[HCDX] the EWE story continues

["Michael Schnitzer" <mschnitzer@xxxxxxxxxxxx>]

Hello again,

some weeks ago I already posted here my first experiences with the
EWE-antenna. In the meantime I wrote a comprehensive article about this
topic, which is published in the newest edition of the German radio magazine
RADIO-KURIER. Here now the English version of my article. I hope that it
will be of some interest to the hcdx-community.


The EWE in the Garden
A Tropical Band Antenna with good Receiving Characteristics

The EWE-antenna is fascinating. If you have it, you will ask yourself, why
you didn't happen earlier on that simple antenna form, which is very
effective for DXing on the tropical bands. Since some time I tried to find
an antenna, which first of all would have its maximum performance on the
tropical bands. Secondly the antenna should be directive; thirdly the
antenna should reduce the usual substantial noise level on the lower
frequencies and should finally fit in a normal garden. The previous
favorits, K9AY and Beverage, didn't come into consideration. The K9AY, by
the way an advancement of the EWE, is a special MW antenna with moderate
performance only on the tropical bands and the Beverage exceeds my property
boundaries. The EWE-antenna now fulfills all criteria specified above.

This type of antenna was described first in the year 1995 by the American
radio amateur Floyd Koontz. He developed the EWE particularly for the
application on 80m and 160m. In accordance with the specification of Koontz
I copied the 80m version. By the way, "Ewe" is the English word for a female
sheep (just an explanation to all non English native speakers), which is
pronounced like the letter "U". Koontz obviously used a phonetic similarity
as designation and alluded thereby to the form of the antenna.

Construction principle
At first sight the antenna is nothing else as an inverted U of approx. 7,5 m
length and with a height of three meters above the soil. These are
dimensions, which fit in each average garden. One end is grounded over a
resistor, the other end is attached over a core transformer (balun) to
commercial coaxial cable RG 58. The main direction of reception is the end
with the balun and the coax connexion. The zero point is towards the
terminating resistor. Depending on space conditions one can give preference
to different mounting versions. Thus e.g. length and height can be changed
as well as the position of the feed-in, which can be attached likewise at
the upper end of the vertical front element (bottom feed vs. top feed). You
can find an illustration and other diagrams in the internet articles
mentioned at the end.

A few antenna theory
The EWE resembles a simple vertical antenna system consisting of directive
element and a grounded reflector, it's behavior however is completely
different. The horizontal wire thereby acts as supply line between the two
vertical parts and contributes insignificantly only to reception. The
excellent directivity of the antenna results from three combining phenomena:

1. Due to the different feed (feed element from down and reflector element
from above) a phase shift of 180 degrees results between the two elements.
2. In the reflector the antenna current is approx. 65-70% lower than in the
feed element. This fact alone however would cause only one foreward/back
ratio of max. 8 dB.
3. At the same time the terminating resistor causes a decrease of the wave
velocity in the reflector element. The higher the value of the terminating
resistor is, the lower becomes the propagation speed in the reflector.

The combination of all three effects leads to the partial extinction of the
signal arriving from the back and produces in this way a distinct rear zero
point. One could say also, the EWE is "phasing" itself and causes therefore
the excellent F/B ratio. Theoretically more than 35 dB can be achieved.
According to the phenomena described above the EWE belongs to the category
of the travelling wave antenna (e.g. the Beverage). In contrary to a simple
vertical 2-element-antenna the EWE doesn't produce standing waves, which
also explains the broad band behavior.

The terminating resistor
The value of the terminating resistor depends on several variables. The
respective ground conductivity represents such an important variable. Poor
ground conductivity means a fewer decrease of the wave velocity in the
reflector. Therefore the value of the terminating resistor must be
increased. Beyond that the resistor depends on whether the bottom feed or
the top feed version is preferred. And modifications of the total dimensions
of the system exert influence on the value of the terminating resistor, too.
There always is to consider however that for each version the respective
R-value is to be inferred either from relevant tables or from computer
calculations or however must be determined experimentally. In the last case
a rear signal is tuned to maximum suppression with a suitable potentiometer.
Concerning my EWE-version with 7.5 m length and 3 m height John Devoldere
recomments the following data on 3.65 MHz: 1600 Ohms for poor conductivity,
975 Ohms with good ground conductivity and 700 Ohms for very good
conductivity. If the EWE is bound for higher frequencies, the R-value should
be decreased additionally.

