Antena Kaleng

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Sebenarnya Web Yogyafree 2004 pernah publish link pembuatan antena kaleng ke blog noesapati in d'house, tapi karena ada kiriman e-mail yang membutuhkan keberadaan artikel ini maka saya post, apalagi berkaitan dengan topic wireless.

Kutipan dari blog noesapati in d'house cara membuat Antena Kaleng :

Antena Kaleng

hidup gue bergantung banget ama internet.
kalo mata gue melek komputer gue mesti hidup dan konek ke internet.
di kantor gue di bangkok ini punya koneksi 145Mbps ke backbone.
jadi bisa dibayangin betapa kencengnya tuh internet.
ada satu sisi buruknya, begitu gue balik ke apartemen berasa lelet banget dialup di tempat sendiri.

gue mau langganan adsl, alas... harus term setahun minimal. sedangkan kerjaan gue butuh pindah2 mulu. gue punya 3 lokasi kantor dan jauh satu sama lain.
biasanya gue pindah apartemen ke deket kantor mana yg gue butuh waktu banyak kerja disitu.

cari punya cari ada satu provider wireless access internet yang punya hotspot di banyak lokasi, salah satu hotspotnya 2 blocks away dari apartemen gue.
tapi masalahnya kalo gue pake "cool laptop" gue sinyalnya kagak sampe kesana.
trus gue browse kesana kemari, dan ketemulah satu antena yang simpel dan murah.

antenna kaleng!!!!!


nyek nyek nyek.. ini antena gak lebih dari guyonan konyol, but the most important thing is... it works.
juga ini gue udah lakuin beberapa lama, tapi baru kali ini gue tulis, kali aja ada yang butuh infonya gue bisa dapet pahala karena bagi2 pengalaman... ting....

ini card ama kabel (pigtail) yang gue punya berikut si "cool laptop" yang setia ikut kemana daku pergi.


ini barang2 yg gue butuhin dan tools yg digunakan


bikinnya gampang, cari aja kaleng diameter 10cm panjangnya paling nggak 133mm
gue nemu kaleng coklat cocoa van houten yang pas diameternya 10cm.
gue coba habisin tuh coklat yang pada akhirnya nggak sabar dan akhirnya gue buang isinya. hehehehehe.... males lah nambah berat badan gampang, ngurusin yang susah setengah hidup.

gue bikin elemen dari pipa kuningan diameter 4mm, kalo gak punya boleh pake kabel listrik biasa yg agak gede ukuran 2.5 sqmm.
solderin aja ke konektor N bulk type.
panjang elemen dari ujung ke dasar konektor adalah 1/4 lambda yakni 31mm.


trus ni kaleng gue potong panjangnya dari 145mm menjadi 133mm sesuai dengan perhitungan di web ini http://www.saunalahti.fi/elepal/antenna2calc.php.
aslinya panjang kaleng ini 145mm, nyari yang pas 133mm gak ada bok..
so workaround is the best effort.
katanya si website itu kalengnya boleh diameter antara 9-11cm.


jangan lupa ujung yang bekas dipotong diamankan dengan tape isolator atau apa aja. yang penting jangan sampai bikin tangan berdarah2. masa sih demi internet harus sampe berdarah2 kayak perang ngelawan belanda aja.

trus bolongin kaleng dengan jarak 44mm dari dasar kaleng, ingat ya bukan ujung kaleng tapi dasar kaleng.
karena ujung kaleng ama dasar kaleng beda bbrp mm. lihat aja biasanya kaleng dasarnya agak menjorok ke dalam sedikit.

bolongin 4 buah untuk naruh sekrup.
biar gampang, lubang yang pertama jangan bikin gede dulu, bikin asal masuk aja pin N connectornya. setelah itu tempelin konektornya, dengan gitu kita bisa tandain lubang sesuai dengan konektor.


terakhir pasang dari luar N bulk konektor di kaleng yg telah dilubangi tadi.


nah saat2 mendebarkan tiba, ehhh gue point tuh antenna ke arah hospot beberapa blok jauhnya dari jendela gue.
walhasil dapet sinyal yg cukup, padahal sebelumnya wireless lan card gue nggak bisa ngendus tuh signal.

konon antenna ini punya gain antara 9dBi - 11dBi sayangnya gue gak punya instrumen buat ngukur2, lagian udah happy dengan hasil yang ada

then life continue as usual....

