many more, or just

having a braai.

All ham’s from all divisions are very welcome to take part.

Venue: 19. and 20. February at Oakdal Sports Club

Participants arriving 09:30 for 10:00

Briefing and listing ends 10:30

Testing from 11:00 onwards

ZS1OAK is on standby on the 145.750 repeater for giving directions to the club

Klaus ZS1QO

“ The best of all....".

Preliminary answer : We all won. It was an event out of the ordinary and we

all had a lot of fun.

I still struggle with the results. Its not an easy task. Results from receiving test

and transmitting test in a few cases were contrary. It also was decided to not

only see the technical performance but the design and installation as well. There

was excellent results with one HUSTLER and with another HUSTLER it was

disatrous. Two home brew antennas. One performing well on receive but not on

transmit the other just visus versa.

Antennae without antenna tuner performed well even by qsy plus/minus 20KHz.

Antennae with ATU on 7080KHz showed different results on plus/minus 20KHz.

I am tempted to announce winners, one for best performance and one for

excellent ingenuity of his home brew antenna.

This to decide I shall think it all over and over again. What is your opinion?

Now a little about the transmission/receiving test:

At the dedicated transmission test site installed was a 8.5m long vertical

antenna proper matched to the 50 ohms output of a Rohde & Schwarz RF

Generator delivering 20mW into 50 ohms. At the receiving test site using a

Rohde & Schwarz test receiver type ESH3, connected to a certified calibrated

omni-directional antenna, the field strength of the signal from the 8.5m antenna

was recorded on centre frequency 7.080 and 7.100 and 7.060.

All participants, one after the other, one at the time, moved their cars to the

receiving test site and the test receiver was connected via coax cable to the

respective mobile antenna. The signal strength was compared to the signal

strength of the 8.5m test antenna. These results were recorded. If there was a

request to test the receiving performance on another frequency we changed the

test frequency accordingly.

Best result was achieved with a hustler mounted on the roof of the car without

using a tuner .

After receiving tests concluded all vehicles, one after the other moved to the

transmitter test site (only one at the time). Now the signal from the R & S

Generator was fed into the mobile antennas, both, the one without and with

antenna tuner.

At the test receiver their signals were compared to the recorded figures of the

8.5m test antenna. In average the three test frequencies showed only 1.14 uV

difference between the afore mentioned hustler and an Atas automatic antenna.

Well, the aforesaid long Hustler proper tuned on the centre frequency was better

than the much shorter Atas but the Atas better on the 7.100 and 7.060.

All together there were four Hustlers. One of them with similar installation as

two others fell though by very bad performance, both, transmitting and

receiving. This possibly due to corrotion inside the antenna and or thirty year old

coax cable, whilst the others did fairly well.

It is my opinion backed by the test results that the roof-mounted Hustler and

the home brew antenna, see Dirks picture, won the "Shootout" on comparable

level.

As prize was set out one of the 8.5m telescopic mast already delivered to 142

hams in the recent past. I leave it in the discreation of the over all winner to

decide taking the mast or to prefere a cash amount in the value of the mast

which is R 695.00

It is my opinion that ZS1AFU should be the lucky winner. If I do not

receive any objections until coming weekend it shall be final and OM Deon

Lamprecht may contact me by e-mail: zs1qo@global.co.za

It remains to thank the Oakdal Club for their hospitality and Kobus ZS1K and

Hank ZS1VDP for their technical assistance manning the transmitter test site and

coordinating the tests. Last but not least I thank all who participated

enthusiastically. …Klaus ZS1QO

Well, we didn't have a rotating platform with built-in hydraulic lift. What we had was

some first class test equipment and an idea to do something out of the ordinary and we

had numbers of interested mobile radio enthusiast.

The latter is the point. - Mobile Radio.

It was clearly expressed that we shall not evaluate an antenna type of whatsoever make

but the entire mobile antenna installation. I am certain if I would have used my 8.5m

long vertical antenna designed to fit into a specially made bracket on my (Jeep) towbar.

