The "Cantenna" has not 12 dBi!!!

[o***@gmx.de]

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

[Jeff Liebermann]

Post by o***@gmx.de
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.

Post by o***@gmx.de
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.

Post by o***@gmx.de
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>

[o***@gmx.de]

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

[o***@gmx.de]

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

[Jeff Liebermann]

Post by o***@gmx.de
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/coffee2400/coffee.nec
http://802.11junk.com/jeffl/antennas/FullWavePlateReflector/Plate02.nec
http://802.11junk.com/jeffl/antennas/HandHeld/HandHeld.nec
http://802.11junk.com/jeffl/antennas/HawkDish08/HawkDish08.nec
I'll make them visible when I figure out how.

Post by o***@gmx.de
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.

Post by o***@gmx.de
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.

Post by o***@gmx.de
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.

Post by o***@gmx.de
Also all warnings in your model should be removed or checked!
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.

Post by o***@gmx.de
Otherwise, you will get wrong results.

Some warnings can be safely ignored.

Post by o***@gmx.de
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.

Post by o***@gmx.de
Regards,
Aziz

[o***@gmx.de]

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) f�r 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 Erregerst�cks


#if !CANTENNA_CALC
Feed_Len = 0.0308 // Antennendrahtl�nge
#else
Feed_Len = lambda/4 // Antennendrahtl�nge (Wellenl�nge/4)
#endif

Feed_Delta = Feed_Len/Feed_nSeg // Segment-L�nge (Antennendraht)


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

TrichternSegLen = 12 // Anzahl der Segmente in Trichter-L�nge
TrichternSegMantel = 32 // Anzahl der Segmente im Trichter-Mantel

TubusDurchmesser = 0.1 // Tubus-Durchmesser
TrichterDurchmesser = 0.198 // Trichter-Durchmesser
TrichterLen = 0.086 // Trichter-L�nge

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


#if !CANTENNA_CALC
//--- Cantenna Parameter manuell ---
TubusLen = 0.135 // Tubus-L�nge
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-L�nge
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 N�he keine Objekte generieren) ---
#Hotspot point=_HS_OUTSIDE Feed_Dist 0 Feedzpos 0.005


// F�r hintere Wand des Tubus n�tig, da Vierecke im Mittelpunkt zu
Dreiecken werden.
#pragma limits=1, minwirelen=0.001, minareasize=0.000001

//--- Tubus generieren ---

#if CANTENNA_WRMODE
// Parameter f�r 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-------------------

[Dudley]

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.."

[fablept]

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


------------------------------------------------------------------------
View this thread: http://www.wirelessforums.org/showthread.php?t=23505
http://www.wirelessforums.org

[Jeff Liebermann]

Post by fablept
cantenna with maximum 24dBi? --> 'WLAN-SAT-FORUM
Forums-viewtopic-Ultimate wifi antenna TinCan Enhancers - part-2 ...'
(http://www.wlan-sat.com/modules.php?name=Forums&file=viewtopic&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"
Loading Image...
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.

[fablept]

Post by Jeff Liebermann
This is not exactly a cantenna, but a horn antenna uses the same
<http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=12624>
<http://users.skynet.be/chricat/horn/horn-javascript.html>
<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.

itŽs some kind of "booster" to a cantenna...i didint get 24dB, but
around 17dB..itŽs 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)


------------------------------------------------------------------------
View this thread: http://www.wirelessforums.org/showthread.php?t=23505
http://www.wirelessforums.org

[Jeff Liebermann]

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've never heard of a booster.

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)

The download site is full.
I suggest you get it from the authors web site at:
<http://www.w1ghz.org/software/hdl_3b4.zip>
<http://www.w1ghz.org/antbook/contents.htm> (see other programs)
It is a nifty program for designing horns, but it's not terribly
interactive or educational. For example, you have to know in advance
the size of 2.4GHz WR-340 waveguide. Hint:
<http://www.microwaves101.com/encyclopedia/waveguidedimensions.cfm>

Although this dish feed horn design spreadsheet doesn't generate sheet
metal templates, it's much more useful:
<http://www.setileague.org/software/feedhorn.xls>
More of the same:
<http://www.setileague.org/software/spreadsh.htm>

[fablept]

Post by Jeff Liebermann
I've never heard of a booster.

a booter is what i call a conical horn..

