Testing Two "KAZ" Squashed Delta Antennas
by John Bryant
I was really excited when veteran
MW DXer Neil Kazaross began using the EZNEC antenna
modeling software to optimize various large loop
antennas for MW DX use. As far as I know, most of
the previous work with K9AYs etc. has been optimized
for the 160 meter radio amateur band.
The first design that Neil actually
constructed was what he has been calling a "squashed
loop". This design, with a 1 to 4 "aspect
ratio", is one that the modeling software shows
to reject low arrival angle signals from the backside
even better than the classic equilateral pennant/delta.
The dimensions of the loop were 10' high by 40'
long. For convenience, I have come to refer to this
antenna as a "KAZ-10x40" or just the KAZ.
I've operated a four-loop K9AY
antenna for two years now, both in my winter home
in Oklahoma and at my summer cottage on Orcas Island
north of Seattle. I'm interested in finding an even
better antenna than the K9AY for use in both locations.
In Oklahoma, I DX Mexican MW
stations and the primary concern is the rejection
of unwanted co-channel signals. Gain is not so important,
since signal levels, in general, are quite high
during the prime DXing hours. In the Pacific NW,
my main interest is DXing Trans-Pacific MW signals.
There, gain is king, since the majority of those
very weak signals are almost alone in between the
10 kHz channels of the North American stations and
since Trans-Pacific conditions are often extraordinarily
I've tested quite a few antennas
over the years, often with well-known Lowfer, Bill
Bowers. He has a wide array of laboratory-grade
equipment. We've both pretty well concluded that
it is impossible to measure the actual F/B ratio
of an antenna on MW.
We usually work in the very middle
of the day to eliminate as much ionospheric skip
as possible, but we still have great difficulty
finding stations that are totally alone on their
channel to use in the tests. Even when there seems
to be no other station "in the null" of
the target, the antenna is still likely receiving
several weak carriers, thus partly filling in the
null and reducing the measured F/B quite significantly
over the absolute value determined by the antenna
configuration. We've found that doing direct A/B
comparison tests between two or more antennas simultaneously
tends to give us a more useful idea of which antenna
is performing best. Since my semi-permanent K9AY
is in a pasture with plenty of room to spare, I
decided to try both methods of testing.
My K9AY is a classic equilateral
delta, 28 feet on a side, with the lower wire about
1.5 feet above ground. My KAZ-10x40 was mounted
on a piece of ABS plastic pipe, with the apex at
11 feet and the lower (40 foot) wire at about 1
foot above ground. The KAZ-10x40 was constructed
of multi-strand 12 ga. wire and terminated with
885 ohms of resistance. The impedance transformer
was hand wound on an Amidon FT-114-43 (10 turns
and 44 turns). The two terminations were attached
to the antenna with banana plugs so that the ends
of the KAZ could be swapped without actually moving
the loop itself. The coax antenna leads enter my
shack where I can switch instantaneously between
the K9AY and the KAZ. Signal strengths were measured
with my Ten Tec 340 that has an S-meter which is
calibrated in -dBM as well as S-units.
For initial testing, I selected
10 stations located in Southwest Oklahoma or in/near
Northeast Oklahoma. These stations were on both
ends of the dial and were generally in a direct
line diagonally across the state with me in the
middle. The antennas pointed right down the diagonal
Front to Back Ratios & Relative Gain:
K9AY vs. KAZ
of the ten stations had a fairly strong co-channel
when the primary station was nulled: GREAT for DXing,
but impossible for F/B measurement. Four of the
remaining five stations were running less than 20
dB above the noise floor when peaked. When nulled,
they went into noise, of course, but that doesn't
really indicate an accurate F/B ratio.
I was able to do
a reasonably accurate F/B ratio only on KGGF, 690
in Coffeyville, KS. The K9AY provided a 20 dB ratio
and the KAZ-10x40 did 23 dB. I trust the validity,
though not the level, of this reading. KGGF is exactly
in line with the antenna, to my NE, and puts an
S-9 plus signal here via a directional pattern.
It is important note, though, that there is a 250
w. ND station directly off the SW end of the antenna
(KPET in Lamesa, TX). It is very likely that this
station, though not audible during my F/B measurement
on 690 KGGF, was probably acting to "fill in
the null" during the test. How much did it
contribute? Who knows, though 8 to 10 dB does sound
reasonable to me.
During the Front-to-Back
testing process, I was able to record accurate "relative
gain" figures on eight of the ten stations,
while they were directly off the front of the antennas.
My figures varied between 10 and 15 dB more gain
for the (unamplified) K9AY over the (unamplified)
KAZ-10x40. Also refer to more formal gain measurements
later in this article.
Comparison testing: K9AY vs. KAZ
When comparing the two antennas
during prime time DX hours in the evening and early
morning, things got really interesting. The signal
levels were high enough that it was impossible to
tell the difference between the native gain of the
two antennas "by ear," I had to look at
the S-Meter. In about 80 to 90 percent of the cases,
the content and quality of the two signals was identical,
as well. In that other 15 percent or so, the KAZ
out-performed the K9AY!