gue coba pake netstumbler http://www.netstumbler.com/downloads/
ternyata gue bisa ngelihat 7 access point di sekitar apartemen gue.
you know what...? 5 dari 7 AP nggak diprotect apapun jadi bisa konek dengan bebas hahahaha...

kantor gw yg sekarang ada di lantai 18, bisa kelihatan jelas dari jendela apartemen gue. jaraknya kira2 400meter.
sekali gue coba wireless access point gue taruh dekat jendela di kantor, gue pake power output standard 15dBm. antennanya pake buatan trendnet 4dBi indoor omni.
dengan antenna kaleng gue bisa konek dengan sinyal full.
habis itu gue cabut lagi hehehehe...
takut ntar ada yg ngehack ke kantor ntar gue yang disalahin.
padahal sejauh ini yang gue tahu belon ada orang thailand yg jadi hacker seorangpun.
tapi who knows, shit happened.

Sumber :
Blog noesapati in d'house

Enjoy it

Calculation for Wireless Antenna

http://www.saunalahti.fi/elepal/antenna2calc.php

WLAN antenna 2.4 GHz Do-It-Yourself

                    WLAN antenna 2.4 GHz Do-It-Yourself

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Homebrew outdoor antenna to 2.4 GHz band.

Antenna gain is comparable to panel antennas including the Freedom Antenna Set sold in Finland. Comparing is made simple by connecting antennas to same computer with Orinoco WLAN card and indicating results in Link Test of the Client Manager. My antenna has been found about 2 dB better gain than the Freedom antenna, which is specified as 12 dBi antenna. And prices ... Oh, I need not even mention this! In Europe there is a maximum allowable output power of 20 dBm (100 mW) because of the ETSI standard we use. While Orinoco "red" card is transmitting 8 dBm signal and my antenna gain is about 14 dBi there has to be only 2 dB cable and connector loss to keep output level below 20 dBm. The Orinoco Adapter Cable takes about 1 dB and H1000 antenna cable takes 2 dB/10m. So using 5 metres antenna cable there is no risk of exceeding the output power within the ETSI standard. This antenna can also be built without the Ring to decrease antenna gain if needed especially with very short antenna cable.

Dimensioning

The very first point in antenna dimensioning is to calculate the wavelength (the Lambda character has been replaced with letter L ):
L /mm = 300 / (f/GHz)   ->  at 2.45 GHz  L = 122 mm.

Antenna picture without mast fasteners:

With the cover                 Without the cover

Main parts can been found even in mama's dish cabinet but maybe safer to buy them from a department store. The Reflector is made from an aluminium cake pan and the Cover from a plastic microwave bulb, both 240--250 mm dia. The pan must be straight and smooth without profilations and the sides will be orthogonal with the bottom. If you find a pan made from stainless steel may be that may be  better. I used a pan from italo ottinetti code 140024 , whose sides were 60 mm and I cut them to 32 mm.

Other parts needed:
A piece of copper water conduit, internal dia 10 mm, length below 40 mm
A piece of brass rod, outer dia 4-4.5 mm, length < 40 mm
Copper wire about 2 mm dia, length < 70 mm
N-connector, panel socket
A couple pieces of tinned steel sheet  e.g. from tin can
A piece of PVC coated electric wire 1,5 mm2
Screws and bolts M3, solder tin etc.
 

Antenna construction:

The Reflector (aluminium pan) dia = L x 2, the height of the sides = ^L/₄.
In the centre of the bottom there is the N connector to left and the dipole to right. A distance from bottom to the dipole is little more than ^L/₄. The Dipole is mounted with an air-insulated coaxial type foot, whose impedance is 50 ohm and length ^L/₄. Inner wire of the coaxial is made of 4 to 4.5 mm rod or conduit and shield made from split copper conduit which internal dia is 10 mm. To the right of the dipole there is a disc whose dia is L x 0.4 (= 49 mm) and distance from the dipole is again ^L/₄. Disc material can be thin aluminium or tinned steel sheet.

At same distance as the disc, there is also a ring made from pvc-coated electric wire 1,5 mm² by binding it to ring diameter about L x 2. It is not neccessary to short the ends of the ring, I left ~ 1 mm space. If you want you can short the ends together as well. PVC coating on the wire has no magic, you can use e.g 2 mm clear copper wire as well.

