WiMo: EH Antennas

The design principle of the EH antenna has be discussed (often controversely) for some years. After many practical tests and positive findings of many amateurs these antennas are now available in a professional version for the ham radio sector.

EH antennas work differently than the known principle of the Hertz dipole. WIth a traditional Hertz dipole the E and H field components are not in phase, this effects that the radiation field is not properly built up until some distance (>1 wavelength). An EH antenna uses a phasing network to align the phase of both E and H field components, thus leading to a radiation field which is built up much faster and closer to the antenna. The net result are much smaller antennas with an effectiveness comparable to a usually larger dipole. Typical sizes are 2-3% of the wavelength.

EH antennas are mono band antennas, due to the design the entire band can be used. With it's compact sizes the antennas can be easily used in space restricted environments, especially on the low bands like 80 and 160m. Additionally these antennas are comparatively quiet, reducing the often strong noise level on these bands.

The radiation pattern is not published by the manufacturer at this time. EH antennas are vertical antennas, so the azimuth diagramm is similiar to any omni directional antenna. The elevation diagram is comparable to that of any traditional vertical antenna, e.g. a quarter wavelength radiator with a gain of 0 to +2 dBD.

The connector is a PL female jack on the side of the antenna. The feedline is 50 Ω, an antenna tuner is not required. Mounting hardware is provided for mast mounting.
To adjust the center frequency a simple alignment is possible. A copper belt can be adjusted in height on the antenna, influencing the center frequency on the band. A simple SWR meter is sufficient for this adjustment.

Technical data EH antennas

Model	Aspis	Cobra	Venus
Band	6	11	10	11	12	15	17	20	30	40	80	160
Length [cm]	66	68	90	93	248
Diameter [cm]	8	12,5	8/12,5 *1)
Weight [g]	1300	1500	3500	4900
Max.Power (SSB) [W]	300	600	2000
Max.Power (FM) [W]	75	150	500
Max. Mast diameter [mm]	40 *2)	35	40 *2)
Price	167.89 (163.00) EUR	116.39 (113.00) EUR	167.89 (163.00) EUR	167.89 (163.00) EUR	167.89 (163.00) EUR	167.89 (163.00) EUR	167.89 (163.00) EUR	167.89 (163.00) EUR	167.89 (163.00) EUR	167.89 (163.00) EUR	300.76 (292.00) EUR	300.76 (292.00) EUR

*1) The 80m and 160m models have a diameter of 8cm Durchmesser, at the lower end a thicker part of about 12,5 cm diameter.
*2) The 40mm clamps can be extended to 50mm by removing one of the brackets.

ASPIS 11m

Order No.
12010.6	Aspis-6	167.89 (163.00) EUR	Buy now
12010.11	Aspis-11	116.39 (113.00) EUR	Buy now
12000.10	Cobra-10	167.89 (163.00) EUR	Buy now
12000.11	Cobra-11	167.89 (163.00) EUR	Buy now
12000.12	Cobra-12	167.89 (163.00) EUR	Buy now
12000.15	Cobra-15	167.89 (163.00) EUR	Buy now
12000.17	Cobra-17	167.89 (163.00) EUR	Buy now
12000.20	Cobra-20	167.89 (163.00) EUR	Buy now
12000.30	Cobra-30	167.89 (163.00) EUR	Buy now
12000.40	Cobra-40	167.89 (163.00) EUR	Buy now
12000.80	Venus-80	300.76 (292.00) EUR	Buy now
12000.160	Venus-160	300.76 (292.00) EUR	Buy now

Compact EH-Antenne for CB radio
ASPIS 11 EH ANtenne

The smaller version of the 'Cobra 11' with astonishing specs: Length only 68cm, frequency range 26,5 to 28MHz, wide bandwidth of approx. 2MHz at a SWR of 2:1 or better. Max. power load 600 Watt SSB/CW, 150 Watt AM/FM.
Like all EH antennas pre-tuned, fine tuning is possible with the outer sleeve. Efficiency 95%, gain 0 dBD (like a dipole). Includes mast clamps, connector PL jack. Unobtrusive, due to it's compact size ideal for campers, balconies etc. Diameter 8cm, weight 1.3kg.