This antenna would have performed best, but it hardly could be qualified as a MOBILE

ANTENNA.

The requirement was to use an antenna you could drive safe on a public road with lets

say 100Km/h or off-road.

Another interesting aspect, at least for a few non participating "experts", questioning the

sense of using only 20mW as test signal, and claiming it as useless due to the "noise

floor" and QRM proved non-substantial. All receiving tests performed with an RX set to

200Hz bandwidth and 10dB attenuation made evaluating the received signals as simple

as (you name it) . On other occasions, in CW, I had Q5 communication over 130Km

as the crow flies on 40 meters with a 7,85m long ships whip on top of my 20 feet steel

container I am using as shack and workshop, and last but not least, look at the beacon

on 7.025 . QRP is fun but not only this, it allows to achieve contacts without making

ESKOM rich. Many hams called for a repetition of this venue. Surely it will be done. And

all what we learned during the first one will help to improve the quality of the next one.

Unfortunately extented test, i.e. rotating the vehicles at least in four directions, is very

time consuming. We just managed to test twelve units during the whole day by placing

the vehicles always in the same direction and antenna facing the transmitting site

exactly on the same (marked) spot. Maybe somebody provides a two-wheel flatbed

trailer. Turning it with the car on top would save a lot of time and the test would be

much closer to installations as can be seen on official test sites.

Finally please note: Nobody claimed that a Hustler is the "best antenna" but ZS1AFU's

installation proofed to be the best performing.

Klaus, ZS1QO

ZS1AFU Homebrew Screwdriver Antenna

At the Receiving Station:

On the LHS John ZS1JHG , then Fred ZS1FCS on RHS in chair Klaus ZS1QO (test engineer) in black

shirt filling in forms Deon ZS1AFU ,with sunglasses ZS1K Kobus

Some of the vehicles waiting for the Receiving Test at the HF Mobile Antenna Shootout.

The roof mounted Hustler best on receive .

Homebrew antenna

At the Testing Station :

HF Mobile Antenna Shootout Winner ….Ford Ranger with homebrew Screwdriver Antenna of Deon

ZS1AFU bumper mounted.

VW Touran with Yaesu Atas 120 motorised antenna lip mounted.

Toyota Hilux with 102 CB whip

Outbacker clone multiband antenna

THE TEST EQUIPMENT

The Receiver : Rohde & Schwarz ESH 3 receiving a signal from a mobile antenna on 7.100 Mhz

The Exciters : Rohde & Schwarz Signal Generator SM5 and above RK 043

The Receiving broadband antenna : ANTENNA RESEARCH ASSOCIATES

Photos taken by Dirk ZS1VDB and Deon ZS1AFU

The Cool Uncles and their Radios

Radio has many facets to the hobby

A workshop to test how mobile radio antennas perform was presented on Saturday 19 February by

the Oakdale Amateur Radio Club. At the gathering antennas of mobile stations , in this case motor

vehicles were tested using specialised test equipment and the antennas were calibrated.

Kobus ZS1K a member of the club said that amateur radio is more than just two people chatting to

each other. The other aspects include public service ie sports events , emergency comms use of

digital modes via a laptop computer. Kobus then explained how the mobile antennas were tested

to establish their performance. ( translation summary by ZS1JHG)

So what did we learn ? Read the article Antenna Shootouts to find out.

Antenna Shootouts

By Alan R Applegate K0BG

Introduction

In the April 1960 issue of QST was a short blurb on page 57 about the second annual

California Mobilecade and Field Trials, to be held in San Luis Obispo. To my

knowledge, these were the first antenna shootouts. The rules make very good

reading, and one standout is the fact the receiving antenna was to be located 4,900

feet away! Additional stations 10 to 100 miles away were going to be used to verify

the closer-in measurements. Keep this fact in mind while reading the remainder of

this article.

The result of the third trial were published in the July

1961 issue of QST. Included with the article was a

montage of 16 photos. Probably the most interesting fact

was, almost without exception, each entrant's antenna

sported a cap hat. One of those was nearly identical to

the one I currently use.