I mounted the Disc and the Ring to the plastic cover made from microwave oven bulb. A piece of plastic sheet and glue are needed to mount the disk. The ring I glued inside the cover, so the diameter of the ring becomes somewhat smaller than ^L/₄.

Assembling:

The sides of the reflector (cake pan) must be ^L/₄ or 32 mm, so extra height must be cut away. In the centre of the pan there will be a hole 12 dia and four 3.5 mm holes according the N-connector. The feet of the dipole is made of split copper conduit and inside it a rod or a pipe. The impedance of the feet must be 50 ohm which actually means the ratio of inner dia of the outer conduit and dia of the inner rod be 2.3. It is quite near when inner rod or pipe has 4 to 4.5 mm outer dia and copper conduit has 10 mm inner dia. The exact equation of  Impedance versus Diameter ratio is: 

Z = 138 * Log(^D/_d)
 

The table of Impedance and Diameter Ratio D = inner diameter of the tube d = outer dia of the rod Z = impedance in free air
D / d	Z / Ohm
2.2	47.3
2.3	50
2.4	52.5
2.5	54.9

If the inner wire is made from rod it is good idea to drill axially a 3 mm hole on the end of it so the rod can be solder firmly to the inner tap of the N connector. The length of the rod becomes about ^L/₄, but it is better first to leave it longer and cut it later after the parts are first pre-assembled.

The copper conduit must be split with a metal saw as accurately as possible and deburred with a file. The end of the split conduit is then  fastened to the centre of the pan. It is not possible to solder it directly to aluminium but we made a flange from tinned steel sheet to same dimensions as the flange of the N connector. In the middle of the flange is drilled a hole equal the outer dia of the conduit and four 3.5 mm holes as in the N connector. The one end of the split conduit is then soldered in the centre hole of the flange while keeping the width of the slots between halves to 1-1.5 mm.

The split conduit is then cut so that the length of the open slots becomes a very accurate  ^L/₄. This is the most accurate point in the antenna construction. Among with many roles, the slot acts as a band pass filter which rejects other frequencies than nominal HF.

Now is good time to pre-assemble parts. With four 3 mm screws, the N connector with the centre rod and the flange with split conduit are assembled on opposite sides of the centre hole of the pan, N connector to the outer side. The centre rod is now cut to same length as the split conduit.

The Dipole was made from 2 mm enamelled wire. The one arm of the dipole is soldered both to the centre rod and to the half of the copper conduit. The second arm of the dipole is soldered only to the second half of the conduit. The arms of the dipole are cut to ^L/₄ from axle, so total width of the dipole becomes ^L/₂.
Before soldering it is good idea to file grooves for dipole wire to the centre rod and the halves of the conduit.

To the right of the dipole there is the disc and the wire ring which can be assembled to the cover bulb so that their distance from dipole becomes to ^L/₄.

The cover bulb can be locked with three 3 mm screws and sealed with silicone mass as well as the N connector joint.

On the very lowest point of the pan there must be drilled a small hole for condensed water exhaust.

Frequently asked details
The most important dimension of the antenna is the length of the slot, which must be 31 mm @2.45 GHz. I don't know the optimum width of the slot. I made it with metal handsaw inserting two blades parallel. So it becomes ca. 1.5 mm.	Yes really! The one arm of the dipole is soldered both to the centre rod (2) and to the half of the copper conduit (1). The second arm of the dipole is soldered only to the second half of the conduit (3). It doesn't mean a "short circuit".  Remember the signal here is not direct current but high frequency ! See: Special Cases of Quarter Wavelength

Mast mounting of the antenna

Mast fasteners can be made from exhaust pipe clamps. See above some mounting ideas. Be careful not to mount clamps in the centre line otherwise the mast prevents connection of cable to the N connector. The rightmost picture is from back side.

Lightning protection

When the antenna is mounted above the roof there becomes a risk of lightning damage to the WLAN card.

The mast has to be grounded firmly e.g with 16 mm² copper rope to a good earthing point. Lightning protection module is recommended between antenna cable at the  place where the cable enters the roof.

Antenna cable and connectors

Cable type Belden H1000 is found to be low loss on microwave band and it is not very expensive. All cable and connector impedances must be 50 ohm. Outdoor connections are not watertight enough as such. So called self vulcanizing tape is best choice to wind over connection and above all there have to be wound black electrical tape to protect the vulcanizing tape against ultraviolet light. See cabling details .