Frequently asked questions:

Order No.
12010.11	Aspis-11	116.39 (113.00) EUR	Buy now

Q: Are EH antennas suitable for multiple bands?
A: No, EH antennas are mono band antennas, suitable only for the designed band which is covered entirely.

Q: What bandwidth can I expect from EH antennas?
A: An EH antenna can be used on the entire band with good SWR.

Q: Is there an EH antenna for 11m CB?
A: Yes.

Q: Can the 10m (12m) EH antenna be used on 11m (CB)?
A: No, we offer an own antenna for 11m (CB).

Q: Is there an antenna for the 45m pirate band?
A: Yes, on request.

Q: Must the EH antennas be adjusted?
A: All models have the possibility to adject the center frequency on the specific band. A simple SWR meter is sufficient for alignment.

Q: Are EH antennas suitable for SWLs, i.e. only for listening?
A: Yes, within the specified band the EH antennas are very well suitable for reception.

Q: How should the EH antenna be installed?
A: Like any other antenna - clear of other conductive items, as high as possible. A distance of a half wavelength to other resonant objects (masts, tubes etc.) is recommended. The antenna can be installöed on the ground but at least 2 to 3 meters above ground (model "Cobra"), model "Venus" best 3 to 4 meters above ground.

Q: What effect do other objects (Trees, houses etc.) in the vicinity of the antenna have?
A: Compared to most trees, buildings etc. EH antennas are small. This results very easily in strong obscuration and influence on the antenna by these other objects. So an distance of about half wavelength to other objects would be ideal.

W: Does an EH antenna require radials?
A: No.

Q: Does the EH antenna require specific length of coax feed line?
A: No, you can use a coax feed of any length.

Report from a customer:
Dear Julie
The last weekend I did more experience with the EH-Cobra. First I tuned  it on
SWR abt. 1:1.1. I climbed on the Pizzo di Vogorno (2'448m asl) in Canton Ticino
and worked  with an output power of 5 W.
Between 11:50 and 13:15 UTC i worked the following stations:
SK0QO, RX3AP, YO8YF, IR0BP, UT2FA/p, YO9WF/j, SM6FPZ, EW8WW, IK0OVJ,  LY2FE/qrp.
I'm very satisfied with this antenna.
You'll find several pictures of this micro DX-Expedition....
Iwish you a very nice time, with best regards
HB9DGV
Rolf von Allmen

Bericht eines Kunden:

From: Tom Corcoran
Sent: Saturday, April 17, 2004 8:39 PM
To: info
Subject: New Cobra 20 User

Hello,
I just wanted to give you an early report on my Cobra  240.
I have been following the intellectual debates on the EH antenna
for over a year now and thought the best thing to do was to jump
in and try it for myself. The antenna arrived Friday (3 days after
ordered on line from WIMO) so first opportunity to do anything was
this morning (Saturday) - 0600 local time ... I felt like a kid at
Christmas ...
I set the unit up in my garden with the antenna mounted on a wooden
stake 4 feet long to allow adjustments. Using my mfj259 analyser I
established a flat 1:1 swr across the part of the 20 meter band that
I use most often. 14.0 - 14.150 (took 10 minutes,  mostly because I
had to walk back and forth from shack to garden). My first qso was
with a VK followed by a ZL followed by a number of locals in Moscow.
Wow ... I'm in Bristol, England. I'm afraid to move it from the current
position where the top of the antenna is about 6 feet above the ground!!
Too bad this is a monobander ... oh well, big decision now is how many
more to put up!