Post by Jeff Liebermann
The download site is full.
<http://www.w1ghz.org/software/hdl_3b4.zip>
<http://www.w1ghz.org/antbook/contents.htm> (see other programs)
It is a nifty program for designing horns, but it's not terribly
interactive or educational. For example, you have to know in advance
<http://www.microwaves101.com/encyclopedia/waveguidedimensions.cfm>
Although this dish feed horn design spreadsheet doesn't generate sheet
<http://www.setileague.org/software/feedhorn.xls>
<http://www.setileague.org/software/spreadsh.htm>

great sites, thanks!

'Wi-Fi. Krasnodar. Horn antenna. Ðóïîðíûå àíòåííû.'
(http://vbm.lan23.ru/wifi/horn.html) --> here it is a rectangular Horn
antenna for 2.4ghz with 33dB, itŽs not very pratical to use...but itŽs
impressive.


at this moment iŽm using Patch microstrip antennas, very simple to
build...and give good results, the problem in building PCB patch
antennas is to find the correct type of PCB due to his dielectric
values, i have a 14dBi in a bad bakelite-PCB that works great, but in
other antennas dont work very well...maybe FR-4 PCB would have better
results.


------------------------------------------------------------------------
View this thread: http://www.wirelessforums.org/showthread.php?t=23505
http://www.wirelessforums.org

[Jeff Liebermann]

Post by fablept
'Wi-Fi. Krasnodar. Horn antenna. Ðóïîðíûå àíòåííû.'
(http://vbm.lan23.ru/wifi/horn.html) --> here it is a rectangular Horn
antenna for 2.4ghz with 33dB, it´s not very pratical to use...but it´s
impressive.

Nice. There was also some ham radio 2.4GHz horns with a similar case
of elephantitis. It's actually not a horrible as it looks and is
very easy to fabricate. It's also not a critical in construction and
tuning as a parabolic dish. However, a horn is big and ugly.

Post by fablept
at this moment i´m using Patch microstrip antennas, very simple to
build...and give good results, the problem in building PCB patch
antennas is to find the correct type of PCB due to his dielectric
values, i have a 14dBi in a bad bakelite-PCB that works great, but in
other antennas dont work very well...maybe FR-4 PCB would have better
results.

Bakelite? I think you mean phenolic, which is the light brown paper
and glue cheap junk that absorbs moisture like a sponge and is very
lossy at 2.4GHz. Even G10/FR4 is better than phenolic. However, if
you want quality, look into air dielectric (standoffs), polysulfone,
or PTFE (RTDuriod).

[fablept]

Post by Jeff Liebermann
Nice. There was also some ham radio 2.4GHz horns with a similar case
of elephantitis. It's actually not a horrible as it looks and is
very easy to fabricate. It's also not a critical in construction and
tuning as a parabolic dish. However, a horn is big and ugly.

check out the FA-20 antenna in the link..itŽs a very simple high gain
antenna.
I build also two 14dBi patch antennas showed in the link...they work
great.

Post by Jeff Liebermann
Bakelite? I think you mean phenolic, which is the light brown paper
and glue cheap junk that absorbs moisture like a sponge and is very
lossy at 2.4GHz. Even G10/FR4 is better than phenolic. However, if
you want quality, look into air dielectric (standoffs), polysulfone,
-or PTFE (RTDuriod).

i know its terrible for 2.4ghz...but yet itŽs the cheapest PCB i can
get.

i know this is getting very offtopic, but i have this link for a omni
PCB antenna: 'David Kittle's Collinear Antenna'
(http://people.wwc.edu/student/kittda/Prop/collinear/)
iŽm trying to understand the design to use in different PCBŽs..

i think the omni is made according to this:
-for the 57mm section= (lambda/2)*copper velocity factor
-for the 27mm section= (lambda/4)*copper velocity factor

-for the microstrip width i just use a simple software like AppCAD to
calculate a 50ohm microstrip line according to the PCB specifications,
right?

-regarding about feeding the antenna, a balun to connect the two
sections of the antenna? in the link nothing is mentioned how to feed
the antenna.

I appreciate any help...


------------------------------------------------------------------------
View this thread: http://www.wirelessforums.org/showthread.php?t=23505
http://www.wirelessforums.org

[Jeff Liebermann]

i know its terrible for 2.4ghz...but yet it´s the cheapest PCB i can
get.

