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G8MNY  > TECH     06.05.22 07:26z 58 Lines 2333 Bytes #20 (0) @ WW
BID : 1523_GB7CIP
Subj: 13cms Dipole & Reflector
Path: SP7YDD<SR1BSZ<IW0QNL<ON0AR<DB0RES<DB0ERF<OK0NAG<F3KT<CX2SA<ED1ZAC<
      GB7CIP
Sent: 220506/0719Z @:GB7CIP.#32.GBR.EURO #:1523 [Caterham Surrey GBR] $:1523_GB
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
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 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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