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G8MNY > TECH 14.02.25 17:12l 59 Lines 2334 Bytes #1 (0) @ WW
BID : 25854_GB7CIP
Subj: 13cms Dipole & Reflector
Path: JH4XSY<N3HYM<KE0GB<GB7YEW<GB7CIP
Sent: 250214/0807Z @:GB7CIP.#32.GBR.EURO #:25854 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
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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.
ｳ ｳ
ﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ <-- 2.4GHz Dipole
ｳｳｳ
ｳｳｳ
ｳｳｳ <--Tube with centre conductor
ｳｳｳ
ﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾁﾁﾁﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ <-- GroundPlane
ｳ
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 at onequarter 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
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