1510 kHz. has WLAC, Nashville
and XEQI, Monterrey at about equal distance from
me. Looking toward Monterrey, the KAZ must have
less side-lobe than the K9AY, because the XEQI signal
was always clearer on the KAZ, even when I attenuated
the K9AY by 10 dB to equalize the gain of the two
700 kHz. has nearly unnullable WLW on it. Pointed
southwest, mostly away from Cincinnati, The K9AY
gave me a signal of -80 dBM, while the KAZ provided
a -103 dBM, much weaker. If you factor in the 10
dB or so of difference in native gain of the two
antennas, it appears that, in this instance, the
KAZ nulled WLW by an additional 13 dB! What's more,
for the first time ever, I could actually listen
to a station co-channel with WLW! While writing
the first half of this article, I enjoyed listening
to XEDG, 700 kHz. Radio Romantica in Hidalgo del
Parral, Chih. With the KAZ, Radio Romantica was
in the clear about 50% of the time and in a jumble
the rest. The K9AY can manage to "hear"
the Mexican about 2/3 of the time, but always rather
far beneath WLW. One of the nicest things about
the KAZ that both Kazaross and I have noticed is
the ease of shifting its direction. The next morning,
I took 5 minutes and shifted the KAZ 25 degrees
more toward east-west to get WLW in the exact rear
null and now I often listen to Radio Romantica totally
Some examples of equal performance
of the K9AY vs. KAZ:
580 kHz. Both antennas eliminated
semi-local WIBW in Topeka, KS and revealed XEMU,
Piedras Negras running at "about S-8."
780 kHz. WGN puts in an above
S-9 signal here at night. With both antennas turned
to the southwest, XEMF, Montclova, Coah. ran "about
S-6" with WGN about 95% gone.
Both of the later two tests were
done with the S-meter covered
. I could tell
no difference "by ear" between the two
antennas and just estimated the signal strength.
After reading a
draft of the first half of this article, antenna
guru K6SE cautioned that gain is not really an issue
in a receiving antenna since actually hearing the
signal was dependant upon the signal-to-noise ratio
rather than the absolute gain of the antenna. There
is an old truism which states that "if you
can hear the basic band noise well, you'll hear
any signal peaking above that band noise even better.
Of course, that is true, as far as it goes. However,
it's been my experience that there are more occasions
than people realize where the absolute gain of a
receiving antenna is the limiting factor. Mostly,
these occasions may arise when you are listening
to a very quiet band, with a very quiet receiver.
Since I'm using a new Ten Tec 340 and since I'm
fortunate enough to live away from virtually all
man-made noise (hey, it's a big cow pasture!) I
was very interested in finding out if the 40' KAZ
was "gain-limited" in any meaningful way.
About a week ago, I built "Super
KAZ," a 28'x112' version of KAZ, using 22 gage
wire and one of the fine 10 meter telescoping fiberglass
masts from Germany. Using the much smaller gage
wire, Neil figured the impedance at about 1060 ohms.
I ended up winding a new impedance transformer (50
turns vs 10 turns on a FT-114-43 Amidon toroid)
and boosting the far-end resistor to 1057 ohms.
While testing the smaller KAZ
at mid-day, I had noticed several rather weak signals
coming from the southwest (the center of gain) seemingly
all alone on their channels. Further, there were
no strong signals on immediate adjacent channels
and my daytime MW conditions are as near noise-free
as it gets. So, this seemed a perfect opportunity
to model the conditions that I R*E*A*L*L*Y care
about: that marvelous 90 minutes, centered on dawn,
when (on the Washington coast) the band noise often
drops to near zero and the whole of East Asia opens
up for MW DXing.
Gain Does Seem
Working about mid-day, I was
able to find six stations at threshold audio levels
on the 40' KAZ. Two were located at the low end
of the band, two at the middle and two at the top.
I put the KAZ adjacent to the Super KAZ on my antenna
switch and began to compare. In every instance,
the apparent signal-to-noise ratio was significantly
better on the Super KAZ. In other words, the S-meter
showed a much stronger signal on the Super KAZ...
as expected... but, there was also a very significant
improvement in the quality of the signal. All or
almost all of the "band noise" left the
signal on the Super KAZ.
I rechecked all of my connections
and thought about the whole thing for a while. Since
the basic signal-to-noise ratio of an antenna is
related to its sensitivity pattern and since the
pattern (but not the gain) of the KAZ and the Super
KAZ should be identical, the 40' KAZ must be "gain
limited" under the specific conditions tested.
In other words, what I was hearing on the 40' KAZ
was not band noise, but rather the noise floor of
my receiver! I added about 10 dB of amplification
to the KAZ signal and attenuated the Super KAZ a
like amount; this pretty well equalized the apparent
gain of the two antennas. As expected, the KAZ signals
remained much noisier than the same previously marginal
signals when received with the Super KAZ.