Within the last two years, there has been a lot of

malicious palaver over the trials, or tests if you please,

carried on by the 3905 Group. Most of this was

promulgated by one person who also happens to manufacture a remotely-tuned HF

mobile antenna. He believes, as do others, that the tests results are inherently

accurate. They're not, and this article explains why they are not.

However accurate they may or may not be, they are representative as a whole, as

long as you think outsidethe box! This will become evident, as you read the

remainder of this article.

Basics

One of the most popular mystery novels of all time, gave away the whodunit in the

first few sentences. It was the story behind the perpetrator which made the novel

what it is. I'll do the same thing here by stating; "Antenna shootouts

prove (almost) nothing!" Why they don't is very difficult to put into simple, easily

understood terms.

Not too long ago, I made reference to two cars with two different antennas, where in

switching the antennas would improve the performance of both mobiles. I even

predicted at least a 3 to 5 dB increase in both. Why this is so, it part of the mystery

we're trying to solve here.

Part of the problem is understanding the factors which determine an antenna's

efficiency, and this article, Antenna Efficiency, covers the basics. But it is more than

just efficiency per sé, it is antenna performance which counts. Unfortunately, very

little thought goes into antenna performance at purchase time. Nominally, the

choices are made based on ease of installation, including size and length, and to a

lessor degree on purchase cost.

The best quality, highest efficiency, antenna money can buy, isn't any better than the

ground plane it is mounted atop. As pointed out in the aforementioned article, and

others on this web site, mounting methodology (where and how) is the prime factor

in reducing ground losses.

One very important point needs to be inserted here. A vehicle is not a ground plane,

but rather acts like a capacitor between the antenna and the surface under the vehicle

which acts as the ground plane. Since the surface in question is a poor conductor of

RF, ground losses occur. The term ground plane in the following text is therefore a

bit of a misnomer, but is used to differentiate it from DC and RF grounds.

Mobile HF antennas come with a variety of coil sizes, overall length, diameter, and

where within the antenna the coil is located. For any given antenna, coils mounted

higher up require more inductance to obtain resonance, than ones mounted closer to

the bottom. What's more, the optimum position of the coil is directly related to how

much ground loss there is, and to a lessor degree the coil's Q.

Ground losses aren't easy to calculate or measure, and neither is coil Q, especially

when the coil is mounted within the antenna. Making matters worse, we really don't

know, at least with certainty, the radiation resistance (Rr). One thing we do know, Rr

is a function of length. Double the length of the antenna, and the Rr increases by four

times. This means, that a 9 foot antenna will have twice the Rr as a 6 foot one, all else

being equal.

Another issue which comes to light quite often is using NEC and EZNEC to predict a

given installation's efficiency. While these programs are good for what they are, they

do not predict ground losses accurately. When folks enter the data manually, they

almost always under estimate the losses (and over estimate coil Q). One of those

overlooked losses, is the whip itself, as we'll soon learn. The Antenna Efficiency

article does cover a methodology which compares calculated to empirical

measurements to estimate an antenna's efficiency, but that's exactly what it is, an

estimate. One unfortunate aspect of calculating efficiency, folks tend to take the data

out of context, and apply it where it really doesn't fit. Apples to oranges as they say.

There's another important item with respect to ground losses, and that is consistency

in ground conductivity. While the mean deviation over a large statistical area may be

fairly narrow, over a small statistical area the mean deviation can be rather drastic.

What's more, the mean deviation in soil conductivity changes as the moisture

content, and surface temperature changes. In fact, the changes are often great

enough, that you can measure the difference in input impedance between morning,

and evening. I have never witnessed a shootout where this factor was considered, or

even mentioned!

Rudy Severns', N6LF, wrote a series of white papers on the effects of ground loss. His

empirical testing confirmed an important fact about vertical antennas. To wit; Any

practical ground system will not affect the radiation angle or far-field pattern! The

ground system around the antenna does nothing for the far-field pattern except to

increase the power radiated for a given input power.