In my eyes however an accurate R-value is very theoretical and cannot be
fixed exactly.
Practically only on mediumwave one can find a clear notch in the signal
strength of a rear station by the potentiometer approach. Thus I used a rear
local mediumwave station in order to determine the ideal value of the
terminating resistor for maximum signal suppression. This value amounts to
922 Ohms. On shortwave however this procedure is substantially more
difficult. The signals are not so stable, and a clear R-value could not be
found in such a way. In practice I could observe rather an interval of
R-values. Within the range of 750 up to approximately 950 Ohms I could
observe a rear signal suppression from 20 to 25 dB on my EWE-version. Due to
the fact that my EWE-antennas first of all are bound for DXing on the
tropical bands I determined the amount of the terminating resistor - half
empirically, half theoretically and intuitively - on 820 Ohms.

Construction versions
Devoldere and Koontz describe several mounting versions of the EWE. Hanging
the horizontal wire on five meters height above the ground instead of three
meters the antenna gain will increase 2-4 dB. Likewise the length can be
changed. Further combinations result, if two EWEs are connected in parallel
or in series, or if there is a cross-shaped arrangement in a quadripartite
group with different switching possibilities.

East west combination
By chance I have in my garden three fruit trees exactly in a series, into
the preferred DX directions east-west and accurately in the correct distance
from each other. On that reason I decided to install two EWE-antennas
exactly one behind the other. Thus I have now one EWE towards South America
(direction 260°) and the other EWE towards Asia (direction 80°). I chose the
bottom feed version, in order to can leed in the coax cable to the house
exclusively in the earth. The length of the horizontal element amounts to
7,5 m and the height is three meters over the ground.

Feedpoint and balun
The antenna feedpoint impedance of the EWE varies between 300 and 700 Ohms.
An impedance-matching transformer with turn ratio 3:1 (transformation 9:1)
enables an adequate adjustment to the 50 Ohm coaxial cable. Naturally one
can use the commercial transformers without any problems, e.g. the MLB from
RF Systems. I myself prefered a self-made version, which is working very
well.

Practical operation and reception results
The signal strengths: Meanwhile I often had the opportunity to compare the
two EWEs to my remaining antennas, a 25m long wire and the DX-One
Professional. Already at the very beginning of this chapter I would like to
warn all those, who are interested exclusively in strong deflections of the
receiver's S-indicator. The signal strengths produced by the EWE basicly are
below those of the other antenna types on all frequency ranges. Depending on
the reception situation the observed signals are approx. 5-10 dB weaker.
Only if the station is located exactly in the main direction of the EWE, the
signal loss amounts 2-3 dB compared to long wire and DX-One. In practice
however these data hardly are of relevant importance and aren't noticeable
in average DX-operations. In more difficult cases I can connect a quite
useful HF-amplifier, which additionally raises the signal around 7-8 dB and
which so adjusts the "losses" compared to long wire and DX-One.

Another comparison should be of some interest, too. Using the neightbour's
garden I temporarily established a 70m Beverage antenna with 1.20m height
above the ground. This special kind of short-Beverage was directed to
Indonesia, Australia and Papua New Guinea, which enabled to compare the
Beverage to the Asia-EWE. All relevant tropical band frequencies of this
region were tested. The EWE-Beverage comparison supplied a result quite
surprising for me: Both regarding the signal strengths and regarding the
noise level and the audio impression generally, these two antenna types were
completely identical! Thus the 70m Beverage wire produced no better results
than a 7.5m EWE antenna. Who would have thought that?

The directivity
By installation of two EWE-antennas "radiating" in two opposite directions
the F/B ratio can be demonstrated quite well. If the station is situated in
the antenna main direction e.g. the east-EWE and one switches then to the
west-EWE, the signal strength decreases approx. 20-25 dB. With this
arrangement however I could not achieve the value of max. 35 dB signal
suppression as postulated in the antenna-theoretical discussions. The
following example may clarify, which practical effects the rear zero point
can have. One evening I could receive RRI Jambi on 4925.2 kHz at around
22.15 UTC on the Asia-EWE. Switching over to the South America EWE I could
listen to Radio San Miguel from Bolivia, audible on same frequency without
any interferences caused by RRI Jambi. Such a clear differentiation of two
co-channel stations was not possible on the long wire and on the DX-One.
Something similar was to observe concerning the Peruvian station Radio
Libertad from Junín on 5039.2 kHz. In the late evening there are sometimes
interferences by a Chinese station on 5040 kHz, which can be suppressed
almost completely by the application of the LA-EWE.

My domestic satellite TV set so far made impossible DX on 90m and 120m
absolutely. Long wire as well as DX-One cannot eliminate the electric noise
level. Using the Asia-EWE I succeeded for the first time to listen to ABC
Alice Springs on 2310 kHz, despite of TV consuming family.

