The "Cantenna" has not 12 dBi!!!

The Cantenna can not be have 12 dBi gain. Any Cantenna design, I have
testet, had only a performance from 7 to 8.5 dBi.
I found some Canntenna models (.NEC-files) on internet, which
calculates indeed 12 dBi. But the average gain test, which is almost
not done, shows the error in the design model.
If you check and correct this desing errors, you will get only a
performance of 8 dBi.

It is not true, which the cantenna has 12 dBi! Keep in mind.
Aziz

(E-Mail Removed) hath wroth:

>The Cantenna can not be have 12 dBi gain. Any Cantenna design, I have
>testet, had only a performance from 7 to 8.5 dBi.
>I found some Canntenna models (.NEC-files) on internet, which
>calculates indeed 12 dBi. But the average gain test, which is almost
>not done, shows the error in the design model.

Show me. I do designs and models.

>If you check and correct this desing errors, you will get only a
>performance of 8 dBi.

The final gain really depends heavily on the waveguide geometry. The
typical coffee can will do about 9dBi. Pringles cans are about 7dBi.
Extra long extensions with horns can be as high as 14dBi.

>It is not true, which the cantenna has 12 dBi! Keep in mind.
>Aziz

I show 8.5 to 9.8 dBi gain:
<http://802.11junk.com/jeffl/antennas/coffee2400/index.html>
Note that the gain varies with frequency:
<http://802.11junk.com/jeffl/antennas/coffee2400/slides/gain-01.html>
The NEC model is directly stolen from Trevor Marshall's at:
<http://www.nec2.org/wlan.htm>

That's also without any additional losses such as surface conduction
losses, connector loss, coax loss, etc. The final antenna at the end
of a few feet of lossy coax cable will probably be about 2-3dB less.

If you paid for 12dBi and are only getting 8dBi, ask the vendor for
your decibels back.

If you want to do something useful, figure out what I did wrong with
the coffee can design speadsheet. It's close, but not perfect.
<http://802.11junk.com/jeffl/rf-calc/Coffee-can05.xls>


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Dear Jeff,

I have seen your cantenne model. But where is your NEC-file for the
cantenna? I will show you, where you have model errors. Did you ever
performed an average gain test? If not, you should do this allways
first. Also all warnings in your model should be removed or checked!
Otherwise, you will get wrong results.
Especially, you should not have surface patches (tin can) nearby your
feed point!

Regards,
Aziz

Hell Jeff,

I have found your excel sheet and did the model calculation. Your feed
have to be optimized. Also, some parts (surface patches) nearby the
feed, must be removed.

My model with surface patches:
Tin can diameter: 100 mm
Length: 135 mm
Lg/4: 44.452 mm
My model gets round about 7.7 dBi with the same dimensions. Calculated
total gain is 8.3 dBi, average gain test correction is 0.6 dBi. 8.3 -
0.6 = 7.7 dBi.

Model with wire grid (more accurate):
Total gain is 8.4 dBi without error (average gain test=1.0 (-0 dBi
correcting factor)).

Of course, with 198 mm diameter flare for the cantenna, you get 12 dBi
gain.
But the original cantenna can not be have 12 dBi!!!! It is a cheap
marketing issue.

Aziz

(E-Mail Removed) hath wroth:

>I have seen your cantenne model. But where is your NEC-file for the
>cantenna?

Sorry. My Jalbum 7.1 photo album software buried the NEC2 files. Some
of the various NEC2 files are:
http://802.11junk.com/jeffl/antennas...400/coffee.nec
http://802.11junk.com/jeffl/antennas...or/Plate02.nec
http://802.11junk.com/jeffl/antennas...d/HandHeld.nec
http://802.11junk.com/jeffl/antennas...HawkDish08.nec
I'll make them visible when I figure out how.

>I will show you, where you have model errors.

Sure. I'm interested. However, I would prefer you find whatever we
did wrong with the Excel speadsheet which can generate the NEC file.

>Did you ever
>performed an average gain test?

Yep. It fails with a value of about 2.0. 1.0 is perfect. I haven't
chased down the cause. I've made it worse, but not better. L.B.
Cebik offered some sage advice from about 2.5 years ago on the model,
which none of the perpetrators (including me) have done anything
about:
<http://www.robomod.net/mailman/private/nec-list/2005-January/001398.html>
You may need to register to view this. Please ask if you want me to
email the message.

>If not, you should do this allways
>first.

I did, but couldn't determine how to fix it. Believe me, I tried. I
think the problem is fairly universal because all of the coffee can
models I've found on the web have exactly the same problem. The model
is even included as a sample with several packages. Despite the
errors, the field test results closely resembles the model.

>Also all warnings in your model should be removed or checked!

4NEC2 shows:
> Warn.: too sharp angle or too short/thick segment(s) for Wires 2 (tag 2) and 3 (tag 3)
> Warn.: too sharp angle or too short/thick segment(s) for Wires 2 (tag 2) and 4 (tag 4)
> Warn.: too sharp angle or too short/thick segment(s) for Wires 2 (tag 2) and 5 (tag 5)
etc...