Final Gain Comparisons
To complete the study, I ran
final gain comparisons between all three antennas,
again at about mid-day. The K9AY is listed both
first and last in the following chart:
K9AY vs KAZ vs Super KAZ vs K9AY
K9AY is a 28' delta,
KAZ is 10' x 40', Super KAZ is 28' x 112'
I also rechecked the front-to-back
ratios of each KAZ antenna, again at high noon,
again using KGGF, Coffeyville, KS, 690 kHz as my
target. This time the KAZ measured only 18 dB (it
had previously measured 23) while the Super KAZ
measured 23 dB of F/B.
The differences in the two measurements
of the 10x40 KAZ simply reinforce the vagaries of
measuring F/B ratios on MW, even at high noon on
a carefully selected station. I have noticed real
differences in the day-to-day daytime propagation
here at the solar peak. My guess is that the station
in Lamesa, Texas was filling in more of the null
as I noticed that XEWA on 540 was actually audible
at good levels at mid-day, very unusual for my location.
What the test did show, unequivocally, is that the
Super KAZ had a F/B ratio at least as good and probably
somewhat better than the KAZ, at least as I've constructed
The F/B ratios of these
two KAZ designs ought to be identical, I think.
Probably, too, the termination resistor of the smaller
KAZ is not quite the correct value. Neil calculated
the gain difference between the two versions of
the KAZ at 17 dB, where I measured 23 dB. That,
too, argues that my small KAZ is not quite operating
at the optimum.
Although I intend to run many
more tests of the Super KAZ and a mid-sized KAZ
in the Pacific Northwest this summer, I think I've
come to at least a few useful findings:
- The useable directivity of
the 40 foot KAZ is at least as good and probably
just a bit better than my classic K9AY at both
the top and bottom of the band. That's great news,
since the KAZ is so much smaller/cheaper. Neil
designed the 40 footer as small as he dared, hoping
to develop an antenna that could be erected in
an urban back yard, a rooftop or even in a large
- The classic K9AY outgains
the 40 foot KAZ by just about 12 to 14 dB. I measured
this before I read the upload where Andy Ikin
was quoted as saying that an increase in cross-sectional
area of a loop by double gets ya about 12 dB of
gain. The area of the KAZ-10x40 is 200 sq.ft.
the area of the classic K9AY is 350 sq. ft. Later,
Kaz calculated the difference between my two antennas
and got 10 dB. How 'bout that... It pleases me
that my measurements and science come close to
agreement... adds confidence about my process
and about the prediction models.
- Given the relatively high
signal levels at night, the 12 to 14 dB difference
in gain between the K9AY and the smaller KAZ was
ALMOST NEVER perceivable in the audio. When I
covered the S-meter for a while, I simply couldn't
tell the difference between the two antennas,
most of the time. Occasionally, as discussed above,
the KAZ was actually was superior - due to reduced
backside slop. It also pleases me that this very
small KAZ, a real "urban DXer's" antenna,
can perform on a par with the K9AY for almost
all real-world DX situations.
- H*O*W*E*V*E*R ... In the
Pacific Northwest, under those marvelous dawn
conditions on medium wave, I need all the gain
that I can get. The K9AY is pretty non-competitive
with Beverages out there without its 10 to 13
dB of switchable amplification... and I'd really
like more native gain from the KAZ... so, out
there, I'll darn sure be trying the Super KAZ
as a potential Beverage beater!
Obviously, a good deal more work
needs to be done to optimize both the K9AY and the
KAZ for MW DXing in various parts of the US and
abroad. A number of questions come to mind:
- What is the smallest KAZ that
will not be "gain-limited" even at the
bottom of the broadcast band? Is there any theoretical
work available on this???
- What happens to a K9AY when
one goes to the full 1 to 4 KAZ aspect ratio?
The one undeniable advantage of the K9AY configuration
is the ease of loop switching arrangements.
- Will the added gain plus
the excellent front-to-back ratio allow the 120
foot Super KAZ to compete with Beverages on the
West Coast at dawn? Truly, I suspect not, though
the F/B may really help us in DXing the hard-to-hear
Hawaiian channels and the Trans-Pacific stations
where the 9 kHz per channel and the 10 kHz per
channel rhythms coincide.
- I wonder what a phased array
of two KAZs of about 15 x 60 and spaced about
250 feet apart would look like. I can just fit
that in my Okie cow pasture
- Speaking of phased arrays,
I just purchased one of Gerry Thomas' new Quantum
Phasers and it has been love at first sight. I
can routinely and easily lay at least 45 dB of
null on local pests during the day. Night operation
of any phasing unit is much more of an art form,
of course. While I was testing the F/B of the
two KAZ designs against KGGF, I phased the two
of them against each other while they were pointed
directly away from the station. The total F/B
of the system was 55 dB! That's taking an S-9
+ 20 dB signal just about down to the noise floor
and in a cardioid pattern at that.
Neil Kazaross' work modifying
the K9SE delta is certainly pointing the way to
some VERY useful antennas for us all and has led
to a lot of fun for me. BRAVO Neil!
Written in April
published on DXing.info on June 25th 2002