Concerning mediumwave-DX the two opposite EWEs are a real enrichment. It
makes fun to check the entire mediumwave scale in the evening hours shifting
up and down the two EWE-antennas on certain frequencies. The Asia-EWE opens
a great part of the Middle East. Numerous Arab speaking stations become
audible, which otherwise perish completely in the overcrowded European
MW-powerband. Some examples of the later afternoon and early evening in
October and November 2000:

198 kHz: BBC on the west-EWE; using the east-EWE PR 1 Raszyn came through.

738 kHz: RNE Barcelona on the west-EWE, Kol Israel with Arab program on the
east-EWE.

1017 kHz: The local SWR as expected on the west-EWE. The east-EWE suppressed
the SWR completely and a Turkish station became audible.

1053 kHz: On 80° Romania came in quite well, on 260° a UK station.
Separation almost completely.

1413 kHz: BBC Oman on the east-EWE with O=4-5. Long wire and DX-One produced
noise here only.

1458 kHz: Here one could choose between Radio Tirana and Sunrise Radio by
switching the two EWE-antennas.

Frequency range
Contrary to "standing wave antennas" (e.g. dipoles) the EWE enables
broad-band reception. The directivity is provable from approx. 150 kHz up to
approximately 10 MHz. The EWE therefore can be used without any problems
from longwave up to the 31m-band. One evening I could observe six Brazilian
stations on 31m using the LA-EWE between 21.30 and 22.00 UTC. The signal
level thereby was about 5 dB lower compared to the long wire. The
directivity of the system could be demonstrated quite clearly. After
switching to the Asia-EWE practically nothing more was to be heard from the
Brazilians. Above 10 MHz the signal strengths substantially decrease in
comparison to the long wire, and a rear zero point cannot be found any more.

Noise level and other disturbances
The actual highlight of the EWE-antenna is the quietude of the signal! As we
all know, the main problem of low-band DXing is the considerable noise. In
particular long wire antennas pick up each electrical disturbance from
ionosphere and atmosphere (thunderstorms etc.), or caused by the
neighbourhood (computer, TV set etc.). Using the EWE for the first time the
DXer learns an absolutely striking new experience: He often can enjoy a
clearer and fewer disturbed signal. Regarding the entire audio impression
and cleanness of reception the EWE is unbeatable in many cases. Especially
the long wire is beaten concerning this criterion. The EWE does not only
reduce a part of the electrical noises, but beyond that it also suppresses
all those reception impairments, which are due to rear stations. Annoying
interference whistling can disappear only by switching from long wire to
EWE, or disturbances caused by a European power station on the adjacent
channel can be reduced under certain conditions.

Construction tips
Basically no other regularities apply to the construction of an EWE as to
other antennas, too. Proximity to metallic articles such as gutters,
gutter-pipes etc. has to be avoided. Beyond that the location of the antenna
should be far away from the house, as far as the garden size permits. Balun
and terminating resistor can be accommodated comfortably and weather-proofed
in small current distribution boxes, which are available in each market for
household goods. These boxes can be fastened easily to the ground rods.

Summary
Also the EWE will not and cannot solve each reception problem. It doesn't
replace other antenna forms under any circumstances. Who exclusively prefers
listening to international radio stations certainly can use the classical
long wire or a magnetic antenna without any problems. The DXer however
usually is hunting local radio stations, far away and with poor transmitter
power only. And all these African, Indonesian or South American stations,
which are to be found normally on the tropical bands of 60m and 90m, often
disappear in the noise of electrical disturbances. Here the EWE can be a
certain remedy indeed. If one has several antennas, then one chooses the
best one in each case anyway. Concerning all stations, coming in from the
correct direction, there can be said: The EWE-antenna almost always produces
the calmest signal!

Erecting and assembling are remarkably simple. All needed parts are
available for a few money only. The dimensions of the EWE enable the
mounting in each average garden. I also want to recomment the relevant
literature to this topic. It supplies an additional view on the theory of
the EWE and on its function principles and gives suggestions for further
construction versions. Finally I would like to thank the DXers Thomas Adam
and Thomas Berner, who advised me concerning the antenna-theoretical
reflections.


Sources:
John Devoldere, ON4UN:  "Low-Band DXing", USA, 1999
Floyd Koontz, WA2WVL:  "Is this EWE for You?", QST Volume 79, 1995

The article of  F. Koontz in the internet:
http://www.arrl.org/tis/info/pdf/9502031.pdf
http://www.arrl.org/tis/info/pdf/9601032.pdf


Michael Schnitzer, Germany


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