That's from the overlapping wires at the base of the conical feed. It
was too much work to try to get them each positioned so there's no
overlap. I'll replace the cone with a single wire feed (as in the
spreadsheet), which gets rid of that error but narrows the bandwidth.

>Otherwise, you will get wrong results.

Some warnings can be safely ignored.

>Especially, you should not have surface patches (tin can) nearby your
>feed point!

Yep. It is quite close, but not touching. I'll try punching a hole
in the side of the can, under the conical feed, and see if that helps.
However, not for a few days. I've got too many projects going and
this one is going to take some real work.

>Regards,
>Aziz

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

The construction of a waveguide requires a
minimum amount of understanding of E and H
fields. In order to realize the maximum gain
quite few principles must be gotten right..My
opinion, "it's not for everybody.."

Hello Jeff,

I have sent you some cantenna models via email. They are very long, I
couldnt post it here.

Here is the source code of my cantenna model (not 4nec2/nec2/nec4
compatible!):
As I mentioned in email, the source antenna model have to be compiled.
---------------------------------
CM Cantenna WLAN Antenna Model at 2.437 GHz
CM (C) 2007 by Aziz Oeguet
CM File: Cantenna2G4Hz.txt
CE

#include "Common.txt"
#include "PP4NEC2Defs.txt"

ofsx = -0.05 // Offset x-Achsenverschiebung (zur besseren 3D-
Darstellung)

//--- Kontrollschalter (Switches) für Modellkonfiguration ---
#ifndef CANTENNA_TRICHTER
CANTENNA_TRICHTER = 1 // Trichter-Blende (0=kein, 1=mit)
#endif

#ifndef CANTENNA_WRMODE
CANTENNA_WRMODE = 1 // Drahtmodus (0=Surface-Path, 1=Wire-Modus)
#endif

#ifndef CANTENNA_CALC
CANTENNA_CALC = 0 // Cantenna parameter berechnen (1=berechnen,
0=auf manuellen Wert lassen)
#endif

#pragma symode = _SYMODE_REUSE

//--- Feeder(Erreger)-Parameter (Lambda/4-Element) ---
Feed_Durchmesser = 0.0015 // Antennendrahtdurchmesser
Feed_Rad = Feed_Durchmesser/2 // Antennendrahtradius
Feed_nSeg = 9 // Anzahl Segmente des
Antennendrahtes
Feed_Tagnr = 1000 // Draht Tagnummer-Start
Feed_Segnr = 1 // Segment-Number des Erregerstücks


#if !CANTENNA_CALC
Feed_Len = 0.0308 // Antennendrahtlänge
#else
Feed_Len = lambda/4 // Antennendrahtlänge (Wellenlänge/4)
#endif

Feed_Delta = Feed_Len/Feed_nSeg // Segment-Länge (Antennendraht)


//--- Cantenna-Parameter (Tubus) ---
TubusnSegLen = 15 // Anzahl der Segmente in Tubus-Länge
TubusnSegRad = 6 // Anzahl der Segmente im Tubus-Radius
TubusnSegMantel = 32 // Anzahl der Segmente im Tubus-Mantel

TrichternSegLen = 12 // Anzahl der Segmente in Trichter-Länge
TrichternSegMantel = 32 // Anzahl der Segmente im Trichter-Mantel

TubusDurchmesser = 0.1 // Tubus-Durchmesser
TrichterDurchmesser = 0.198 // Trichter-Durchmesser
TrichterLen = 0.086 // Trichter-Länge

TubusRadius = TubusDurchmesser/2 // Tubus-Radius
TrichterRadius = TrichterDurchmesser/2 // Trichter-Radius


#if !CANTENNA_CALC
//--- Cantenna Parameter manuell ---
TubusLen = 0.135 // Tubus-Länge
Feed_Dist = 0.044452 // Erregerabstand zu hinteren Wand
#else
//--- Cantenna Parameter berechnen ---
DLc = 1.706*TubusDurchmesser
DLg = 1/sqr((1/(lambda*lambda))-(1/(DLc*DLc)))
TubusLen = DLg*3/4 // Tubus-Länge
Feed_Dist = DLg/4 // Erregerabstand zu hinteren Wand
#endif

Feedzpos = -TubusRadius // Erregerfusspunkt (unten)

//--- Feeder ---
// Erregerspeisedraht
GW Feed_Tagnr Feed_nSeg 0 0 Feedzpos-Feed_Delta/2 0 0 Feedzpos
+Feed_Len-Feed_Delta/2 Feed_Rad

// winziger Anschlussstummel unten (NEC2 Warnung umgehen)
GW Feed_Tagnr+1 1 0 0 Feedzpos-Feed_Delta/2 0 0 Feedzpos-Feed_Delta/
2-Feed_Delta Feed_Rad

p1x = Feed_Dist-0.04
p1y = -0.03
p1z =-0.03
p2x = Feed_Dist+0.11
p2y = 0.05
p2z = 0.03
rad = 0.04