With the last two paragraphs in mind, there is one more factor to consider. Every

single object in the near field has an affect on the antenna—and its measured

parameters—within that field. Those objects may be trees, bushes, vehicles, other

antennas, signs, billboards, people, you name it, all will have an affect.

The Art of Abstraction

The term abstraction refers to the process of considering something independently

of its (other) associations. In a recent post oneham.net, Todd Moore, K1TM, said it

best: "Antenna shoot outs crack me up. We live in a world where it is the complete

system that counts and the shoot out is trying (to) extrapolate the performance of

the antenna from a measure of the system and none of the systems have been

normalized. They are indeed a very unscientific comparison."

The key word here is, normalized. In fact, most shootout organizers go out of their

way to make sure they're not, albeit unintentionally. One very popular way to

minimize the changes in ground loss between vehicles, is to use just one vehicle as a

test bed. All of the antennas under test are then mounted on this vehicle. Aside from

the mounting logistics, this doesn't address any issues with respect to ground losses

versus coil position; the factor I was alluding to in the second paragraph of

the Basics section.

The next question should be, where on the test vehicle are the antennas mounted? If

the mounting position is low, trailer hitch mounting for example, then the antenna

with the least mast diameter is going to have an advantage. In simple terms, the

larger the mast diameter, the more shunt (capacitive) coupling to the ground and

vehicle body becomes a factor. You can't measure this coupling with any degree of

accuracy, so it is typically ignored. It should be noted that you can easily measure the

increase in input impedance caused by shunt coupling, but not shunt coupling

(capacitance) directly.

I should add here, that the shunt coupling increases with increasing frequency. As a

result, antennas mounted close to the body become less efficient as the frequency

increases, which is the exact opposite that one would otherwise conclude. If one

wanted to address this issue, then multiple measurements (multiple bands) would be

necessary. I've not seen this factor considered either.

One obvious need is a calibrated RF generator. Ideally it would be battery powered,

and exhibit a long-term stability of at least one-tenth dB. There isn't an amateur

transceiver on the planet that's this stable, yet most shootouts employ one.

Irrespective of the use of a wattmeter, the reliance on an amateur transceiver as a

repeatable, calibrated output source is pure folly.

You also need a calibrated receiver. Here too, you cannot rely on an amateur

transceiver, no matter how you go about it. This includes the use of switched

attenuators, and padders of any kind. Perhaps not so obvious, most transceiver

readouts vary with ambient temperature changes with no correlation between them.

Most modern transceivers are capable of receiving very weak signals. For example,

the Icom IC-7000 will produce a S+N/N ratio of 10 dB (SSB, 1.8 to 30 MHz), with as

little as .15 uV. However, the vast majority of the time, band conditions require

signals much stronger than this to produce the same S+N/N ratio. How strong is the

issue, but even more of an issue is the fact band conditions change very rapidly,

irrespective of the sampling period (minutes, hours, or days). These changes affect

both near and far field signals, and cannot be normalized.

And what about the antenna? Not the antenna under test mind you, but the one

you're using to transmit with (or receive on)? The first question is, why do most

shootouts use a loop receiving antenna? If you know anything about antenna

patterns, you sure wouldn't be using a loop! Especially one with an unknown

impedance. Keep in mind that amateur transceivers are designed to transmit into a

50 ohm load. That fact does not mean the receiver is also 50 ohms. In fact, most

aren't. As a result, the change in signal strength caused by a variation in VSWR can

easily exceed the measured difference between the various antennas under test. If

you doubt this premise, you can empirically test it with a stepped attenuator and

calibrated signal generator.

At the onset of this article, I mentioned antenna performance, rather than gain (or

lack of it). The reason is simply this; While thereciprocity gain rule applies to all

antennas, transmit versus receive performance does not! This is especially true of HF

mobile antennas where the body of the vehicle distorts the pattern. Albeit

considerably less than most folks believe, the difference is enough to negate any

single point of measurement scheme, no matter the style of the opposing antenna!

