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VK3ABK > WIFI 18.05.07 16:18l 54 Lines 2251 Bytes #999 (0) @ WW
BID : 18015_VK3ATM
Read: OE3GMW DL1BAH DO5MC GUEST
Subj: Re: Flat plate antennae. (ZS6MI)
Path: DB0FHN<DB0NOE<DB0GAP<DB0GPP<DB0LX<DB0RBS<DB0SWR<DK0WUE<7M3TJZ<ON0AR<
VK6HGR<VK3AYM<VK3AC<VK3APC<VK3ATM
Sent: 070420/0440Z @:VK3ATM.#MEL.VIC.AUS.OC #:18015 XFBB7.04j Bid:18015_VK3ATM
From: VK3ABK@VK3ATM.#MEL.VIC.AUS.OC
To : WIFI@WW
Hello insects!
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
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, and 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 and 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 and 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 and many formulas.(formulae?!)
You could be more fundamental (and domestic) and you just want to see if
WIFI can be received, by using a toilet roll tube wound and spaced with 3 or
4 turns of wire to form a 2.4 GHz helix (just the right diameter for a full
wave) and mount this alone or on a ground plane.
Many ways to spend a cold night playing with microwave antennas, and using
an array of dipoles mounted on a 'flat plate' is a good way to go.
Hope this helps.
73. Dick. VK3ABK.
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