Sources

Antenna construction is from page  http://6mt.com/2304tech.htm where is found an item MICROWAVE ANTENNA YOU CAN BUILD (73 10-82) c56.zip . I have dimensioned it to 2.4 GHz band and made some additions.
 

11 July 2001

Martti Palomaki
Ilmajoki, Finland

 

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Overview

This model is from picture  http://www.gbonline.com/~multiplx/wireless/pics/tincanant.jpg where is not found any theoretical principles but same construction is used in waveguide tube to coaxial adapters.

The antenna is constucted only of a cylindrical can and a N connector with centre tap lengthened. Just point the open end of the can to the ISP station and begin surfing. Oh, of cource there is needed some cable between the antenna and wlan card, see: Cabling details .

The can diameter is about 100 mm at 2.4 GHz band. It can be constructed e.g. from old time coffee tin can. Nowadays I haven't seen these in stores but maybe somewhere they can be found. The can dia have to be between 90 and 110 mm, side and bottom must be smooth and direct. If there are some burrs on the open end they have to smoothen e.g with hammer against base.

Dimensioning

Creech Lambda is replaced to L letter.

The length of the can is as is but best length maybe 3/4 Lg or more. The centre tap of  the N connector is lengthened with 4 mm dia brass rod to Lo/4. Lo depends only on nominal frequency. Lo = 122 mm @ 2.45 GHz so Lo / 4 = 31 mm.

Lg depends on dia of the tube, here are some values:
 

Lg  function of tube diameter @ 2.45 GHz
Inner dia of tube D / mm	Standing wave length Lg / mm	Lg / 4
90	202,7	51
95	186,7	47
100	175,7	44
105	167,6	42
110	161,5	40

***** NEW ***** The Calculator Engine for dimensioning

For a N-connector there is needed a 12 mm dia hole which distance is Lg / 4 from closed end. According the flange of the connector there are needed also four 3.5 mm holesi. The inner tap of the N connector is lengthened to Lo/4 or 31 mm with brass rod about 4 mm dia. Actually the length of the tap is not needed to be very accurate. I've proved several lengths from 25 to 40 mm and not found big differences although the impedance of the antenna is depending of the tap length. It's good idea to drill a 3mm hole axially to the end of the brass rod where the centre tap of the connector tightly goes. So the rod soldering becomes very firm.

N connector is fixed with four 3 mm screws so that bolts are pushed from inside of the tube and nuts screwed outside, so there becomes inside so less as possible extra taps, which can disturb the antenna function. The jointing of the connector and tube is sealed watertight with silicone mass. In the very lowest point of the tube there have be drilled a small hole for condensed water outlet.

The open end of the can needs a cap. The plastic material needed here must pass microwave oven test .

Antenna mounting to the antenna mast conduit can be made e.g. with some kind of band round the cylinder to prevent the can flatten or dent.

 

Improved model

If the bottom of the can is not smooth a extra bottom can be added inside the can. It can be made from tinned steel or aluminium which is cutted according inside diameter of the can. How it is mounted inside the can there are countless means. It is not neccessary be tight, microwaves are not passing through narrow slots. Between the extra bottom and original bottom there becomes a space with no need.
 
 
 
 
 
 

 

More effective version

The waveguide antenna can be equipped with a funnel which increases the sensitivity of the antenna simply by collecting hf signal from larger area. This adding increases the gain of the antenna by twice or 3 dB.

The right hand picture shows how the funnel is cutted from smooth tinned steel. Dotted lines are showing margins needed to joints. I made this antenna by air conditioning conduit with dia D = 100 mm where I added a bottom from tinned steel. The antenna dimensions are then:  D = R1 = 100 mm,  D2 = R2 = 170 mm, Lg/4 = 44 mm, Lo/4 = 31 mm, 3/4 Lg = 132 mm.

I used this antenna during about a week with good results until I got a even more effective antenna ready.

I haven't tested if it is possible to increase the outer dia D2 even more. The idea of the funnel is from the satellite receiver horn found in ARRL antenna book.

The open end of the funnel is closed with a microwave proof plastic cap. Tighting of the joint of the N connector and condenced water hole are similar as in the basic model.
 