There are additional problems hidden in the last two paragraphs. Considering the

receiver's input impedance, the antenna's capacitive coupling and input impedance,

and the distortion in the antenna's pattern caused by the body, there will be a

difference between transmit and receive signal strengths, all else being equal. This

fact could favor one antenna over another, irrespective of their quality, perceived or

otherwise.

As mentioned in the Antenna Efficiency article, Dr. Belrose, VE2CV, authored an

article for the September 1953 issue of QST (page 30). An updated version appears in

the ARRL Antenna Compendium #4, starting on page 83. The established ground

plane losses based on the original article are still used today (2 through 10 ohms, 10

meters through 80 meters, respectively). However, poor mounting techniques can

easily double this, and remember, ground and shunt losses can't be measured

directly.

Taking all of the variables into account, it is evident that normalizing an antenna

shootout is almost an insurmountable task. That said, there is some data one can

take from those shootouts albeit general in nature. First, the antennas which win are

almost always mounted in the center of the roof. The main reason is, ground losses

are at a minimum. What's more, they're usually longer than local conditions would

otherwise allow. In other words, they're there to win shootouts, not to drive around

with. By the way, this was addressed in the original field trails, as one of the rules

stated the antenna had to be on the vehicle during the drive to the airport where the

trial was carried out.

Almost as good are those well mounted atop quarter panels or bed rails. Then there

is usually a big measurement gap (no middle ground seemingly). These toward-the-

bottom-of-the-list antennas tend to be spirally wound and/or short and stubby, and

mounted on lip type mounts.

Probably the most glaring data is this fact; antennas mounted on trailer hitches and

frame mounts (low to the ground), are typically at the bottom of the list, regardless of

their overall length. Adding a little insult, most are heavy antennas with large

diameter masts. All of these factors increase apparent ground losses, and are

reflective in the (unmatched) input impedance. As John Belrose, VE2CV, stated in

the aforementioned Antenna Compendium #4, "There is more to consider than

appearance and convenience when installing your HF mobile antenna, since the

frame and body of the vehicle are a part of the radiating system."

There are some variances of course, especially when cap

hats are used. However, far too many folks are led astray by

the change in input impedance when they install a cap hat.

Thinking, of course, that the Rr increased, when in reality

the Rc losses increased (they're both part of the total input

impedance). You can generally say they do increase

efficiency, but that largely depends on implementation.

For example, too low (close proximity of the coil as shown

left), and they're a detriment, not an asset! Small ones, no matter how they are

configured, aren't worth the effort. Putting all of this another way, cap hats are

(almost) always too small in diameter, their spokes are usually not electrically

connected, and they're typically mounted too close to the coil.

If you want a cap hat to work correctly, it must be at the top of the whip, at least as

large as its height above the coil, and the ends must be electrically connected.

Tech Talk: Since this article was originally written, I have added one specifically

about cap hats. However, there are a few points which need to be emphasized with

respect to shootouts.

First, any cap hat will exhibit the same capacitance affect qualitatively, no matter

where within the antenna's superstructure it is mounted. And, the changes seen in

the input impedance will be about the same; it will increase! Whether that increase

is caused by an increase in radiation resistance, or by a reduction in coil Q, depends

on the implementation of said cap hat. Let's look at this from a slightly different

angle.

Assuming we have two, absolutely identical antennas, replete with cap hat

installed. It really doesn't make much difference if the cap hat is correctly, or

incorrectly implemented, although the affect is greater in the latter case as will

become apparent. We mount said antennas on different vehicles, but with identical

ground losses (a rare case indeed). Could we therefore assume the measured results

would be the same? The answer is no! If you read the cap hat article, you'd already

know the answer, but here's a hint; it is the difference in capacitive loading between

the antenna structure, and the body of the vehicle it is mounted atop. This fact adds

a level of complexity which can't be normalized, because you can't measure the

coupling directly. This is also why, multiple, and large tubular cap hats are a lousy

idea! It should also become apparent why large cap hats should be mounted as far

away from the vehicles superstructure as mechanically possible.

