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ing in a metal cage on the porch showed no ill
effects from my DXing.
The antenna is grounded with a short length
of four-conductor wire (again courtesy of
Pacific Telephone) to a three-foot ground
rod driven into adobe earth. A 65-foot dual
counterpoise (full-wave at 20 meters) was
tried briefly, but d iscontinued when I d iscovered
that keying up on )5 meters triggered
the fluorescent lights in my slide-viewing
table.
Total COSIS for the system were approximately
$3(for the ground rod). I already had
the antenna tuner and the feedl ine. Ofcourse,
I also already had the awning , sav ing me
some $400 to $500 right there.
Performance
The CLA antenna has been successfully
used on all standard amat eur bands from
10 to 80 meters, and tunes quickly to I : I
(or nearly so) on all of them. It does show a
certain sensitivity on some bands, but on
othe rs it is nearly fl at across the entire
spectrum.
Due to this impressive performance. I o nly
need one antenna, and therefore neve r have to
worry about whether the correct antenna is in
the circu it. I have been known to nab DX
stations while friends were still switching
antennas.
The predicted and measured radiation patterns
for the system are shown in Fig. Ia and
I b. The pattern turned out 10 be a sort of
casual cardioid, with a definite dip towards
the north-northwest. This dip is probably
caused by the signal going directly through
the mobile bome. although we-re no( certain.
As mentioned. the system points almost
precisely east-west, but radiation measurements
show no particular preference in these
directions (or , for that matter, in any others).
However, as of this writing, I have used it at
looW to work all 50 states and nearly as
many cocnmes. Signal reports tend to be
only fair (typically 515-5m, but, after all .
DXCC certificates don't come with special
endorsemenlS for being 20 over 9.
Unfortunately , the system does lack
pointability. Orienting it 10 a certain direction
would involve rotating the enure house,
which would subsequently res ult in major
probiems-especially with the neighbors. On
the other hand , I neve r have 10 worry about
which way my antenna is pointed, since I
have 00 choice in the maner. I can concentrate
on calling while oebe rs are still fussing
over great-circle maps.
Polarizat ion, direction of current. and
phase relationships in d ifferent parts of the
system have not been measured. Neither, unfortunately
, has gain, since r have been unable
to move the antenna 10 a proper testing
facility for precise analysis. However our
guesstimates put the gain somewhere between
-3 and OdB.
Additional Benefits
The CLA antenna requires no maintenance,
aside from occasionally sweeping the
leaves out of it. In fact. no adjustments are
possible , a boon to those ofus who like to just
•
., . 100
Fig. la. The predicted radiation pauem for
the CU.
hook up the equipment and go-althoug h admittedly
frustrating 10 those who feci obliged
10 tinker with their amateur radio gear.
Since there are no moving parts . the re' s
really nothing that can fail. I never have to
worry about my rotor dying with the antenna
pointed south just as lY I comes on the air.
(Of course, I probably won't even hear him
anyway, so I won 't suffer by knowing what
I'm missing.)
The system has the addit ional advantage of
providing shade on hot days-a benefit that
hams with much more expensive (and supposedly
better) multi-element beams certainly
cannot claim.
Backup system
In case my primary antenna should ever fail
(i.e.. fall down). a backup system is kept
nearby (see Photo C). This system is averted
vee. a variation on the more common inverted
vee . Informally, this type of antenna is
known as " rabbit ears."
One problem with the vetted vee is the
e xceedingly high capacitance between the elements;
it's evident that the phrase " dumb
bunny" was not created haphazardly. On the
other hand, the high density d ielectric results
in a high amount of capacity loading, thus
accounting for its ability to resonate eve n on
75 meters despite its apparently short element
lengths.
Unfortunately, the vetted vee system is
more appropriate for mobile operation. It is,
in fact , overly mobile. and keeping it connected
to the radio presents considerable d ifficulties.
Luckily, I have neve r had to use it.
Pos.sible Improvements
Although the CLA system has been working
very satisfactcn ly, several uninvited suggestions
have been made for improving it.
The most obvious is to hook togethe r all the
mobile home awnings I possibly can, to
provide an effectively larger antenna. With
some 800 homes in this park alone , and three
similar parks nearby , the prospects are truly
awesome (or aw ful, as the case may be) .
Better yet , of course, would be a system thai
"
,
Fig. lb. The actual radiation panern for the
CL