Theory of the Waveguide Antenna

There are three different wavelengths in the waveguide tube. Here they are marked as Lo, Lc and Lg.

Lo is the wavelength of  the hf signal in open air or  Lo/mm = 300 / (f/GHz).
Lc is the wavelength of the low cut frequency which depends on tube dia only  Lc = 1,706 x D
Lg is standing wavelength inside the tube, it is function of both Lo and Lc

A waveguide which is closed on the other end acts similar as a short circuited coaxial cable. The coming hf signal reflects from ending point and there forms so called standing wave when incoming and reflecting signals in different places are either weakening or amplifiering each others:

If there is a measuring probe which is moving in axial direction inside the tube there can be found some minimum and maximum points in certain intervals. At the closed end the signal is zero and so will be in halfwave intervals. The first maximum point is quarterwavelength from the closed end. This will be the best place to outlet signal to coaxial line. You can notice that maximum area is quite flat. So the place of the outlet must not be very accurate.

It is important to notice that the standing wavelength Lg is not the same as wavelength Lo counted from hf signal. Large tubes are near as open air where Lg and Lo are almost same but when tube diameter becomes smaller the Lg increases effective until there becomes a point when Lg becomes infinite. It corresponds the diameter when hf signal doesn't come to the tube at all. So the waveguide tube acts as a high pass filter which limit wavelength Lc = 1.706 x D. Lo can be calculated from nominal frequency: Lo/mm = 300/(f/GHz). Inverse values of Lo, Lc and Lg forms a right angled triangle where becomes the equation of Pythagoras:

(1/Lo)² = (1/Lc)² + (1/Lg) ²

which can be solved

Lg = 1 / SQR((1/Lo)² - (1/Lc)²)

In the antenna the N connector is situated in maximum point or length of Lg/4 from the closed end. Total length of the tube is selected so that the next maximum place hits on the open end of the tube or 3/4xLg from the closed end. The latter is only supposed by my own and found be not the worst decision.
 

A Fiction

I cast here a model I have thinked. Why not use waveguide tube instead of antenna cable too. The tube shall be so height that the lower end reaches to near the wlan card of the computer. The tube shall be made of 100mm air conditioning conduit with a curve and a funnel. The construction is very resistance against lightnings too I believe. There it will be like a horn of a steamboat. If someone will build this please feedback results.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Sources:

ARRL Antenna Book
ARRL UHF/Microwave Experimenter's Manual ISBN: 0-87259-312-6
 

17. July 2001
29. September 2002 The Calculator added

Martti Palomaki
Ilmajoki

Wlan-antennas

Failed to start slapd. Attempting debug start to determine error. daemon: bind(7) failed errno=99 (Cannot assign requested address) slap_open_listener: failed on ldap://perbutyl.nofjkt.co.id:389

zmcontrol start
Host perbutyl.nofjkt.co.id
        Starting ldap...Done.
FAILED
/opt/zimbra/bin/ldap: line 65: kill: (23236) - No such process
/opt/zimbra/bin/ldap: line 65: kill: (23236) - No such process
/opt/zimbra/bin/ldap: line 65: kill: (23236) - No such process
/opt/zimbra/bin/ldap: line 65: kill: (23236) - No such process
/opt/zimbra/bin/ldap: line 65: kill: (23236) - No such process
/opt/zimbra/bin/ldap: line 65: kill: (23236) - No such process
/opt/zimbra/bin/ldap: line 65: kill: (23236) - No such process
Failed to start slapd.  Attempting debug start to determine error.
daemon: bind(7) failed errno=99 (Cannot assign requested address)
slap_open_listener: failed on ldap://perbutyl.nofjkt.co.id:389

I was RUN zimbra behind NAT, but i forget to setup IP address as the new IP after NAT

here the hierarchi

10.10.10.1 --> NAT----> 202.171.20.86 ---> internet

my machine should be has ip 202.171.20.86 because of the DNS tells that my host perbutyl.nofjkt.co.id is 202.171.20.86

finally i just SET eth0:1 to 202.171.20.86,
Alhamdulillah it solved


Salam Suwidi (suwidi.or.id)

another refference
http://www.zimbra.com/forums/installation/9049-ldap-error.html
http://www.zimbra.com/forums/installation/10725-installation-error-during-ldap-setup-2.html