Lets look at this a little deeper. Efforts to build cap hats in elongated configurations,

whether they be bent into circular shapes, box shaped, or otherwise spread out over

the length of that portion of the antenna above the coil, they will be less than ideal

performers. Again, where we want the extra capacitance is as far away from the

coil structure as possible.

Lastly, consider this; If a standard, 102 inch, CB whip will out perform any cap hat

design, then the design or the implementation of the cap hat is suspect!

Esoteric Variables

As alluded to above, the mean angle of radiation (point

of maximum power) doesn't vary with the amount of

ground loss. However, the power at any given take off

angle does vary as can be clearly seen in the chart at left.

Since the receiving antenna is at a fixed height, a case

could be made wherein a winning antenna would actually have less low angle

radiation, than a losing one. The question then would be, which one is a better DX

antenna? The answer is moot of course, but it does add one more variable to the

equation.

It also exemplifies (one reason) why antennas have different levels of receive verses

transmit performance. Please note, I didn't say gain (or lack of it). This concept is

difficult for some to understand, even when they model their antennas in EZNEC.

Again, this harkens back to ground loss figures, which are almost always under

estimated, even by the well informed.

Less obvious is the need to measure antenna performance on more than just one

receiving height. While I realize the added cost, and record keeping these multiple

measurements would entail, the results from such tests would bring us closer to the

real winner! This is the reason why the organizers of the earlier Mobilecade and

Field Trials, backed up their close-in measurement with ones made many miles

away.

Probably the most misunderstood variable is the permeability of the materials

making up the antenna, especially the whip. Whips are made up of 17-7 stainless

steel which has a relative permeability (µi) of 120. This compares to copper or

aluminum of ≈1. What this means is, the resistive losses in an 8 foot CB whip on 80

meters is just over 2 Ω, or very close to the radiation resistance (Rr) of a 10.5 foot-

long antenna! For more information, read this web page written by Owen Duffy,

VK1OD.

Esoteric Truths

A major design faux pas, is to use large, metallic end caps, and place them within the

field of the coil. Doing so greatly reduces the coil's inherent Q, just like cap hats do

when they're mounted to close to the coil! In one design, there is a large, aluminum

shorting plunger which slides up and down within the coil's superstructure. Besides

the additional losses incurred by short tapping the coil (shorting out unused turns),

this metal mass causes the coil to operate very close to its self resonant point, thus

further increasing coil losses (reduced Q). At some point, these Q reducing

factors add up, and the Q effectively becomes zero. At that point, the coil starts

acting more like a rather lossy capacitor (operating above self resonance) than an

inductor. At which point this occurs in any given antenna design, depends on a lot of

factors, and ones which aren't easy to measure or calculate. They aren't easy to

comprehend either, unless you have a fair understanding of how loading coils

behave.

The Antenna Efficiency article lists the parameters required to achieve an efficient

design; at least as efficient as the inherent design constraints allow; overall length for

example. Or the use of a cap hat. It is difficult for some people to comprehend the

notion, that a lowly hamstick could out score a well designed, sturdily made, remote-

controlled, HF mobile antenna. Yet, it does happen, and for good reason.

All of this points out yet another esoteric truth, and that is, mobile HF antennas are a

lot more complex than a synergistic assembly consisting of a mast, a coil, and a whip.

Design one correctly, and you have a winner. Design one incorrectly, and you have

the proverbial dummy load on a stick!

Conclusion

As mentioned above, you must view every component, especially the unknown ones

(variables), as part of the overall system. When you don't, the differences between

individual antennas, measured in a few micro volts or tenths of a dB, becomes very

suspect. It might be more meaningful if shootouts rated antennas in a tiered system

(poor, good, best for example), but that's not likely to happen.

If there is but one thought to take away from this article, it is this; Reducing ground

loss (and to a lessor degree, shunt capacitance losses) is the key to improving

efficiency. While you can't measure it directly, you can measure a change in ground

loss by using an antenna analyzer, but you still have to be careful. That is to say,

assume nothing you can't measure and/or compute directly.

Article reproduced per kind permission of Alan R Applegate K0BG (email between ZS1JHG and K0BG

dated 25/2/2011).