It's crap. G10/FR4 is cheap and commonly available.

i know this is getting very offtopic, but i have this link for a omni
PCB antenna: 'David Kittle's Collinear Antenna'
(http://people.wwc.edu/student/kittda/Prop/collinear/)
i´m trying to understand the design to use in different PCB´s..
-for the 57mm section= (lambda/2)*copper velocity factor
-for the 27mm section= (lambda/4)*copper velocity factor

Correct. Although there's a bit of a question of from where to where
to measure. Hmmmm.... No NEC cards included so I can't run his
numbers through 4NEC2. The first paragraph on the page is speculative
baloney.

-for the microstrip width i just use a simple software like AppCAD to
calculate a 50ohm microstrip line according to the PCB specifications,
right?

Nope. The traces between the feed point and the beginning of the
dipole elements might be 50 ohms (they're not, but close enough).
However, the other elements a fairly high impedance and should be
quite a bit thinner than shown.

-regarding about feeding the antenna, a balun to connect the two
sections of the antenna? in the link nothing is mentioned how to feed
the antenna.

Yep, 1:1 balun is needed. That can be made from coax cable. The
"extra" two quarter wave sections between the feed point and the
dipole is rather questionable and mostly useless.

I appreciate any help...

What are you trying to accomplish?
Duz it have anything to do with the original question?

[fablept]

Post by Jeff Liebermann
Nope. The traces between the feed point and the beginning of the
dipole elements might be 50 ohms (they're not, but close enough).
However, the other elements a fairly high impedance and should be
quite a bit thinner than shown.

how can i find the impedance for the microstrip width?

Post by Jeff Liebermann
What are you trying to accomplish?
Duz it have anything to do with the original question?

sorry, this has nothing to do with the original topic of cantenna..

i which to build that omni PCB, but i only recently started at RF..so i
dont have enough knowledge to make the antenna.

Post by Jeff Liebermann
Here's another large 2.4GHz horn antenna used in the 2003 WiFi long
<http://www.wifi-shootout.com/archive/2003/index.htm>
(Near bottom of page). Made with a metal tubing frame and covered
with aluminium window screen wire mesh.

thatŽs a very big horn, how much dBi that antenna will have?

the world record wireless distance is 237.36miles, 'link'
(http://tinyurl.com/2tyz2m)


------------------------------------------------------------------------
View this thread: http://www.wirelessforums.org/showthread.php?t=23505
http://www.wirelessforums.org

[Jeff Liebermann]

Post by fablept

Post by Jeff Liebermann
Nope. The traces between the feed point and the beginning of the
dipole elements might be 50 ohms (they're not, but close enough).
However, the other elements a fairly high impedance and should be
quite a bit thinner than shown.

how can i find the impedance for the microstrip width?

<http://mcalc.sourceforge.net/>
<http://www.microwaves101.com/encyclopedia/calmstrip.cfm>
<http://www.microwaves101.com/encyclopedia/calsstrip.cfm>
<http://www.emclab.umr.edu/pcbtlc/strip.html>
Lots more under stripline and microstrip.

Post by fablept
i which to build that omni PCB, but i only recently started at RF..so i
dont have enough knowledge to make the antenna.

Well, ok. Low gain antennas are easy enough. High gains antennas are
difficult.

Post by fablept

Post by Jeff Liebermann
Here's another large 2.4GHz horn antenna used in the 2003 WiFi long
<http://www.wifi-shootout.com/archive/2003/index.htm>
(Near bottom of page). Made with a metal tubing frame and covered
with aluminium window screen wire mesh.

that´s a very big horn, how much dBi that antenna will have?

Dunno. I need dimensions to run a model. It's late. I'm tired.
Maybe later...

Post by fablept
the world record wireless distance is 237.36miles, 'link'
(http://tinyurl.com/2tyz2m)

Amazing.

[Jeff Liebermann]

Post by fablept
'Wi-Fi. Krasnodar. Horn antenna. Ðóïîðíûå àíòåííû.'
(http://vbm.lan23.ru/wifi/horn.html) --> here it is a rectangular Horn
antenna for 2.4ghz with 33dB, it´s not very pratical to use...but it´s
impressive.

Here's another large 2.4GHz horn antenna used in the 2003 WiFi long
distance (DX) contest:
<http://www.wifi-shootout.com/archive/2003/index.htm>
(Near bottom of page). Made with a metal tubing frame and covered
with aluminium window screen wire mesh.