| |
G8MNY > TECH 30.12.09 09:18l 60 Lines 2422 Bytes #999 (0) @ WW
BID : 45955_GB7CIP
Read: GUEST
Subj: 13cms Dipole & Reflector
Path: IZ3LSV<IK2XDE<DB0RES<ON0AR<F4BWT<GB7COW<GB7CIP
Sent: 091229/2354Z @:GB7CIP.#32.GBR.EU #:45955 [Caterham] $:45955_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By Dick VK3ABK (Tech list on Apr 07)
Roy, ZS6MI, has asked for details of a 2.4GHz 'antennae' (!)
I take this as a challenge, but with some reservation.
Hey, Roy. Insects have 'antennae', Hams have 'antennas'!
But just to stay friends, here is a suggestion for your flat plate antenna.
³ ³
ÄÄÄÄÄÄÄÄÄÄÄ´ÚÄÄÄÄÄÄÄÄÄÄ <-- 2.4GHz Dipole
³³³
³³³
³³³ <--Tube with centre conductor
³³³
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÁÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄ <-- GroundPlane
³
Coax
A dipole for 2.4GHz (300/2400 X .95 divided by 2 = 5.9 cm) can be made from
any stiff copper wire, one half soldered to a copper or brass tube, say 10mm
OD which would be about 8mm ID, & the other half soldered to a centre
coaxial conductor. This is done down the end of the 10mm tube,which is big
enough for a 60 Watt soldering iron. The 8mm ID tube & a 3.5mm centre
conductor, near enough to 1/8 inch welding rod, would give you a 50 Ohm
transmission line (Z = 138 log D/d) near enough for the dipole.
This forms a 'stub fed' dipole (see the recent coaxial dipole bulletins) at
one quarter wave (half the dipole dimension will do) from the ground plane,
or plate, of any large dimension. The advantages of this construction are,
an electrically & mechanically solid construction, with an inbuilt support
for the dipole that is 'electrically ground' at the ground plane support.
The antenna is easily water-proofed, or can be mounted inside a plastic
cake box or similar.
I just worked this out as an exercise to show how you can design an antenna
from 'principles', rather than looking up texts & many formulas.(formulae?!)
You could be more fundamental (& domestic) & you just want to see if
WIFI can be received, by using a toilet roll tube wound & spaced with 3 or
4 turns of wire to form a 2.4 GHz helix (just the right diameter for a full
wave) & mount this alone or on a ground plane.
Many ways to spend a cold night playing with microwave antennas, & using
an array of dipoles mounted on a 'flat plate' is a good way to go.
Hope this helps.
73. Dick. VK3ABK.
-----------------
Y don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