Regards,
Tom Corcoran
Bristol, England
M0DHB/VE3NY

Da: Matteo
Inviato: sabato 15 gennaio 2005 9.06
A: EH antenna
Oggetto: aspis 11
EH antenna mod. ASPIS 11
Hello,
at present I have only tried the antenna at 3 metres from the ground in the
parking of the block of flats where I live and have obtained excellent
results.
Although propagation this morning was scarce, I was able to connect area 43
(Australia) with R5 S5. After that I listened to a station in 112 (Lebanon)
and finally a station on the sea in the Gulf of Guinea, both with good
signals.
Unfortunately, at least for today, I wasn't able to try the antenna in local
QSO ...
The values of VSWR registered during my tests were really good (power
100watts):
Frequency (MHz)                         VSWR
26.100                               2.1
26.600                               1.5
27.100                               1.0
27.600                               1.0
28.100                               1.6
During the entire test, the frequency was clean and without QRN, something
very difficult to obtain with a classic vertical antenna!
The station I used:
Kenwood TS-50 100watts
Original microphone
VSWRmater ZG HP201 / ZG HP500
Coax line RG58 (about 11 meters)
Well, for the moment I am very satisfied!
Best regards and once more thanks,
Matteo

Da: Stefano IK1ZYO
Inviato: lunedì 19 luglio 2004 15.01
A: eheuroantenna
Oggetto: eh 160
I purchased a Venus 160 from you more or less six months ago. Because of
various works done to my home, I was able to install and try the antenna
only last Saturday.
I put the eh on a 45 mm mast and put the antenna at about 4 meters from the
roof. There are no other metallic obstacles or whatsoever around it that may
jeopardize the irradiation. I used a very normal rg213, having a length of
about 25 meters.
As soon as I verified the VSWR, amazingly I verified a 1:1,4 resonance at
1,820KHz and a bandwidth of well over 30 KHz. This made me hope very well
for my tests on air.
Unfortunately, the only station I was able to find in telegraphy (during the
time I had available and at that time of the day) was a station of the Czech
Republic  OK  which gave me a 559 report. I was using my usual 100 watts
power. I make the tuning with the one inside my receiver. It only takes 7 /
10 seconds to find the right resonance for the entire system.
In the next days I'll send you my QSOs and some photos of the installation.
Best 73s IK1ZYO

EH Antennas at I2MTW

Click for larger view

From: thorpo
Sent: Thursday, January 26, 2006 7:47 PM
To: wimo
Subject: Bilder EH-Antenne 11 m Band

Guten Tag,

auch ich besitze eine WIMO-Antenne EH-Monobandantenne für das 11 Meter Band.

Mit erfreulichen Ergebnisse kann man auch in einer begrenzden Umgebung ( Balkon im Hinterhof, 3. OG ) mit der EH-Antenne DX-QSO´s führen.

Kann ich nur empfehlen, für 15 / 12 / 11 oder 10 Meter Bändern.

Vy 73

Da: Piero IK1JLL [mail: ]
Inviato: martedì 24 gennaio 2006 20.30
A: eheuroantenna
Oggetto: cobra 30 metri
Dear Julie,
At last, I finally installed my EH 30 metres bought from you at Ham fair in Genoa 2004.
After a few sporadic tests, and, honestly, without actually taking into consideration that the
antenna could really perform as described here and there, and after having heard so many
unfavourable opinions of a few radioamateurs, I decided to install it seriously on the roof
of my home. Since I already have a dipole performing on this band, I was able to carry out a few comparative tests.
Consider that the dipole is mounted very well, with its top at 6 metres above the roof of the house and about 20 metres from the ground.
I am enthusiastic. The antenna receives like the dipole and sometimes definitely better,
especially on long distances and considering the dimensions that's not at all little.
Probably many OM buy the antenna and then place it in narrow spaces or locate it in an
abnormal position (It's very small and will fit anywhere). And then they say it doesn't work.
I feel I can assert that the antenna does work!
Here are some QSO done in these days on the 30 metre band, naturally in CW:
VK6DU 06/01/06
EA8CN 06/01/06
4Z8GC 06/01/06
UN8GZ 06/01/06
VK6GU 10/01/06
ZB2/G3TXF 19/01/06
A22/JA4ATV 20/01/06
VK2GWK 23/01/06
6O0N 24/01/06
The power used is that of my Icom IC775DSP, about 200 watts.
As promised I'm sending some photos of the antenna. Naturally you can publish them.
Thank you for everything
Pierangelo (IK1JLL)