//--- Hotspot (am Erreger in der Nähe keine Objekte generieren) ---
#Hotspot point=_HS_OUTSIDE Feed_Dist 0 Feedzpos 0.005


// Für hintere Wand des Tubus nötig, da Vierecke im Mittelpunkt zu
Dreiecken werden.
#pragma limits=1, minwirelen=0.001, minareasize=0.000001

//--- Tubus generieren ---

#if CANTENNA_WRMODE
// Parameter für Wire-Modus
#pragma mode= _MODE_WR, wrnumseg = 1, wrtagstart=2000, wrtaginc = 1,
wrradius = Feed_Rad
#else
#pragma mode= _MODE_SP
#endif

//--- Tubus um Erregerabstand nach hinten verschieben ---

#Move -Feed_Dist 0 0

w1 = 180
w2 = w1+360

// Tubus generieren
#Pipe TubusnSegMantel TubusnSegLen 0 0 0 w1 w2 TubusRadius TubusRadius
TubusRadius TubusRadius TubusLen _R1|_R2|_A1

// Hintere Wand (Ring) generieren
#SPArc TubusnSegMantel TubusnSegRad 0 0 0 w1 w2 0 0 TubusRadius
TubusRadius _A1

// Trichter generieren
#if CANTENNA_TRICHTER
#Pipe TrichternSegMantel TrichternSegLen TubusLen 0 0 w1 w2
TubusRadius TubusRadius TrichterRadius TrichterRadius TrichterLen _R2|
_A1
#endif


#Transform // Transformation abschliessen (Move)
//--- Ende Tubus-Verschiebung ---


// Achsen-Transformation (um aus dem Nahfeld rauszukommen)
#if !CANTENNA_TRICHTER
GM 0 0 0 0 0 -TubusLen+Feed_Dist+ofsx 0 0 0
#else
GM 0 0 0 0 0 -TubusLen+Feed_Dist-TrichterLen+ofsx 0 0 0
#endif


// End-Of-Geometry
GE 0

//--- Wire-Load (HF-Speisung) ---
EX 0 Feed_Tagnr Feed_Segnr 0 1.0 0.0
LD 5 0 0 0 62900000

// Extended-Wire-Kernel einschalten
EK 1

//--- Frequency Parameter and Execute ---
FR 0 1 0 0 freq 1
RP 0 91 181 1001 -180 0 2 2
EN
-----------------------END-------------------

cantenna with maximum 24dBi? --> 'WLAN-SAT-FORUM
Forums-viewtopic-Ultimate wifi antenna TinCan Enhancers - part-2 ...'
(http://www.wlan-sat.com/modules.php?...ewtopic&t=4782)


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fablept <(E-Mail Removed)> hath wroth:

>cantenna with maximum 24dBi? --> 'WLAN-SAT-FORUM
>Forums-viewtopic-Ultimate wifi antenna TinCan Enhancers - part-2 ...'
>(http://www.wlan-sat.com/modules.php?...ewtopic&t=4782)

This is not exactly a cantenna, but a horn antenna uses the same
principle. 16dBi gain:
<http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=12624>

How to grind the numbers for a horn antenna:
<http://users.skynet.be/chricat/horn/horn-javascript.html>

The cardboard and aluminum foil horn antenna:
<http://www.seattlewireless.net/index.cgi/CardboardHorn>

SETI "horn of plenty"
http://www.setileague.org/photos/wghorn/pyramid.jpg
http://www.setileague.org/photos/wghorn.htm
20dBi gain at 1500MHz. My guess(tm) is about 24dBi at 2.4GHz. Note
the size of the horn required to get that gain as compared to the
Slovanian cantenna.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann;120986 Wrote:
>
>
> This is not exactly a cantenna, but a horn antenna uses the same
> principle. 16dBi gain:
> <http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=12624>
>
> How to grind the numbers for a horn antenna:
> <http://users.skynet.be/chricat/horn/horn-javascript.html>
>
> The cardboard and aluminum foil horn antenna:
> <http://www.seattlewireless.net/index.cgi/CardboardHorn>
>
> SETI "horn of plenty"
> http://www.setileague.org/photos/wghorn/pyramid.jpg
> 'The SETI League, Inc.: Waveguide Horn Antenna Photos'
> (http://www.setileague.org/photos/wghorn.htm)
> 20dBi gain at 1500MHz. My guess(tm) is about 24dBi at 2.4GHz. Note
> the size of the horn required to get that gain as compared to the
> Slovanian cantenna.
>
>

it´s some kind of "booster" to a cantenna...i didint get 24dB, but
around 17dB..it´s not bad for very low-cost antenna.

I use this freeware for horn antennas / conical horns /parabolic /lens,
its great because gives a template according to the frequency we want. i
import the postscript file to corel draw.

hdl_3b4 --> 'Download hdl_3b4.zip - DepositFiles.com - the best upload
and file sharing service!' (http://depositfiles.com/files/1078122)


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